thioridazine (Rx)

Schizophrenia

Initial 50-100 mg PO q8hr, THEN

200-800 mg/day PO divided q6-12hr

Depressive Disorders

25 mg PO q8hr; may titrate to effect (20-200 mg/day)

Renal Impairment

Dose adjustment not necessary in dialysis

Hepatic Disease

Initiate treatment at lower dose and titrate to effect (monitor)

Other Indications & Uses

Psychotic disorders, geriatric psychoneurotic manifestations, pediatric behavioral disorders

Schizophrenia

<2 years: Safety and efficacy not established

2-12 years: 0.5-3 mg/kg/day divided q8hr PO, no more than 3 mg/kg/day  

>12 years: Initial 50-100 mg PO q8hr; titrate to 200-800 mg/day PO divided q6-12hr

Potential toxic dose <6 years old: 3 mg/kg

Initiate treatment at lower dose and titrate to effect (monitor)

Schizophrenia

Initial 50-100 mg PO q8hr, THEN

200-800 mg/day PO divided q6-12hr

Debilitated patients: Initiate treatment at lower dose

Depressive disorders

25 mg PO q8hr; may titrate to effect (20-200 mg/day)

Contraindicated (63)

• albuterol

  albuterol and thioridazine both increase QTc interval. Contraindicated.

• alfuzosin

  alfuzosin and thioridazine both increase QTc interval. Contraindicated.

• amiodarone

  thioridazine and amiodarone both increase QTc interval. Contraindicated.

• amisulpride

  amisulpride and thioridazine both increase QTc interval. Contraindicated.
  
  amisulpride, thioridazine. Either increases toxicity of the other by Other (see comment). Contraindicated. Comment: Increases risk of neuroleptic malignant syndrome.

• anagrelide

  anagrelide and thioridazine both increase QTc interval. Contraindicated.

• apomorphine

  apomorphine and thioridazine both increase QTc interval. Contraindicated.

• arformoterol

  arformoterol and thioridazine both increase QTc interval. Contraindicated.

• aripiprazole

  aripiprazole and thioridazine both increase QTc interval. Contraindicated.

• artemether

  artemether and thioridazine both increase QTc interval. Contraindicated.

• asenapine

  asenapine and thioridazine both increase QTc interval. Contraindicated.

• asenapine transdermal

  asenapine transdermal and thioridazine both increase QTc interval. Contraindicated.

• atomoxetine

  atomoxetine and thioridazine both increase QTc interval. Contraindicated.

• buprenorphine

  buprenorphine and thioridazine both increase QTc interval. Contraindicated.

• ceritinib

  ceritinib and thioridazine both increase QTc interval. Contraindicated.

• clomipramine

  thioridazine will increase the level or effect of clomipramine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• clozapine

  clozapine and thioridazine both increase QTc interval. Contraindicated.

• crizotinib

  crizotinib and thioridazine both increase QTc interval. Contraindicated. Thioridazine is contraindicated with drugs that may prolong the QT interval.

• degarelix

  degarelix and thioridazine both increase QTc interval. Contraindicated.

• desipramine

  thioridazine will increase the level or effect of desipramine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• disopyramide

  thioridazine and disopyramide both increase QTc interval. Contraindicated.

• dofetilide

  dofetilide increases toxicity of thioridazine by QTc interval. Contraindicated.

• donepezil

  donepezil and thioridazine both increase QTc interval. Contraindicated.

• doxepin

  thioridazine will increase the level or effect of doxepin by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• eliglustat

  thioridazine increases levels of eliglustat by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated. If coadministered with strong or moderate CYP2D6 inhibitors, reduce eliglustat dose from 84 mg BID to 84 mg once daily in extensive and intermediate metabolizers; eliglustat is contraindiated if strong or moderate CYP2D6 inhibitors are given concomitantly with strong or moderate CYP3A inhibitors.
  
  eliglustat and thioridazine both increase QTc interval. Contraindicated.

• escitalopram

  escitalopram increases toxicity of thioridazine by QTc interval. Contraindicated.

• fingolimod

  fingolimod and thioridazine both increase QTc interval. Contraindicated.

• fluoxetine

  thioridazine will increase the level or effect of fluoxetine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.
  
  thioridazine and fluoxetine both increase QTc interval. Contraindicated.
  
  fluoxetine increases levels of thioridazine by decreasing metabolism. Contraindicated. Risk of long QT syndrome.

• gemifloxacin

  gemifloxacin and thioridazine both increase QTc interval. Contraindicated.

• gilteritinib

  gilteritinib and thioridazine both increase QTc interval. Contraindicated.

• goserelin

  goserelin increases toxicity of thioridazine by QTc interval. Contraindicated. Increases risk of torsades de pointes.

• granisetron

  granisetron and thioridazine both increase QTc interval. Contraindicated.

• hydroxyzine

  hydroxyzine and thioridazine both increase QTc interval. Contraindicated.

• ibutilide

  thioridazine and ibutilide both increase QTc interval. Contraindicated.

• imipramine

  thioridazine will increase the level or effect of imipramine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• indapamide

  thioridazine and indapamide both increase QTc interval. Contraindicated.

• isoflurane

  isoflurane and thioridazine both increase QTc interval. Contraindicated.

• leuprolide

  leuprolide increases toxicity of thioridazine by QTc interval. Contraindicated. Increases risk of torsades de pointes.

• lithium

  lithium and thioridazine both increase QTc interval. Contraindicated.

• metrizamide

  thioridazine, metrizamide. Mechanism: unknown. Contraindicated. Risk of seizure. D/C phenothiazine 24h before admin. of metrizamide.

• mifepristone

  mifepristone, thioridazine. QTc interval. Contraindicated.

• mirtazapine

  mirtazapine and thioridazine both increase QTc interval. Contraindicated.

• nortriptyline

  thioridazine will increase the level or effect of nortriptyline by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• olanzapine

  olanzapine and thioridazine both increase QTc interval. Contraindicated.

• oxaliplatin

  oxaliplatin and thioridazine both increase QTc interval. Contraindicated.

• paroxetine

  paroxetine increases levels of thioridazine by decreasing metabolism. Contraindicated. Risk of long QT syndrome.

• pasireotide

  thioridazine and pasireotide both increase QTc interval. Contraindicated.

• pentamidine

  thioridazine and pentamidine both increase QTc interval. Contraindicated.

• pimozide

  thioridazine and pimozide both increase QTc interval. Contraindicated.

• primaquine

  primaquine and thioridazine both increase QTc interval. Contraindicated.

• procainamide

  thioridazine and procainamide both increase QTc interval. Contraindicated.

• quinidine

  thioridazine and quinidine both increase QTc interval. Contraindicated.

• quinine

  thioridazine and quinine both increase QTc interval. Contraindicated.

• rolapitant

  rolapitant will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated. Rolapitant moderately inhibits CYP2D6. Coadministration with thioridazine, a CYP2D6 substrate, causes a significant increase in thioridazine plasma concentration that may result in QT prolongation and torsades de pointes.

• sertraline

  sertraline increases levels of thioridazine by decreasing metabolism. Contraindicated. Risk of long QT syndrome.
  
  sertraline and thioridazine both increase QTc interval. Contraindicated.

• sevoflurane

  sevoflurane and thioridazine both increase QTc interval. Contraindicated.

• siponimod

  siponimod and thioridazine both increase QTc interval. Contraindicated.

• solifenacin

  solifenacin and thioridazine both increase QTc interval. Contraindicated.

• sorafenib

  sorafenib and thioridazine both increase QTc interval. Contraindicated.

• sotalol

  thioridazine and sotalol both increase QTc interval. Contraindicated.

• sunitinib

  sunitinib and thioridazine both increase QTc interval. Contraindicated.

• tacrolimus

  tacrolimus and thioridazine both increase QTc interval. Contraindicated.

• toremifene

  thioridazine and toremifene both increase QTc interval. Contraindicated. Concurrent use of thioridazine with other agents that prolong QTc interval is contraindicated.

• vorinostat

  vorinostat and thioridazine both increase QTc interval. Contraindicated.

Serious - Use Alternative (125)

• aminolevulinic acid oral

  aminolevulinic acid oral, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Avoid administering other phototoxic drugs with aminolevulinic acid oral for 24 hr during perioperative period.

• aminolevulinic acid topical

  thioridazine increases toxicity of aminolevulinic acid topical by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration of photosensitizing drugs may enhance the phototoxic reaction to photodynamic therapy with aminolevulinic acid.

• amiodarone

  amiodarone will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  amiodarone increases levels of thioridazine by decreasing metabolism. Contraindicated.

• amitriptyline

  thioridazine and amitriptyline both increase QTc interval. Avoid or Use Alternate Drug.

• amoxapine

  thioridazine and amoxapine both increase QTc interval. Avoid or Use Alternate Drug.

• apomorphine

  thioridazine decreases effects of apomorphine by pharmacodynamic antagonism. Avoid or Use Alternate Drug.

• arsenic trioxide

  thioridazine and arsenic trioxide both increase QTc interval. Avoid or Use Alternate Drug.

• artemether/lumefantrine

  artemether/lumefantrine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  thioridazine and artemether/lumefantrine both increase QTc interval. Avoid or Use Alternate Drug.

• asenapine

  asenapine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• benzhydrocodone/acetaminophen

  benzhydrocodone/acetaminophen, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation. Increased risk of hypotension if ability to maintain blood pressure has been compromised by a reduced blood volume or concurrent administration of certain CNS depressant drugs (eg, phenothiazines or general anesthetics).

• bremelanotide

  bremelanotide will decrease the level or effect of thioridazine by Other (see comment). Avoid or Use Alternate Drug. Bremelanotide may slow gastric emptying and potentially reduces the rate and extent of absorption of concomitantly administered oral medications. Avoid use when taking any oral drug that is dependent on threshold concentrations for efficacy. Interactions listed are representative examples and do not include all possible clinical examples.

• bromocriptine

  thioridazine decreases effects of bromocriptine by pharmacodynamic antagonism. Avoid or Use Alternate Drug.

• bupropion

  bupropion will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• cabergoline

  thioridazine decreases effects of cabergoline by pharmacodynamic antagonism. Contraindicated.

• calcium/magnesium/potassium/sodium oxybates

  thioridazine, calcium/magnesium/potassium/sodium oxybates. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• carvedilol

  carvedilol, thioridazine. Either increases levels of the other by decreasing metabolism. Contraindicated. Not all beta blockers share this interaction (e.g., atenolol, nadolol, sotalol do not interact).

• celecoxib

  celecoxib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• chloroquine

  chloroquine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• chlorpromazine

  chlorpromazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• cimetidine

  cimetidine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• citalopram

  thioridazine and citalopram both increase QTc interval. Avoid or Use Alternate Drug. Thioridazine should be avoided in combination with drugs that are known to prolong QTc interval.

• clarithromycin

  thioridazine and clarithromycin both increase QTc interval. Avoid or Use Alternate Drug.

• clomipramine

  thioridazine and clomipramine both increase QTc interval. Avoid or Use Alternate Drug.

• dacomitinib

  dacomitinib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Avoid use with CYP2D6 substrates where minimal increases in concentration of the CYP2D6 substrate may lead to serious or life-threatening toxicities.

• darifenacin

  darifenacin will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• desipramine

  thioridazine and desipramine both increase QTc interval. Avoid or Use Alternate Drug.

• diphenhydramine

  diphenhydramine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• dofetilide

  thioridazine and dofetilide both increase QTc interval. Avoid or Use Alternate Drug.

• dopamine

  thioridazine decreases effects of dopamine by pharmacodynamic antagonism. Contraindicated.

• dosulepin

  thioridazine and dosulepin both increase QTc interval. Avoid or Use Alternate Drug.

• doxepin

  thioridazine and doxepin both increase QTc interval. Avoid or Use Alternate Drug.

• dronedarone

  dronedarone will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.
  
  thioridazine and dronedarone both increase QTc interval. Avoid or Use Alternate Drug.

• droperidol

  thioridazine and droperidol both increase QTc interval. Avoid or Use Alternate Drug.

• duloxetine

  duloxetine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.
  
  thioridazine will increase the level or effect of duloxetine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• encorafenib

  encorafenib and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Encorafenib is associated with dose-dependent QTc interval prolongation. Avoid with drugs known to prolong QT interval.

• entrectinib

  thioridazine and entrectinib both increase QTc interval. Avoid or Use Alternate Drug.

• epinephrine

  epinephrine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• epinephrine racemic

  epinephrine racemic and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• eribulin

  eribulin and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Potential for enhanced QTc-prolonging effects; if concurrent use is necessary then ECG monitoring is recommended.

• erythromycin base

  thioridazine and erythromycin base both increase QTc interval. Avoid or Use Alternate Drug.

• erythromycin ethylsuccinate

  thioridazine and erythromycin ethylsuccinate both increase QTc interval. Avoid or Use Alternate Drug.

• erythromycin lactobionate

  thioridazine and erythromycin lactobionate both increase QTc interval. Avoid or Use Alternate Drug.

• erythromycin stearate

  thioridazine and erythromycin stearate both increase QTc interval. Avoid or Use Alternate Drug.

• fentanyl

  fentanyl, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration with other CNS depressants, such as skeletal muscle relaxants, may cause respiratory depression, hypotension, profound sedation, coma, and/or death. Consider dose reduction of either or both agents to avoid serious adverse effects. Monitor for hypotension, respiratory depression, and profound sedation.

• fentanyl intranasal

  fentanyl intranasal, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration with other CNS depressants, such as skeletal muscle relaxants, may cause respiratory depression, hypotension, profound sedation, coma, and/or death. Consider dose reduction of either or both agents to avoid serious adverse effects. Monitor for hypotension, respiratory depression, and profound sedation.

• fentanyl transdermal

  fentanyl transdermal, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration with other CNS depressants, such as skeletal muscle relaxants, may cause respiratory depression, hypotension, profound sedation, coma, and/or death. Consider dose reduction of either or both agents to avoid serious adverse effects. Monitor for hypotension, respiratory depression, and profound sedation.

• fentanyl transmucosal

  fentanyl transmucosal, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration with other CNS depressants, such as skeletal muscle relaxants, may cause respiratory depression, hypotension, profound sedation, coma, and/or death. Consider dose reduction of either or both agents to avoid serious adverse effects. Monitor for hypotension, respiratory depression, and profound sedation.

• fexinidazole

  fexinidazole and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Avoid coadministration of fexinidazole with drugs known to block potassium channels and/or prolong QT interval.

• fluconazole

  thioridazine and fluconazole both increase QTc interval. Avoid or Use Alternate Drug.

• fluoxetine

  fluoxetine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• fluphenazine

  fluphenazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• fluvoxamine

  fluvoxamine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP1A2 metabolism. Contraindicated.
  
  fluvoxamine and thioridazine both increase QTc interval. Contraindicated.

• formoterol

  thioridazine and formoterol both increase QTc interval. Avoid or Use Alternate Drug.

• givosiran

  givosiran will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sensitive CYP2D6 substrates with givosiran. If unavoidable, decrease the CYP2D6 substrate dosage in accordance with approved product labeling.

• glasdegib

  thioridazine and glasdegib both increase QTc interval. Avoid or Use Alternate Drug. If coadministration unavoidable, monitor for increased risk of QTc interval prolongation.

• haloperidol

  haloperidol will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  thioridazine and haloperidol both increase QTc interval. Avoid or Use Alternate Drug.

• histrelin

  histrelin increases toxicity of thioridazine by QTc interval. Avoid or Use Alternate Drug. Increases risk of torsades de pointes.

• hydrocodone

  hydrocodone, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation. Increased risk of hypotension if ability to maintain blood pressure has been compromised by a reduced blood volume or concurrent administration of certain CNS depressant drugs (eg, phenothiazines or general anesthetics).

• hydroxychloroquine sulfate

  hydroxychloroquine sulfate and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• imatinib

  imatinib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• imipramine

  thioridazine and imipramine both increase QTc interval. Avoid or Use Alternate Drug.

• inotuzumab

  inotuzumab and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. If unable to avoid concomitant use, obtain ECGs and electrolytes before and after initiation of any drug known to prolong QTc, and periodically monitor as clinically indicated during treatment.

• itraconazole

  thioridazine and itraconazole both increase QTc interval. Avoid or Use Alternate Drug.

• ivosidenib

  ivosidenib and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Avoid coadministration of QTc prolonging drugs with ivosidenib or replace with alternate therapies. If coadministration of a QTc prolonging drug is unavoidable, monitor for increased risk of QTc interval prolongation.

• ketoconazole

  thioridazine and ketoconazole both increase QTc interval. Avoid or Use Alternate Drug.

• lefamulin

  lefamulin and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• levodopa

  thioridazine decreases effects of levodopa by pharmacodynamic antagonism. Avoid or Use Alternate Drug.

• levodopa inhaled

  thioridazine decreases effects of levodopa inhaled by pharmacodynamic antagonism. Avoid or Use Alternate Drug. Phenothiazine/1st generation antipsychotics inhibit dopamine D2 receptors in varying degrees.

• levoketoconazole

  thioridazine and levoketoconazole both increase QTc interval. Avoid or Use Alternate Drug.

• lisuride

  thioridazine decreases effects of lisuride by pharmacodynamic antagonism. Contraindicated.

• lofepramine

  thioridazine and lofepramine both increase QTc interval. Avoid or Use Alternate Drug.

• lumefantrine

  lumefantrine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  thioridazine and lumefantrine both increase QTc interval. Avoid or Use Alternate Drug.

• macimorelin

  macimorelin and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Macimorelin causes an increase of ~11 msec in the corrected QT interval. Avoid coadministration with drugs that prolong QT interval, which could increase risk for developing torsade de pointes-type ventricular tachycardia. Allow sufficient washout time of drugs that are known to prolong the QT interval before administering macimorelin.

• maprotiline

  thioridazine and maprotiline both increase QTc interval. Avoid or Use Alternate Drug.

• maraviroc

  maraviroc will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• marijuana

  marijuana will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• mefloquine

  mefloquine increases toxicity of thioridazine by QTc interval. Avoid or Use Alternate Drug. Mefloquine may enhance the QTc prolonging effect of high risk QTc prolonging agents.

• methyl aminolevulinate

  thioridazine, methyl aminolevulinate. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Each drug may increase the photosensitizing effect of the other.

• methyldopa

  thioridazine decreases effects of methyldopa by pharmacodynamic antagonism. Contraindicated.

• metoclopramide intranasal

  thioridazine will increase the level or effect of metoclopramide intranasal by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Concurrent use of metoclopramide intranasal and strong CYP2D6 inhibitors is not recommended since the metoclopramide intranasal dose cannot be adjusted.
  
  thioridazine, metoclopramide intranasal. Either increases effects of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Avoid use of metoclopramide intranasal or interacting drug, depending on importance of drug to patient.
  
  thioridazine increases toxicity of metoclopramide intranasal by pharmacodynamic synergism. Avoid or Use Alternate Drug. Potential for additive effects, including increased frequency and severity of tardive dyskinesia, other extrapyramidal symptoms, and neuroleptic malignant syndrome.

• metoprolol

  metoprolol, thioridazine. Either increases levels of the other by decreasing metabolism. Contraindicated. Not all beta blockers share this interaction (e.g., atenolol, nadolol, sotalol do not interact).

• mobocertinib

  mobocertinib and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. If coadministration unavoidable, reduce mobocertinib dose and monitor QTc interval more frequently.

• moxifloxacin

  thioridazine and moxifloxacin both increase QTc interval. Avoid or Use Alternate Drug.

• nilotinib

  nilotinib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.
  
  thioridazine and nilotinib both increase QTc interval. Avoid or Use Alternate Drug.

• nortriptyline

  thioridazine and nortriptyline both increase QTc interval. Avoid or Use Alternate Drug.

• octreotide

  thioridazine and octreotide both increase QTc interval. Avoid or Use Alternate Drug.

• octreotide (Antidote)

  thioridazine and octreotide (Antidote) both increase QTc interval. Avoid or Use Alternate Drug.

• ondansetron

  thioridazine and ondansetron both increase QTc interval. Avoid or Use Alternate Drug. Avoid with congenital long QT syndrome; ECG monitoring recommended with concomitant medications that prolong QT interval, electrolyte abnormalities, CHF, or bradyarrhythmias.

• panobinostat

  thioridazine and panobinostat both increase QTc interval. Avoid or Use Alternate Drug. Panobinostat is known to significantly prolong QT interval. Panobinostat prescribing information states use with drugs known to prolong QTc is not recommended.

• parecoxib

  parecoxib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• paroxetine

  paroxetine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  thioridazine will increase the level or effect of paroxetine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  thioridazine and paroxetine both increase QTc interval. Avoid or Use Alternate Drug.

• perphenazine

  perphenazine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  perphenazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• pimavanserin

  pimavanserin and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Coadministration may increase the risk of QT prolongation and cardiac arrhythmia.

• pitolisant

  thioridazine and pitolisant both increase QTc interval. Avoid or Use Alternate Drug.

• pramipexole

  thioridazine decreases effects of pramipexole by pharmacodynamic antagonism. Contraindicated.

• prochlorperazine

  prochlorperazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• promazine

  promazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• promethazine

  promethazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• propafenone

  propafenone will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. The concurrent administration of thioridazine and agents that prolong the QT interval, such as Class I antiarrhythmic agents, is contraindicated.
  
  thioridazine will increase the level or effect of propafenone by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. The concurrent administration of thioridazine and agents that prolong the QT interval, such as Class I antiarrhythmic agents, is contraindicated.

• propranolol

  thioridazine will increase the level or effect of propranolol by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Due to the potential for significant, possibly life-threatening, proarrhythmic effects, concurrent administration of thioridazine and propranolol is contraindicated.
  
  propranolol, thioridazine. Either increases levels of the other by decreasing metabolism. Contraindicated. Not all beta blockers share this interaction (e.g., atenolol, nadolol, sotalol do not interact).

• protriptyline

  thioridazine and protriptyline both increase QTc interval. Avoid or Use Alternate Drug.

• quinacrine

  quinacrine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• quinidine

  quinidine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  quinidine, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Additive cardiac effects.

• ranolazine

  ranolazine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• ribociclib

  ribociclib and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• ritonavir

  ritonavir will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• ropinirole

  thioridazine decreases effects of ropinirole by pharmacodynamic antagonism. Contraindicated.

• safinamide

  thioridazine decreases effects of safinamide by pharmacodynamic antagonism. Avoid or Use Alternate Drug. Dopamine antagonists may decrease safinamide effects and exacerbate Parkinson disease symptoms.

• selinexor

  selinexor, thioridazine. unspecified interaction mechanism. Avoid or Use Alternate Drug. Patients treated with selinexor may experience neurological toxicities. Avoid taking selinexor with other medications that may cause dizziness or confusion.

• sertraline

  sertraline will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• sodium oxybate

  thioridazine, sodium oxybate. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• tipranavir

  tipranavir will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• trazodone

  thioridazine and trazodone both increase QTc interval. Avoid or Use Alternate Drug.

• tretinoin

  thioridazine, tretinoin. Mechanism: pharmacodynamic synergism. Avoid or Use Alternate Drug. Increased phototoxicity.

• tretinoin topical

  thioridazine, tretinoin topical. Mechanism: pharmacodynamic synergism. Avoid or Use Alternate Drug. Increased phototoxicity.

• trifluoperazine

  thioridazine and trifluoperazine both increase QTc interval. Avoid or Use Alternate Drug.

• trimipramine

  thioridazine and trimipramine both increase QTc interval. Avoid or Use Alternate Drug.

• triptorelin

  triptorelin increases toxicity of thioridazine by QTc interval. Avoid or Use Alternate Drug. Increases risk of torsades de pointes.

• umeclidinium bromide/vilanterol inhaled

  thioridazine increases toxicity of umeclidinium bromide/vilanterol inhaled by QTc interval. Avoid or Use Alternate Drug. Exercise extreme caution when vilanterol coadministered with drugs that prolong QTc interval; adrenergic agonist effects on the cardiovascular system may be potentiated.

• vandetanib

  thioridazine, vandetanib. Either increases toxicity of the other by QTc interval. Avoid or Use Alternate Drug. Avoid coadministration with drugs known to prolong QT interval; if a drug known to prolong QT interval must be used, more frequent ECG monitoring is recommended.

• vemurafenib

  vemurafenib increases levels of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Concomitant use of vemurafenib with agents with narrow therapeutic windows is not recommended as vemurafenib may alter their concentrations. If coadministration cannot be avoided, use caution and consider dose reduction of concomitant CYP2D6 substrate drug. Combination may increase risk QT prolongation.

• venlafaxine

  venlafaxine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  thioridazine and venlafaxine both increase QTc interval. Avoid or Use Alternate Drug.

• vilanterol/fluticasone furoate inhaled

  thioridazine increases toxicity of vilanterol/fluticasone furoate inhaled by QTc interval. Avoid or Use Alternate Drug. Exercise extreme caution when vilanterol coadministered with drugs that prolong QTc interval; adrenergic agonist effects on the cardiovascular system may be potentiated.

• yohimbe

  yohimbe decreases effects of thioridazine by pharmacodynamic antagonism. Contraindicated.

• ziprasidone

  thioridazine and ziprasidone both increase QTc interval. Avoid or Use Alternate Drug.

Monitor Closely (311)

• abiraterone

  abiraterone increases levels of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Avoid coadministration of abiraterone with substrates of CYP2D6. If alternative therapy cannot be used, exercise caution and consider a dose reduction of the CYP2D6 substrate.

• abobotulinumtoxinA

  abobotulinumtoxinA increases effects of thioridazine by pharmacodynamic synergism. Use Caution/Monitor. Use of anticholinergic drugs after administration of botulinum toxin-containing products may potentiate systemic anticholinergic effects.

• aclidinium

  aclidinium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of aclidinium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• albiglutide

  thioridazine, albiglutide. Other (see comment). Use Caution/Monitor. Comment: Phenothiazines may increase or decrease glucose levels, monitor therapy closely when these agents are concurrently administered.

• albuterol

  thioridazine increases and albuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• alfentanil

  alfentanil and thioridazine both increase sedation. Use Caution/Monitor.

• alfuzosin

  thioridazine and alfuzosin both increase QTc interval. Use Caution/Monitor.

• alprazolam

  alprazolam and thioridazine both increase sedation. Use Caution/Monitor.

• amifampridine

  thioridazine increases toxicity of amifampridine by Other (see comment). Modify Therapy/Monitor Closely. Comment: Amifampridine can cause seizures. Coadministration with drugs that lower seizure threshold may increase this risk.

• amitriptyline

  thioridazine and amitriptyline both increase sedation. Use Caution/Monitor.

• amobarbital

  amobarbital and thioridazine both increase sedation. Use Caution/Monitor.

• amoxapine

  thioridazine and amoxapine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and amoxapine both increase sedation. Use Caution/Monitor.

• anticholinergic/sedative combos

  anticholinergic/sedative combos decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  anticholinergic/sedative combos decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of anticholinergic/sedative combos by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• arformoterol

  thioridazine increases and arformoterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• aripiprazole

  aripiprazole and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  aripiprazole and thioridazine both increase sedation. Use Caution/Monitor.

• armodafinil

  thioridazine increases and armodafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• atomoxetine

  thioridazine will increase the level or effect of atomoxetine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• atracurium

  atracurium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  atracurium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of atracurium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• atropine

  atropine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  atropine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of atropine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• atropine IV/IM

  thioridazine increases effects of atropine IV/IM by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
  
  atropine IV/IM decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  atropine IV/IM decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.

• azelastine

  azelastine and thioridazine both increase sedation. Use Caution/Monitor.

• azithromycin

  thioridazine and azithromycin both increase QTc interval. Use Caution/Monitor.

• baclofen

  baclofen and thioridazine both increase sedation. Use Caution/Monitor.

• bedaquiline

  thioridazine and bedaquiline both increase QTc interval. Modify Therapy/Monitor Closely. ECG should be monitored closely

• belladonna alkaloids

  belladonna alkaloids decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  belladonna alkaloids decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of belladonna alkaloids by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• belladonna and opium

  belladonna and opium and thioridazine both increase sedation. Use Caution/Monitor.
  
  belladonna and opium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  belladonna and opium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of belladonna and opium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• benperidol

  benperidol and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  benperidol and thioridazine both increase sedation. Use Caution/Monitor.

• benzhydrocodone/acetaminophen

  thioridazine will increase the level or effect of benzhydrocodone/acetaminophen by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Hydromorphone (<3% of the circulating parent hydrocodone [benzhydrocodone is prodrug of hydrocodone]) is mainly formed by CYP2D6 mediated O-demethylation of hydrocodone. Hydromorphone may contribute to the total analgesic effect of hydrocodone.

• benzphetamine

  thioridazine increases and benzphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, benzphetamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• benztropine

  thioridazine increases effects of benztropine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic adverse effects may be seen with concurrent use. .

• berotralstat

  berotralstat will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Monitor or titrate substrate dose when berotralstat is coadministered with narrow therapeutic index drugs that are CYP2D6 substrates.

• brexanolone

  brexanolone, thioridazine. Either increases toxicity of the other by sedation. Use Caution/Monitor.

• brexpiprazole

  thioridazine will increase the level or effect of brexpiprazole by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Administer a quarter of brexpiprazole dose if coadministered with a moderate CYP2D6 inhibitor PLUS a strong/moderate CYP3A4 inhibitor.

• brompheniramine

  brompheniramine and thioridazine both increase sedation. Use Caution/Monitor.

• buprenorphine

  buprenorphine and thioridazine both increase sedation. Use Caution/Monitor.

• buprenorphine buccal

  buprenorphine buccal and thioridazine both increase sedation. Use Caution/Monitor.

• buprenorphine, long-acting injection

  thioridazine increases toxicity of buprenorphine, long-acting injection by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of buprenorphine and benzodiazepines or other CNS depressants increases risk of adverse reactions including overdose, respiratory depression, and death. Cessation of benzodiazepines or other CNS depressants is preferred in most cases. In some cases, monitoring at a higher level of care for tapering CNS depressants may be appropriate. In others, gradually tapering a patient off of a prescribed benzodiazepine or other CNS depressant or decreasing to the lowest effective dose may be appropriate.

• butabarbital

  butabarbital and thioridazine both increase sedation. Use Caution/Monitor.

• butalbital

  butalbital and thioridazine both increase sedation. Use Caution/Monitor.

• butorphanol

  butorphanol and thioridazine both increase sedation. Use Caution/Monitor.

• caffeine

  thioridazine increases and caffeine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• carbinoxamine

  carbinoxamine and thioridazine both increase sedation. Use Caution/Monitor.

• carisoprodol

  carisoprodol and thioridazine both increase sedation. Use Caution/Monitor.

• carvedilol

  thioridazine will increase the level or effect of carvedilol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• cenobamate

  cenobamate, thioridazine. Either increases effects of the other by sedation. Use Caution/Monitor.

• chloral hydrate

  chloral hydrate and thioridazine both increase sedation. Use Caution/Monitor.

• chlordiazepoxide

  chlordiazepoxide and thioridazine both increase sedation. Use Caution/Monitor.

• chloroquine

  chloroquine increases toxicity of thioridazine by QTc interval. Use Caution/Monitor.

• chlorpheniramine

  chlorpheniramine and thioridazine both increase sedation. Use Caution/Monitor.

• chlorpromazine

  chlorpromazine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  chlorpromazine and thioridazine both increase sedation. Use Caution/Monitor.

• chlorzoxazone

  chlorzoxazone and thioridazine both increase sedation. Use Caution/Monitor.

• cigarette smoking

  cigarette smoking decreases levels of thioridazine by increasing metabolism. Use Caution/Monitor. Interaction mainly seen w/chlorpromazine & thioridazine, but may occur w/other phenothiazines.

• cinnarizine

  cinnarizine and thioridazine both increase sedation. Use Caution/Monitor.

• ciprofloxacin

  ciprofloxacin and thioridazine both increase QTc interval. Use Caution/Monitor. Ciprofloxacin elicits minimal effects on QT interval. Caution if used in combination with other drugs known to affect QT interval or in patients with other risk factors.

• cisatracurium

  cisatracurium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  cisatracurium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of cisatracurium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• clemastine

  clemastine and thioridazine both increase sedation. Use Caution/Monitor.

• clobazam

  clobazam will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Lower doses of drugs metabolized by CYP2D6 may be required when used concomitantly.
  
  thioridazine, clobazam. Other (see comment). Use Caution/Monitor. Comment: Concomitant administration can increase the potential for CNS effects (e.g., increased sedation or respiratory depression).

• clomipramine

  thioridazine and clomipramine both increase sedation. Use Caution/Monitor.

• clonazepam

  clonazepam and thioridazine both increase sedation. Use Caution/Monitor.

• clonidine

  clonidine, thioridazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

• clorazepate

  clorazepate and thioridazine both increase sedation. Use Caution/Monitor.

• clozapine

  clozapine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  clozapine and thioridazine both increase sedation. Use Caution/Monitor.

• cobicistat

  cobicistat will increase the level or effect of thioridazine by Other (see comment). Modify Therapy/Monitor Closely. A decrease in the dose of antipsychotics that are metabolized by CYP3A or CYP2D6 may be needed upon coadministration.

• codeine

  thioridazine decreases effects of codeine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Prevents conversion of codeine to its active metabolite morphine.
  
  codeine and thioridazine both increase sedation. Use Caution/Monitor.

• cyclizine

  cyclizine and thioridazine both increase sedation. Use Caution/Monitor.
  
  cyclizine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  cyclizine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of cyclizine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• cyclobenzaprine

  cyclobenzaprine and thioridazine both increase sedation. Use Caution/Monitor.
  
  cyclobenzaprine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  cyclobenzaprine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of cyclobenzaprine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• cyproheptadine

  cyproheptadine and thioridazine both increase sedation. Use Caution/Monitor.

• dantrolene

  dantrolene and thioridazine both increase sedation. Use Caution/Monitor.

• daridorexant

  thioridazine and daridorexant both increase sedation. Modify Therapy/Monitor Closely. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.

• darifenacin

  darifenacin decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  darifenacin decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of darifenacin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• dasatinib

  thioridazine and dasatinib both increase QTc interval. Modify Therapy/Monitor Closely.

• desflurane

  desflurane and thioridazine both increase sedation. Use Caution/Monitor.

• desipramine

  thioridazine and desipramine both increase sedation. Use Caution/Monitor.

• desvenlafaxine

  desvenlafaxine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Desvenlafaxine inhibits CYP2D6; with higher desvenlafaxine doses (ie, 400 mg) decrease the CYP2D6 substrate dose by up to 50%; no dosage adjustment needed with desvenlafaxine doses <100 mg

• deutetrabenazine

  thioridazine and deutetrabenazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Modify Therapy/Monitor Closely. The risk for parkinsonism, neuroleptic malignant syndrome, and akathisia may be increased by concomitant use of deutetrabenazine and dopamine antagonists or antipsychotics.
  
  thioridazine and deutetrabenazine both increase QTc interval. Use Caution/Monitor. At the maximum recommended dose, deutetrabenazine does not prolong QT interval to a clinically relevant extent. Certain circumstances may increase risk of torsade de pointes and/or sudden death in association with drugs that prolong the QTc interval (eg, bradycardia, hypokalemia or hypomagnesemia, coadministration with other drugs that prolong QTc interval, presence of congenital QT prolongation).
  
  thioridazine will increase the level or effect of deutetrabenazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Strong CYP2D6 inhibitors increase the systemic exposure to the active dihydro-metabolites of deutetrabenazine by approximately 3-fold. Do not exceed 18 mg/dose and 36 mg/day of deutetrabenazine if coadministered with strong CYP2D6 inhibitors.

• dexchlorpheniramine

  dexchlorpheniramine and thioridazine both increase sedation. Use Caution/Monitor.

• dexfenfluramine

  thioridazine increases and dexfenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, dexfenfluramine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• dexmedetomidine

  dexmedetomidine and thioridazine both increase sedation. Use Caution/Monitor.

• dexmethylphenidate

  thioridazine increases and dexmethylphenidate decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, dexmethylphenidate. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• dextroamphetamine

  thioridazine increases and dextroamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, dextroamphetamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• dextroamphetamine transdermal

  thioridazine will increase the level or effect of dextroamphetamine transdermal by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Initiate with lower doses and monitor patients for signs and symptoms of serotonin syndrome, particularly during dextroamphetamine initiation and after a dosage increase. If serotonin syndrome occurs, discontinue dextroamphetamine transdermal and CYP2D6 inhibitor.

• dextromoramide

  dextromoramide and thioridazine both increase sedation. Use Caution/Monitor.

• diamorphine

  diamorphine and thioridazine both increase sedation. Use Caution/Monitor.

• diazepam

  diazepam and thioridazine both increase sedation. Use Caution/Monitor.

• dicyclomine

  dicyclomine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  dicyclomine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of dicyclomine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• diethylpropion

  thioridazine increases and diethylpropion decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, diethylpropion. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• difelikefalin

  difelikefalin and thioridazine both increase sedation. Use Caution/Monitor.

• difenoxin hcl

  difenoxin hcl and thioridazine both increase sedation. Use Caution/Monitor.

• dimenhydrinate

  dimenhydrinate and thioridazine both increase sedation. Use Caution/Monitor.

• diphenhydramine

  diphenhydramine and thioridazine both increase sedation. Use Caution/Monitor.
  
  diphenhydramine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  diphenhydramine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• diphenoxylate hcl

  diphenoxylate hcl and thioridazine both increase sedation. Use Caution/Monitor.

• dipipanone

  dipipanone and thioridazine both increase sedation. Use Caution/Monitor.

• dobutamine

  thioridazine increases and dobutamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, dobutamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• dolasetron

  thioridazine and dolasetron both increase QTc interval. Modify Therapy/Monitor Closely.

• donepezil transdermal

  donepezil transdermal, thioridazine. Either decreases effects of the other by pharmacodynamic antagonism. Use Caution/Monitor.

• dopamine

  thioridazine increases and dopamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, dopamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• dopexamine

  thioridazine increases and dopexamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dosulepin

  thioridazine and dosulepin both increase sedation. Use Caution/Monitor.

• doxepin

  thioridazine and doxepin both increase sedation. Use Caution/Monitor.

• doxylamine

  doxylamine and thioridazine both increase sedation. Use Caution/Monitor.

• droperidol

  droperidol and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  droperidol and thioridazine both increase sedation. Use Caution/Monitor.

• eliglustat

  eliglustat increases levels of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Monitor therapeutic drug concentrations, as indicated, or consider reducing the dosage of the concomitant drug and titrate to clinical effect.

• elvitegravir/cobicistat/emtricitabine/tenofovir DF

  elvitegravir/cobicistat/emtricitabine/tenofovir DF increases levels of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Cobicistat is a CYP2D6 inhibitor; a decrease in dose of the neuroleptic may be needed when coadministered.

• ephedrine

  thioridazine increases and ephedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, ephedrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• epinephrine

  thioridazine increases and epinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, epinephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine decreases effects of epinephrine by pharmacodynamic antagonism. Use Caution/Monitor. Block pressor response to epinephrine, which may result in severe hypotension and tachycardia.

• epinephrine racemic

  thioridazine increases and epinephrine racemic decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine decreases effects of epinephrine racemic by pharmacodynamic antagonism. Use Caution/Monitor. Block pressor response to epinephrine, which may result in severe hypotension and tachycardia.

• esketamine intranasal

  esketamine intranasal, thioridazine. Either increases toxicity of the other by sedation. Modify Therapy/Monitor Closely.

• estazolam

  estazolam and thioridazine both increase sedation. Use Caution/Monitor.

• ethanol

  thioridazine and ethanol both increase sedation. Use Caution/Monitor.

• ezogabine

  ezogabine, thioridazine. Either increases toxicity of the other by QTc interval. Use Caution/Monitor. Slight and transient QT-prolongation observed with ezogabine, particularly when dose titrated to 1200 mg/day. QT interval should be monitored when ezogabine is prescribed with agents known to increase QT interval.

• fedratinib

  fedratinib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP2D6 substrates as necessary.

• fenfluramine

  thioridazine increases and fenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, fenfluramine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• ferric maltol

  ferric maltol, thioridazine. Either increases levels of the other by unspecified interaction mechanism. Modify Therapy/Monitor Closely. Coadministration of ferric maltol with certain oral medications may decrease the bioavailability of either ferric maltol and some oral drugs. For oral drugs where reductions in bioavailability may cause clinically significant effects on its safety or efficacy, separate administration of ferric maltol from these drugs. Duration of separation may depend on the absorption of the medication concomitantly administered (eg, time to peak concentration, whether the drug is an immediate or extended release product).

• fesoterodine

  fesoterodine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  fesoterodine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of fesoterodine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• flavoxate

  flavoxate decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  flavoxate decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of flavoxate by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• flecainide

  thioridazine will increase the level or effect of flecainide by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  thioridazine and flecainide both increase QTc interval. Modify Therapy/Monitor Closely.

• fluphenazine

  fluphenazine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  fluphenazine and thioridazine both increase sedation. Use Caution/Monitor.

• flurazepam

  flurazepam and thioridazine both increase sedation. Use Caution/Monitor.

• formoterol

  thioridazine increases and formoterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• foscarnet

  thioridazine and foscarnet both increase QTc interval. Modify Therapy/Monitor Closely.

• fostemsavir

  thioridazine and fostemsavir both increase QTc interval. Use Caution/Monitor. QTc prolongation reported with higher than recommended doses of fostemsavir.

• gadobenate

  gadobenate and thioridazine both increase QTc interval. Use Caution/Monitor.

• ganaxolone

  thioridazine and ganaxolone both increase sedation. Use Caution/Monitor.

• gemtuzumab

  thioridazine and gemtuzumab both increase QTc interval. Use Caution/Monitor.

• glycopyrrolate

  thioridazine increases effects of glycopyrrolate by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• glycopyrrolate inhaled

  glycopyrrolate inhaled decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  glycopyrrolate inhaled decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of glycopyrrolate inhaled by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• glycopyrronium tosylate topical

  glycopyrronium tosylate topical, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Coadministration of glycopyrronium tosylate topical with other anticholinergic medications may result in additive anticholinergic adverse effects.

• guanfacine

  guanfacine, thioridazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

• guselkumab

  guselkumab, thioridazine. Other (see comment). Use Caution/Monitor. Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, normalizing the formation of CYP450 enzymes. Upon initiation or discontinuation of guselkumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.

• haloperidol

  thioridazine will increase the level or effect of haloperidol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  haloperidol and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  haloperidol and thioridazine both increase sedation. Use Caution/Monitor.

• henbane

  henbane decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  henbane decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of henbane by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• homatropine

  homatropine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  homatropine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of homatropine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• hydrocodone

  thioridazine will increase the level or effect of hydrocodone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Hydromorphone (<3% of the circulating parent hydrocodone) is mainly formed by CYP2D6 mediated O-demethylation of hydrocodone. Hydromorphone may contribute to the total analgesic effect of hydrocodone.

• hydromorphone

  thioridazine will increase the level or effect of hydromorphone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  hydromorphone and thioridazine both increase sedation. Use Caution/Monitor.

• hydroxyzine

  hydroxyzine and thioridazine both increase sedation. Use Caution/Monitor.

• hyoscyamine

  hyoscyamine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  hyoscyamine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• hyoscyamine spray

  thioridazine increases effects of hyoscyamine spray by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
  
  hyoscyamine spray decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  hyoscyamine spray decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.

• iloperidone

  thioridazine will increase the level or effect of iloperidone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  iloperidone and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and iloperidone both increase QTc interval. Modify Therapy/Monitor Closely.
  
  iloperidone and thioridazine both increase sedation. Use Caution/Monitor.

• imipramine

  thioridazine and imipramine both increase sedation. Use Caution/Monitor.

• incobotulinumtoxinA

  thioridazine increases effects of incobotulinumtoxinA by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• indacaterol, inhaled

  indacaterol, inhaled, thioridazine. QTc interval. Use Caution/Monitor. Drugs that are known to prolong the QTc interval may have an increased the risk of ventricular arrhythmias.

• insulin degludec

  thioridazine decreases effects of insulin degludec by Other (see comment). Use Caution/Monitor. Comment: Phenothiazines may increase blood glucose concentrations.

• insulin degludec/insulin aspart

  thioridazine decreases effects of insulin degludec/insulin aspart by Other (see comment). Use Caution/Monitor. Comment: Phenothiazines may increase blood glucose concentrations.

• insulin inhaled

  thioridazine decreases effects of insulin inhaled by Other (see comment). Use Caution/Monitor. Comment: Phenothiazines may increase blood glucose concentrations.

• ipratropium

  ipratropium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  ipratropium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of ipratropium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• isoproterenol

  thioridazine increases and isoproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, isoproterenol. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• ketamine

  ketamine and thioridazine both increase sedation. Use Caution/Monitor.

• ketotifen, ophthalmic

  thioridazine and ketotifen, ophthalmic both increase sedation. Use Caution/Monitor.

• lapatinib

  thioridazine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

• lasmiditan

  lasmiditan, thioridazine. Either increases effects of the other by sedation. Use Caution/Monitor. Coadministration of lasmiditan and other CNS depressant drugs, including alcohol have not been evaluated in clinical studies. Lasmiditan may cause sedation, as well as other cognitive and/or neuropsychiatric adverse reactions.

• lemborexant

  lemborexant will increase the level or effect of thioridazine by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.

• lenvatinib

  thioridazine and lenvatinib both increase QTc interval. Use Caution/Monitor. Lenvatinib prescribing information recommends monitoring ECG closely when coadministered with QT prolonging drugs.

• levalbuterol

  thioridazine increases and levalbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• levofloxacin

  thioridazine and levofloxacin both increase QTc interval. Modify Therapy/Monitor Closely.

• levorphanol

  levorphanol and thioridazine both increase sedation. Use Caution/Monitor.

• liraglutide

  thioridazine, liraglutide. Other (see comment). Use Caution/Monitor. Comment: Phenothiazines may increase or decrease glucose levels, monitor therapy closely when these agents are concurrently administered.

• lisdexamfetamine

  thioridazine increases and lisdexamfetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, lisdexamfetamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• lithium

  lithium, thioridazine. Other (see comment). Use Caution/Monitor. Comment: Risk of neurotoxicity. Multiple mechanisms involved.

• lofepramine

  thioridazine will increase the level or effect of lofepramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  thioridazine and lofepramine both increase sedation. Use Caution/Monitor.

• lofexidine

  thioridazine and lofexidine both increase sedation. Use Caution/Monitor.
  
  thioridazine will increase the level or effect of lofexidine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Concomitant use of lofexidine with strong CYP2D6 inhibitors may increase lofexidine plasma levels. Monitor for symptoms of orthostasis and bradycardia if coadministered with a CYP2D6 inhibitor. Consider lofexidine dose reduction.
  
  thioridazine and lofexidine both increase QTc interval. Use Caution/Monitor. ECG monitoring is recommended.

• loprazolam

  loprazolam and thioridazine both increase sedation. Use Caution/Monitor.

• lorazepam

  lorazepam and thioridazine both increase sedation. Use Caution/Monitor.

• lorcaserin

  lorcaserin will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• lormetazepam

  lormetazepam and thioridazine both increase sedation. Use Caution/Monitor.

• loxapine

  loxapine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  loxapine and thioridazine both increase sedation. Use Caution/Monitor.

• loxapine inhaled

  loxapine inhaled and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  loxapine inhaled and thioridazine both increase sedation. Use Caution/Monitor.

• lurasidone

  lurasidone, thioridazine. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity.

• maprotiline

  thioridazine and maprotiline both increase sedation. Use Caution/Monitor.

• marijuana

  thioridazine and marijuana both increase sedation. Use Caution/Monitor.

• meclizine

  meclizine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  meclizine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of meclizine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• melatonin

  thioridazine and melatonin both increase sedation. Use Caution/Monitor.

• meperidine

  meperidine and thioridazine both increase sedation. Use Caution/Monitor.

• meprobamate

  thioridazine and meprobamate both increase sedation. Use Caution/Monitor.

• metaproterenol

  thioridazine increases and metaproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• metaxalone

  metaxalone and thioridazine both increase sedation. Use Caution/Monitor.

• metformin

  thioridazine decreases effects of metformin by pharmacodynamic antagonism. Use Caution/Monitor. Patient should be closely observed for loss of blood glucose control; when drugs are withdrawn from a patient receiving metformin, patient should be observed closely for hypoglycemia.

• methadone

  thioridazine and methadone both increase QTc interval. Modify Therapy/Monitor Closely.
  
  methadone and thioridazine both increase sedation. Use Caution/Monitor.

• methamphetamine

  thioridazine will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  thioridazine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, methamphetamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• methocarbamol

  methocarbamol and thioridazine both increase sedation. Use Caution/Monitor.

• methoxsalen

  methoxsalen, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Additive photosensitizing effects.

• methscopolamine

  methscopolamine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  methscopolamine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of methscopolamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• methylenedioxymethamphetamine

  thioridazine increases and methylenedioxymethamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, methylenedioxymethamphetamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• methylphenidate

  thioridazine, methylphenidate. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• metoclopramide

  thioridazine and metoclopramide both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.

• metoprolol

  thioridazine will increase the level or effect of metoprolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• mexiletine

  thioridazine will increase the level or effect of mexiletine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• midazolam

  midazolam and thioridazine both increase sedation. Use Caution/Monitor.

• midazolam intranasal

  midazolam intranasal, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase the risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.

• midodrine

  thioridazine increases and midodrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, midodrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• mirabegron

  mirabegron will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• mirtazapine

  thioridazine and mirtazapine both increase sedation. Use Caution/Monitor.

• modafinil

  thioridazine increases and modafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• morphine

  thioridazine will increase the level or effect of morphine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  morphine and thioridazine both increase sedation. Use Caution/Monitor.

• motherwort

  thioridazine and motherwort both increase sedation. Use Caution/Monitor.

• moxonidine

  thioridazine and moxonidine both increase sedation. Use Caution/Monitor.

• nabilone

  thioridazine and nabilone both increase sedation. Use Caution/Monitor.

• nalbuphine

  nalbuphine and thioridazine both increase sedation. Use Caution/Monitor.

• nebivolol

  thioridazine will increase the level or effect of nebivolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• norepinephrine

  thioridazine increases and norepinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, norepinephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• nortriptyline

  thioridazine and nortriptyline both increase sedation. Use Caution/Monitor.

• ofloxacin

  thioridazine and ofloxacin both increase QTc interval. Modify Therapy/Monitor Closely.

• olanzapine

  olanzapine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  olanzapine and thioridazine both increase sedation. Use Caution/Monitor.

• oliceridine

  thioridazine will increase the level or effect of oliceridine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. If concomitant use is necessary, may require less frequent oliceridine dosing. Closely monitor for respiratory depression and sedation and titrate subsequent doses accordingly. If inhibitor is discontinued, consider increase oliceridine dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal.
  
  oliceridine, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation. Increased risk of hypotension if ability to maintain blood pressure has been compromised by a reduced blood volume or concurrent administration of certain CNS depressant drugs (eg, phenothiazines or general anesthetics).

• olodaterol inhaled

  thioridazine and olodaterol inhaled both increase QTc interval. Use Caution/Monitor. Drugs that prolong the QTc interval and may potentiate the effects of beta2 agonists on the cardiovascular system; increased risk of ventricular arrhythmias

• onabotulinumtoxinA

  onabotulinumtoxinA decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  onabotulinumtoxinA decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of onabotulinumtoxinA by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• opium tincture

  opium tincture and thioridazine both increase sedation. Use Caution/Monitor.

• orphenadrine

  orphenadrine and thioridazine both increase sedation. Use Caution/Monitor.

• osilodrostat

  osilodrostat and thioridazine both increase QTc interval. Use Caution/Monitor.

• osimertinib

  osimertinib and thioridazine both increase QTc interval. Use Caution/Monitor. Conduct periodic monitoring with ECGs and electrolytes in patients taking drugs known to prolong the QTc interval.

• oxaliplatin

  oxaliplatin will increase the level or effect of thioridazine by Other (see comment). Use Caution/Monitor. Monitor for ECG changes if therapy is initiated in patients with drugs known to prolong QT interval.

• oxazepam

  oxazepam and thioridazine both increase sedation. Use Caution/Monitor.

• oxybutynin

  oxybutynin decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  oxybutynin decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• oxybutynin topical

  oxybutynin topical decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  oxybutynin topical decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of oxybutynin topical by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• oxybutynin transdermal

  oxybutynin transdermal decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  oxybutynin transdermal decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of oxybutynin transdermal by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• oxycodone

  thioridazine will increase the level or effect of oxycodone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  oxycodone and thioridazine both increase sedation. Use Caution/Monitor.

• oxymorphone

  thioridazine will increase the level or effect of oxymorphone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  oxymorphone and thioridazine both increase sedation. Use Caution/Monitor.

• ozanimod

  ozanimod and thioridazine both increase QTc interval. Modify Therapy/Monitor Closely. The potential additive effects on heart rate, treatment with ozanimod should generally not be initiated in patients who are concurrently treated with QT prolonging drugs with known arrhythmogenic properties.

• paliperidone

  paliperidone and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and paliperidone both increase QTc interval. Modify Therapy/Monitor Closely.
  
  paliperidone and thioridazine both increase sedation. Use Caution/Monitor.

• pancuronium

  pancuronium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  pancuronium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of pancuronium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• panobinostat

  panobinostat will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Panobinostat can increase the levels and effects of sensitive CYP2D6 substrates or those with a narrow therapeutic index CYP2D6.

• papaveretum

  papaveretum and thioridazine both increase sedation. Use Caution/Monitor.

• papaverine

  thioridazine and papaverine both increase sedation. Use Caution/Monitor.

• pazopanib

  thioridazine and pazopanib both increase QTc interval. Use Caution/Monitor.

• peginterferon alfa 2b

  peginterferon alfa 2b, thioridazine. Other (see comment). Use Caution/Monitor. Comment: When patients are administered peginterferon alpha-2b with CYP2D6 substrates, the therapeutic effect of these drugs may be altered. Peginterferon alpha-2b may increase or decrease levels of CYP2D6 substrate.

• pentazocine

  pentazocine and thioridazine both increase sedation. Use Caution/Monitor.

• pentobarbital

  pentobarbital and thioridazine both increase sedation. Use Caution/Monitor.

• perphenazine

  perphenazine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  perphenazine and thioridazine both increase sedation. Use Caution/Monitor.

• phendimetrazine

  thioridazine increases and phendimetrazine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, phendimetrazine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• phenobarbital

  phenobarbital and thioridazine both increase sedation. Use Caution/Monitor.

• phentermine

  thioridazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• phenylephrine

  thioridazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• phenylephrine PO

  thioridazine increases and phenylephrine PO decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. .
  
  thioridazine, phenylephrine PO. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• pholcodine

  thioridazine and pholcodine both increase sedation. Use Caution/Monitor.

• pimozide

  pimozide and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  pimozide and thioridazine both increase sedation. Use Caution/Monitor.

• pirbuterol

  thioridazine increases and pirbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pitolisant

  thioridazine will increase the level or effect of pitolisant by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. If coadministered with strong CYP2D6 inhibitors, initiate pitolisant at 8.9 mg/day and increase after 7 days to maximum of 17.8 mg/day. For patients currently taking pitolisant, reduce pitolisant dose by half upon initiating strong CYP2D6 inhibitors.

• porfimer

  thioridazine, porfimer. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Enhanced photosensitivity.

• posaconazole

  thioridazine and posaconazole both increase QTc interval. Modify Therapy/Monitor Closely.

• pralidoxime

  pralidoxime decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  pralidoxime decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of pralidoxime by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• primidone

  primidone and thioridazine both increase sedation. Use Caution/Monitor.

• procarbazine

  procarbazine, thioridazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Excessive sedation.

• prochlorperazine

  prochlorperazine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  prochlorperazine and thioridazine both increase sedation. Use Caution/Monitor.

• promethazine

  promethazine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  promethazine and thioridazine both increase sedation. Use Caution/Monitor.

• propantheline

  propantheline decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  propantheline decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of propantheline by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• propofol

  propofol and thioridazine both increase sedation. Use Caution/Monitor.

• propylhexedrine

  thioridazine increases and propylhexedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, propylhexedrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• protriptyline

  thioridazine and protriptyline both increase sedation. Use Caution/Monitor.

• pseudoephedrine

  thioridazine, pseudoephedrine. Mechanism: unknown. Use Caution/Monitor. Consider avoiding use of pseudoephedrine in patients receiving phenothiazines (especially thioridazine) due to the potential risk of cardiac arrhythmia or sudden death. Monitor for evidence of ventricular arrhythmias during concomitant use.

• quazepam

  quazepam and thioridazine both increase sedation. Use Caution/Monitor.

• quetiapine

  quetiapine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  quetiapine and thioridazine both increase sedation. Use Caution/Monitor.
  
  quetiapine, thioridazine. Either increases toxicity of the other by QTc interval. Use Caution/Monitor. Avoid use with drugs that prolong QT and in patients with risk factors for prolonged QT interval. Postmarketing cases show QT prolongation with overdose in patients with concomitant illness or with drugs known to cause electrolyte imbalance or prolong QT.

• ramelteon

  thioridazine and ramelteon both increase sedation. Use Caution/Monitor.

• ranolazine

  thioridazine and ranolazine both increase QTc interval. Modify Therapy/Monitor Closely.

• rapacuronium

  rapacuronium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  rapacuronium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of rapacuronium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• rilpivirine

  rilpivirine increases toxicity of thioridazine by QTc interval. Use Caution/Monitor. Rilpivirine should be used with caution when co-administered with a drug with a known risk of Torsade de Pointes.

• rimabotulinumtoxinB

  thioridazine, rimabotulinumtoxinB. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Anticholinergics may enhance botulinum toxin effects. Closely monitor for increased neuromuscular blockade.

• risperidone

  risperidone and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and risperidone both increase QTc interval. Modify Therapy/Monitor Closely.
  
  risperidone and thioridazine both increase sedation. Use Caution/Monitor.

• rocuronium

  rocuronium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  rocuronium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of rocuronium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• romidepsin

  thioridazine and romidepsin both increase QTc interval. Modify Therapy/Monitor Closely.

• ropeginterferon alfa 2b

  ropeginterferon alfa 2b will increase the level or effect of thioridazine by Other (see comment). Use Caution/Monitor. Certain proinflammatory cytokines, including interferons, can suppress CYP450 enzymes resulting in increased exposures of some CYP substrates. Therefore, monitor patients who are receiving concomitant drugs that are CYP450 substrates with a narrow therapeutic index from toxicities to such drugs.

• salmeterol

  thioridazine increases and salmeterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• saquinavir

  saquinavir, thioridazine. Either increases toxicity of the other by QTc interval. Modify Therapy/Monitor Closely. Use alternatives if available.

• scopolamine

  scopolamine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  scopolamine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of scopolamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• scullcap

  thioridazine and scullcap both increase sedation. Use Caution/Monitor.

• secobarbital

  secobarbital and thioridazine both increase sedation. Use Caution/Monitor.

• selpercatinib

  selpercatinib increases toxicity of thioridazine by QTc interval. Use Caution/Monitor.

• serdexmethylphenidate/dexmethylphenidate

  thioridazine, serdexmethylphenidate/dexmethylphenidate. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• sevoflurane

  sevoflurane and thioridazine both increase sedation. Use Caution/Monitor.

• shepherd's purse

  thioridazine and shepherd's purse both increase sedation. Use Caution/Monitor.

• smoking

  smoking decreases levels of thioridazine by increasing metabolism. Use Caution/Monitor. Interaction mainly seen w/chlorpromazine & thioridazine, but may occur w/other phenothiazines.

• sodium sulfate/?magnesium sulfate/potassium chloride

  sodium sulfate/?magnesium sulfate/potassium chloride increases toxicity of thioridazine by QTc interval. Use Caution/Monitor. Consider predose and post-colonoscopy ECGs in patients at increased risk of serious cardiac arrhythmias. .

• sodium sulfate/potassium sulfate/magnesium sulfate

  sodium sulfate/potassium sulfate/magnesium sulfate increases toxicity of thioridazine by QTc interval. Use Caution/Monitor. Consider predose and post-colonoscopy ECGs in patients at increased risk of serious cardiac arrhythmias. .

• solifenacin

  solifenacin decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  solifenacin decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of solifenacin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• stiripentol

  stiripentol, thioridazine. Either decreases toxicity of the other by sedation. Use Caution/Monitor. Concomitant use stiripentol with other CNS depressants, including alcohol, may increase the risk of sedation and somnolence.

• sufentanil

  sufentanil and thioridazine both increase sedation. Use Caution/Monitor.

• sulfamethoxazole

  thioridazine and sulfamethoxazole both increase QTc interval. Modify Therapy/Monitor Closely.

• tamsulosin

  thioridazine increases levels of tamsulosin by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• tapentadol

  tapentadol and thioridazine both increase sedation. Use Caution/Monitor.

• teduglutide

  teduglutide increases levels of thioridazine by Other (see comment). Use Caution/Monitor. Comment: Teduglutide may increase absorption of concomitant PO medications; caution with with drugs requiring titration or those with a narrow therapeutic index; dose adjustment may be necessary.

• telavancin

  thioridazine and telavancin both increase QTc interval. Modify Therapy/Monitor Closely.

• temazepam

  temazepam and thioridazine both increase sedation. Use Caution/Monitor.

• terbinafine

  terbinafine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Assess need to reduce dose of CYP2D6-metabolized drug.

• terbutaline

  thioridazine increases and terbutaline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• tetrabenazine

  thioridazine and tetrabenazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Modify Therapy/Monitor Closely.

• thiothixene

  thioridazine and thiothixene both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and thiothixene both increase sedation. Use Caution/Monitor.

• timolol

  thioridazine will increase the level or effect of timolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• tiotropium

  tiotropium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  tiotropium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of tiotropium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• tobacco use

  tobacco use decreases levels of thioridazine by increasing metabolism. Use Caution/Monitor. Interaction mainly seen w/chlorpromazine & thioridazine, but may occur w/other phenothiazines.

• tolterodine

  tolterodine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  tolterodine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of tolterodine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• topiramate

  thioridazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• tramadol

  thioridazine decreases effects of tramadol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Decreased conversion of tramadol to active metabolite.
  
  tramadol and thioridazine both increase sedation. Use Caution/Monitor.
  
  thioridazine decreases effects of tramadol by decreasing metabolism. Use Caution/Monitor. Decreased conversion of tramadol to active metabolite.

• trazodone

  thioridazine and trazodone both increase sedation. Use Caution/Monitor.

• triazolam

  triazolam and thioridazine both increase sedation. Use Caution/Monitor.

• triclabendazole

  triclabendazole and thioridazine both increase QTc interval. Use Caution/Monitor.

• triclofos

  triclofos and thioridazine both increase sedation. Use Caution/Monitor.

• trifluoperazine

  thioridazine and trifluoperazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and trifluoperazine both increase sedation. Use Caution/Monitor.

• trihexyphenidyl

  trihexyphenidyl decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of trihexyphenidyl by pharmacodynamic synergism. Use Caution/Monitor. Potential for additive anticholinergic effects.

• trimethoprim

  thioridazine and trimethoprim both increase QTc interval. Modify Therapy/Monitor Closely.

• trimipramine

  thioridazine and trimipramine both increase sedation. Use Caution/Monitor.

• triprolidine

  triprolidine and thioridazine both increase sedation. Use Caution/Monitor.

• tropisetron

  thioridazine and tropisetron both increase QTc interval. Modify Therapy/Monitor Closely.

• trospium chloride

  trospium chloride decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  trospium chloride decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of trospium chloride by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• ustekinumab

  ustekinumab, thioridazine. Other (see comment). Use Caution/Monitor. Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, normalizing the formation of CYP450 enzymes. Upon initiation or discontinuation of ustekinumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.

• vecuronium

  vecuronium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  vecuronium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of vecuronium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• voclosporin

  voclosporin, thioridazine. Either increases effects of the other by QTc interval. Use Caution/Monitor.

• voriconazole

  thioridazine and voriconazole both increase QTc interval. Modify Therapy/Monitor Closely.

• xylometazoline

  thioridazine increases and xylometazoline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, xylometazoline. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• yohimbine

  thioridazine increases and yohimbine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  thioridazine, yohimbine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• ziconotide

  thioridazine and ziconotide both increase sedation. Use Caution/Monitor.

• ziprasidone

  thioridazine and ziprasidone both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and ziprasidone both increase sedation. Use Caution/Monitor.

• zolpidem

  thioridazine will increase the level or effect of zolpidem by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Additive effect of decreased alertness and psychomotor performance

• zotepine

  thioridazine and zotepine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and zotepine both increase sedation. Use Caution/Monitor.

Minor (70)

• amantadine

  amantadine increases toxicity of thioridazine by pharmacodynamic synergism. Minor/Significance Unknown. May increase Parkinsonian tremor.

• amitriptyline

  amitriptyline, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  amitriptyline, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• amobarbital

  thioridazine decreases levels of amobarbital by unspecified interaction mechanism. Minor/Significance Unknown.

• amoxapine

  amoxapine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  amoxapine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• aripiprazole

  thioridazine will increase the level or effect of aripiprazole by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• atropine

  thioridazine increases toxicity of atropine by unknown mechanism. Minor/Significance Unknown.

• atropine IV/IM

  thioridazine increases toxicity of atropine IV/IM by unknown mechanism. Minor/Significance Unknown.

• benazepril

  thioridazine, benazepril. Either increases effects of the other by pharmacodynamic synergism. Minor/Significance Unknown. May increase risk of hypotension.

• brimonidine

  brimonidine increases effects of thioridazine by pharmacodynamic synergism. Minor/Significance Unknown. Increased CNS depression.

• bupropion

  thioridazine increases toxicity of bupropion by unspecified interaction mechanism. Minor/Significance Unknown. May lower seizure threshold; keep bupropion dose as low as possible.

• butabarbital

  thioridazine decreases levels of butabarbital by unspecified interaction mechanism. Minor/Significance Unknown.

• butalbital

  thioridazine decreases levels of butalbital by unspecified interaction mechanism. Minor/Significance Unknown.

• captopril

  thioridazine increases effects of captopril by unspecified interaction mechanism. Minor/Significance Unknown.

• chasteberry

  chasteberry decreases effects of thioridazine by pharmacodynamic antagonism. Minor/Significance Unknown. (Theoretical interaction).

• chloroquine

  chloroquine increases levels of thioridazine by decreasing metabolism. Minor/Significance Unknown.

• chlorpromazine

  thioridazine will increase the level or effect of chlorpromazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• clomipramine

  clomipramine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  clomipramine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• codeine

  thioridazine decreases effects of codeine by decreasing metabolism. Minor/Significance Unknown. Decreased conversion of codeine to active metabolite morphine.

• desipramine

  desipramine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  desipramine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• dexfenfluramine

  thioridazine will increase the level or effect of dexfenfluramine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• dextroamphetamine

  thioridazine will increase the level or effect of dextroamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• dextromethorphan

  thioridazine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• donepezil

  thioridazine will increase the level or effect of donepezil by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• doxepin

  doxepin, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  doxepin, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• enalapril

  thioridazine increases effects of enalapril by unspecified interaction mechanism. Minor/Significance Unknown.

• encainide

  thioridazine will increase the level or effect of encainide by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• ethanol

  ethanol, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive CNS depression.

• eucalyptus

  thioridazine and eucalyptus both increase sedation. Minor/Significance Unknown.

• fesoterodine

  thioridazine will increase the level or effect of fesoterodine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• fluphenazine

  thioridazine will increase the level or effect of fluphenazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• fosinopril

  thioridazine increases effects of fosinopril by unspecified interaction mechanism. Minor/Significance Unknown.

• galantamine

  thioridazine will increase the level or effect of galantamine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• glycopyrrolate

  thioridazine increases toxicity of glycopyrrolate by unknown mechanism. Minor/Significance Unknown.

• glycopyrrolate inhaled

  thioridazine increases toxicity of glycopyrrolate inhaled by unknown mechanism. Minor/Significance Unknown.

• imidapril

  thioridazine increases effects of imidapril by unspecified interaction mechanism. Minor/Significance Unknown.

• imipramine

  imipramine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  imipramine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• lisinopril

  thioridazine increases effects of lisinopril by unspecified interaction mechanism. Minor/Significance Unknown.

• lofepramine

  lofepramine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  lofepramine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• loratadine

  thioridazine will increase the level or effect of loratadine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• maprotiline

  maprotiline, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  maprotiline, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• metyrapone

  thioridazine decreases effects of metyrapone by unspecified interaction mechanism. Minor/Significance Unknown.

• metyrosine

  metyrosine increases toxicity of thioridazine by pharmacodynamic synergism. Minor/Significance Unknown. Increased extrapyramidal symptoms.

• moexipril

  thioridazine increases effects of moexipril by unspecified interaction mechanism. Minor/Significance Unknown.

• nortriptyline

  nortriptyline, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  nortriptyline, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• oxybutynin

  oxybutynin increases toxicity of thioridazine by unspecified interaction mechanism. Minor/Significance Unknown.

• oxybutynin topical

  oxybutynin topical increases toxicity of thioridazine by unspecified interaction mechanism. Minor/Significance Unknown.

• oxybutynin transdermal

  oxybutynin transdermal increases toxicity of thioridazine by unspecified interaction mechanism. Minor/Significance Unknown.

• oxycodone

  thioridazine decreases effects of oxycodone by decreasing metabolism. Minor/Significance Unknown. Decreased conversion of oxycodone to active metabolite morphine.

• pentobarbital

  thioridazine decreases levels of pentobarbital by unspecified interaction mechanism. Minor/Significance Unknown.

• perhexiline

  thioridazine will increase the level or effect of perhexiline by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• perindopril

  thioridazine increases effects of perindopril by unspecified interaction mechanism. Minor/Significance Unknown.

• perphenazine

  thioridazine will increase the level or effect of perphenazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• phenobarbital

  thioridazine decreases levels of phenobarbital by unspecified interaction mechanism. Minor/Significance Unknown.

• primidone

  thioridazine decreases levels of primidone by unspecified interaction mechanism. Minor/Significance Unknown.

• prochlorperazine

  thioridazine will increase the level or effect of prochlorperazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• promazine

  thioridazine will increase the level or effect of promazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• promethazine

  thioridazine will increase the level or effect of promethazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• protriptyline

  protriptyline, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  protriptyline, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• pyrimethamine

  pyrimethamine increases levels of thioridazine by decreasing metabolism. Minor/Significance Unknown.

• quinapril

  thioridazine increases effects of quinapril by unspecified interaction mechanism. Minor/Significance Unknown.

• ramipril

  thioridazine increases effects of ramipril by unspecified interaction mechanism. Minor/Significance Unknown.

• risperidone

  thioridazine will increase the level or effect of risperidone by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• sage

  thioridazine and sage both increase sedation. Minor/Significance Unknown.

• secobarbital

  thioridazine decreases levels of secobarbital by unspecified interaction mechanism. Minor/Significance Unknown.

• tolterodine

  thioridazine will increase the level or effect of tolterodine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• trandolapril

  thioridazine increases effects of trandolapril by unspecified interaction mechanism. Minor/Significance Unknown.

• trazodone

  trazodone, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive hypotensive effects.
  
  trazodone, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.

• trifluoperazine

  thioridazine will increase the level or effect of trifluoperazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• trimipramine

  trimipramine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  trimipramine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• tropisetron

  thioridazine will increase the level or effect of tropisetron by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• abiraterone

  Monitor Closely (1)abiraterone increases levels of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Avoid coadministration of abiraterone with substrates of CYP2D6. If alternative therapy cannot be used, exercise caution and consider a dose reduction of the CYP2D6 substrate.

• abobotulinumtoxinA

  Monitor Closely (1)abobotulinumtoxinA increases effects of thioridazine by pharmacodynamic synergism. Use Caution/Monitor. Use of anticholinergic drugs after administration of botulinum toxin-containing products may potentiate systemic anticholinergic effects.

• aclidinium

  Monitor Closely (2)aclidinium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of aclidinium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• albiglutide

  Monitor Closely (1)thioridazine, albiglutide. Other (see comment). Use Caution/Monitor. Comment: Phenothiazines may increase or decrease glucose levels, monitor therapy closely when these agents are concurrently administered.

• albuterol

  Contraindicated (1)albuterol and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)thioridazine increases and albuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• alfentanil

  Monitor Closely (1)alfentanil and thioridazine both increase sedation. Use Caution/Monitor.

• alfuzosin

  Contraindicated (1)alfuzosin and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)thioridazine and alfuzosin both increase QTc interval. Use Caution/Monitor.

• alprazolam

  Monitor Closely (1)alprazolam and thioridazine both increase sedation. Use Caution/Monitor.

• amantadine

  Minor (1)amantadine increases toxicity of thioridazine by pharmacodynamic synergism. Minor/Significance Unknown. May increase Parkinsonian tremor.

• amifampridine

  Monitor Closely (1)thioridazine increases toxicity of amifampridine by Other (see comment). Modify Therapy/Monitor Closely. Comment: Amifampridine can cause seizures. Coadministration with drugs that lower seizure threshold may increase this risk.

• aminolevulinic acid oral

  Serious - Use Alternative (1)aminolevulinic acid oral, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Avoid administering other phototoxic drugs with aminolevulinic acid oral for 24 hr during perioperative period.

• aminolevulinic acid topical

  Serious - Use Alternative (1)thioridazine increases toxicity of aminolevulinic acid topical by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration of photosensitizing drugs may enhance the phototoxic reaction to photodynamic therapy with aminolevulinic acid.

• amiodarone

  Contraindicated (1)thioridazine and amiodarone both increase QTc interval. Contraindicated.Serious - Use Alternative (2)amiodarone increases levels of thioridazine by decreasing metabolism. Contraindicated.
  
  amiodarone will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• amisulpride

  Contraindicated (2)amisulpride and thioridazine both increase QTc interval. Contraindicated.
  
  amisulpride, thioridazine. Either increases toxicity of the other by Other (see comment). Contraindicated. Comment: Increases risk of neuroleptic malignant syndrome.

• amitriptyline

  Monitor Closely (1)thioridazine and amitriptyline both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and amitriptyline both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)amitriptyline, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  amitriptyline, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• amobarbital

  Monitor Closely (1)amobarbital and thioridazine both increase sedation. Use Caution/Monitor.Minor (1)thioridazine decreases levels of amobarbital by unspecified interaction mechanism. Minor/Significance Unknown.

• amoxapine

  Monitor Closely (2)thioridazine and amoxapine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and amoxapine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and amoxapine both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)amoxapine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  amoxapine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• anagrelide

  Contraindicated (1)anagrelide and thioridazine both increase QTc interval. Contraindicated.

• anticholinergic/sedative combos

  Monitor Closely (3)anticholinergic/sedative combos decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  anticholinergic/sedative combos decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of anticholinergic/sedative combos by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• apomorphine

  Contraindicated (1)apomorphine and thioridazine both increase QTc interval. Contraindicated.Serious - Use Alternative (1)thioridazine decreases effects of apomorphine by pharmacodynamic antagonism. Avoid or Use Alternate Drug.

• arformoterol

  Contraindicated (1)arformoterol and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)thioridazine increases and arformoterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• aripiprazole

  Contraindicated (1)aripiprazole and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (2)aripiprazole and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  aripiprazole and thioridazine both increase sedation. Use Caution/Monitor.Minor (1)thioridazine will increase the level or effect of aripiprazole by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• armodafinil

  Monitor Closely (1)thioridazine increases and armodafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• arsenic trioxide

  Serious - Use Alternative (1)thioridazine and arsenic trioxide both increase QTc interval. Avoid or Use Alternate Drug.

• artemether

  Contraindicated (1)artemether and thioridazine both increase QTc interval. Contraindicated.

• artemether/lumefantrine

  Serious - Use Alternative (2)artemether/lumefantrine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  thioridazine and artemether/lumefantrine both increase QTc interval. Avoid or Use Alternate Drug.

• asenapine

  Contraindicated (1)asenapine and thioridazine both increase QTc interval. Contraindicated.Serious - Use Alternative (1)asenapine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• asenapine transdermal

  Contraindicated (1)asenapine transdermal and thioridazine both increase QTc interval. Contraindicated.

• atomoxetine

  Contraindicated (1)atomoxetine and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)thioridazine will increase the level or effect of atomoxetine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• atracurium

  Monitor Closely (3)atracurium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  atracurium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of atracurium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• atropine

  Monitor Closely (3)atropine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  atropine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of atropine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)thioridazine increases toxicity of atropine by unknown mechanism. Minor/Significance Unknown.

• atropine IV/IM

  Monitor Closely (3)thioridazine increases effects of atropine IV/IM by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
  
  atropine IV/IM decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  atropine IV/IM decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.Minor (1)thioridazine increases toxicity of atropine IV/IM by unknown mechanism. Minor/Significance Unknown.

• azelastine

  Monitor Closely (1)azelastine and thioridazine both increase sedation. Use Caution/Monitor.

• azithromycin

  Monitor Closely (1)thioridazine and azithromycin both increase QTc interval. Use Caution/Monitor.

• baclofen

  Monitor Closely (1)baclofen and thioridazine both increase sedation. Use Caution/Monitor.

• bedaquiline

  Monitor Closely (1)thioridazine and bedaquiline both increase QTc interval. Modify Therapy/Monitor Closely. ECG should be monitored closely

• belladonna alkaloids

  Monitor Closely (3)belladonna alkaloids decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  belladonna alkaloids decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of belladonna alkaloids by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• belladonna and opium

  Monitor Closely (4)belladonna and opium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  belladonna and opium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of belladonna and opium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
  
  belladonna and opium and thioridazine both increase sedation. Use Caution/Monitor.

• benazepril

  Minor (1)thioridazine, benazepril. Either increases effects of the other by pharmacodynamic synergism. Minor/Significance Unknown. May increase risk of hypotension.

• benperidol

  Monitor Closely (2)benperidol and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  benperidol and thioridazine both increase sedation. Use Caution/Monitor.

• benzhydrocodone/acetaminophen

  Monitor Closely (1)thioridazine will increase the level or effect of benzhydrocodone/acetaminophen by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Hydromorphone (<3% of the circulating parent hydrocodone [benzhydrocodone is prodrug of hydrocodone]) is mainly formed by CYP2D6 mediated O-demethylation of hydrocodone. Hydromorphone may contribute to the total analgesic effect of hydrocodone.Serious - Use Alternative (1)benzhydrocodone/acetaminophen, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation. Increased risk of hypotension if ability to maintain blood pressure has been compromised by a reduced blood volume or concurrent administration of certain CNS depressant drugs (eg, phenothiazines or general anesthetics).

• benzphetamine

  Monitor Closely (2)thioridazine, benzphetamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and benzphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• benztropine

  Monitor Closely (1)thioridazine increases effects of benztropine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic adverse effects may be seen with concurrent use. .

• berotralstat

  Monitor Closely (1)berotralstat will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Monitor or titrate substrate dose when berotralstat is coadministered with narrow therapeutic index drugs that are CYP2D6 substrates.

• bremelanotide

  Serious - Use Alternative (1)bremelanotide will decrease the level or effect of thioridazine by Other (see comment). Avoid or Use Alternate Drug. Bremelanotide may slow gastric emptying and potentially reduces the rate and extent of absorption of concomitantly administered oral medications. Avoid use when taking any oral drug that is dependent on threshold concentrations for efficacy. Interactions listed are representative examples and do not include all possible clinical examples.

• brexanolone

  Monitor Closely (1)brexanolone, thioridazine. Either increases toxicity of the other by sedation. Use Caution/Monitor.

• brexpiprazole

  Monitor Closely (1)thioridazine will increase the level or effect of brexpiprazole by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Administer a quarter of brexpiprazole dose if coadministered with a moderate CYP2D6 inhibitor PLUS a strong/moderate CYP3A4 inhibitor.

• brimonidine

  Minor (1)brimonidine increases effects of thioridazine by pharmacodynamic synergism. Minor/Significance Unknown. Increased CNS depression.

• bromocriptine

  Serious - Use Alternative (1)thioridazine decreases effects of bromocriptine by pharmacodynamic antagonism. Avoid or Use Alternate Drug.

• brompheniramine

  Monitor Closely (1)brompheniramine and thioridazine both increase sedation. Use Caution/Monitor.

• buprenorphine

  Contraindicated (1)buprenorphine and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)buprenorphine and thioridazine both increase sedation. Use Caution/Monitor.

• buprenorphine buccal

  Monitor Closely (1)buprenorphine buccal and thioridazine both increase sedation. Use Caution/Monitor.

• buprenorphine, long-acting injection

  Monitor Closely (1)thioridazine increases toxicity of buprenorphine, long-acting injection by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration of buprenorphine and benzodiazepines or other CNS depressants increases risk of adverse reactions including overdose, respiratory depression, and death. Cessation of benzodiazepines or other CNS depressants is preferred in most cases. In some cases, monitoring at a higher level of care for tapering CNS depressants may be appropriate. In others, gradually tapering a patient off of a prescribed benzodiazepine or other CNS depressant or decreasing to the lowest effective dose may be appropriate.

• bupropion

  Serious - Use Alternative (1)bupropion will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.Minor (1)thioridazine increases toxicity of bupropion by unspecified interaction mechanism. Minor/Significance Unknown. May lower seizure threshold; keep bupropion dose as low as possible.

• butabarbital

  Monitor Closely (1)butabarbital and thioridazine both increase sedation. Use Caution/Monitor.Minor (1)thioridazine decreases levels of butabarbital by unspecified interaction mechanism. Minor/Significance Unknown.

• butalbital

  Monitor Closely (1)butalbital and thioridazine both increase sedation. Use Caution/Monitor.Minor (1)thioridazine decreases levels of butalbital by unspecified interaction mechanism. Minor/Significance Unknown.

• butorphanol

  Monitor Closely (1)butorphanol and thioridazine both increase sedation. Use Caution/Monitor.

• cabergoline

  Serious - Use Alternative (1)thioridazine decreases effects of cabergoline by pharmacodynamic antagonism. Contraindicated.

• caffeine

  Monitor Closely (1)thioridazine increases and caffeine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• calcium/magnesium/potassium/sodium oxybates

  Serious - Use Alternative (1)thioridazine, calcium/magnesium/potassium/sodium oxybates. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• captopril

  Minor (1)thioridazine increases effects of captopril by unspecified interaction mechanism. Minor/Significance Unknown.

• carbinoxamine

  Monitor Closely (1)carbinoxamine and thioridazine both increase sedation. Use Caution/Monitor.

• carisoprodol

  Monitor Closely (1)carisoprodol and thioridazine both increase sedation. Use Caution/Monitor.

• carvedilol

  Monitor Closely (1)thioridazine will increase the level or effect of carvedilol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)carvedilol, thioridazine. Either increases levels of the other by decreasing metabolism. Contraindicated. Not all beta blockers share this interaction (e.g., atenolol, nadolol, sotalol do not interact).

• celecoxib

  Serious - Use Alternative (1)celecoxib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• cenobamate

  Monitor Closely (1)cenobamate, thioridazine. Either increases effects of the other by sedation. Use Caution/Monitor.

• ceritinib

  Contraindicated (1)ceritinib and thioridazine both increase QTc interval. Contraindicated.

• chasteberry

  Minor (1)chasteberry decreases effects of thioridazine by pharmacodynamic antagonism. Minor/Significance Unknown. (Theoretical interaction).

• chloral hydrate

  Monitor Closely (1)chloral hydrate and thioridazine both increase sedation. Use Caution/Monitor.

• chlordiazepoxide

  Monitor Closely (1)chlordiazepoxide and thioridazine both increase sedation. Use Caution/Monitor.

• chloroquine

  Monitor Closely (1)chloroquine increases toxicity of thioridazine by QTc interval. Use Caution/Monitor.Serious - Use Alternative (1)chloroquine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.Minor (1)chloroquine increases levels of thioridazine by decreasing metabolism. Minor/Significance Unknown.

• chlorpheniramine

  Monitor Closely (1)chlorpheniramine and thioridazine both increase sedation. Use Caution/Monitor.

• chlorpromazine

  Monitor Closely (2)chlorpromazine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  chlorpromazine and thioridazine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)chlorpromazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.Minor (1)thioridazine will increase the level or effect of chlorpromazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• chlorzoxazone

  Monitor Closely (1)chlorzoxazone and thioridazine both increase sedation. Use Caution/Monitor.

• cigarette smoking

  Monitor Closely (1)cigarette smoking decreases levels of thioridazine by increasing metabolism. Use Caution/Monitor. Interaction mainly seen w/chlorpromazine & thioridazine, but may occur w/other phenothiazines.

• cimetidine

  Serious - Use Alternative (1)cimetidine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• cinnarizine

  Monitor Closely (1)cinnarizine and thioridazine both increase sedation. Use Caution/Monitor.

• ciprofloxacin

  Monitor Closely (1)ciprofloxacin and thioridazine both increase QTc interval. Use Caution/Monitor. Ciprofloxacin elicits minimal effects on QT interval. Caution if used in combination with other drugs known to affect QT interval or in patients with other risk factors.

• cisatracurium

  Monitor Closely (3)cisatracurium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  cisatracurium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of cisatracurium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• citalopram

  Serious - Use Alternative (1)thioridazine and citalopram both increase QTc interval. Avoid or Use Alternate Drug. Thioridazine should be avoided in combination with drugs that are known to prolong QTc interval.

• clarithromycin

  Serious - Use Alternative (1)thioridazine and clarithromycin both increase QTc interval. Avoid or Use Alternate Drug.

• clemastine

  Monitor Closely (1)clemastine and thioridazine both increase sedation. Use Caution/Monitor.

• clobazam

  Monitor Closely (2)clobazam will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Lower doses of drugs metabolized by CYP2D6 may be required when used concomitantly.
  
  thioridazine, clobazam. Other (see comment). Use Caution/Monitor. Comment: Concomitant administration can increase the potential for CNS effects (e.g., increased sedation or respiratory depression).

• clomipramine

  Contraindicated (1)thioridazine will increase the level or effect of clomipramine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.Monitor Closely (1)thioridazine and clomipramine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and clomipramine both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)clomipramine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  clomipramine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• clonazepam

  Monitor Closely (1)clonazepam and thioridazine both increase sedation. Use Caution/Monitor.

• clonidine

  Monitor Closely (1)clonidine, thioridazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

• clorazepate

  Monitor Closely (1)clorazepate and thioridazine both increase sedation. Use Caution/Monitor.

• clozapine

  Contraindicated (1)clozapine and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (2)clozapine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  clozapine and thioridazine both increase sedation. Use Caution/Monitor.

• cobicistat

  Monitor Closely (1)cobicistat will increase the level or effect of thioridazine by Other (see comment). Modify Therapy/Monitor Closely. A decrease in the dose of antipsychotics that are metabolized by CYP3A or CYP2D6 may be needed upon coadministration.

• codeine

  Monitor Closely (2)thioridazine decreases effects of codeine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Prevents conversion of codeine to its active metabolite morphine.
  
  codeine and thioridazine both increase sedation. Use Caution/Monitor.Minor (1)thioridazine decreases effects of codeine by decreasing metabolism. Minor/Significance Unknown. Decreased conversion of codeine to active metabolite morphine.

• crizotinib

  Contraindicated (1)crizotinib and thioridazine both increase QTc interval. Contraindicated. Thioridazine is contraindicated with drugs that may prolong the QT interval.

• cyclizine

  Monitor Closely (4)cyclizine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  cyclizine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of cyclizine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
  
  cyclizine and thioridazine both increase sedation. Use Caution/Monitor.

• cyclobenzaprine

  Monitor Closely (4)cyclobenzaprine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  cyclobenzaprine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of cyclobenzaprine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
  
  cyclobenzaprine and thioridazine both increase sedation. Use Caution/Monitor.

• cyproheptadine

  Monitor Closely (1)cyproheptadine and thioridazine both increase sedation. Use Caution/Monitor.

• dacomitinib

  Serious - Use Alternative (1)dacomitinib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Avoid use with CYP2D6 substrates where minimal increases in concentration of the CYP2D6 substrate may lead to serious or life-threatening toxicities.

• dantrolene

  Monitor Closely (1)dantrolene and thioridazine both increase sedation. Use Caution/Monitor.

• daridorexant

  Monitor Closely (1)thioridazine and daridorexant both increase sedation. Modify Therapy/Monitor Closely. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.

• darifenacin

  Monitor Closely (3)darifenacin decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  darifenacin decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of darifenacin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Serious - Use Alternative (1)darifenacin will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• dasatinib

  Monitor Closely (1)thioridazine and dasatinib both increase QTc interval. Modify Therapy/Monitor Closely.

• degarelix

  Contraindicated (1)degarelix and thioridazine both increase QTc interval. Contraindicated.

• desflurane

  Monitor Closely (1)desflurane and thioridazine both increase sedation. Use Caution/Monitor.

• desipramine

  Contraindicated (1)thioridazine will increase the level or effect of desipramine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.Monitor Closely (1)thioridazine and desipramine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and desipramine both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)desipramine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  desipramine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• desvenlafaxine

  Monitor Closely (1)desvenlafaxine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Desvenlafaxine inhibits CYP2D6; with higher desvenlafaxine doses (ie, 400 mg) decrease the CYP2D6 substrate dose by up to 50%; no dosage adjustment needed with desvenlafaxine doses <100 mg

• deutetrabenazine

  Monitor Closely (3)thioridazine and deutetrabenazine both increase QTc interval. Use Caution/Monitor. At the maximum recommended dose, deutetrabenazine does not prolong QT interval to a clinically relevant extent. Certain circumstances may increase risk of torsade de pointes and/or sudden death in association with drugs that prolong the QTc interval (eg, bradycardia, hypokalemia or hypomagnesemia, coadministration with other drugs that prolong QTc interval, presence of congenital QT prolongation).
  
  thioridazine and deutetrabenazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Modify Therapy/Monitor Closely. The risk for parkinsonism, neuroleptic malignant syndrome, and akathisia may be increased by concomitant use of deutetrabenazine and dopamine antagonists or antipsychotics.
  
  thioridazine will increase the level or effect of deutetrabenazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Strong CYP2D6 inhibitors increase the systemic exposure to the active dihydro-metabolites of deutetrabenazine by approximately 3-fold. Do not exceed 18 mg/dose and 36 mg/day of deutetrabenazine if coadministered with strong CYP2D6 inhibitors.

• dexchlorpheniramine

  Monitor Closely (1)dexchlorpheniramine and thioridazine both increase sedation. Use Caution/Monitor.

• dexfenfluramine

  Monitor Closely (2)thioridazine, dexfenfluramine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and dexfenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)thioridazine will increase the level or effect of dexfenfluramine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• dexmedetomidine

  Monitor Closely (1)dexmedetomidine and thioridazine both increase sedation. Use Caution/Monitor.

• dexmethylphenidate

  Monitor Closely (2)thioridazine, dexmethylphenidate. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and dexmethylphenidate decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dextroamphetamine

  Monitor Closely (2)thioridazine, dextroamphetamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and dextroamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)thioridazine will increase the level or effect of dextroamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• dextroamphetamine transdermal

  Monitor Closely (1)thioridazine will increase the level or effect of dextroamphetamine transdermal by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Initiate with lower doses and monitor patients for signs and symptoms of serotonin syndrome, particularly during dextroamphetamine initiation and after a dosage increase. If serotonin syndrome occurs, discontinue dextroamphetamine transdermal and CYP2D6 inhibitor.

• dextromethorphan

  Minor (1)thioridazine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• dextromoramide

  Monitor Closely (1)dextromoramide and thioridazine both increase sedation. Use Caution/Monitor.

• diamorphine

  Monitor Closely (1)diamorphine and thioridazine both increase sedation. Use Caution/Monitor.

• diazepam

  Monitor Closely (1)diazepam and thioridazine both increase sedation. Use Caution/Monitor.

• dicyclomine

  Monitor Closely (3)dicyclomine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  dicyclomine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of dicyclomine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• diethylpropion

  Monitor Closely (2)thioridazine, diethylpropion. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and diethylpropion decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• difelikefalin

  Monitor Closely (1)difelikefalin and thioridazine both increase sedation. Use Caution/Monitor.

• difenoxin hcl

  Monitor Closely (1)difenoxin hcl and thioridazine both increase sedation. Use Caution/Monitor.

• dimenhydrinate

  Monitor Closely (1)dimenhydrinate and thioridazine both increase sedation. Use Caution/Monitor.

• diphenhydramine

  Monitor Closely (4)diphenhydramine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  diphenhydramine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of diphenhydramine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
  
  diphenhydramine and thioridazine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)diphenhydramine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• diphenoxylate hcl

  Monitor Closely (1)diphenoxylate hcl and thioridazine both increase sedation. Use Caution/Monitor.

• dipipanone

  Monitor Closely (1)dipipanone and thioridazine both increase sedation. Use Caution/Monitor.

• disopyramide

  Contraindicated (1)thioridazine and disopyramide both increase QTc interval. Contraindicated.

• dobutamine

  Monitor Closely (2)thioridazine, dobutamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and dobutamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dofetilide

  Contraindicated (1)dofetilide increases toxicity of thioridazine by QTc interval. Contraindicated.Serious - Use Alternative (1)thioridazine and dofetilide both increase QTc interval. Avoid or Use Alternate Drug.

• dolasetron

  Monitor Closely (1)thioridazine and dolasetron both increase QTc interval. Modify Therapy/Monitor Closely.

• donepezil

  Contraindicated (1)donepezil and thioridazine both increase QTc interval. Contraindicated.Minor (1)thioridazine will increase the level or effect of donepezil by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• donepezil transdermal

  Monitor Closely (1)donepezil transdermal, thioridazine. Either decreases effects of the other by pharmacodynamic antagonism. Use Caution/Monitor.

• dopamine

  Monitor Closely (2)thioridazine, dopamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and dopamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine decreases effects of dopamine by pharmacodynamic antagonism. Contraindicated.

• dopexamine

  Monitor Closely (1)thioridazine increases and dopexamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dosulepin

  Monitor Closely (1)thioridazine and dosulepin both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and dosulepin both increase QTc interval. Avoid or Use Alternate Drug.

• doxepin

  Contraindicated (1)thioridazine will increase the level or effect of doxepin by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.Monitor Closely (1)thioridazine and doxepin both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and doxepin both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)doxepin, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  doxepin, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• doxylamine

  Monitor Closely (1)doxylamine and thioridazine both increase sedation. Use Caution/Monitor.

• dronedarone

  Serious - Use Alternative (2)thioridazine and dronedarone both increase QTc interval. Avoid or Use Alternate Drug.
  
  dronedarone will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• droperidol

  Monitor Closely (2)droperidol and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  droperidol and thioridazine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and droperidol both increase QTc interval. Avoid or Use Alternate Drug.

• duloxetine

  Serious - Use Alternative (2)duloxetine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.
  
  thioridazine will increase the level or effect of duloxetine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• eliglustat

  Contraindicated (2)thioridazine increases levels of eliglustat by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated. If coadministered with strong or moderate CYP2D6 inhibitors, reduce eliglustat dose from 84 mg BID to 84 mg once daily in extensive and intermediate metabolizers; eliglustat is contraindiated if strong or moderate CYP2D6 inhibitors are given concomitantly with strong or moderate CYP3A inhibitors.
  
  eliglustat and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)eliglustat increases levels of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Monitor therapeutic drug concentrations, as indicated, or consider reducing the dosage of the concomitant drug and titrate to clinical effect.

• elvitegravir/cobicistat/emtricitabine/tenofovir DF

  Monitor Closely (1)elvitegravir/cobicistat/emtricitabine/tenofovir DF increases levels of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Cobicistat is a CYP2D6 inhibitor; a decrease in dose of the neuroleptic may be needed when coadministered.

• enalapril

  Minor (1)thioridazine increases effects of enalapril by unspecified interaction mechanism. Minor/Significance Unknown.

• encainide

  Minor (1)thioridazine will increase the level or effect of encainide by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• encorafenib

  Serious - Use Alternative (1)encorafenib and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Encorafenib is associated with dose-dependent QTc interval prolongation. Avoid with drugs known to prolong QT interval.

• entrectinib

  Serious - Use Alternative (1)thioridazine and entrectinib both increase QTc interval. Avoid or Use Alternate Drug.

• ephedrine

  Monitor Closely (2)thioridazine, ephedrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and ephedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• epinephrine

  Monitor Closely (3)thioridazine, epinephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine decreases effects of epinephrine by pharmacodynamic antagonism. Use Caution/Monitor. Block pressor response to epinephrine, which may result in severe hypotension and tachycardia.
  
  thioridazine increases and epinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)epinephrine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• epinephrine racemic

  Monitor Closely (2)thioridazine decreases effects of epinephrine racemic by pharmacodynamic antagonism. Use Caution/Monitor. Block pressor response to epinephrine, which may result in severe hypotension and tachycardia.
  
  thioridazine increases and epinephrine racemic decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)epinephrine racemic and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• eribulin

  Serious - Use Alternative (1)eribulin and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Potential for enhanced QTc-prolonging effects; if concurrent use is necessary then ECG monitoring is recommended.

• erythromycin base

  Serious - Use Alternative (1)thioridazine and erythromycin base both increase QTc interval. Avoid or Use Alternate Drug.

• erythromycin ethylsuccinate

  Serious - Use Alternative (1)thioridazine and erythromycin ethylsuccinate both increase QTc interval. Avoid or Use Alternate Drug.

• erythromycin lactobionate

  Serious - Use Alternative (1)thioridazine and erythromycin lactobionate both increase QTc interval. Avoid or Use Alternate Drug.

• erythromycin stearate

  Serious - Use Alternative (1)thioridazine and erythromycin stearate both increase QTc interval. Avoid or Use Alternate Drug.

• escitalopram

  Contraindicated (1)escitalopram increases toxicity of thioridazine by QTc interval. Contraindicated.

• esketamine intranasal

  Monitor Closely (1)esketamine intranasal, thioridazine. Either increases toxicity of the other by sedation. Modify Therapy/Monitor Closely.

• estazolam

  Monitor Closely (1)estazolam and thioridazine both increase sedation. Use Caution/Monitor.

• ethanol

  Monitor Closely (1)thioridazine and ethanol both increase sedation. Use Caution/Monitor.Minor (1)ethanol, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive CNS depression.

• eucalyptus

  Minor (1)thioridazine and eucalyptus both increase sedation. Minor/Significance Unknown.

• ezogabine

  Monitor Closely (1)ezogabine, thioridazine. Either increases toxicity of the other by QTc interval. Use Caution/Monitor. Slight and transient QT-prolongation observed with ezogabine, particularly when dose titrated to 1200 mg/day. QT interval should be monitored when ezogabine is prescribed with agents known to increase QT interval.

• fedratinib

  Monitor Closely (1)fedratinib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP2D6 substrates as necessary.

• fenfluramine

  Monitor Closely (2)thioridazine, fenfluramine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and fenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• fentanyl

  Serious - Use Alternative (1)fentanyl, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration with other CNS depressants, such as skeletal muscle relaxants, may cause respiratory depression, hypotension, profound sedation, coma, and/or death. Consider dose reduction of either or both agents to avoid serious adverse effects. Monitor for hypotension, respiratory depression, and profound sedation.

• fentanyl intranasal

  Serious - Use Alternative (1)fentanyl intranasal, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration with other CNS depressants, such as skeletal muscle relaxants, may cause respiratory depression, hypotension, profound sedation, coma, and/or death. Consider dose reduction of either or both agents to avoid serious adverse effects. Monitor for hypotension, respiratory depression, and profound sedation.

• fentanyl transdermal

  Serious - Use Alternative (1)fentanyl transdermal, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration with other CNS depressants, such as skeletal muscle relaxants, may cause respiratory depression, hypotension, profound sedation, coma, and/or death. Consider dose reduction of either or both agents to avoid serious adverse effects. Monitor for hypotension, respiratory depression, and profound sedation.

• fentanyl transmucosal

  Serious - Use Alternative (1)fentanyl transmucosal, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration with other CNS depressants, such as skeletal muscle relaxants, may cause respiratory depression, hypotension, profound sedation, coma, and/or death. Consider dose reduction of either or both agents to avoid serious adverse effects. Monitor for hypotension, respiratory depression, and profound sedation.

• ferric maltol

  Monitor Closely (1)ferric maltol, thioridazine. Either increases levels of the other by unspecified interaction mechanism. Modify Therapy/Monitor Closely. Coadministration of ferric maltol with certain oral medications may decrease the bioavailability of either ferric maltol and some oral drugs. For oral drugs where reductions in bioavailability may cause clinically significant effects on its safety or efficacy, separate administration of ferric maltol from these drugs. Duration of separation may depend on the absorption of the medication concomitantly administered (eg, time to peak concentration, whether the drug is an immediate or extended release product).

• fesoterodine

  Monitor Closely (3)fesoterodine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  fesoterodine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of fesoterodine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)thioridazine will increase the level or effect of fesoterodine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• fexinidazole

  Serious - Use Alternative (1)fexinidazole and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Avoid coadministration of fexinidazole with drugs known to block potassium channels and/or prolong QT interval.

• fingolimod

  Contraindicated (1)fingolimod and thioridazine both increase QTc interval. Contraindicated.

• flavoxate

  Monitor Closely (3)flavoxate decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  flavoxate decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of flavoxate by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• flecainide

  Monitor Closely (2)thioridazine will increase the level or effect of flecainide by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  thioridazine and flecainide both increase QTc interval. Modify Therapy/Monitor Closely.

• fluconazole

  Serious - Use Alternative (1)thioridazine and fluconazole both increase QTc interval. Avoid or Use Alternate Drug.

• fluoxetine

  Contraindicated (3)thioridazine will increase the level or effect of fluoxetine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.
  
  thioridazine and fluoxetine both increase QTc interval. Contraindicated.
  
  fluoxetine increases levels of thioridazine by decreasing metabolism. Contraindicated. Risk of long QT syndrome.Serious - Use Alternative (1)fluoxetine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• fluphenazine

  Monitor Closely (2)fluphenazine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  fluphenazine and thioridazine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)fluphenazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.Minor (1)thioridazine will increase the level or effect of fluphenazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• flurazepam

  Monitor Closely (1)flurazepam and thioridazine both increase sedation. Use Caution/Monitor.

• fluvoxamine

  Serious - Use Alternative (2)fluvoxamine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP1A2 metabolism. Contraindicated.
  
  fluvoxamine and thioridazine both increase QTc interval. Contraindicated.

• formoterol

  Monitor Closely (1)thioridazine increases and formoterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and formoterol both increase QTc interval. Avoid or Use Alternate Drug.

• foscarnet

  Monitor Closely (1)thioridazine and foscarnet both increase QTc interval. Modify Therapy/Monitor Closely.

• fosinopril

  Minor (1)thioridazine increases effects of fosinopril by unspecified interaction mechanism. Minor/Significance Unknown.

• fostemsavir

  Monitor Closely (1)thioridazine and fostemsavir both increase QTc interval. Use Caution/Monitor. QTc prolongation reported with higher than recommended doses of fostemsavir.

• gadobenate

  Monitor Closely (1)gadobenate and thioridazine both increase QTc interval. Use Caution/Monitor.

• galantamine

  Minor (1)thioridazine will increase the level or effect of galantamine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• ganaxolone

  Monitor Closely (1)thioridazine and ganaxolone both increase sedation. Use Caution/Monitor.

• gemifloxacin

  Contraindicated (1)gemifloxacin and thioridazine both increase QTc interval. Contraindicated.

• gemtuzumab

  Monitor Closely (1)thioridazine and gemtuzumab both increase QTc interval. Use Caution/Monitor.

• gilteritinib

  Contraindicated (1)gilteritinib and thioridazine both increase QTc interval. Contraindicated.

• givosiran

  Serious - Use Alternative (1)givosiran will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sensitive CYP2D6 substrates with givosiran. If unavoidable, decrease the CYP2D6 substrate dosage in accordance with approved product labeling.

• glasdegib

  Serious - Use Alternative (1)thioridazine and glasdegib both increase QTc interval. Avoid or Use Alternate Drug. If coadministration unavoidable, monitor for increased risk of QTc interval prolongation.

• glycopyrrolate

  Monitor Closely (1)thioridazine increases effects of glycopyrrolate by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)thioridazine increases toxicity of glycopyrrolate by unknown mechanism. Minor/Significance Unknown.

• glycopyrrolate inhaled

  Monitor Closely (3)glycopyrrolate inhaled decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  glycopyrrolate inhaled decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of glycopyrrolate inhaled by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)thioridazine increases toxicity of glycopyrrolate inhaled by unknown mechanism. Minor/Significance Unknown.

• glycopyrronium tosylate topical

  Monitor Closely (1)glycopyrronium tosylate topical, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Coadministration of glycopyrronium tosylate topical with other anticholinergic medications may result in additive anticholinergic adverse effects.

• goserelin

  Contraindicated (1)goserelin increases toxicity of thioridazine by QTc interval. Contraindicated. Increases risk of torsades de pointes.

• granisetron

  Contraindicated (1)granisetron and thioridazine both increase QTc interval. Contraindicated.

• guanfacine

  Monitor Closely (1)guanfacine, thioridazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

• guselkumab

  Monitor Closely (1)guselkumab, thioridazine. Other (see comment). Use Caution/Monitor. Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, normalizing the formation of CYP450 enzymes. Upon initiation or discontinuation of guselkumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.

• haloperidol

  Monitor Closely (3)thioridazine will increase the level or effect of haloperidol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  haloperidol and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  haloperidol and thioridazine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (2)thioridazine and haloperidol both increase QTc interval. Avoid or Use Alternate Drug.
  
  haloperidol will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• henbane

  Monitor Closely (3)henbane decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  henbane decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of henbane by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• histrelin

  Serious - Use Alternative (1)histrelin increases toxicity of thioridazine by QTc interval. Avoid or Use Alternate Drug. Increases risk of torsades de pointes.

• homatropine

  Monitor Closely (3)homatropine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  homatropine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of homatropine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• hydrocodone

  Monitor Closely (1)thioridazine will increase the level or effect of hydrocodone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Hydromorphone (<3% of the circulating parent hydrocodone) is mainly formed by CYP2D6 mediated O-demethylation of hydrocodone. Hydromorphone may contribute to the total analgesic effect of hydrocodone.Serious - Use Alternative (1)hydrocodone, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation. Increased risk of hypotension if ability to maintain blood pressure has been compromised by a reduced blood volume or concurrent administration of certain CNS depressant drugs (eg, phenothiazines or general anesthetics).

• hydromorphone

  Monitor Closely (2)thioridazine will increase the level or effect of hydromorphone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  hydromorphone and thioridazine both increase sedation. Use Caution/Monitor.

• hydroxychloroquine sulfate

  Serious - Use Alternative (1)hydroxychloroquine sulfate and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• hydroxyzine

  Contraindicated (1)hydroxyzine and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)hydroxyzine and thioridazine both increase sedation. Use Caution/Monitor.

• hyoscyamine

  Monitor Closely (3)hyoscyamine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  hyoscyamine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of hyoscyamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• hyoscyamine spray

  Monitor Closely (3)thioridazine increases effects of hyoscyamine spray by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.
  
  hyoscyamine spray decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  hyoscyamine spray decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.

• ibutilide

  Contraindicated (1)thioridazine and ibutilide both increase QTc interval. Contraindicated.

• iloperidone

  Monitor Closely (4)thioridazine will increase the level or effect of iloperidone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  thioridazine and iloperidone both increase QTc interval. Modify Therapy/Monitor Closely.
  
  iloperidone and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  iloperidone and thioridazine both increase sedation. Use Caution/Monitor.

• imatinib

  Serious - Use Alternative (1)imatinib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• imidapril

  Minor (1)thioridazine increases effects of imidapril by unspecified interaction mechanism. Minor/Significance Unknown.

• imipramine

  Contraindicated (1)thioridazine will increase the level or effect of imipramine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.Monitor Closely (1)thioridazine and imipramine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and imipramine both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)imipramine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  imipramine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• incobotulinumtoxinA

  Monitor Closely (1)thioridazine increases effects of incobotulinumtoxinA by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• indacaterol, inhaled

  Monitor Closely (1)indacaterol, inhaled, thioridazine. QTc interval. Use Caution/Monitor. Drugs that are known to prolong the QTc interval may have an increased the risk of ventricular arrhythmias.

• indapamide

  Contraindicated (1)thioridazine and indapamide both increase QTc interval. Contraindicated.

• inotuzumab

  Serious - Use Alternative (1)inotuzumab and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. If unable to avoid concomitant use, obtain ECGs and electrolytes before and after initiation of any drug known to prolong QTc, and periodically monitor as clinically indicated during treatment.

• insulin degludec

  Monitor Closely (1)thioridazine decreases effects of insulin degludec by Other (see comment). Use Caution/Monitor. Comment: Phenothiazines may increase blood glucose concentrations.

• insulin degludec/insulin aspart

  Monitor Closely (1)thioridazine decreases effects of insulin degludec/insulin aspart by Other (see comment). Use Caution/Monitor. Comment: Phenothiazines may increase blood glucose concentrations.

• insulin inhaled

  Monitor Closely (1)thioridazine decreases effects of insulin inhaled by Other (see comment). Use Caution/Monitor. Comment: Phenothiazines may increase blood glucose concentrations.

• ipratropium

  Monitor Closely (3)ipratropium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  ipratropium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of ipratropium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• isoflurane

  Contraindicated (1)isoflurane and thioridazine both increase QTc interval. Contraindicated.

• isoproterenol

  Monitor Closely (2)thioridazine, isoproterenol. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and isoproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• itraconazole

  Serious - Use Alternative (1)thioridazine and itraconazole both increase QTc interval. Avoid or Use Alternate Drug.

• ivosidenib

  Serious - Use Alternative (1)ivosidenib and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Avoid coadministration of QTc prolonging drugs with ivosidenib or replace with alternate therapies. If coadministration of a QTc prolonging drug is unavoidable, monitor for increased risk of QTc interval prolongation.

• ketamine

  Monitor Closely (1)ketamine and thioridazine both increase sedation. Use Caution/Monitor.

• ketoconazole

  Serious - Use Alternative (1)thioridazine and ketoconazole both increase QTc interval. Avoid or Use Alternate Drug.

• ketotifen, ophthalmic

  Monitor Closely (1)thioridazine and ketotifen, ophthalmic both increase sedation. Use Caution/Monitor.

• lapatinib

  Monitor Closely (1)thioridazine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

• lasmiditan

  Monitor Closely (1)lasmiditan, thioridazine. Either increases effects of the other by sedation. Use Caution/Monitor. Coadministration of lasmiditan and other CNS depressant drugs, including alcohol have not been evaluated in clinical studies. Lasmiditan may cause sedation, as well as other cognitive and/or neuropsychiatric adverse reactions.

• lefamulin

  Serious - Use Alternative (1)lefamulin and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• lemborexant

  Monitor Closely (1)lemborexant will increase the level or effect of thioridazine by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.

• lenvatinib

  Monitor Closely (1)thioridazine and lenvatinib both increase QTc interval. Use Caution/Monitor. Lenvatinib prescribing information recommends monitoring ECG closely when coadministered with QT prolonging drugs.

• leuprolide

  Contraindicated (1)leuprolide increases toxicity of thioridazine by QTc interval. Contraindicated. Increases risk of torsades de pointes.

• levalbuterol

  Monitor Closely (1)thioridazine increases and levalbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• levodopa

  Serious - Use Alternative (1)thioridazine decreases effects of levodopa by pharmacodynamic antagonism. Avoid or Use Alternate Drug.

• levodopa inhaled

  Serious - Use Alternative (1)thioridazine decreases effects of levodopa inhaled by pharmacodynamic antagonism. Avoid or Use Alternate Drug. Phenothiazine/1st generation antipsychotics inhibit dopamine D2 receptors in varying degrees.

• levofloxacin

  Monitor Closely (1)thioridazine and levofloxacin both increase QTc interval. Modify Therapy/Monitor Closely.

• levoketoconazole

  Serious - Use Alternative (1)thioridazine and levoketoconazole both increase QTc interval. Avoid or Use Alternate Drug.

• levorphanol

  Monitor Closely (1)levorphanol and thioridazine both increase sedation. Use Caution/Monitor.

• liraglutide

  Monitor Closely (1)thioridazine, liraglutide. Other (see comment). Use Caution/Monitor. Comment: Phenothiazines may increase or decrease glucose levels, monitor therapy closely when these agents are concurrently administered.

• lisdexamfetamine

  Monitor Closely (2)thioridazine, lisdexamfetamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and lisdexamfetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lisinopril

  Minor (1)thioridazine increases effects of lisinopril by unspecified interaction mechanism. Minor/Significance Unknown.

• lisuride

  Serious - Use Alternative (1)thioridazine decreases effects of lisuride by pharmacodynamic antagonism. Contraindicated.

• lithium

  Contraindicated (1)lithium and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)lithium, thioridazine. Other (see comment). Use Caution/Monitor. Comment: Risk of neurotoxicity. Multiple mechanisms involved.

• lofepramine

  Monitor Closely (2)thioridazine will increase the level or effect of lofepramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  thioridazine and lofepramine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and lofepramine both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)lofepramine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  lofepramine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• lofexidine

  Monitor Closely (3)thioridazine and lofexidine both increase QTc interval. Use Caution/Monitor. ECG monitoring is recommended.
  
  thioridazine will increase the level or effect of lofexidine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Concomitant use of lofexidine with strong CYP2D6 inhibitors may increase lofexidine plasma levels. Monitor for symptoms of orthostasis and bradycardia if coadministered with a CYP2D6 inhibitor. Consider lofexidine dose reduction.
  
  thioridazine and lofexidine both increase sedation. Use Caution/Monitor.

• loprazolam

  Monitor Closely (1)loprazolam and thioridazine both increase sedation. Use Caution/Monitor.

• loratadine

  Minor (1)thioridazine will increase the level or effect of loratadine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• lorazepam

  Monitor Closely (1)lorazepam and thioridazine both increase sedation. Use Caution/Monitor.

• lorcaserin

  Monitor Closely (1)lorcaserin will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• lormetazepam

  Monitor Closely (1)lormetazepam and thioridazine both increase sedation. Use Caution/Monitor.

• loxapine

  Monitor Closely (2)loxapine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  loxapine and thioridazine both increase sedation. Use Caution/Monitor.

• loxapine inhaled

  Monitor Closely (2)loxapine inhaled and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  loxapine inhaled and thioridazine both increase sedation. Use Caution/Monitor.

• lumefantrine

  Serious - Use Alternative (2)lumefantrine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  thioridazine and lumefantrine both increase QTc interval. Avoid or Use Alternate Drug.

• lurasidone

  Monitor Closely (1)lurasidone, thioridazine. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity.

• macimorelin

  Serious - Use Alternative (1)macimorelin and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Macimorelin causes an increase of ~11 msec in the corrected QT interval. Avoid coadministration with drugs that prolong QT interval, which could increase risk for developing torsade de pointes-type ventricular tachycardia. Allow sufficient washout time of drugs that are known to prolong the QT interval before administering macimorelin.

• maprotiline

  Monitor Closely (1)thioridazine and maprotiline both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and maprotiline both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)maprotiline, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  maprotiline, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• maraviroc

  Serious - Use Alternative (1)maraviroc will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• marijuana

  Monitor Closely (1)thioridazine and marijuana both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)marijuana will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• meclizine

  Monitor Closely (3)meclizine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  meclizine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of meclizine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• mefloquine

  Serious - Use Alternative (1)mefloquine increases toxicity of thioridazine by QTc interval. Avoid or Use Alternate Drug. Mefloquine may enhance the QTc prolonging effect of high risk QTc prolonging agents.

• melatonin

  Monitor Closely (1)thioridazine and melatonin both increase sedation. Use Caution/Monitor.

• meperidine

  Monitor Closely (1)meperidine and thioridazine both increase sedation. Use Caution/Monitor.

• meprobamate

  Monitor Closely (1)thioridazine and meprobamate both increase sedation. Use Caution/Monitor.

• metaproterenol

  Monitor Closely (1)thioridazine increases and metaproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• metaxalone

  Monitor Closely (1)metaxalone and thioridazine both increase sedation. Use Caution/Monitor.

• metformin

  Monitor Closely (1)thioridazine decreases effects of metformin by pharmacodynamic antagonism. Use Caution/Monitor. Patient should be closely observed for loss of blood glucose control; when drugs are withdrawn from a patient receiving metformin, patient should be observed closely for hypoglycemia.

• methadone

  Monitor Closely (2)thioridazine and methadone both increase QTc interval. Modify Therapy/Monitor Closely.
  
  methadone and thioridazine both increase sedation. Use Caution/Monitor.

• methamphetamine

  Monitor Closely (3)thioridazine will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  thioridazine, methamphetamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• methocarbamol

  Monitor Closely (1)methocarbamol and thioridazine both increase sedation. Use Caution/Monitor.

• methoxsalen

  Monitor Closely (1)methoxsalen, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Additive photosensitizing effects.

• methscopolamine

  Monitor Closely (3)methscopolamine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  methscopolamine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of methscopolamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• methyl aminolevulinate

  Serious - Use Alternative (1)thioridazine, methyl aminolevulinate. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Each drug may increase the photosensitizing effect of the other.

• methyldopa

  Serious - Use Alternative (1)thioridazine decreases effects of methyldopa by pharmacodynamic antagonism. Contraindicated.

• methylenedioxymethamphetamine

  Monitor Closely (2)thioridazine, methylenedioxymethamphetamine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and methylenedioxymethamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• methylphenidate

  Monitor Closely (1)thioridazine, methylphenidate. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• metoclopramide

  Monitor Closely (1)thioridazine and metoclopramide both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.

• metoclopramide intranasal

  Serious - Use Alternative (3)thioridazine will increase the level or effect of metoclopramide intranasal by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Concurrent use of metoclopramide intranasal and strong CYP2D6 inhibitors is not recommended since the metoclopramide intranasal dose cannot be adjusted.
  
  thioridazine, metoclopramide intranasal. Either increases effects of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Avoid use of metoclopramide intranasal or interacting drug, depending on importance of drug to patient.
  
  thioridazine increases toxicity of metoclopramide intranasal by pharmacodynamic synergism. Avoid or Use Alternate Drug. Potential for additive effects, including increased frequency and severity of tardive dyskinesia, other extrapyramidal symptoms, and neuroleptic malignant syndrome.

• metoprolol

  Monitor Closely (1)thioridazine will increase the level or effect of metoprolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)metoprolol, thioridazine. Either increases levels of the other by decreasing metabolism. Contraindicated. Not all beta blockers share this interaction (e.g., atenolol, nadolol, sotalol do not interact).

• metrizamide

  Contraindicated (1)thioridazine, metrizamide. Mechanism: unknown. Contraindicated. Risk of seizure. D/C phenothiazine 24h before admin. of metrizamide.

• metyrapone

  Minor (1)thioridazine decreases effects of metyrapone by unspecified interaction mechanism. Minor/Significance Unknown.

• metyrosine

  Minor (1)metyrosine increases toxicity of thioridazine by pharmacodynamic synergism. Minor/Significance Unknown. Increased extrapyramidal symptoms.

• mexiletine

  Monitor Closely (1)thioridazine will increase the level or effect of mexiletine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• midazolam

  Monitor Closely (1)midazolam and thioridazine both increase sedation. Use Caution/Monitor.

• midazolam intranasal

  Monitor Closely (1)midazolam intranasal, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase the risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.

• midodrine

  Monitor Closely (2)thioridazine, midodrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and midodrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• mifepristone

  Contraindicated (1)mifepristone, thioridazine. QTc interval. Contraindicated.

• mirabegron

  Monitor Closely (1)mirabegron will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• mirtazapine

  Contraindicated (1)mirtazapine and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)thioridazine and mirtazapine both increase sedation. Use Caution/Monitor.

• mobocertinib

  Serious - Use Alternative (1)mobocertinib and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. If coadministration unavoidable, reduce mobocertinib dose and monitor QTc interval more frequently.

• modafinil

  Monitor Closely (1)thioridazine increases and modafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• moexipril

  Minor (1)thioridazine increases effects of moexipril by unspecified interaction mechanism. Minor/Significance Unknown.

• morphine

  Monitor Closely (2)thioridazine will increase the level or effect of morphine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  morphine and thioridazine both increase sedation. Use Caution/Monitor.

• motherwort

  Monitor Closely (1)thioridazine and motherwort both increase sedation. Use Caution/Monitor.

• moxifloxacin

  Serious - Use Alternative (1)thioridazine and moxifloxacin both increase QTc interval. Avoid or Use Alternate Drug.

• moxonidine

  Monitor Closely (1)thioridazine and moxonidine both increase sedation. Use Caution/Monitor.

• nabilone

  Monitor Closely (1)thioridazine and nabilone both increase sedation. Use Caution/Monitor.

• nalbuphine

  Monitor Closely (1)nalbuphine and thioridazine both increase sedation. Use Caution/Monitor.

• nebivolol

  Monitor Closely (1)thioridazine will increase the level or effect of nebivolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• nilotinib

  Serious - Use Alternative (2)thioridazine and nilotinib both increase QTc interval. Avoid or Use Alternate Drug.
  
  nilotinib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• norepinephrine

  Monitor Closely (2)thioridazine, norepinephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and norepinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• nortriptyline

  Contraindicated (1)thioridazine will increase the level or effect of nortriptyline by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.Monitor Closely (1)thioridazine and nortriptyline both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and nortriptyline both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)nortriptyline, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  nortriptyline, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• octreotide

  Serious - Use Alternative (1)thioridazine and octreotide both increase QTc interval. Avoid or Use Alternate Drug.

• octreotide (Antidote)

  Serious - Use Alternative (1)thioridazine and octreotide (Antidote) both increase QTc interval. Avoid or Use Alternate Drug.

• ofloxacin

  Monitor Closely (1)thioridazine and ofloxacin both increase QTc interval. Modify Therapy/Monitor Closely.

• olanzapine

  Contraindicated (1)olanzapine and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (2)olanzapine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  olanzapine and thioridazine both increase sedation. Use Caution/Monitor.

• oliceridine

  Monitor Closely (2)thioridazine will increase the level or effect of oliceridine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. If concomitant use is necessary, may require less frequent oliceridine dosing. Closely monitor for respiratory depression and sedation and titrate subsequent doses accordingly. If inhibitor is discontinued, consider increase oliceridine dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal.
  
  oliceridine, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation. Increased risk of hypotension if ability to maintain blood pressure has been compromised by a reduced blood volume or concurrent administration of certain CNS depressant drugs (eg, phenothiazines or general anesthetics).

• olodaterol inhaled

  Monitor Closely (1)thioridazine and olodaterol inhaled both increase QTc interval. Use Caution/Monitor. Drugs that prolong the QTc interval and may potentiate the effects of beta2 agonists on the cardiovascular system; increased risk of ventricular arrhythmias

• onabotulinumtoxinA

  Monitor Closely (3)onabotulinumtoxinA decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  onabotulinumtoxinA decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of onabotulinumtoxinA by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• ondansetron

  Serious - Use Alternative (1)thioridazine and ondansetron both increase QTc interval. Avoid or Use Alternate Drug. Avoid with congenital long QT syndrome; ECG monitoring recommended with concomitant medications that prolong QT interval, electrolyte abnormalities, CHF, or bradyarrhythmias.

• opium tincture

  Monitor Closely (1)opium tincture and thioridazine both increase sedation. Use Caution/Monitor.

• orphenadrine

  Monitor Closely (1)orphenadrine and thioridazine both increase sedation. Use Caution/Monitor.

• osilodrostat

  Monitor Closely (1)osilodrostat and thioridazine both increase QTc interval. Use Caution/Monitor.

• osimertinib

  Monitor Closely (1)osimertinib and thioridazine both increase QTc interval. Use Caution/Monitor. Conduct periodic monitoring with ECGs and electrolytes in patients taking drugs known to prolong the QTc interval.

• oxaliplatin

  Contraindicated (1)oxaliplatin and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)oxaliplatin will increase the level or effect of thioridazine by Other (see comment). Use Caution/Monitor. Monitor for ECG changes if therapy is initiated in patients with drugs known to prolong QT interval.

• oxazepam

  Monitor Closely (1)oxazepam and thioridazine both increase sedation. Use Caution/Monitor.

• oxybutynin

  Monitor Closely (3)oxybutynin decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  oxybutynin decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of oxybutynin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)oxybutynin increases toxicity of thioridazine by unspecified interaction mechanism. Minor/Significance Unknown.

• oxybutynin topical

  Monitor Closely (3)oxybutynin topical decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  oxybutynin topical decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of oxybutynin topical by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)oxybutynin topical increases toxicity of thioridazine by unspecified interaction mechanism. Minor/Significance Unknown.

• oxybutynin transdermal

  Monitor Closely (3)oxybutynin transdermal decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  oxybutynin transdermal decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of oxybutynin transdermal by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)oxybutynin transdermal increases toxicity of thioridazine by unspecified interaction mechanism. Minor/Significance Unknown.

• oxycodone

  Monitor Closely (2)thioridazine will increase the level or effect of oxycodone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  oxycodone and thioridazine both increase sedation. Use Caution/Monitor.Minor (1)thioridazine decreases effects of oxycodone by decreasing metabolism. Minor/Significance Unknown. Decreased conversion of oxycodone to active metabolite morphine.

• oxymorphone

  Monitor Closely (2)thioridazine will increase the level or effect of oxymorphone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  oxymorphone and thioridazine both increase sedation. Use Caution/Monitor.

• ozanimod

  Monitor Closely (1)ozanimod and thioridazine both increase QTc interval. Modify Therapy/Monitor Closely. The potential additive effects on heart rate, treatment with ozanimod should generally not be initiated in patients who are concurrently treated with QT prolonging drugs with known arrhythmogenic properties.

• paliperidone

  Monitor Closely (3)thioridazine and paliperidone both increase QTc interval. Modify Therapy/Monitor Closely.
  
  paliperidone and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  paliperidone and thioridazine both increase sedation. Use Caution/Monitor.

• pancuronium

  Monitor Closely (3)pancuronium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  pancuronium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of pancuronium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• panobinostat

  Monitor Closely (1)panobinostat will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Panobinostat can increase the levels and effects of sensitive CYP2D6 substrates or those with a narrow therapeutic index CYP2D6.Serious - Use Alternative (1)thioridazine and panobinostat both increase QTc interval. Avoid or Use Alternate Drug. Panobinostat is known to significantly prolong QT interval. Panobinostat prescribing information states use with drugs known to prolong QTc is not recommended.

• papaveretum

  Monitor Closely (1)papaveretum and thioridazine both increase sedation. Use Caution/Monitor.

• papaverine

  Monitor Closely (1)thioridazine and papaverine both increase sedation. Use Caution/Monitor.

• parecoxib

  Serious - Use Alternative (1)parecoxib will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• paroxetine

  Contraindicated (1)paroxetine increases levels of thioridazine by decreasing metabolism. Contraindicated. Risk of long QT syndrome.Serious - Use Alternative (3)paroxetine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  thioridazine will increase the level or effect of paroxetine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  thioridazine and paroxetine both increase QTc interval. Avoid or Use Alternate Drug.

• pasireotide

  Contraindicated (1)thioridazine and pasireotide both increase QTc interval. Contraindicated.

• pazopanib

  Monitor Closely (1)thioridazine and pazopanib both increase QTc interval. Use Caution/Monitor.

• peginterferon alfa 2b

  Monitor Closely (1)peginterferon alfa 2b, thioridazine. Other (see comment). Use Caution/Monitor. Comment: When patients are administered peginterferon alpha-2b with CYP2D6 substrates, the therapeutic effect of these drugs may be altered. Peginterferon alpha-2b may increase or decrease levels of CYP2D6 substrate.

• pentamidine

  Contraindicated (1)thioridazine and pentamidine both increase QTc interval. Contraindicated.

• pentazocine

  Monitor Closely (1)pentazocine and thioridazine both increase sedation. Use Caution/Monitor.

• pentobarbital

  Monitor Closely (1)pentobarbital and thioridazine both increase sedation. Use Caution/Monitor.Minor (1)thioridazine decreases levels of pentobarbital by unspecified interaction mechanism. Minor/Significance Unknown.

• perhexiline

  Minor (1)thioridazine will increase the level or effect of perhexiline by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• perindopril

  Minor (1)thioridazine increases effects of perindopril by unspecified interaction mechanism. Minor/Significance Unknown.

• perphenazine

  Monitor Closely (2)perphenazine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  perphenazine and thioridazine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (2)perphenazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.
  
  perphenazine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.Minor (1)thioridazine will increase the level or effect of perphenazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• phendimetrazine

  Monitor Closely (2)thioridazine, phendimetrazine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and phendimetrazine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• phenobarbital

  Monitor Closely (1)phenobarbital and thioridazine both increase sedation. Use Caution/Monitor.Minor (1)thioridazine decreases levels of phenobarbital by unspecified interaction mechanism. Minor/Significance Unknown.

• phentermine

  Monitor Closely (2)thioridazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• phenylephrine

  Monitor Closely (2)thioridazine, phenylephrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• phenylephrine PO

  Monitor Closely (2)thioridazine, phenylephrine PO. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and phenylephrine PO decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. .

• pholcodine

  Monitor Closely (1)thioridazine and pholcodine both increase sedation. Use Caution/Monitor.

• pimavanserin

  Serious - Use Alternative (1)pimavanserin and thioridazine both increase QTc interval. Avoid or Use Alternate Drug. Coadministration may increase the risk of QT prolongation and cardiac arrhythmia.

• pimozide

  Contraindicated (1)thioridazine and pimozide both increase QTc interval. Contraindicated.Monitor Closely (2)pimozide and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  pimozide and thioridazine both increase sedation. Use Caution/Monitor.

• pirbuterol

  Monitor Closely (1)thioridazine increases and pirbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pitolisant

  Monitor Closely (1)thioridazine will increase the level or effect of pitolisant by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. If coadministered with strong CYP2D6 inhibitors, initiate pitolisant at 8.9 mg/day and increase after 7 days to maximum of 17.8 mg/day. For patients currently taking pitolisant, reduce pitolisant dose by half upon initiating strong CYP2D6 inhibitors.Serious - Use Alternative (1)thioridazine and pitolisant both increase QTc interval. Avoid or Use Alternate Drug.

• porfimer

  Monitor Closely (1)thioridazine, porfimer. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Enhanced photosensitivity.

• posaconazole

  Monitor Closely (1)thioridazine and posaconazole both increase QTc interval. Modify Therapy/Monitor Closely.

• pralidoxime

  Monitor Closely (3)pralidoxime decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  pralidoxime decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of pralidoxime by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• pramipexole

  Serious - Use Alternative (1)thioridazine decreases effects of pramipexole by pharmacodynamic antagonism. Contraindicated.

• primaquine

  Contraindicated (1)primaquine and thioridazine both increase QTc interval. Contraindicated.

• primidone

  Monitor Closely (1)primidone and thioridazine both increase sedation. Use Caution/Monitor.Minor (1)thioridazine decreases levels of primidone by unspecified interaction mechanism. Minor/Significance Unknown.

• procainamide

  Contraindicated (1)thioridazine and procainamide both increase QTc interval. Contraindicated.

• procarbazine

  Monitor Closely (1)procarbazine, thioridazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Excessive sedation.

• prochlorperazine

  Monitor Closely (2)prochlorperazine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  prochlorperazine and thioridazine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)prochlorperazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.Minor (1)thioridazine will increase the level or effect of prochlorperazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• promazine

  Serious - Use Alternative (1)promazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.Minor (1)thioridazine will increase the level or effect of promazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• promethazine

  Monitor Closely (2)promethazine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  promethazine and thioridazine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)promethazine and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.Minor (1)thioridazine will increase the level or effect of promethazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• propafenone

  Serious - Use Alternative (2)propafenone will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. The concurrent administration of thioridazine and agents that prolong the QT interval, such as Class I antiarrhythmic agents, is contraindicated.
  
  thioridazine will increase the level or effect of propafenone by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. The concurrent administration of thioridazine and agents that prolong the QT interval, such as Class I antiarrhythmic agents, is contraindicated.

• propantheline

  Monitor Closely (3)propantheline decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  propantheline decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of propantheline by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• propofol

  Monitor Closely (1)propofol and thioridazine both increase sedation. Use Caution/Monitor.

• propranolol

  Serious - Use Alternative (2)thioridazine will increase the level or effect of propranolol by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Due to the potential for significant, possibly life-threatening, proarrhythmic effects, concurrent administration of thioridazine and propranolol is contraindicated.
  
  propranolol, thioridazine. Either increases levels of the other by decreasing metabolism. Contraindicated. Not all beta blockers share this interaction (e.g., atenolol, nadolol, sotalol do not interact).

• propylhexedrine

  Monitor Closely (2)thioridazine, propylhexedrine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and propylhexedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• protriptyline

  Monitor Closely (1)thioridazine and protriptyline both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and protriptyline both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)protriptyline, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  protriptyline, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• pseudoephedrine

  Monitor Closely (1)thioridazine, pseudoephedrine. Mechanism: unknown. Use Caution/Monitor. Consider avoiding use of pseudoephedrine in patients receiving phenothiazines (especially thioridazine) due to the potential risk of cardiac arrhythmia or sudden death. Monitor for evidence of ventricular arrhythmias during concomitant use.

• pyrimethamine

  Minor (1)pyrimethamine increases levels of thioridazine by decreasing metabolism. Minor/Significance Unknown.

• quazepam

  Monitor Closely (1)quazepam and thioridazine both increase sedation. Use Caution/Monitor.

• quetiapine

  Monitor Closely (3)quetiapine and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  quetiapine and thioridazine both increase sedation. Use Caution/Monitor.
  
  quetiapine, thioridazine. Either increases toxicity of the other by QTc interval. Use Caution/Monitor. Avoid use with drugs that prolong QT and in patients with risk factors for prolonged QT interval. Postmarketing cases show QT prolongation with overdose in patients with concomitant illness or with drugs known to cause electrolyte imbalance or prolong QT.

• quinacrine

  Serious - Use Alternative (1)quinacrine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• quinapril

  Minor (1)thioridazine increases effects of quinapril by unspecified interaction mechanism. Minor/Significance Unknown.

• quinidine

  Contraindicated (1)thioridazine and quinidine both increase QTc interval. Contraindicated.Serious - Use Alternative (2)quinidine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
  
  quinidine, thioridazine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Additive cardiac effects.

• quinine

  Contraindicated (1)thioridazine and quinine both increase QTc interval. Contraindicated.

• ramelteon

  Monitor Closely (1)thioridazine and ramelteon both increase sedation. Use Caution/Monitor.

• ramipril

  Minor (1)thioridazine increases effects of ramipril by unspecified interaction mechanism. Minor/Significance Unknown.

• ranolazine

  Monitor Closely (1)thioridazine and ranolazine both increase QTc interval. Modify Therapy/Monitor Closely.Serious - Use Alternative (1)ranolazine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• rapacuronium

  Monitor Closely (3)rapacuronium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  rapacuronium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of rapacuronium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• ribociclib

  Serious - Use Alternative (1)ribociclib and thioridazine both increase QTc interval. Avoid or Use Alternate Drug.

• rilpivirine

  Monitor Closely (1)rilpivirine increases toxicity of thioridazine by QTc interval. Use Caution/Monitor. Rilpivirine should be used with caution when co-administered with a drug with a known risk of Torsade de Pointes.

• rimabotulinumtoxinB

  Monitor Closely (1)thioridazine, rimabotulinumtoxinB. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Anticholinergics may enhance botulinum toxin effects. Closely monitor for increased neuromuscular blockade.

• risperidone

  Monitor Closely (3)thioridazine and risperidone both increase QTc interval. Modify Therapy/Monitor Closely.
  
  risperidone and thioridazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  risperidone and thioridazine both increase sedation. Use Caution/Monitor.Minor (1)thioridazine will increase the level or effect of risperidone by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• ritonavir

  Serious - Use Alternative (1)ritonavir will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• rocuronium

  Monitor Closely (3)rocuronium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  rocuronium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of rocuronium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• rolapitant

  Contraindicated (1)rolapitant will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated. Rolapitant moderately inhibits CYP2D6. Coadministration with thioridazine, a CYP2D6 substrate, causes a significant increase in thioridazine plasma concentration that may result in QT prolongation and torsades de pointes.

• romidepsin

  Monitor Closely (1)thioridazine and romidepsin both increase QTc interval. Modify Therapy/Monitor Closely.

• ropeginterferon alfa 2b

  Monitor Closely (1)ropeginterferon alfa 2b will increase the level or effect of thioridazine by Other (see comment). Use Caution/Monitor. Certain proinflammatory cytokines, including interferons, can suppress CYP450 enzymes resulting in increased exposures of some CYP substrates. Therefore, monitor patients who are receiving concomitant drugs that are CYP450 substrates with a narrow therapeutic index from toxicities to such drugs.

• ropinirole

  Serious - Use Alternative (1)thioridazine decreases effects of ropinirole by pharmacodynamic antagonism. Contraindicated.

• safinamide

  Serious - Use Alternative (1)thioridazine decreases effects of safinamide by pharmacodynamic antagonism. Avoid or Use Alternate Drug. Dopamine antagonists may decrease safinamide effects and exacerbate Parkinson disease symptoms.

• sage

  Minor (1)thioridazine and sage both increase sedation. Minor/Significance Unknown.

• salmeterol

  Monitor Closely (1)thioridazine increases and salmeterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• saquinavir

  Monitor Closely (1)saquinavir, thioridazine. Either increases toxicity of the other by QTc interval. Modify Therapy/Monitor Closely. Use alternatives if available.

• scopolamine

  Monitor Closely (3)scopolamine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  scopolamine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of scopolamine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• scullcap

  Monitor Closely (1)thioridazine and scullcap both increase sedation. Use Caution/Monitor.

• secobarbital

  Monitor Closely (1)secobarbital and thioridazine both increase sedation. Use Caution/Monitor.Minor (1)thioridazine decreases levels of secobarbital by unspecified interaction mechanism. Minor/Significance Unknown.

• selinexor

  Serious - Use Alternative (1)selinexor, thioridazine. unspecified interaction mechanism. Avoid or Use Alternate Drug. Patients treated with selinexor may experience neurological toxicities. Avoid taking selinexor with other medications that may cause dizziness or confusion.

• selpercatinib

  Monitor Closely (1)selpercatinib increases toxicity of thioridazine by QTc interval. Use Caution/Monitor.

• serdexmethylphenidate/dexmethylphenidate

  Monitor Closely (1)thioridazine, serdexmethylphenidate/dexmethylphenidate. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• sertraline

  Contraindicated (2)sertraline increases levels of thioridazine by decreasing metabolism. Contraindicated. Risk of long QT syndrome.
  
  sertraline and thioridazine both increase QTc interval. Contraindicated.Serious - Use Alternative (1)sertraline will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated.

• sevoflurane

  Contraindicated (1)sevoflurane and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (1)sevoflurane and thioridazine both increase sedation. Use Caution/Monitor.

• shepherd's purse

  Monitor Closely (1)thioridazine and shepherd's purse both increase sedation. Use Caution/Monitor.

• siponimod

  Contraindicated (1)siponimod and thioridazine both increase QTc interval. Contraindicated.

• smoking

  Monitor Closely (1)smoking decreases levels of thioridazine by increasing metabolism. Use Caution/Monitor. Interaction mainly seen w/chlorpromazine & thioridazine, but may occur w/other phenothiazines.

• sodium oxybate

  Serious - Use Alternative (1)thioridazine, sodium oxybate. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• sodium sulfate/?magnesium sulfate/potassium chloride

  Monitor Closely (1)sodium sulfate/?magnesium sulfate/potassium chloride increases toxicity of thioridazine by QTc interval. Use Caution/Monitor. Consider predose and post-colonoscopy ECGs in patients at increased risk of serious cardiac arrhythmias. .

• sodium sulfate/potassium sulfate/magnesium sulfate

  Monitor Closely (1)sodium sulfate/potassium sulfate/magnesium sulfate increases toxicity of thioridazine by QTc interval. Use Caution/Monitor. Consider predose and post-colonoscopy ECGs in patients at increased risk of serious cardiac arrhythmias. .

• solifenacin

  Contraindicated (1)solifenacin and thioridazine both increase QTc interval. Contraindicated.Monitor Closely (3)solifenacin decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  solifenacin decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of solifenacin by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• sorafenib

  Contraindicated (1)sorafenib and thioridazine both increase QTc interval. Contraindicated.

• sotalol

  Contraindicated (1)thioridazine and sotalol both increase QTc interval. Contraindicated.

• stiripentol

  Monitor Closely (1)stiripentol, thioridazine. Either decreases toxicity of the other by sedation. Use Caution/Monitor. Concomitant use stiripentol with other CNS depressants, including alcohol, may increase the risk of sedation and somnolence.

• sufentanil

  Monitor Closely (1)sufentanil and thioridazine both increase sedation. Use Caution/Monitor.

• sulfamethoxazole

  Monitor Closely (1)thioridazine and sulfamethoxazole both increase QTc interval. Modify Therapy/Monitor Closely.

• sunitinib

  Contraindicated (1)sunitinib and thioridazine both increase QTc interval. Contraindicated.

• tacrolimus

  Contraindicated (1)tacrolimus and thioridazine both increase QTc interval. Contraindicated.

• tamsulosin

  Monitor Closely (1)thioridazine increases levels of tamsulosin by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• tapentadol

  Monitor Closely (1)tapentadol and thioridazine both increase sedation. Use Caution/Monitor.

• teduglutide

  Monitor Closely (1)teduglutide increases levels of thioridazine by Other (see comment). Use Caution/Monitor. Comment: Teduglutide may increase absorption of concomitant PO medications; caution with with drugs requiring titration or those with a narrow therapeutic index; dose adjustment may be necessary.

• telavancin

  Monitor Closely (1)thioridazine and telavancin both increase QTc interval. Modify Therapy/Monitor Closely.

• temazepam

  Monitor Closely (1)temazepam and thioridazine both increase sedation. Use Caution/Monitor.

• terbinafine

  Monitor Closely (1)terbinafine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Assess need to reduce dose of CYP2D6-metabolized drug.

• terbutaline

  Monitor Closely (1)thioridazine increases and terbutaline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• tetrabenazine

  Monitor Closely (1)thioridazine and tetrabenazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Modify Therapy/Monitor Closely.

• thiothixene

  Monitor Closely (2)thioridazine and thiothixene both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and thiothixene both increase sedation. Use Caution/Monitor.

• timolol

  Monitor Closely (1)thioridazine will increase the level or effect of timolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• tiotropium

  Monitor Closely (3)tiotropium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  tiotropium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of tiotropium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• tipranavir

  Serious - Use Alternative (1)tipranavir will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• tobacco use

  Monitor Closely (1)tobacco use decreases levels of thioridazine by increasing metabolism. Use Caution/Monitor. Interaction mainly seen w/chlorpromazine & thioridazine, but may occur w/other phenothiazines.

• tolterodine

  Monitor Closely (3)tolterodine decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  tolterodine decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of tolterodine by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.Minor (1)thioridazine will increase the level or effect of tolterodine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• topiramate

  Monitor Closely (1)thioridazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• toremifene

  Contraindicated (1)thioridazine and toremifene both increase QTc interval. Contraindicated. Concurrent use of thioridazine with other agents that prolong QTc interval is contraindicated.

• tramadol

  Monitor Closely (3)thioridazine decreases effects of tramadol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Decreased conversion of tramadol to active metabolite.
  
  tramadol and thioridazine both increase sedation. Use Caution/Monitor.
  
  thioridazine decreases effects of tramadol by decreasing metabolism. Use Caution/Monitor. Decreased conversion of tramadol to active metabolite.

• trandolapril

  Minor (1)thioridazine increases effects of trandolapril by unspecified interaction mechanism. Minor/Significance Unknown.

• trazodone

  Monitor Closely (1)thioridazine and trazodone both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and trazodone both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)trazodone, thioridazine. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive hypotensive effects.
  
  trazodone, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.

• tretinoin

  Serious - Use Alternative (1)thioridazine, tretinoin. Mechanism: pharmacodynamic synergism. Avoid or Use Alternate Drug. Increased phototoxicity.

• tretinoin topical

  Serious - Use Alternative (1)thioridazine, tretinoin topical. Mechanism: pharmacodynamic synergism. Avoid or Use Alternate Drug. Increased phototoxicity.

• triazolam

  Monitor Closely (1)triazolam and thioridazine both increase sedation. Use Caution/Monitor.

• triclabendazole

  Monitor Closely (1)triclabendazole and thioridazine both increase QTc interval. Use Caution/Monitor.

• triclofos

  Monitor Closely (1)triclofos and thioridazine both increase sedation. Use Caution/Monitor.

• trifluoperazine

  Monitor Closely (2)thioridazine and trifluoperazine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and trifluoperazine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and trifluoperazine both increase QTc interval. Avoid or Use Alternate Drug.Minor (1)thioridazine will increase the level or effect of trifluoperazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• trihexyphenidyl

  Monitor Closely (2)trihexyphenidyl decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of trihexyphenidyl by pharmacodynamic synergism. Use Caution/Monitor. Potential for additive anticholinergic effects.

• trimethoprim

  Monitor Closely (1)thioridazine and trimethoprim both increase QTc interval. Modify Therapy/Monitor Closely.

• trimipramine

  Monitor Closely (1)thioridazine and trimipramine both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and trimipramine both increase QTc interval. Avoid or Use Alternate Drug.Minor (2)trimipramine, thioridazine. Either increases levels of the other by decreasing metabolism. Minor/Significance Unknown. Additive anticholinergic effects.
  
  trimipramine, thioridazine. Either increases levels of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive anticholinergic effects.

• triprolidine

  Monitor Closely (1)triprolidine and thioridazine both increase sedation. Use Caution/Monitor.

• triptorelin

  Serious - Use Alternative (1)triptorelin increases toxicity of thioridazine by QTc interval. Avoid or Use Alternate Drug. Increases risk of torsades de pointes.

• tropisetron

  Monitor Closely (1)thioridazine and tropisetron both increase QTc interval. Modify Therapy/Monitor Closely.Minor (1)thioridazine will increase the level or effect of tropisetron by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• trospium chloride

  Monitor Closely (3)trospium chloride decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  trospium chloride decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of trospium chloride by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• umeclidinium bromide/vilanterol inhaled

  Serious - Use Alternative (1)thioridazine increases toxicity of umeclidinium bromide/vilanterol inhaled by QTc interval. Avoid or Use Alternate Drug. Exercise extreme caution when vilanterol coadministered with drugs that prolong QTc interval; adrenergic agonist effects on the cardiovascular system may be potentiated.

• ustekinumab

  Monitor Closely (1)ustekinumab, thioridazine. Other (see comment). Use Caution/Monitor. Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, normalizing the formation of CYP450 enzymes. Upon initiation or discontinuation of ustekinumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.

• vandetanib

  Serious - Use Alternative (1)thioridazine, vandetanib. Either increases toxicity of the other by QTc interval. Avoid or Use Alternate Drug. Avoid coadministration with drugs known to prolong QT interval; if a drug known to prolong QT interval must be used, more frequent ECG monitoring is recommended.

• vecuronium

  Monitor Closely (3)vecuronium decreases levels of thioridazine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.
  
  vecuronium decreases levels of thioridazine by pharmacodynamic antagonism. Use Caution/Monitor.
  
  thioridazine increases effects of vecuronium by pharmacodynamic synergism. Use Caution/Monitor. Additive anticholinergic effects, possible hypoglycemia.

• vemurafenib

  Serious - Use Alternative (1)vemurafenib increases levels of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Concomitant use of vemurafenib with agents with narrow therapeutic windows is not recommended as vemurafenib may alter their concentrations. If coadministration cannot be avoided, use caution and consider dose reduction of concomitant CYP2D6 substrate drug. Combination may increase risk QT prolongation.

• venlafaxine

  Serious - Use Alternative (2)thioridazine and venlafaxine both increase QTc interval. Avoid or Use Alternate Drug.
  
  venlafaxine will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• vilanterol/fluticasone furoate inhaled

  Serious - Use Alternative (1)thioridazine increases toxicity of vilanterol/fluticasone furoate inhaled by QTc interval. Avoid or Use Alternate Drug. Exercise extreme caution when vilanterol coadministered with drugs that prolong QTc interval; adrenergic agonist effects on the cardiovascular system may be potentiated.

• voclosporin

  Monitor Closely (1)voclosporin, thioridazine. Either increases effects of the other by QTc interval. Use Caution/Monitor.

• voriconazole

  Monitor Closely (1)thioridazine and voriconazole both increase QTc interval. Modify Therapy/Monitor Closely.

• vorinostat

  Contraindicated (1)vorinostat and thioridazine both increase QTc interval. Contraindicated.

• xylometazoline

  Monitor Closely (2)thioridazine, xylometazoline. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and xylometazoline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• yohimbe

  Serious - Use Alternative (1)yohimbe decreases effects of thioridazine by pharmacodynamic antagonism. Contraindicated.

• yohimbine

  Monitor Closely (2)thioridazine, yohimbine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and yohimbine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ziconotide

  Monitor Closely (1)thioridazine and ziconotide both increase sedation. Use Caution/Monitor.

• ziprasidone

  Monitor Closely (2)thioridazine and ziprasidone both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and ziprasidone both increase sedation. Use Caution/Monitor.Serious - Use Alternative (1)thioridazine and ziprasidone both increase QTc interval. Avoid or Use Alternate Drug.

• zolpidem

  Monitor Closely (1)thioridazine will increase the level or effect of zolpidem by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Additive effect of decreased alertness and psychomotor performance

• zotepine

  Monitor Closely (2)thioridazine and zotepine both increase antidopaminergic effects, including extrapyramidal symptoms and neuroleptic malignant syndrome. Use Caution/Monitor.
  
  thioridazine and zotepine both increase sedation. Use Caution/Monitor.