Dosing & Uses
Dosage Forms & Strengths
tablet: Schedule IV
- 15mg
- 16.2mg
- 30mg
- 32.4mg
- 60mg
- 64.8mg
- 97.2
- 100mg
elixir: Schedule IV
- 20mg/5mL
injectable solution: Schedule IV
- 65mg/mL
- 130mg/mL
Status Epilepticus
Typically used after benzodiazepines and phenytoin fail to abort status epilepticus
15-20 mg/kg IV loading dose infused at 25-100 mg/min; may repeat once after 10 min with additional 5-10 mg/kg; respiratory support may be necessary when maximum dose administered
Seizures
All types of seizure disorders, including partial, tonic-clonic, and myoclonic seizures
1-3 mg/kg/day PO/IV in 1-2 divided doses initially; adjust accordingly to maintain at a therapeutic steady state level of 20 mg/L
Sedation
30-120 mg/day PO divided BID/TID; do not exceed 400 mg/day
Hypnotic
100-320 mg/day PO/IV/IM; do not administer for >2 weeks
Insomnia
100-200 mg PO qHS; do not exceed 400 mg/day
Dosing Considerations
Antiepileptic therapeutic concentration range: 10-40 mcg/L (43-172 micromoles/L)
Long half-life permits once-daily dosing, if tolerated, for seizures; single daily dosing at bedtime recommended because of sedation
Dosage Forms & Strengths
tablet: Schedule IV
- 15mg
- 16.2mg
- 30mg
- 32.4mg
- 60mg
- 64.8mg
- 97.2mg
- 100mg
elixir: Schedule IV
- 20mg/5mL
injectable solution: Schedule IV
- 65mg/mL
- 130mg/mL
injectable, lyophilized powder for reconstitution: Schedule IV
- 100mg/vial (Sezaby)
Status Epilepticus
Infants and children: 15-20 mg/kg IV infused at a rate not to exceed 2 mg/kg/min; not to exceed 1000 mg/dose
<60 kg: IV rate at <30 mg/min
May repeat with 5-10 mg/kg bolus dose after 15-30 min PRN; not to exceed cumulative dose of 40 mg/kg
Seizures
Neonates (<28 days): 3-5 mg/kg/day IV/PO in 1-2 divided doses
Infants: 5-6 mg/kg/day IV/PO in 1-2 divided doses
1-5 years: 6-8 mg/kg/day IV/PO in 1-2 divided doses
6-12 years: 4-6 mg/kg/day IV/PO in 1-2 divided doses
>12 years: 1-3 mg/kg/day IV/PO in 1-2 divided doses, OR 50-100 mg BID/TID
Neonatal Seizures
Sezaby only
Indicated for treatment of neonatal seizures in term and preterm infants
Loading dose
- 20 mg/kg IV over 15 minutes into large peripheral vein
-
Second loading dose
- At least 15 minutes after completing initial loading dose, may administer a second loading dose if clinically indicated
- Term infants: 20 mg/kg
- Preterm infants: 10-20 mg/kg
- Maximum total loading dose: 40 mg/kg
Maintenance dose
- Start 8-12 hr after first loading dose
- 1.5 mg/kg IV q8hr OR 2.25 mg/kg IV q12hr for up to 5 days
Sedation
Hypnotic
Preoperative Sedation
1-3 mg/kg PO/IV/IM 1-1.5 hours before procedure
Dosing Considerations
<6 years: Potential toxic dose 8 mg/kg
Antiepileptic therapeutic concentration range: 15-30 mcg/L (43-129 micromoles/L)
Long half-life permits once-daily dosing, if tolerated, for seizures; single daily dosing at bedtime recommended because of sedation
Hyperbilirubinemia (Off-label)
Neonates: 5 mg/kg/day PO/IV qDay, OR divided q12hr for 3-6 days following birth
<12 years (chronic cholestasis): 1.5-4 mg/kg PO q12hr
Encephalopathy (Orphan)
Orphan designation for treatment of neonatal hypoxic ischemic encephalopathy to prevent seizures
Orphan sponsor
- Fera Pharmaceuticals, LLC; 134 Birch Hill Road; Locust Valley, NY 11560
Neonatal Seizures (Orphan)
Orphan designation for treatment of neonatal seizures
Sponsor
- Renaissance SSA, LLC; 411 South State Street, Suite E100; Newtown, Pennsylvania 18940
Interactions
Interaction Checker
No Results

Contraindicated
Serious - Use Alternative
Significant - Monitor Closely
Minor

Contraindicated (34)
- artemether/lumefantrine
phenobarbital will decrease the level or effect of artemether/lumefantrine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration with strong CYP3A4 inducers can result in decreased serum concentrations and loss of antimalarial efficacy
- atazanavir
phenobarbital will decrease the level or effect of atazanavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
- cabotegravir
phenobarbital will decrease the level or effect of cabotegravir by increasing metabolism. Contraindicated. Cabotegravir is metabolized by UGT1A1 and UGT1A9. Strong UGT1A1 or UGT1A9 inducers decrease cabotegravir systemic exposure, thereby increasing potential for loss of virologic response.
- calcium/magnesium/potassium/sodium oxybates
phenobarbital, calcium/magnesium/potassium/sodium oxybates. Either increases effects of the other by pharmacodynamic synergism. Contraindicated. Prescribing information for sodium oxybate states coadministration with alcohol or insomnia drugs is contraindicated because of additive CNS depression.
- cariprazine
phenobarbital will decrease the level or effect of cariprazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. CYP3A4 is responsible for the formation and elimination of cariprazine's active metabolites. The effect of CYP3A4 inducers on cariprazine exposure has not been evaluated and the net effect is unclear.
- cobimetinib
phenobarbital will decrease the level or effect of cobimetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Avoid coadministration. Strong or moderate CYP3A inducers may decrease cobimetinib systemic exposure by >80% and reduce its efficacy.
- darunavir
phenobarbital will decrease the level or effect of darunavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration with phenobarbital may result in loss of therapeutic effect and development of resistance to darunavir
- dienogest/estradiol valerate
phenobarbital will decrease the level or effect of dienogest/estradiol valerate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Women should not choose estradiol valerate/dienogest as their contraceptive while using strong CYP3A4 inducers due to potential decrease in contraceptive efficacy. Estradiol valerate/dienogest should not be used for at least 28 days after discontinuation of the inducer due to possibility of decreased contraceptive efficacy.
- doravirine
phenobarbital will decrease the level or effect of doravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of doravirine with a strong CYP3A inducer may decrease doravirine plasma concentrations and/or effects. Potential for loss of virologic response and possible resistance to doravirine.
- elbasvir/grazoprevir
phenobarbital will decrease the level or effect of elbasvir/grazoprevir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. The therapeutic effect of elbasvir/grazoprevir may be reduced if coadministered with strong CYP3A inducers and is therefore contraindicated.
- elvitegravir/cobicistat/emtricitabine/tenofovir DF
phenobarbital decreases levels of elvitegravir/cobicistat/emtricitabine/tenofovir DF by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. May lead to loss of virologic response and possible resistance.
- etravirine
phenobarbital decreases levels of etravirine by increasing metabolism. Contraindicated.
- fostemsavir
phenobarbital will decrease the level or effect of fostemsavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of fostemsavir (prodrug) with strong CYP3A4 inducers significantly decreases temsavir (active moiety) plasma concentrations, which may lead to loss of virologic response and resistance.
- isavuconazonium sulfate
phenobarbital will decrease the level or effect of isavuconazonium sulfate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
- ledipasvir/sofosbuvir
phenobarbital will decrease the level or effect of ledipasvir/sofosbuvir by P-glycoprotein (MDR1) efflux transporter. Contraindicated. P-gp inducers decrease sofosbuvir levels, and therefore decrease conversion to sofosbuvir's active metabolite (GS-331007) responsible for 90% of pharmacologic effect
- lonafarnib
phenobarbital will decrease the level or effect of lonafarnib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Lonafarnib is a sensitive CYP3A4 substrate. Coadministration with strong or moderate CYP3A4 inducers is contraindicated.
- lorlatinib
phenobarbital will decrease the level or effect of lorlatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of lorlatinib with strong CYP3A inducers is contraindicated. Discontinue the strong CYP3A inducer for 3 plasma half-lives before initiating lorlatinib.
- lumacaftor/ivacaftor
phenobarbital will decrease the level or effect of lumacaftor/ivacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A inducers have minimal effect on lumacaftor exposure, but decreased ivacaftor exposure (AUC) by 57%. This may reduce the effectiveness of lumacaftor/ivacaftor. Therefore, coadministration is not recommended.
- lumefantrine
phenobarbital will decrease the level or effect of lumefantrine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration with strong CYP3A4 inducers can result in decreased serum concentrations and loss of antimalarial efficacy
- lurasidone
phenobarbital decreases levels of lurasidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Contraindicated.
- mavacamten
phenobarbital will decrease the level or effect of mavacamten by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
- naloxegol
phenobarbital will decrease the level or effect of naloxegol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Use of naloxegol with strong CYP3A4 inducers is not recommended
- nirmatrelvir
phenobarbital will decrease the level or effect of nirmatrelvir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Nirmatrelvir, a CYP3A4 substrate, is contraindicated with strong CYP3A4 inducers. Significantly reduced nirmatrelvir plasma concentrations may be associated with potential for loss of virologic response and possible resistance. Do not initiate nirmatrelvir/ritonavir immediately after discontinuing a strong 3A4 inducer owing to time needed for systemic clearance of the inducer.
- nirmatrelvir/ritonavir
phenobarbital will decrease the level or effect of nirmatrelvir/ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Nirmatrelvir, a CYP3A4 substrate, is contraindicated with strong CYP3A4 inducers. Significantly reduced nirmatrelvir plasma concentrations may be associated with potential for loss of virologic response and possible resistance. Do not initiate nirmatrelvir/ritonavir immediately after discontinuing a strong 3A4 inducer owing to time needed for systemic clearance of the inducer.
- ombitasvir/paritaprevir/ritonavir & dasabuvir (DSC)
phenobarbital will decrease the level or effect of ombitasvir/paritaprevir/ritonavir & dasabuvir (DSC) by increasing metabolism. Contraindicated. Strong CYP2C8 inducers may reduce dasabuvir levels, and therefore decreased efficacy of Viekira Pak
phenobarbital will decrease the level or effect of ombitasvir/paritaprevir/ritonavir & dasabuvir (DSC) by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A4 inducers may reduce partiaprevir and ritonavir levels, and therefore decreased efficacy of Viekira Pak - panobinostat
phenobarbital decreases levels of panobinostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A4 inducers can reduce panobinostat levels by ~70% and lead to treatment failure.
- pirfenidone
phenobarbital will decrease the level or effect of pirfenidone by affecting hepatic enzyme CYP1A2 metabolism. Contraindicated. Use of strong CYP1A2 inducers should be discontinued before initiating pirfenidone and avoided during treatment
- praziquantel
phenobarbital decreases levels of praziquantel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP450 inducers significantly decrease praziquantel blood levels.
- regorafenib
phenobarbital, regorafenib. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A4 inducers decrease regorafenib levels and increase exposure of the active metabolite M-5.
- rilpivirine
phenobarbital decreases levels of rilpivirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Contraindicated. Rilpivirine should not be co-administered with strong CYP 3A4 inducers. Potential for loss of virologic response and possible resistance to rilpivirine or to the NNRTI class.
- roflumilast
phenobarbital will decrease the level or effect of roflumilast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration not recommended; strong cytochrome P450 enzyme inducers decrease systemic exposure to roflumilast and may reduce the therapeutic effectiveness
phenobarbital will decrease the level or effect of roflumilast by affecting hepatic enzyme CYP1A2 metabolism. Contraindicated. Coadministration not recommended; strong cytochrome P450 enzyme inducers decrease systemic exposure to roflumilast and may reduce the therapeutic effectiveness - sodium oxybate
phenobarbital, sodium oxybate. Either increases effects of the other by pharmacodynamic synergism. Contraindicated. Prescribing information for sodium oxybate states coadministration with alcohol or insomnia drugs is contraindicated because of additive CNS depression.
- vandetanib
phenobarbital decreases levels of vandetanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Avoid coadministration with potent CYP3A4 inducers; these drugs reduce exposure to vandetanib by up to 40%.
- voriconazole
phenobarbital decreases levels of voriconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
Serious - Use Alternative (183)
- abemaciclib
phenobarbital will decrease the level or effect of abemaciclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of abemaciclib with strong CYP3A4 inducers reduces plasma concentration of abemaciclib and its metabolites.
- acalabrutinib
phenobarbital will decrease the level or effect of acalabrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of acalabrutinib with strong CYP3A inducers. If a strong CYP3A inducer must be used, increase acalabrutinib dose to 200 mg twice daily.
- adagrasib
phenobarbital will decrease the level or effect of adagrasib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
adagrasib will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C9/10 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of adagrasib, a CYP2C9 inhibitor, with sensitive CYP2C9 substrates unless otherwise recommended in the prescribing information for these substrates. - afatinib
phenobarbital decreases levels of afatinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Increase afatinib daily dose by 10 mg as tolerated if chronic therapy with P-gp inducer required; resume previous afatinib dose 2-3 days after P-gp inducer discontinued.
- alosetron
phenobarbital will decrease the level or effect of alosetron by affecting hepatic enzyme CYP1A2 metabolism. Avoid or Use Alternate Drug.
- alpelisib
phenobarbital will decrease the level or effect of alpelisib by pharmacodynamic synergism. Avoid or Use Alternate Drug. Avoid coadministration of alpelisib (CYP3A4 substrate) with strong CYP3A4 inducers.
phenobarbital will decrease the level or effect of alpelisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. - antithrombin alfa
phenobarbital decreases effects of antithrombin alfa by increasing metabolism. Avoid or Use Alternate Drug.
- antithrombin III
phenobarbital decreases effects of antithrombin III by increasing metabolism. Avoid or Use Alternate Drug.
- apalutamide
apalutamide will decrease the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug. Coadministration of apalutamide, a strong CYP2C19 inducer, with drugs that are CYP2C19 substrates can result in lower exposure to these medications. Avoid or substitute another drug for these medications when possible. Evaluate for loss of therapeutic effect if medication must be coadministered.
- apixaban
phenobarbital will decrease the level or effect of apixaban by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
- apremilast
phenobarbital will decrease the level or effect of apremilast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with strong CYP inducers results in a significant decrease of systemic exposure of apremilast, which may result in loss of efficacy
- argatroban
phenobarbital decreases effects of argatroban by increasing metabolism. Avoid or Use Alternate Drug.
- avapritinib
phenobarbital will decrease the level or effect of avapritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- axitinib
phenobarbital decreases levels of axitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Selection of concomitant medication with no or minimal CYP3A4 induction potential is recommended.
- bedaquiline
phenobarbital will decrease the level or effect of bedaquiline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of bedaquiline with strong CYP3A4 inducers due to potential for decreased therapeutic effect
- bemiparin
phenobarbital decreases effects of bemiparin by increasing metabolism. Avoid or Use Alternate Drug.
- benzhydrocodone/acetaminophen
benzhydrocodone/acetaminophen, phenobarbital. 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.
benzhydrocodone/acetaminophen and phenobarbital both increase sedation. Avoid or Use Alternate Drug. Limit use to patients for whom alternative treatment options are inadequate - berotralstat
phenobarbital decreases levels of berotralstat by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.
- bictegravir
phenobarbital will decrease the level or effect of bictegravir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of strong CYP3A and UGT1A1 inducers can substantially decrease bictegravir plasma concentrations. This may result in the loss of therapeutic effect and development of resistance to bictegravir. Coadministration with another anticonvulsant should be considered.
- bivalirudin
phenobarbital decreases effects of bivalirudin by increasing metabolism. Avoid or Use Alternate Drug.
- bosutinib
phenobarbital decreases levels of bosutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A4 inducers decreased bosutinib plasma concentration by ~85%.
- bremelanotide
bremelanotide will decrease the level or effect of phenobarbital 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.
- brigatinib
phenobarbital will decrease the level or effect of brigatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with strong CYP3A4 inducers may decrease brigatinib efficacy.
- buprenorphine subdermal implant
buprenorphine subdermal implant and phenobarbital both increase sedation. Avoid or Use Alternate Drug. Limit use to patients for whom alternative treatment options are inadequate
- buprenorphine transdermal
buprenorphine transdermal and phenobarbital both increase sedation. Avoid or Use Alternate Drug. Limit use to patients for whom alternative treatment options are inadequate
- buprenorphine, long-acting injection
buprenorphine, long-acting injection and phenobarbital both increase sedation. Avoid or Use Alternate Drug. Limit use to patients for whom alternative treatment options are inadequate
- cabozantinib
phenobarbital will decrease the level or effect of cabozantinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of cabozantinib with strong CYP3A4 inducers. If a strong CYP3A4 inducer is required, increase cabozantinib dose by 40 mg/day (Cometriq) or by 20 mg/day (Cabometyx). Resume previous dose 2-3 days after strong CYP3A4 inducer discontinued.
- capmatinib
phenobarbital will decrease the level or effect of capmatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- ceritinib
phenobarbital decreases levels of ceritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- cobicistat
phenobarbital will decrease the level or effect of cobicistat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration is necessary, monitor for lack or loss of virologic response from cobicistat
- copanlisib
phenobarbital will decrease the level or effect of copanlisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of copanlisib with strong CYP3A4 inducers.
- dabigatran
phenobarbital will decrease the level or effect of dabigatran by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Avoid coadministration. P-gp inducers reduce systemic exposure of dabigatran
- dabrafenib
phenobarbital decreases levels of dabrafenib by increasing metabolism. Avoid or Use Alternate Drug. Strong CYP2C8 inducers may decrease dabrafenib levels.
phenobarbital decreases levels of dabrafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. - dalteparin
phenobarbital decreases effects of dalteparin by increasing metabolism. Avoid or Use Alternate Drug.
- dantrolene
phenobarbital will decrease the level or effect of dantrolene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- daridorexant
phenobarbital will decrease the level or effect of daridorexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- darolutamide
phenobarbital will increase the level or effect of darolutamide by Other (see comment). Avoid or Use Alternate Drug. Darolutamide is a P-gp and CYP3A4 substrate. Avoid coadminstration of darolutamide with combined P-gp and strong or moderate CYP3A4 inducers.
- deflazacort
phenobarbital will decrease the level or effect of deflazacort by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of deflazacort with moderate or strong CYP3A4 inducers.
- dexlansoprazole
phenobarbital will decrease the level or effect of dexlansoprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- dihydroergotamine
phenobarbital will decrease the level or effect of dihydroergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- dihydroergotamine intranasal
phenobarbital will decrease the level or effect of dihydroergotamine intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- dolutegravir
phenobarbital will decrease the level or effect of dolutegravir by increasing metabolism. Avoid or Use Alternate Drug. Avoid coadministration; insufficient data to recommend dosage adjustment
- dronedarone
phenobarbital will decrease the level or effect of dronedarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- duloxetine
phenobarbital will decrease the level or effect of duloxetine by affecting hepatic enzyme CYP1A2 metabolism. Avoid or Use Alternate Drug.
- duvelisib
phenobarbital will decrease the level or effect of duvelisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with a strong CYP3A inducer decreases duvelisib area under the curve (AUC), which may reduce duvelisib efficacy.
- edoxaban
phenobarbital will decrease the level or effect of edoxaban by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Avoid coadministration of edoxaban with potent P-gp inducers
- elacestrant
phenobarbital will decrease the level or effect of elacestrant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- eliglustat
phenobarbital will decrease the level or effect of eliglustat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A inducers significantly decreases eliglustat exposure; coadministration not recommended
- elvitegravir
phenobarbital will decrease the level or effect of elvitegravir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid; coadministration with CYP3A inducers may result in decreased plasma concentrations of elvitegravir and/or a concomitantly administered protease inhibitor and lead to loss of therapeutic effect and to possible resistance
- encorafenib
phenobarbital will decrease the level or effect of encorafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- enoxaparin
phenobarbital decreases effects of enoxaparin by increasing metabolism. Avoid or Use Alternate Drug.
- entrectinib
phenobarbital will decrease the level or effect of entrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- enzalutamide
phenobarbital will decrease the level or effect of enzalutamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- erdafitinib
phenobarbital will decrease the level or effect of erdafitinib by altering metabolism. Avoid or Use Alternate Drug. Avoid coadministration of strong CYP2C9 or CYP3A4 inducers with erdafitinib.
- ergotamine
phenobarbital will decrease the level or effect of ergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- erythromycin base
phenobarbital will decrease the level or effect of erythromycin base by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- erythromycin ethylsuccinate
phenobarbital will decrease the level or effect of erythromycin ethylsuccinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- erythromycin lactobionate
phenobarbital will decrease the level or effect of erythromycin lactobionate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- erythromycin stearate
phenobarbital will decrease the level or effect of erythromycin stearate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- esomeprazole
phenobarbital will decrease the level or effect of esomeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- eszopiclone
phenobarbital will decrease the level or effect of eszopiclone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- ethinylestradiol
phenobarbital will decrease the level or effect of ethinylestradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. The efficacy of hormonal contraceptives may be reduced. Use of a nonhormonal contraceptive is recommended.
- everolimus
phenobarbital will decrease the level or effect of everolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
phenobarbital will decrease the level or effect of everolimus by P-glycoprotein (MDR1) efflux transporter. Contraindicated. - fedratinib
phenobarbital will decrease the level or effect of fedratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Effect of coadministering a strong CYP3A4 inducer with fedratinib has not been studied.
- fexinidazole
phenobarbital will increase the level or effect of fexinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. CYP450 inducers may significantly increase plasma concentrations of fexinidazole?s active metabolites: fexinidazole sulfoxide (M1) and fexinidazole sulfone (M2). M2 plasma concentrations associated with increased QT prolongation risks.
- finerenone
phenobarbital will decrease the level or effect of finerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- flurazepam
phenobarbital will decrease the level or effect of flurazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- fondaparinux
phenobarbital decreases effects of fondaparinux by increasing metabolism. Avoid or Use Alternate Drug.
- fostamatinib
phenobarbital will decrease the level or effect of fostamatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- ganaxolone
phenobarbital will decrease the level or effect of ganaxolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of ganaxolone with moderate or strong CYP3A4 inducers. If coadministration unavoidable, consider increasing ganaxolone dose; however, do not exceed maximum daily dose for weight.
- gilteritinib
phenobarbital will decrease the level or effect of gilteritinib by Other (see comment). Avoid or Use Alternate Drug. Gilteritinib is a P-gp and CYP3A4 substrates. Coadministration of gilteritinib with a combined P-gp and strong CYP3A inducer decreases gilteritinib exposure and efficacy.
- glasdegib
phenobarbital will decrease the level or effect of glasdegib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of glasdegib with strong CYP3A inducers.
- heparin
phenobarbital decreases effects of heparin by increasing metabolism. Avoid or Use Alternate Drug.
- hydrocodone
hydrocodone, phenobarbital. 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.
- ibrutinib
phenobarbital decreases levels of ibrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A inducers decrease ibrutinib plasma concentrations by ~10-fold.
- idelalisib
phenobarbital will decrease the level or effect of idelalisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration; strong CYP3A4 inducers significantly decrease idelalisib systemic exposure
- infigratinib
phenobarbital will decrease the level or effect of infigratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- irinotecan
phenobarbital will decrease the level or effect of irinotecan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- irinotecan liposomal
phenobarbital will decrease the level or effect of irinotecan liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- isocarboxazid
isocarboxazid, phenobarbital. Other (see comment). Avoid or Use Alternate Drug. Comment: CNS depressants such as barbiturates should not be used in combination with isocarboxazid.
- isosorbide dinitrate
phenobarbital will decrease the level or effect of isosorbide dinitrate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- isosorbide mononitrate
phenobarbital will decrease the level or effect of isosorbide mononitrate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- istradefylline
phenobarbital will decrease the level or effect of istradefylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of istradefylline with strong CYP3A4 inducers.
- ivabradine
phenobarbital will decrease the level or effect of ivabradine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of ivabradine with moderate CYP3A4 inducers.
- ivacaftor
phenobarbital decreases levels of ivacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration with strong CYP3A4 inducers; systemic exposure of ivacaftor substantially reduced (ie, ~9-fold).
- ivosidenib
phenobarbital will decrease the level or effect of ivosidenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of ivosidenib with strong CYP3A4 inducers decreased ivosidenib plasma concentrations.
- ixazomib
phenobarbital will decrease the level or effect of ixazomib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of ixazomib with strong CYP3A inducers. Strong inducers have been shown to decrease ixazomib Cmax by 54% and AUC by 74%.
- larotrectinib
phenobarbital will decrease the level or effect of larotrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of larotrectinib with strong CYP3A4 inducers is unavoidable, double larotrectinib dose. Resume prior larotrectinib dose once CYP3A4 inducer discontinued for 3-5 half-lives
- lefamulin
phenobarbital will decrease the level or effect of lefamulin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of lefamulin with strong or moderate CYP3A inducers unless the benefit outweighs risks. Monitor for reduced efficacy.
- lemborexant
phenobarbital will decrease the level or effect of lemborexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- lenacapavir
phenobarbital will decrease the level or effect of lenacapavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of lenacapavir with moderate CYP3A4 inducers.
- leniolisib
phenobarbital will decrease the level or effect of leniolisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- letermovir
phenobarbital will decrease the level or effect of letermovir by Other (see comment). Avoid or Use Alternate Drug. Coadministration of letermovir with UCT1A1/3 inducers is not recommended.
phenobarbital will decrease the level or effect of letermovir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Coadministration of letermovir with P-gp inducers is not recommended. - lomitapide
phenobarbital will decrease the level or effect of lomitapide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- lovastatin
phenobarbital will decrease the level or effect of lovastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- lumateperone
phenobarbital will decrease the level or effect of lumateperone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- lurbinectedin
phenobarbital will decrease the level or effect of lurbinectedin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- macimorelin
phenobarbital will decrease the level or effect of macimorelin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Potential for false positive test results if macimorelin and strong CYP3A4 inducers are coadministered. Discontinue strong CYP3A4 inducer, allowing for sufficient washout time, before testing.
- macitentan
phenobarbital will decrease the level or effect of macitentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministering macitentan with strong CYP3A4 inducers
- mestranol
phenobarbital decreases levels of mestranol by increasing metabolism. Avoid or Use Alternate Drug. May result in contraceptive failure.
- methoxyflurane
phenobarbital increases toxicity of methoxyflurane by increasing metabolism. Contraindicated. Increased metabolism of methoxyflurane to nephrotoxic compounds.
- metoclopramide intranasal
phenobarbital, 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.
- midostaurin
phenobarbital will decrease the level or effect of midostaurin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A4 inducers may decrease midostaurin concentrations resulting in reduced efficacy.
- mobocertinib
phenobarbital will decrease the level or effect of mobocertinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- modafinil
phenobarbital will decrease the level or effect of modafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- naldemedine
phenobarbital will decrease the level or effect of naldemedine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration with strong CYP3A4 inducers.
- neratinib
phenobarbital will decrease the level or effect of neratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of neratinib with strong/moderate CYP3A4 inducers.
- netupitant/palonosetron
phenobarbital will decrease the level or effect of netupitant/palonosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Netupitant is mainly metabolized by CYP3A4; avoid use in patients who are chronically using a strong CYP3A4 inducer
- nintedanib
phenobarbital decreases levels of nintedanib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Avoid coadministration, particularly for P-gp inducers that are also CYP3A4 inducers; nintedanib is a substrate of P-gp and to a less extent CYP3A4.
- norethindrone
phenobarbital will decrease the level or effect of norethindrone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).
- norethindrone acetate
phenobarbital will decrease the level or effect of norethindrone acetate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).
- norethindrone transdermal
phenobarbital will decrease the level or effect of norethindrone transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).
- norgestrel
phenobarbital will decrease the level or effect of norgestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Contraceptive failure is possible owing to decreased serum concentration of norgestrel. Advise patients to use an alternative method of contraception or a back-up method during coadministration, and to continue back-up contraception for 28 days after discontinuing the strong CYP3A4 inducer to ensure contraceptive reliability
- olaparib
phenobarbital will decrease the level or effect of olaparib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of olaparib with strong CYP3A4 inducers.
- olopatadine intranasal
phenobarbital and olopatadine intranasal both increase sedation. Avoid or Use Alternate Drug. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.
- olutasidenib
phenobarbital will decrease the level or effect of olutasidenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong or moderate CYP3A inducers decrease olutasidenib (a CYP3A4 substrate) plasma concentrations and efficacy.
- omaveloxolone
phenobarbital will decrease the level or effect of omaveloxolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- omeprazole
phenobarbital will decrease the level or effect of omeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- osimertinib
phenobarbital will decrease the level or effect of osimertinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of osimertinib with strong CYP3A inducers.
- ozanimod
phenobarbital will decrease the level or effect of ozanimod by Other (see comment). Avoid or Use Alternate Drug. Coadministration of ozanimod (a CYP2C8 substrate) with strong CYP2C8 inducers decreases the exposure of the active metabolites (CC112273 and CC1084037) of ozanimod, which may decrease the effiicacy of ozanimod. Therefore, coadministration of ozanimod with strong CYP2C8 inducers is not recommended.
- palbociclib
phenobarbital will decrease the level or effect of palbociclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A inducers decrease palbociclib plasma exposure by ~85%.
- palovarotene
phenobarbital will decrease the level or effect of palovarotene by affecting hepatic enzyme CYP2E1 metabolism. Avoid or Use Alternate Drug.
- pemigatinib
phenobarbital will decrease the level or effect of pemigatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- perampanel
phenobarbital will decrease the level or effect of perampanel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- pexidartinib
phenobarbital will decrease the level or effect of pexidartinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- phenindione
phenobarbital decreases effects of phenindione by increasing metabolism. Avoid or Use Alternate Drug.
- pirtobrutinib
phenobarbital will decrease the level or effect of pirtobrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- pomalidomide
phenobarbital decreases levels of pomalidomide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
phenobarbital decreases levels of pomalidomide by affecting hepatic enzyme CYP1A2 metabolism. Avoid or Use Alternate Drug. - ponatinib
phenobarbital decreases levels of ponatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid unless the coadministration outweighs the possible risk of ponatinib underexposure; monitor for signs of reduced efficacy.
- pralsetinib
phenobarbital will decrease the level or effect of pralsetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid, double current pralsetinib dose starting on Day 7 of coadministration with strong CYP3A inducer. After inducer has been discontinued for at least 14 days, resume previous pralsetinib dose.
- pretomanid
phenobarbital will decrease the level or effect of pretomanid by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Pretomanid is a CYP3A4 substrate. Avoid coadministration of strong or moderate CYP3A4 inducers
- protamine
phenobarbital decreases effects of protamine by increasing metabolism. Avoid or Use Alternate Drug.
- quizartinib
phenobarbital will decrease the level or effect of quizartinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- ranolazine
phenobarbital will decrease the level or effect of ranolazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- ribociclib
phenobarbital will decrease the level or effect of ribociclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of ribociclib with strong CYP3A inducers should be avoided.
- rimegepant
phenobarbital will decrease the level or effect of rimegepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- ripretinib
phenobarbital will decrease the level or effect of ripretinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with a strong CYP3A inhibitor will decrease systemic exposure to ripretinib and its active metabolite (DP-5439), which may decrease risk of adverse reactions.
- ritlecitinib
phenobarbital will decrease the level or effect of ritlecitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with strong CYP3A inducers may decrease ritlecitinib AUC and peak plasma concentration, which may result in loss of or reduced efficacy.
- rivaroxaban
phenobarbital will decrease the level or effect of rivaroxaban by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
- rolapitant
phenobarbital will decrease the level or effect of rolapitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Long-term coadministration of strong CYP3A4 inducers with rolapitant may significantly decrease rolapitant efficacy.
- romidepsin
phenobarbital will decrease the level or effect of romidepsin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- ropeginterferon alfa 2b
ropeginterferon alfa 2b and phenobarbital both increase Other (see comment). Avoid or Use Alternate Drug. Narcotics, hypnotics or sedatives can produce additive neuropsychiatric side effects. Avoid use and monitor patients receiving the combination for effects of excessive CNS toxicity.
- selinexor
selinexor, phenobarbital. 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
phenobarbital will decrease the level or effect of selpercatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- selumetinib
phenobarbital will decrease the level or effect of selumetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- sildenafil
phenobarbital will decrease the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Potent CYP3A4 inducers are expected to cause substantial decreases in sildenafil plasma levels
- silodosin
phenobarbital will decrease the level or effect of silodosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- simvastatin
phenobarbital will decrease the level or effect of simvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- siponimod
phenobarbital will decrease the level or effect of siponimod by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of siponimod with a drug that causes moderate CYP2C9 plus a moderate or strong CYP3A4 inducer is not recommended. Coadministration with moderate or strong CYP3A4 inducers alone is not recommended for patients with CYP2C9*1/*3 and*2/*3 genotype.
- sirolimus
phenobarbital will decrease the level or effect of sirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- sofosbuvir
phenobarbital will decrease the level or effect of sofosbuvir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. P-gp inducers decrease sofosbuvir levels, and therefore decrease conversion to sofosbuvir's active metabolite (GS-331007) responsible for 90% of pharmacologic effect
- sofosbuvir/velpatasvir
phenobarbital will decrease the level or effect of sofosbuvir/velpatasvir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Sofosbuvir and velpatasvir are substrates of the drug transporter P-gp. Potent P-gp inducers may significantly decrease sofosbuvir and velpatasvir plasma concentrations, leading to potentially reduced therapeutic effect.
phenobarbital will decrease the level or effect of sofosbuvir/velpatasvir by affecting hepatic enzyme CYP2B6 metabolism. Avoid or Use Alternate Drug. Velpatasvir is a substrate of CYP2B6, CYP2C8, and CYP3A4. Drugs that are moderate-to-potent inducers of CYP2B6, CYP2C8, or CYP3A4 may significantly decrease velpatasvir plasma concentrations, leading to potentially reduced therapeutic effect.
phenobarbital will decrease the level or effect of sofosbuvir/velpatasvir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Velpatasvir is a substrate of CYP2B6, CYP2C8, and CYP3A4. Drugs that are moderate-to-potent inducers of CYP2B6, CYP2C8, or CYP3A4 may significantly decrease velpatasvir plasma concentrations, leading to potentially reduced therapeutic effect. - sonidegib
phenobarbital will decrease the level or effect of sonidegib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sonidegib with strong or moderate CYP3A4 inducers.
- sorafenib
phenobarbital will decrease the level or effect of sorafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- sotagliflozin
phenobarbital will decrease the level or effect of sotagliflozin by Other (see comment). Avoid or Use Alternate Drug. Glucuronidation by UGT1A9, to form the 3-O-glucuronide, was identified as a major metabolic pathway for sotagliflozin. Coadministration of UGT1A9 inducers may decrease exposure to sotagliflozin, which may decrease efficacy.
- sotorasib
phenobarbital will decrease the level or effect of sotorasib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- sparsentan
phenobarbital will decrease the level or effect of sparsentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- stiripentol
phenobarbital will decrease the level or effect of stiripentol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid coadministration of stiripentol with strong CYP3A4 inducers, increase stiripentol dose.
phenobarbital will decrease the level or effect of stiripentol by affecting hepatic enzyme CYP1A2 metabolism. Avoid or Use Alternate Drug. If unable to avoid coadministration of stiripentol with strong CYP1A2 inducers, increase stiripentol dose.
stiripentol, phenobarbital. Either increases effects of the other by sedation. Avoid or Use Alternate Drug. Concomitant use stiripentol with other CNS depressants, including alcohol, may increase the risk of sedation and somnolence. - sufentanil SL
sufentanil SL, phenobarbital. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration may result in hypotension, profound sedation, respiratory depression, coma, and death. 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.
- tamsulosin
phenobarbital will decrease the level or effect of tamsulosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- tazemetostat
phenobarbital will decrease the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- tetracycline
phenobarbital will decrease the level or effect of tetracycline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- tezacaftor
phenobarbital will decrease the level or effect of tezacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- tivozanib
phenobarbital will decrease the level or effect of tivozanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- tizanidine
phenobarbital will decrease the level or effect of tizanidine by affecting hepatic enzyme CYP1A2 metabolism. Avoid or Use Alternate Drug.
- tolvaptan
phenobarbital will decrease the level or effect of tolvaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- trabectedin
phenobarbital will decrease the level or effect of trabectedin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- tucatinib
phenobarbital will decrease the level or effect of tucatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
phenobarbital will decrease the level or effect of tucatinib by Other (see comment). Avoid or Use Alternate Drug. Coadministration of tucatinib (a CYP2C8 substrate) with a strong or moderate CYP2C8 inducer decreases tucatinib plasma concentrations. - ubrogepant
phenobarbital will decrease the level or effect of ubrogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- ulipristal
phenobarbital will decrease the level or effect of ulipristal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- upadacitinib
phenobarbital will decrease the level or effect of upadacitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid upadacitinib coadministration with strong CYP3A4 inducers.
- valbenazine
phenobarbital will decrease the level or effect of valbenazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Concomitant use not recommended.
- valerian
valerian increases effects of phenobarbital by pharmacodynamic synergism. Avoid or Use Alternate Drug. May enhance CNS depression.
- velpatasvir
phenobarbital will decrease the level or effect of velpatasvir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- vemurafenib
phenobarbital decreases levels of vemurafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- venetoclax
phenobarbital will decrease the level or effect of venetoclax by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of venetoclax with strong or moderate CYP3A inducers. Consider alternative treatment with agents that have less CYP3A induction.
- voclosporin
phenobarbital will decrease the level or effect of voclosporin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- vonoprazan
phenobarbital will decrease the level or effect of vonoprazan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- vorapaxar
phenobarbital decreases levels of vorapaxar by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- vortioxetine
phenobarbital will decrease the level or effect of vortioxetine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- voxelotor
phenobarbital will decrease the level or effect of voxelotor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Voxelotor is primarily metabolized by CYP3A4. Avoid coadministration with moderate or strong CYP3A4 inducers. If unable to avoid coadministration, increase voxelotor dose (see Dosage Modifications).
- voxilaprevir
phenobarbital will decrease the level or effect of voxilaprevir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- zanubrutinib
phenobarbital will decrease the level or effect of zanubrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
Monitor Closely (455)
- abiraterone
phenobarbital decreases levels of abiraterone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Avoid coadministration of abiraterone with strong CYP3A4 inducers; if a strong CYP3A4 inducer must be used, increase abiraterone dosage frequency from once daily to twice daily.
- acebutolol
phenobarbital decreases levels of acebutolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- acrivastine
acrivastine and phenobarbital both increase sedation. Use Caution/Monitor.
- albuterol
phenobarbital increases and albuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- alfentanil
phenobarbital and alfentanil both increase sedation. Use Caution/Monitor.
- almotriptan
phenobarbital will decrease the level or effect of almotriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- alprazolam
phenobarbital will decrease the level or effect of alprazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital and alprazolam both increase sedation. Use Caution/Monitor. - amikacin
phenobarbital will decrease the level or effect of amikacin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- amiodarone
phenobarbital will decrease the level or effect of amiodarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- amisulpride
amisulpride and phenobarbital both increase sedation. Use Caution/Monitor.
- amitriptyline
phenobarbital will decrease the level or effect of amitriptyline by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of amitriptyline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.
phenobarbital will decrease the level or effect of amitriptyline by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
phenobarbital and amitriptyline both increase sedation. Use Caution/Monitor. - amlodipine
phenobarbital will decrease the level or effect of amlodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- amobarbital
amobarbital and phenobarbital both increase sedation. Use Caution/Monitor.
- amoxapine
phenobarbital and amoxapine both increase sedation. Use Caution/Monitor.
- apomorphine
phenobarbital and apomorphine both increase sedation. Use Caution/Monitor.
- aprepitant
phenobarbital will decrease the level or effect of aprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- arformoterol
phenobarbital increases and arformoterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- aripiprazole
phenobarbital will decrease the level or effect of aripiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital and aripiprazole both increase sedation. Use Caution/Monitor. - armodafinil
phenobarbital increases and armodafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- artesunate
phenobarbital will decrease the level or effect of artesunate by increasing metabolism. Use Caution/Monitor. Coadministration may decrease AUC and peak plasma concentration of active artesunate metabolite (DHA) by inducing UGT. Monitor for decreased efficacy.
- asenapine
asenapine and phenobarbital both increase sedation. Use Caution/Monitor.
- asenapine transdermal
asenapine transdermal and phenobarbital both increase sedation. Use Caution/Monitor.
- atenolol
phenobarbital decreases levels of atenolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- atogepant
phenobarbital will decrease the level or effect of atogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Recommended atogepant dosage with concomitant use of strong or moderate CYP3A4 inducers is 30 mg or 60 mg qDay.
- atorvastatin
phenobarbital will decrease the level or effect of atorvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of atorvastatin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - avanafil
phenobarbital will decrease the level or effect of avanafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. For patients with ED, monitor response carefully because of potential for decreased effectiveness.
- avapritinib
avapritinib and phenobarbital both increase sedation. Use Caution/Monitor.
- avatrombopag
phenobarbital will decrease the level or effect of avatrombopag by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. When treating ITP, coadministration of avatrombopag with a moderate or strong dual CYP2C9/3A4 inducer requires an increased avatrombopag starting dose. Refer to drug monograph for specific recommendations.
- azelastine
azelastine and phenobarbital both increase sedation. Use Caution/Monitor.
- baclofen
phenobarbital and baclofen both increase sedation. Use Caution/Monitor.
- bazedoxifene/conjugated estrogens
phenobarbital will decrease the level or effect of bazedoxifene/conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of bazedoxifene/conjugated estrogens by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
phenobarbital decreases levels of bazedoxifene/conjugated estrogens by increasing metabolism. Use Caution/Monitor. A reduction in bazedoxifene exposure may be associated with an increase risk of endometrial hyperplasia. - belladonna and opium
phenobarbital and belladonna and opium both increase sedation. Use Caution/Monitor.
- belumosudil
phenobarbital will decrease the level or effect of belumosudil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase belumosudil dosage to 200 mg PO BID when coadministered with strong CYP3A inducers.
- benazepril
phenobarbital, benazepril. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Enhanced hypotensive effects.
- bendamustine
phenobarbital decreases levels of bendamustine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor. Concentrations of active metabolites may be increased.
- benperidol
phenobarbital and benperidol both increase sedation. Use Caution/Monitor.
- benzhydrocodone/acetaminophen
phenobarbital will decrease the level or effect of benzhydrocodone/acetaminophen by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Caution when discontinuing CYP3A4 inducers that are coadministered with benzhydrocodone (prodrug of hydrocodone); plasma concentrations of hydrocodone may increase and can result in potentially fatal respiratory depression.
- benzphetamine
phenobarbital increases and benzphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- betaxolol
phenobarbital decreases levels of betaxolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- bexagliflozin
phenobarbital will decrease the level or effect of bexagliflozin by Other (see comment). Modify Therapy/Monitor Closely. Bexagliflozin is a major substrate of UGT1A9. If coadministered with a UGT1A9 inducer, consider adding another antihyperglycemic agent in patients requiring additional glycemic control.
- bexarotene
phenobarbital will decrease the level or effect of bexarotene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- bisoprolol
phenobarbital decreases levels of bisoprolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- blinatumomab
blinatumomab increases levels of phenobarbital by decreasing metabolism. Modify Therapy/Monitor Closely. Treatment initiation causes transient release of cytokines that may suppress CYP450 enzymes; highest drug-drug interaction risk is during the first 9 days of the first cycle and the first 2 days of the 2nd cycle in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index.
- bortezomib
phenobarbital will decrease the level or effect of bortezomib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- brentuximab vedotin
phenobarbital decreases levels of brentuximab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- brexanolone
brexanolone, phenobarbital. Either increases toxicity of the other by sedation. Use Caution/Monitor.
- brexpiprazole
phenobarbital will decrease the level or effect of brexpiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Double brexpiprazole dose over 1-2 weeks if administered with a strong CYP3A4 inducer.
brexpiprazole and phenobarbital both increase sedation. Use Caution/Monitor. - brimonidine
brimonidine and phenobarbital both increase sedation. Use Caution/Monitor.
- brivaracetam
phenobarbital will decrease the level or effect of brivaracetam by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Brivaracetam plasma concentration decreased by 19%.
brivaracetam and phenobarbital both increase sedation. Use Caution/Monitor. - brodalumab
brodalumab, phenobarbital. Other (see comment). Use Caution/Monitor. Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, brodalumab could normalize the formation of CYP450 enzymes. Upon initiation or discontinuation of brodalumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.
- bromocriptine
phenobarbital will decrease the level or effect of bromocriptine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- brompheniramine
brompheniramine and phenobarbital both increase sedation. Use Caution/Monitor.
- budesonide
phenobarbital will decrease the level or effect of budesonide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of budesonide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - bupivacaine implant
phenobarbital, bupivacaine implant. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Local anesthetics may increase the risk of developing methemoglobinemia when concurrently exposed to drugs that also cause methemoglobinemia.
- buprenorphine
phenobarbital and buprenorphine both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of buprenorphine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - buprenorphine buccal
phenobarbital and buprenorphine buccal both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of buprenorphine buccal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - buprenorphine subdermal implant
phenobarbital will decrease the level or effect of buprenorphine subdermal implant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Monitor patients already on buprenorphine subdermal implant who require newly-initiated treatment with CYP3A4 inducer for signs and symptoms of withdrawal. If the dose of the concomitant CYP3A4 inducer cannot be reduced or discontinued, implant removal may be necessary and the patient should then be treated with a buprenorphine dosage form that permits dose adjustments. If a CYP3A4 inducer is discontinued in a patient who has been stabilized on buprenorphine, monitor the patient for overmedication.
- buprenorphine transdermal
phenobarbital will decrease the level or effect of buprenorphine transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- buprenorphine, long-acting injection
phenobarbital will decrease the level or effect of buprenorphine, long-acting injection by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Patients who transfer to buprenorphine long-acting injection from transmucosal buprenorphine coadministered with CYP3A4 inducers should be monitored to ensure buprenorphine plasma levels are adequate. If the buprenorphine dose is inadequate and the CYP3A4 inducer cannot be reduced or discontinued, transition the patient back to a buprenorphine formulation that permits dose adjustments.
- bupropion
phenobarbital will decrease the level or effect of bupropion by increasing metabolism. Use Caution/Monitor. Decrease levels of bupropion.
- buspirone
phenobarbital will decrease the level or effect of buspirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- butabarbital
butabarbital and phenobarbital both increase sedation. Use Caution/Monitor.
- butalbital
butalbital and phenobarbital both increase sedation. Use Caution/Monitor.
- butorphanol
phenobarbital and butorphanol both increase sedation. Use Caution/Monitor.
- cabazitaxel
phenobarbital will decrease the level or effect of cabazitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of strong CYP3A4 inducers may decrease cabazitaxel concentrations. Avoid coadministration.
- caffeine
phenobarbital increases and caffeine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- calcifediol
phenobarbital, calcifediol. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Drugs that stimulate microsomal hydroxylation reduce the half-life of calcifediol.
- calcitriol
phenobarbital will decrease the level or effect of calcitriol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- canagliflozin
phenobarbital decreases levels of canagliflozin by increasing metabolism. Use Caution/Monitor. Coadministration with potent UGT enzyme inducers: Consider increasing dose to 300 mg qDay if 100 mg/day tolerate and additional glycemic control required (eGFR must be >60 mL/min/1.73 m2 to increase dose); if eGFR <60 mL/min/1.73 m2, consider using a different antihyperglycemic agent.
- cannabidiol
phenobarbital will decrease the level or effect of cannabidiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Consider an increase in cannabidiol dosage (based on clinical response and tolerability) when coadministered with a strong CYP3A4 inducer.
cannabidiol will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Consider reducing the dose of sensitive CYP2C19 substrates, as clinically appropriate, when coadministered with cannabidiol. - captopril
phenobarbital, captopril. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Both drugs lower blood pressure. Monitor blood pressure.
- carbamazepine
phenobarbital will decrease the level or effect of carbamazepine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- carbinoxamine
carbinoxamine and phenobarbital both increase sedation. Use Caution/Monitor.
- carisoprodol
phenobarbital and carisoprodol both increase sedation. Use Caution/Monitor.
- carvedilol
phenobarbital will decrease the level or effect of carvedilol by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
phenobarbital decreases levels of carvedilol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers. - celiprolol
phenobarbital decreases levels of celiprolol by increasing metabolism. Use Caution/Monitor. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- cenobamate
cenobamate will increase the level or effect of phenobarbital by unspecified interaction mechanism. Modify Therapy/Monitor Closely. Concomitant use of phenobarbital with multiple doses of cenobamate 200 mg qDay increased carbamazepine mean Cmax and AUC by 34% and 37%. Consider a dose reduction of phenobarbital, as clinically appropriate, when used concomitantly with cenobamate.
cenobamate will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Consider a dose reduction of CYP2C19 substrates, as clinically appropriate, when used concomitantly with cenobamate.
cenobamate, phenobarbital. Either increases effects of the other by sedation. Use Caution/Monitor. - chloral hydrate
phenobarbital and chloral hydrate both increase sedation. Use Caution/Monitor.
- chloramphenicol
chloramphenicol increases levels of phenobarbital by decreasing metabolism. Use Caution/Monitor.
- chlordiazepoxide
phenobarbital and chlordiazepoxide both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of chlordiazepoxide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - chloroquine
phenobarbital will decrease the level or effect of chloroquine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- chlorpheniramine
chlorpheniramine and phenobarbital both increase sedation. Use Caution/Monitor.
- chlorpromazine
phenobarbital and chlorpromazine both increase sedation. Use Caution/Monitor.
- chlorzoxazone
phenobarbital and chlorzoxazone both increase sedation. Use Caution/Monitor.
- cilostazol
phenobarbital will decrease the level or effect of cilostazol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- cinacalcet
phenobarbital will decrease the level or effect of cinacalcet by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- cinnarizine
cinnarizine and phenobarbital both increase sedation. Use Caution/Monitor.
- citalopram
phenobarbital will decrease the level or effect of citalopram by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- clemastine
clemastine and phenobarbital both increase sedation. Use Caution/Monitor.
- clobazam
phenobarbital, 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
phenobarbital will decrease the level or effect of clomipramine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of clomipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.
phenobarbital and clomipramine both increase sedation. Use Caution/Monitor. - clonazepam
phenobarbital and clonazepam both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of clonazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - clopidogrel
phenobarbital will increase the level or effect of clopidogrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inducers may increase the metabolism of clopidogrel to its active metabolite. Monitor patients for potential increase in antiplatelet effects when CYP3A4 inducers are used in combination with clopidogrel
- clorazepate
phenobarbital and clorazepate both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of clorazepate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - clozapine
phenobarbital will decrease the level or effect of clozapine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of clozapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital and clozapine both increase sedation. Use Caution/Monitor. - codeine
phenobarbital and codeine both increase sedation. Use Caution/Monitor.
- colchicine
phenobarbital will decrease the level or effect of colchicine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- conivaptan
phenobarbital will decrease the level or effect of conivaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- conjugated estrogens
phenobarbital will decrease the level or effect of conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of conjugated estrogens by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - conjugated estrogens, vaginal
phenobarbital will decrease the level or effect of conjugated estrogens, vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of conjugated estrogens, vaginal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - cortisone
phenobarbital will decrease the level or effect of cortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of cortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - crizotinib
phenobarbital decreases levels of crizotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Concomitant use of strong CYP3A inducers should be avoided. .
- cyclizine
cyclizine and phenobarbital both increase sedation. Use Caution/Monitor.
- cyclobenzaprine
phenobarbital and cyclobenzaprine both increase sedation. Use Caution/Monitor.
- cyclophosphamide
phenobarbital will decrease the level or effect of cyclophosphamide by affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor.
- cyclosporine
phenobarbital will decrease the level or effect of cyclosporine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of cyclosporine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - cyproheptadine
cyproheptadine and phenobarbital both increase sedation. Use Caution/Monitor.
- dantrolene
phenobarbital and dantrolene both increase sedation. Use Caution/Monitor.
- daprodustat
phenobarbital will decrease the level or effect of daprodustat by Other (see comment). Modify Therapy/Monitor Closely. CYP2C8 inducers may decrease daprodustat exposure, which may result in loss of efficacy. Monitor hemoglobin and adjust daprodustat dose when initiating or stopping therapy with CYP2C8 inducers during treatment
- dapsone topical
phenobarbital increases toxicity of dapsone topical by altering metabolism. Modify Therapy/Monitor Closely. May induce methemoglobinemia.
- daridorexant
phenobarbital 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
phenobarbital will decrease the level or effect of darifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- dasatinib
phenobarbital will decrease the level or effect of dasatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- deferasirox
phenobarbital decreases levels of deferasirox by Other (see comment). Use Caution/Monitor. Comment: Avoid concomitant use of potent UGT inducers with deferasirox. If co-administration is required then consider increasing initial dose of deferasirox to 30 mg/kg and monitor ferritin levels and clinical response.
- deflazacort
phenobarbital will decrease the level or effect of deflazacort by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- desipramine
phenobarbital and desipramine both increase sedation. Use Caution/Monitor.
- dexamethasone
phenobarbital will decrease the level or effect of dexamethasone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of dexamethasone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - dexchlorpheniramine
dexchlorpheniramine and phenobarbital both increase sedation. Use Caution/Monitor.
- dexfenfluramine
phenobarbital increases and dexfenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- dexmedetomidine
phenobarbital and dexmedetomidine both increase sedation. Use Caution/Monitor.
- dexmethylphenidate
phenobarbital increases and dexmethylphenidate decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- dextroamphetamine
phenobarbital increases and dextroamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- dextromoramide
phenobarbital and dextromoramide both increase sedation. Use Caution/Monitor.
- diamorphine
phenobarbital and diamorphine both increase sedation. Use Caution/Monitor.
- diazepam
phenobarbital will decrease the level or effect of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital and diazepam both increase sedation. Use Caution/Monitor. - diazepam intranasal
phenobarbital will decrease the level or effect of diazepam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong or moderate CYP3A4 inducers may increase rate of diazepam elimination; therefore, efficacy of diazepam may be decreased.
diazepam intranasal, phenobarbital. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Coadministration may potentiate the CNS-depressant effects of each drug. - diethylpropion
phenobarbital increases and diethylpropion decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- difelikefalin
difelikefalin and phenobarbital both increase sedation. Use Caution/Monitor.
- difenoxin hcl
phenobarbital and difenoxin hcl both increase sedation. Use Caution/Monitor.
- digoxin
phenobarbital will decrease the level or effect of digoxin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- diltiazem
phenobarbital will decrease the level or effect of diltiazem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- dimenhydrinate
dimenhydrinate and phenobarbital both increase sedation. Use Caution/Monitor.
- diphenhydramine
diphenhydramine and phenobarbital both increase sedation. Use Caution/Monitor.
- diphenoxylate hcl
phenobarbital and diphenoxylate hcl both increase sedation. Use Caution/Monitor.
- dipipanone
phenobarbital and dipipanone both increase sedation. Use Caution/Monitor.
- dobutamine
phenobarbital increases and dobutamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- docetaxel
phenobarbital will decrease the level or effect of docetaxel by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- dopamine
phenobarbital increases and dopamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- dopexamine
phenobarbital increases and dopexamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- dosulepin
phenobarbital and dosulepin both increase sedation. Use Caution/Monitor.
- doxepin
phenobarbital and doxepin both increase sedation. Use Caution/Monitor.
- doxorubicin
phenobarbital will decrease the level or effect of doxorubicin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital decreases levels of doxorubicin by increasing elimination. Use Caution/Monitor. - doxorubicin liposomal
phenobarbital will decrease the level or effect of doxorubicin liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital decreases levels of doxorubicin liposomal by increasing elimination. Use Caution/Monitor. - doxycycline
phenobarbital decreases levels of doxycycline by increasing metabolism. Use Caution/Monitor.
- doxylamine
phenobarbital and doxylamine both increase sedation. Use Caution/Monitor.
- dronabinol
phenobarbital will decrease the level or effect of dronabinol by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Dronabinol is a CYP2C9 substrate.
phenobarbital will decrease the level or effect of dronabinol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Dronabinol is a CYP3A4 substrate. - droperidol
phenobarbital and droperidol both increase sedation. Use Caution/Monitor.
- dulaglutide
dulaglutide, phenobarbital. Other (see comment). Use Caution/Monitor. Comment: Dulaglutide slows gastric emptying and may impact absorption of concomitantly administered oral medications; be particularly cautious when coadministered with drugs that have a narrow therapeutic index.
- dupilumab
dupilumab, phenobarbital. Other (see comment). Use Caution/Monitor. Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, dupilumab could normalize the formation of CYP450 enzymes. Upon initiation or discontinuation of dupilumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.
- duvelisib
phenobarbital will decrease the level or effect of duvelisib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- elagolix
elagolix will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Elagolix is a weak CYP2C19 inhibitor. Caution with sensitive CYP2C19 substrates.
phenobarbital will decrease the level or effect of elagolix by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - eletriptan
phenobarbital will decrease the level or effect of eletriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- elranatamab
elranatamab will increase the level or effect of phenobarbital by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Elranatamab causes cytokine release syndrome (CRS) that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. This is more likely to occur from initiation of elranatamab step-up dosing up to 14 days after the first treatment dose and during and after CRS.
- eltrombopag
phenobarbital will decrease the level or effect of eltrombopag by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of eltrombopag by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. - enfortumab vedotin
phenobarbital will decrease the level or effect of enfortumab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- epcoritamab
epcoritamab, phenobarbital. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Epcoritamab causes release of cytokines that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. For certain CYP substrates, minimal changes in their concentration may lead to serious adverse reactions. If needed, modify therapy as recommended in the substrate's prescribing information. .
- ephedrine
phenobarbital increases and ephedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- epinephrine
phenobarbital increases and epinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- epinephrine racemic
phenobarbital increases and epinephrine racemic decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- erlotinib
phenobarbital will decrease the level or effect of erlotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- escitalopram
phenobarbital will decrease the level or effect of escitalopram by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of escitalopram by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - eslicarbazepine acetate
phenobarbital will decrease the level or effect of eslicarbazepine acetate by increasing metabolism. Use Caution/Monitor. Higher dosage of eslicarbazepine may be necessary
eslicarbazepine acetate will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. - esmolol
phenobarbital decreases levels of esmolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- esomeprazole
phenobarbital will decrease the level or effect of esomeprazole by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
- estazolam
phenobarbital and estazolam both increase sedation. Use Caution/Monitor.
- estradiol
phenobarbital will decrease the level or effect of estradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of estradiol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - estradiol vaginal
phenobarbital will decrease the level or effect of estradiol vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- estrogens conjugated synthetic
phenobarbital will decrease the level or effect of estrogens conjugated synthetic by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of estrogens conjugated synthetic by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - estrogens esterified
phenobarbital will decrease the level or effect of estrogens esterified by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- estropipate
phenobarbital will decrease the level or effect of estropipate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of estropipate by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - ethanol
phenobarbital and ethanol both increase sedation. Use Caution/Monitor.
- ethosuximide
phenobarbital will decrease the level or effect of ethosuximide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- ethotoin
phenobarbital will decrease the level or effect of ethotoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
- etomidate
etomidate and phenobarbital both increase sedation. Use Caution/Monitor.
- etonogestrel
phenobarbital will decrease the level or effect of etonogestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- etoposide
phenobarbital will decrease the level or effect of etoposide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- etravirine
phenobarbital will decrease the level or effect of etravirine by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of etravirine by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of etravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - exemestane
phenobarbital will decrease the level or effect of exemestane by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. For patients receiving exemestane with a potent CYP3A4 inducer the recommended dose of exemestane is 50 mg daily after a meal.
- fedratinib
fedratinib will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP2C19 substrates as necessary.
- felbamate
phenobarbital will decrease the level or effect of felbamate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- felodipine
phenobarbital will decrease the level or effect of felodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- fenfluramine
phenobarbital increases and fenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
phenobarbital will decrease the level or effect of fenfluramine by Other (see comment). Modify Therapy/Monitor Closely. Coadministration with drugs that increase serotonin may increase the risk of serotonin syndrome. - fentanyl
phenobarbital will decrease the level or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with CYP3A4 inducers could lead to a decrease in fentanyl plasma concentrations, lack of efficacy or, possibly, development of a withdrawal syndrome in a patient who has developed physical dependence to fentanyl. After stopping a CYP3A4 inducer, as the effects of the inducer decline, the fentanyl plasma concentration will increase which could increase or prolong both the therapeutic and adverse effects.
- fentanyl intranasal
phenobarbital will decrease the level or effect of fentanyl intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with CYP3A4 inducers could lead to a decrease in fentanyl plasma concentrations, lack of efficacy or, possibly, development of a withdrawal syndrome in a patient who has developed physical dependence to fentanyl. After stopping a CYP3A4 inducer, as the effects of the inducer decline, the fentanyl plasma concentration will increase which could increase or prolong both the therapeutic and adverse effects.
- fentanyl transdermal
phenobarbital will decrease the level or effect of fentanyl transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with CYP3A4 inducers could lead to a decrease in fentanyl plasma concentrations, lack of efficacy or, possibly, development of a withdrawal syndrome in a patient who has developed physical dependence to fentanyl. After stopping a CYP3A4 inducer, as the effects of the inducer decline, the fentanyl plasma concentration will increase which could increase or prolong both the therapeutic and adverse effects.
- fentanyl transmucosal
phenobarbital will decrease the level or effect of fentanyl transmucosal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with CYP3A4 inducers could lead to a decrease in fentanyl plasma concentrations, lack of efficacy or, possibly, development of a withdrawal syndrome in a patient who has developed physical dependence to fentanyl. After stopping a CYP3A4 inducer, as the effects of the inducer decline, the fentanyl plasma concentration will increase which could increase or prolong both the therapeutic and adverse effects.
- ferric maltol
ferric maltol, phenobarbital. 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
phenobarbital will decrease the level or effect of fesoterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- fexinidazole
fexinidazole will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
- flibanserin
phenobarbital will decrease the level or effect of flibanserin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong CYP3A4 inducers substantially decrease flibanserin systemic exposure.
- fludrocortisone
phenobarbital will decrease the level or effect of fludrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of fludrocortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - fluphenazine
phenobarbital and fluphenazine both increase sedation. Use Caution/Monitor.
- flurazepam
phenobarbital and flurazepam both increase sedation. Use Caution/Monitor.
- fluticasone furoate
phenobarbital will decrease the level or effect of fluticasone furoate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- fluticasone inhaled
phenobarbital will decrease the level or effect of fluticasone inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- formoterol
phenobarbital increases and formoterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- fosamprenavir
phenobarbital will decrease the level or effect of fosamprenavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- fosaprepitant
phenobarbital will decrease the level or effect of fosaprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- fosphenytoin
phenobarbital will decrease the level or effect of fosphenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
- gefitinib
phenobarbital will decrease the level or effect of gefitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase gefitinib to 500 mg daily if coadministered with a strong CYP3A4 inducer. Resume gefitinib dose at 250 mg/day 7 days after discontinuing the strong inducer.
- gentamicin
phenobarbital will decrease the level or effect of gentamicin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- glecaprevir/pibrentasvir
phenobarbital will decrease the level or effect of glecaprevir/pibrentasvir by increasing metabolism. Use Caution/Monitor. Coadministration of drugs that induce CYP3A4 and P-gp with glecaprevir/pibrentasvir may decrease glecaprevir/pibrentasvir plasma concentrations. Potential for loss of therapeutic effect.
phenobarbital will decrease the level or effect of glecaprevir/pibrentasvir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - glofitamab
glofitamab, phenobarbital. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Glofitamab causes release of cytokines that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. For certain CYP substrates, minimal changes in their concentration may lead to serious adverse reactions. If needed, modify therapy as recommended in the substrate's prescribing information. .
- glyburide
phenobarbital decreases levels of glyburide by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Strong CYP2C9 inducers may increase glyburide metabolism.
- gotu kola
gotu kola increases effects of phenobarbital by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.
- guanfacine
phenobarbital will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.
- guselkumab
guselkumab, phenobarbital. 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
phenobarbital and haloperidol both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of haloperidol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - hawthorn
hawthorn increases effects of phenobarbital by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.
- hemin
phenobarbital decreases effects of hemin by pharmacodynamic antagonism. Use Caution/Monitor. Drugs that increase delta-aminolevulinic acid synthetase may decrease hemin effect.
- hops
hops increases effects of phenobarbital by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.
- hydrocodone
phenobarbital will decrease the level or effect of hydrocodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Caution when discontinuing CYP3A4 inducers that are coadministered with hydrocodone; plasma concentrations of hydrocodone may increase and can result in potentially fatal respiratory depression
- hydrocortisone
phenobarbital will decrease the level or effect of hydrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of hydrocortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - hydromorphone
phenobarbital and hydromorphone both increase sedation. Use Caution/Monitor.
- hydroxyprogesterone caproate (DSC)
phenobarbital will decrease the level or effect of hydroxyprogesterone caproate (DSC) by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- hydroxyzine
hydroxyzine and phenobarbital both increase sedation. Use Caution/Monitor.
- ifosfamide
phenobarbital increases effects of ifosfamide by affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor. Coadministration of ifosfamide with CYP2B6 inducers may increase metabolism of ifosfamide to its metabolite. Monitor for increased effects/toxicities if combined with CYP2B6 inducers.
phenobarbital increases toxicity of ifosfamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inducers may increase the metabolism of ifosfamide to its active alkylating metabolites. CYP3A4 inducers may increase the formation of the neurotoxic/nephrotoxic ifosfamide metabolite, chloroacetaldehyde. Closely monitor patients taking ifosfamide with CYP3A4 inducers for toxicities and consider dose adjustment. - iloperidone
phenobarbital will decrease the level or effect of iloperidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital and iloperidone both increase sedation. Use Caution/Monitor. - imatinib
phenobarbital will decrease the level or effect of imatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- imipramine
phenobarbital will decrease the level or effect of imipramine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of imipramine by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of imipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.
phenobarbital and imipramine both increase sedation. Use Caution/Monitor. - indinavir
phenobarbital will decrease the level or effect of indinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of indinavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - isoproterenol
phenobarbital increases and isoproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- itraconazole
phenobarbital will decrease the level or effect of itraconazole by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- ivermectin
phenobarbital will decrease the level or effect of ivermectin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- ixabepilone
phenobarbital will decrease the level or effect of ixabepilone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- ixekizumab
ixekizumab, phenobarbital. Other (see comment). Use Caution/Monitor. Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, ixekizumab could normalize the formation of CYP450 enzymes. Upon initiation or discontinuation of ixekizumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.
- kava
kava increases effects of phenobarbital by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.
- ketamine
ketamine and phenobarbital both increase sedation. Use Caution/Monitor.
- ketotifen, ophthalmic
phenobarbital and ketotifen, ophthalmic both increase sedation. Use Caution/Monitor.
- labetalol
phenobarbital decreases levels of labetalol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- lamotrigine
phenobarbital decreases levels of lamotrigine by increasing hepatic clearance. Use Caution/Monitor.
- lansoprazole
phenobarbital will decrease the level or effect of lansoprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- lapatinib
phenobarbital will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - lasmiditan
lasmiditan, phenobarbital. 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, phenobarbital. Either increases effects of the other by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.
- lesinurad
phenobarbital will decrease the level or effect of lesinurad by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.
- levalbuterol
phenobarbital increases and levalbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- levamlodipine
phenobarbital will decrease the level or effect of levamlodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. No information is available on the quantitative effects of CYP3A4 inducers on amlodipine. Closely monitor blood pressure when amlodipine is coadministered with CYP3A4 inducers.
- levonorgestrel intrauterine
phenobarbital decreases levels of levonorgestrel intrauterine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- levonorgestrel oral
phenobarbital decreases levels of levonorgestrel oral by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- levonorgestrel oral/ethinylestradiol/ferrous bisglycinate
phenobarbital will decrease the level or effect of levonorgestrel oral/ethinylestradiol/ferrous bisglycinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. The efficacy of hormonal contraceptives may be reduced. Use an alternative method of contraception or a backup method when enzyme inducers are used with combined hormonal contraceptives (CHCs), and continue backup contraception for 28 days after discontinuing enzyme inducer to ensure contraceptive reliability.
- levorphanol
phenobarbital and levorphanol both increase sedation. Use Caution/Monitor.
- lidocaine
phenobarbital will decrease the level or effect of lidocaine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
- linagliptin
phenobarbital will decrease the level or effect of linagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Use of alternative treatments is strongly recommended when linagliptin is to be administered with a CYP3A4 inducer.
- lisdexamfetamine
phenobarbital increases and lisdexamfetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- lofepramine
phenobarbital and lofepramine both increase sedation. Use Caution/Monitor.
- lofexidine
phenobarbital and lofexidine both increase sedation. Use Caution/Monitor.
- lonapegsomatropin
lonapegsomatropin will decrease the level or effect of phenobarbital by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates
- loperamide
phenobarbital will decrease the level or effect of loperamide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- lopinavir
phenobarbital will decrease the level or effect of lopinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- loprazolam
phenobarbital and loprazolam both increase sedation. Use Caution/Monitor.
- loratadine
phenobarbital will decrease the level or effect of loratadine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- lorazepam
phenobarbital and lorazepam both increase sedation. Use Caution/Monitor.
- lormetazepam
phenobarbital and lormetazepam both increase sedation. Use Caution/Monitor.
- losartan
phenobarbital will decrease the level or effect of losartan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- lovastatin
phenobarbital will decrease the level or effect of lovastatin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- loxapine
phenobarbital and loxapine both increase sedation. Use Caution/Monitor.
- loxapine inhaled
phenobarbital and loxapine inhaled both increase sedation. Use Caution/Monitor.
- lumacaftor/ivacaftor
lumacaftor/ivacaftor, phenobarbital. affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. In vitro studies suggest that lumacaftor may induce and ivacaftor may inhibit CYP2C19 substrates. .
- lurasidone
lurasidone, phenobarbital. 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
phenobarbital and maprotiline both increase sedation. Use Caution/Monitor.
- maraviroc
phenobarbital will decrease the level or effect of maraviroc by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of maraviroc by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - marijuana
phenobarbital and marijuana both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of marijuana by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - medroxyprogesterone
phenobarbital will decrease the level or effect of medroxyprogesterone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Contraceptirve failure possible
- mefloquine
phenobarbital, mefloquine. Either decreases effects of the other by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- melatonin
phenobarbital and melatonin both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of melatonin by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor. - meperidine
phenobarbital and meperidine both increase sedation. Use Caution/Monitor.
- meprobamate
phenobarbital and meprobamate both increase sedation. Use Caution/Monitor.
- mestranol
phenobarbital will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - metaproterenol
phenobarbital increases and metaproterenol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- metaxalone
phenobarbital and metaxalone both increase sedation. Use Caution/Monitor.
- methadone
phenobarbital will decrease the level or effect of methadone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital and methadone both increase sedation. Use Caution/Monitor. - methamphetamine
phenobarbital increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- methocarbamol
phenobarbital and methocarbamol both increase sedation. Use Caution/Monitor.
- methylenedioxymethamphetamine
phenobarbital increases and methylenedioxymethamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- methylphenidate
methylphenidate will increase the level or effect of phenobarbital by unknown mechanism. Use Caution/Monitor. Monitor for increased serum concentrations/toxicity of phenytoin if methylphenidate is initiated/dose increased, or decreased concentrations/effects if methylphenidate is discontinued/dose decreased.
- methylphenidate transdermal
methylphenidate transdermal will increase the level or effect of phenobarbital by decreasing metabolism. Modify Therapy/Monitor Closely. Consider decreasing the dose of these drugs when given coadministered with methylphenidate. Monitor for drug toxiticities when initiating or discontinuing methylphenidate.
- methylprednisolone
phenobarbital will decrease the level or effect of methylprednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of methylprednisolone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - metoprolol
phenobarbital decreases levels of metoprolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- mexiletine
phenobarbital will decrease the level or effect of mexiletine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
- midazolam
phenobarbital will decrease the level or effect of midazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital and midazolam both increase sedation. Use Caution/Monitor. - midazolam intranasal
midazolam intranasal, phenobarbital. 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
phenobarbital increases and midodrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- mifepristone
phenobarbital will decrease the level or effect of mifepristone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inducers have not been studied, coadministration not recommended by manufacturer
- mipomersen
mipomersen, phenobarbital. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Both drugs have potential to increase hepatic enzymes; monitor LFTs.
- mirtazapine
phenobarbital and mirtazapine both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of mirtazapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - modafinil
phenobarbital increases and modafinil decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- morphine
phenobarbital and morphine both increase sedation. Use Caution/Monitor.
- motherwort
phenobarbital and motherwort both increase sedation. Use Caution/Monitor.
- moxonidine
phenobarbital and moxonidine both increase sedation. Use Caution/Monitor.
- nabilone
phenobarbital and nabilone both increase sedation. Use Caution/Monitor.
- nadolol
phenobarbital decreases levels of nadolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- nalbuphine
phenobarbital and nalbuphine both increase sedation. Use Caution/Monitor.
- nateglinide
phenobarbital will decrease the level or effect of nateglinide by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
- nebivolol
phenobarbital decreases levels of nebivolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- nefazodone
phenobarbital will decrease the level or effect of nefazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- nelfinavir
phenobarbital will decrease the level or effect of nelfinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of nelfinavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - neomycin PO
phenobarbital will decrease the level or effect of neomycin PO by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- nevirapine
phenobarbital, nevirapine. Either decreases effects of the other by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- nicardipine
phenobarbital will decrease the level or effect of nicardipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- nifedipine
phenobarbital will decrease the level or effect of nifedipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.
- nilotinib
phenobarbital will decrease the level or effect of nilotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of nilotinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - nisoldipine
phenobarbital will decrease the level or effect of nisoldipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- norepinephrine
phenobarbital increases and norepinephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- nortriptyline
phenobarbital and nortriptyline both increase sedation. Use Caution/Monitor.
- olanzapine
phenobarbital will decrease the level or effect of olanzapine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
phenobarbital and olanzapine both increase sedation. Use Caution/Monitor. - oliceridine
phenobarbital will decrease the level or effect of oliceridine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. If coadministration with a CYP3A4 inducer is necessary, consider increasing oliceridine dose until stable drug effects are achieved; monitor for signs of opioid withdrawal. If inducer is discontinued, consider oliceridine dosage reduction and monitor for signs of respiratory depression.
- omeprazole
phenobarbital will decrease the level or effect of omeprazole by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
- ondansetron
phenobarbital will decrease the level or effect of ondansetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. No dosage adjustment for ondansetron is recommended for patients on these drugs.
- opium tincture
phenobarbital and opium tincture both increase sedation. Use Caution/Monitor.
- oritavancin
oritavancin will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Oritavancin is a weak CYP2C9 inhibitor; caution if coadministered with CYP2C9 substrates that have a narrow therapeutic index
- orlistat
orlistat decreases levels of phenobarbital by inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Risk of convulsions.
- orphenadrine
phenobarbital and orphenadrine both increase sedation. Use Caution/Monitor.
- osilodrostat
phenobarbital will decrease the level or effect of osilodrostat by Other (see comment). Modify Therapy/Monitor Closely. Osilodrostat is a CYP3A4 and CYP2B6 subtrate. Monitor cortisol concentration and patient?s signs and symptoms during coadministration and discontinuation with strong CYP3A4 and/or CYP2B6 inducers. Adjust dose of osilodrostat if necessary.
- ospemifene
phenobarbital decreases levels of ospemifene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital decreases levels of ospemifene by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. - oxazepam
phenobarbital and oxazepam both increase sedation. Use Caution/Monitor.
- oxycodone
phenobarbital and oxycodone both increase sedation. Use Caution/Monitor.
phenobarbital decreases levels of oxycodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - oxymorphone
phenobarbital and oxymorphone both increase sedation. Use Caution/Monitor.
- paclitaxel
phenobarbital will decrease the level or effect of paclitaxel by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
phenobarbital will decrease the level or effect of paclitaxel by Other (see comment). Use Caution/Monitor. Paclitaxel levels/efficacy may decrease when coadministered with CYP2C8 inducers - paclitaxel protein bound
phenobarbital will decrease the level or effect of paclitaxel protein bound by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
phenobarbital will decrease the level or effect of paclitaxel protein bound by Other (see comment). Use Caution/Monitor. Paclitaxel levels/efficacy may decrease when coadministered with CYP2C8 inducers - paliperidone
phenobarbital will decrease the level or effect of paliperidone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
phenobarbital and paliperidone both increase sedation. Use Caution/Monitor. - papaveretum
phenobarbital and papaveretum both increase sedation. Use Caution/Monitor.
- papaverine
phenobarbital and papaverine both increase sedation. Use Caution/Monitor.
- parecoxib
phenobarbital will decrease the level or effect of parecoxib by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
- paromomycin
phenobarbital will decrease the level or effect of paromomycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- passion flower
passion flower increases effects of phenobarbital by pharmacodynamic synergism. Use Caution/Monitor. May enhance CNS depression.
- pazopanib
phenobarbital will decrease the level or effect of pazopanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- penbutolol
phenobarbital decreases levels of penbutolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- pentazocine
phenobarbital and pentazocine both increase sedation. Use Caution/Monitor.
- pentobarbital
pentobarbital and phenobarbital both increase sedation. Use Caution/Monitor.
- perphenazine
phenobarbital and perphenazine both increase sedation. Use Caution/Monitor.
- phendimetrazine
phenobarbital increases and phendimetrazine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- phentermine
phenobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- phenylephrine
phenobarbital increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- phenylephrine PO
phenobarbital increases and phenylephrine PO decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. .
- phenytoin
phenobarbital will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
- pholcodine
phenobarbital and pholcodine both increase sedation. Use Caution/Monitor.
- pimavanserin
phenobarbital will decrease the level or effect of pimavanserin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Avoid coadministration if possible. Monitor for reduced pimavanserin efficacy. An increase in pimavanserin dosage may be needed.
- pimozide
phenobarbital and pimozide both increase sedation. Use Caution/Monitor.
- pindolol
phenobarbital decreases levels of pindolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- pirbuterol
phenobarbital increases and pirbuterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- pitolisant
phenobarbital will decrease the level or effect of pitolisant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Pitolisant exposure is decreased by 50% if coadministered with strong CYP3A4 inducers. For patients stable on pitolisant 8.9 mg/day or 17.8 mg/day, double the pitolisant dose (ie, 17.8 mg or 35.6 mg, respectively) over 7 days. If the strong CYP3A4 inducer is discontinued, reduce pitolisant dosage by half.
- polatuzumab vedotin
phenobarbital will decrease the level or effect of polatuzumab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Polatuzumab undergoes catabolism to small peptides, amino acids, monomethyl auristatin E (MMAE), and unconjugated MMAE-related catabolites. MMAE is a CYP3A4 substrate. Coadministration of polatuzumab vedotin with a strong CYP3A4 inducer may decrease unconjugated MMAE AUC.
- posaconazole
phenobarbital will decrease the level or effect of posaconazole by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
phenobarbital decreases levels of posaconazole by increasing metabolism. Use Caution/Monitor. - prednisolone
phenobarbital will decrease the level or effect of prednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of prednisolone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - prednisone
phenobarbital will decrease the level or effect of prednisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of prednisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - primaquine
phenobarbital will decrease the level or effect of primaquine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.
- primidone
phenobarbital and primidone both increase sedation. Use Caution/Monitor.
- prochlorperazine
phenobarbital and prochlorperazine both increase sedation. Use Caution/Monitor.
- progesterone intravaginal gel
phenobarbital will decrease the level or effect of progesterone intravaginal gel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.
- progesterone micronized
phenobarbital will decrease the level or effect of progesterone micronized by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.
- progesterone, natural
phenobarbital will decrease the level or effect of progesterone, natural by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.
- promethazine
promethazine and phenobarbital both increase sedation. Use Caution/Monitor.
- propafenone
phenobarbital decreases levels of propafenone by increasing metabolism. Use Caution/Monitor.
- propofol
propofol and phenobarbital both increase sedation. Use Caution/Monitor.
- propranolol
phenobarbital decreases levels of propranolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- propylhexedrine
phenobarbital increases and propylhexedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- protriptyline
phenobarbital and protriptyline both increase sedation. Use Caution/Monitor.
- quazepam
phenobarbital and quazepam both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of quazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - quetiapine
phenobarbital will decrease the level or effect of quetiapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital and quetiapine both increase sedation. Use Caution/Monitor. - quinidine
phenobarbital will decrease the level or effect of quinidine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- ramelteon
phenobarbital will decrease the level or effect of ramelteon by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
phenobarbital and ramelteon both increase sedation. Use Caution/Monitor. - rasagiline
phenobarbital will decrease the level or effect of rasagiline by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
- repaglinide
phenobarbital will decrease the level or effect of repaglinide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- rifabutin
phenobarbital will decrease the level or effect of rifabutin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.
- rifampin
rifampin decreases levels of phenobarbital by increasing metabolism. Use Caution/Monitor.
- riociguat
phenobarbital will decrease the level or effect of riociguat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Data not available for dose adjustment
- risperidone
phenobarbital will decrease the level or effect of risperidone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
phenobarbital and risperidone both increase sedation. Use Caution/Monitor. - ritlecitinib
ritlecitinib will increase the level or effect of phenobarbital by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Ritlecitinib inhibits CYP3A4 substrates; coadministration increases AUC and peak plasma concentration sensitive substrates, which may increase risk of adverse reactions. Additional monitoring and dosage adjustment may be needed in accordance with product labeling of CYP3A substrates.
- ritonavir
phenobarbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - ropinirole
phenobarbital will decrease the level or effect of ropinirole by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
- rucaparib
rucaparib will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Adjust dosage of CYP2C19 substrates, if clinically indicated.
- rufinamide
phenobarbital decreases levels of rufinamide by increasing metabolism. Use Caution/Monitor.
- ruxolitinib
phenobarbital will decrease the level or effect of ruxolitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- ruxolitinib topical
phenobarbital will decrease the level or effect of ruxolitinib topical by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- salmeterol
phenobarbital increases and salmeterol decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- saquinavir
phenobarbital will decrease the level or effect of saquinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of saquinavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - sarilumab
sarilumab, phenobarbital. Other (see comment). Use Caution/Monitor. Comment: Formation of CYP450 enzymes can be altered by increased levels of cytokines such as IL-6. Elevated IL-6 concentration may down-regulate CYP activity, such as in patients with RA, and, hence, increase drug levels compared with subjects without RA. Blockade of IL-6 signaling by IL-6 antagonists (eg, sarilumab) might reverse the inhibitory effect of IL-6 and restore CYP activity, leading to decreased drug concentrations. Caution when initiating or discontinuing sarilumab if coadministered with CYP450 substrates, especially those with a narrow therapeutic index.
- scullcap
phenobarbital and scullcap both increase sedation. Use Caution/Monitor.
- secobarbital
phenobarbital and secobarbital both increase sedation. Use Caution/Monitor.
- secukinumab
secukinumab, phenobarbital. Other (see comment). Use Caution/Monitor. Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, secukinumab could normalize the formation of CYP450 enzymes. Upon initiation or discontinuation of secukinumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.
- selexipag
phenobarbital will decrease the level or effect of selexipag by increasing metabolism. Modify Therapy/Monitor Closely. Increase selexipag dose (up to 2-fold) if coadministered with strong CYP2C8 inducers.
- sevelamer
sevelamer decreases levels of phenobarbital by increasing elimination. Use Caution/Monitor.
- sevoflurane
sevoflurane and phenobarbital both increase sedation. Use Caution/Monitor.
- shepherd's purse
phenobarbital and shepherd's purse both increase sedation. Use Caution/Monitor.
- silodosin
phenobarbital will decrease the level or effect of silodosin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- sirolimus
phenobarbital will decrease the level or effect of sirolimus by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- solifenacin
phenobarbital will decrease the level or effect of solifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- somapacitan
somapacitan will decrease the level or effect of phenobarbital by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates
- somatrogon
somatrogon will decrease the level or effect of phenobarbital by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates
- somatropin
somatropin will decrease the level or effect of phenobarbital by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates
- sorafenib
phenobarbital decreases levels of sorafenib by increasing metabolism. Use Caution/Monitor.
- sotalol
phenobarbital decreases levels of sotalol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- sparsentan
sparsentan will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Sparsentan (a CYP2C19 inducer) decreases exposure of CYP2C19 substrates and reduces efficacy related to these substrates.
- stiripentol
stiripentol will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Consider reducing the dose of CYP2C19 substrates, if adverse reactions are experienced when administered concomitantly with stiripentol.
- streptomycin
phenobarbital will decrease the level or effect of streptomycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- sufentanil
phenobarbital and sufentanil both increase sedation. Use Caution/Monitor.
- sufentanil SL
phenobarbital decreases effects of sufentanil SL by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of CYP3A4 inducers may decrease sufentanil levels and efficacy, possibly precipitating withdrawal syndrome in patients who have developed physical dependence to sufentanil. Discontinuation of concomitantly used CYP3A4 inducers may increase sufentanil plasma concentration.
- sunitinib
phenobarbital will decrease the level or effect of sunitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- suvorexant
phenobarbital will decrease the level or effect of suvorexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong CYP3A4 inducers may decrease suvorexant efficacy; if increased suvorexant dose required, do not exceed 20 mg/day
- tacrolimus
phenobarbital will decrease the level or effect of tacrolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of tacrolimus by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. - tadalafil
phenobarbital will decrease the level or effect of tadalafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Avoid combination in pulmonary HTN patients. For patients with ED, monitor response to tadalafil carefully because of potential for decreased effectiveness.
- talquetamab
talquetamab will increase the level or effect of phenobarbital by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Talquetamab causes cytokine release syndrome (CRS) that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. This is more likely to occur from initiation of talquetamab step-up dosing up to 14 days after the first treatment dose and during and after CRS.
- tamoxifen
phenobarbital will decrease the level or effect of tamoxifen by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of tamoxifen by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - tapentadol
phenobarbital and tapentadol both increase sedation. Use Caution/Monitor.
- tasimelteon
phenobarbital will decrease the level or effect of tasimelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Avoid coadministration of tasimelteon with strong CYP3A4 inducers
- teclistamab
teclistamab will increase the level or effect of phenobarbital by altering metabolism. Use Caution/Monitor. Teclistamab causes release of cytokines that may suppress activity of CYP450 enzymes, resulting in increased exposure of CYP substrates. Monitor for increased concentrations or toxicities of sensitive CYP substrates. Adjust dose of CYP substrate drug as needed.
- tecovirimat
tecovirimat will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Tecovirimat is a weak inhibitor of CYP2C8 and CYP2C19. Monitor for adverse effects if coadministered with sensitive substrates of these enzymes.
- temazepam
phenobarbital and temazepam both increase sedation. Use Caution/Monitor.
- temsirolimus
phenobarbital will decrease the level or effect of temsirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- teniposide
phenobarbital will decrease the level or effect of teniposide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- terbinafine
phenobarbital will decrease the level or effect of terbinafine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of terbinafine by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of terbinafine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - terbutaline
phenobarbital increases and terbutaline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- tetracaine
tetracaine, phenobarbital. Other (see comment). Use Caution/Monitor. Comment: Monitor for signs of methemoglobinemia when methemoglobin-inducing drugs are coadministered.
- thalidomide
thalidomide increases effects of phenobarbital by unspecified interaction mechanism. Use Caution/Monitor. Increased sedative effects.
- theophylline
phenobarbital will decrease the level or effect of theophylline by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.
phenobarbital will decrease the level or effect of theophylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - thioridazine
phenobarbital and thioridazine both increase sedation. Use Caution/Monitor.
- thiothixene
phenobarbital and thiothixene both increase sedation. Use Caution/Monitor.
- tiagabine
phenobarbital will decrease the level or effect of tiagabine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- ticagrelor
phenobarbital decreases levels of ticagrelor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Avoid use of ticagrelor with potent CYP3A inducers.
- timolol
phenobarbital decreases levels of timolol by increasing metabolism. Use Caution/Monitor. Consider a higher beta-blocker dose during coadministration of phenobarbital. Atenolol, sotalol, nadolol less likely to be affected than other beta blockers.
- tinidazole
phenobarbital will decrease the level or effect of tinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- tipranavir
phenobarbital will decrease the level or effect of tipranavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- tobramycin
phenobarbital will decrease the level or effect of tobramycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- tofacitinib
phenobarbital will decrease the level or effect of tofacitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Loss of, or decreased response to tofacitinib may occur when coadministered with potent CYP3A4 inducers
- tolterodine
phenobarbital will decrease the level or effect of tolterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- tolvaptan
phenobarbital will decrease the level or effect of tolvaptan by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- topiramate
phenobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- toremifene
phenobarbital decreases levels of toremifene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inducers increase rate of toremifene metabolism, lowering the steady-state concentration in serum.
- tramadol
phenobarbital and tramadol both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of tramadol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Decreased AUC of tramadol and the active metabolite (O-desmethyltramadol) when coadministered with strong CYP3A4 and CYP2B6 inducers - trazodone
phenobarbital will decrease the level or effect of trazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital and trazodone both increase sedation. Use Caution/Monitor. - triamcinolone acetonide injectable suspension
phenobarbital will decrease the level or effect of triamcinolone acetonide injectable suspension by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- triazolam
phenobarbital will decrease the level or effect of triazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
phenobarbital and triazolam both increase sedation. Use Caution/Monitor. - triclabendazole
triclabendazole will increase the level or effect of phenobarbital by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. If plasma concentrations of the CYP2C19 substrates are elevated during triclabendazole, recheck plasma concentration of the CYP2C19 substrates after discontinuation of triclabendazole.
- triclofos
phenobarbital and triclofos both increase sedation. Use Caution/Monitor.
- trifluoperazine
phenobarbital and trifluoperazine both increase sedation. Use Caution/Monitor.
- trimipramine
phenobarbital and trimipramine both increase sedation. Use Caution/Monitor.
phenobarbital will decrease the level or effect of trimipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - triprolidine
triprolidine and phenobarbital both increase sedation. Use Caution/Monitor.
- trofinetide
trofinetide will increase the level or effect of phenobarbital by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor CYP3A4 substrates for which a small increase in plasma concentration may lead to serious toxicities if coadministered with trofinetide (a weak CYP3A4 inhibitor).
- ustekinumab
ustekinumab, phenobarbital. 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.
- vardenafil
phenobarbital will decrease the level or effect of vardenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- verapamil
phenobarbital will decrease the level or effect of verapamil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- vilanterol/fluticasone furoate inhaled
phenobarbital will decrease the level or effect of vilanterol/fluticasone furoate inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- vilazodone
phenobarbital decreases levels of vilazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Consider increasing vilazodone dose up to 2-fold (not to exceed 80 mg/day) when coadministered with strong CYP3A4 inducers for >14 days.
- vinblastine
phenobarbital will decrease the level or effect of vinblastine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- vincristine
phenobarbital will decrease the level or effect of vincristine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- vincristine liposomal
phenobarbital will decrease the level or effect of vincristine liposomal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
- vitamin D
phenobarbital decreases effects of vitamin D by Other (see comment). Use Caution/Monitor. Comment: Vitamin D supplementation or dosage adjustments may be required in patients who are receiving chronic treatment with anticonvulsants.
- vortioxetine
phenobarbital increases levels of vortioxetine by increasing metabolism. Modify Therapy/Monitor Closely. Consider increasing the vortioxetine dose when coadministered with strong CYP inducers for >14 days; not to exceed 3 times original vortioxetine dose.
- warfarin
phenobarbital will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.
- xylometazoline
phenobarbital increases and xylometazoline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- yohimbine
phenobarbital increases and yohimbine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- ziconotide
phenobarbital and ziconotide both increase sedation. Use Caution/Monitor.
- ziprasidone
phenobarbital and ziprasidone both increase sedation. Use Caution/Monitor.
- zotepine
phenobarbital and zotepine both increase sedation. Use Caution/Monitor.
Minor (151)
- acetaminophen
phenobarbital decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- acetaminophen IV
phenobarbital decreases levels of acetaminophen IV by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- acetaminophen rectal
phenobarbital decreases levels of acetaminophen rectal by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- acetazolamide
acetazolamide, phenobarbital. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Increased risk of anticonvulsant induced osteomalacia.
- alfentanil
phenobarbital will decrease the level or effect of alfentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- alfuzosin
phenobarbital will decrease the level or effect of alfuzosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- alosetron
phenobarbital will decrease the level or effect of alosetron by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
phenobarbital will decrease the level or effect of alosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. - alvimopan
phenobarbital will decrease the level or effect of alvimopan by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.
- ambrisentan
phenobarbital will decrease the level or effect of ambrisentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- amitriptyline
phenobarbital, amitriptyline. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- amoxapine
phenobarbital, amoxapine. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- amphotericin B deoxycholate
phenobarbital decreases levels of amphotericin B deoxycholate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- antipyrine
phenobarbital will decrease the level or effect of antipyrine by affecting hepatic enzyme CYP1A2 metabolism. Minor/Significance Unknown.
- armodafinil
phenobarbital will decrease the level or effect of armodafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
phenobarbital will decrease the level or effect of armodafinil by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown. - ascorbic acid
phenobarbital decreases levels of ascorbic acid by increasing elimination. Minor/Significance Unknown.
- asenapine
phenobarbital will decrease the level or effect of asenapine by affecting hepatic enzyme CYP1A2 metabolism. Minor/Significance Unknown.
- ashwagandha
ashwagandha increases effects of phenobarbital by pharmacodynamic synergism. Minor/Significance Unknown. May enhance CNS depression.
- atracurium
phenobarbital decreases effects of atracurium by pharmacodynamic antagonism. Minor/Significance Unknown.
- biotin
phenobarbital decreases levels of biotin by unspecified interaction mechanism. Minor/Significance Unknown. Biotin supplementation may be necessary.
- bosentan
phenobarbital will decrease the level or effect of bosentan by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
phenobarbital will decrease the level or effect of bosentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. - brimonidine
brimonidine increases effects of phenobarbital by pharmacodynamic synergism. Minor/Significance Unknown. Increased CNS depression.
- brinzolamide
brinzolamide, phenobarbital. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Increased risk of anticonvulsant induced osteomalacia.
- caffeine
phenobarbital will decrease the level or effect of caffeine by affecting hepatic enzyme CYP1A2 metabolism. Minor/Significance Unknown.
- celecoxib
phenobarbital will decrease the level or effect of celecoxib by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
- cevimeline
phenobarbital will decrease the level or effect of cevimeline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- chloramphenicol
phenobarbital decreases levels of chloramphenicol by increasing metabolism. Minor/Significance Unknown.
- chlorpromazine
phenobarbital decreases levels of chlorpromazine by increasing metabolism. Minor/Significance Unknown.
- cimetidine
phenobarbital will decrease the level or effect of cimetidine by affecting hepatic enzyme CYP2C19 metabolism. Minor/Significance Unknown.
- cisatracurium
phenobarbital decreases effects of cisatracurium by pharmacodynamic antagonism. Minor/Significance Unknown.
- clarithromycin
phenobarbital will decrease the level or effect of clarithromycin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
phenobarbital decreases levels of clarithromycin by increasing elimination. Minor/Significance Unknown. - clomipramine
phenobarbital, clomipramine. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- clotrimazole
phenobarbital decreases levels of clotrimazole by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- cocaine topical
phenobarbital will decrease the level or effect of cocaine topical by affecting hepatic enzyme CYP2B6 metabolism. Minor/Significance Unknown.
- cyanocobalamin
phenobarbital decreases levels of cyanocobalamin by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- dapsone
phenobarbital will decrease the level or effect of dapsone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- desipramine
phenobarbital, desipramine. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- dexmethylphenidate
dexmethylphenidate increases effects of phenobarbital by decreasing metabolism. Minor/Significance Unknown.
- diazepam
phenobarbital will decrease the level or effect of diazepam by affecting hepatic enzyme CYP2C19 metabolism. Minor/Significance Unknown.
- diclofenac
phenobarbital will decrease the level or effect of diclofenac by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
- disopyramide
phenobarbital will decrease the level or effect of disopyramide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- docetaxel
phenobarbital will decrease the level or effect of docetaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- donepezil
phenobarbital will decrease the level or effect of donepezil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- dosulepin
phenobarbital, dosulepin. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- doxepin
phenobarbital, doxepin. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- dutasteride
phenobarbital will decrease the level or effect of dutasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- efavirenz
phenobarbital will decrease the level or effect of efavirenz by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- eplerenone
phenobarbital will decrease the level or effect of eplerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- erythromycin base
phenobarbital decreases levels of erythromycin base by increasing elimination. Minor/Significance Unknown.
- erythromycin ethylsuccinate
phenobarbital decreases levels of erythromycin ethylsuccinate by increasing elimination. Minor/Significance Unknown.
- erythromycin lactobionate
phenobarbital decreases levels of erythromycin lactobionate by increasing elimination. Minor/Significance Unknown.
- erythromycin stearate
phenobarbital decreases levels of erythromycin stearate by increasing elimination. Minor/Significance Unknown.
- ethosuximide
ethosuximide decreases effects of phenobarbital by pharmacodynamic antagonism. Minor/Significance Unknown.
- ethotoin
phenobarbital decreases levels of ethotoin by increasing metabolism. Minor/Significance Unknown. Phenobarbital may occasionally not change or even increase (via competitive inhibition) phenytoin levels.
- eucalyptus
phenobarbital will decrease the level or effect of eucalyptus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
phenobarbital and eucalyptus both increase sedation. Minor/Significance Unknown. - felbamate
felbamate increases levels of phenobarbital by decreasing metabolism. Minor/Significance Unknown.
- fexofenadine
phenobarbital will decrease the level or effect of fexofenadine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.
- finasteride
phenobarbital will decrease the level or effect of finasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- fluconazole
phenobarbital decreases levels of fluconazole by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- flurbiprofen
phenobarbital will decrease the level or effect of flurbiprofen by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
- fluvastatin
phenobarbital will decrease the level or effect of fluvastatin by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
- folic acid
folic acid decreases levels of phenobarbital by increasing metabolism. Minor/Significance Unknown.
phenobarbital decreases levels of folic acid by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown. - fosphenytoin
phenobarbital decreases levels of fosphenytoin by increasing metabolism. Minor/Significance Unknown. Phenobarbital may occasionally not change or even increase (via competitive inhibition) phenytoin levels.
- frovatriptan
phenobarbital will decrease the level or effect of frovatriptan by affecting hepatic enzyme CYP1A2 metabolism. Minor/Significance Unknown.
- furosemide
phenobarbital decreases levels of furosemide by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- galantamine
phenobarbital will decrease the level or effect of galantamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- green tea
phenobarbital will decrease the level or effect of green tea by increasing metabolism. Minor/Significance Unknown. Green tea products may contain caffeine. The metabolism of xanthines, such as caffeine, can be increased by concurrent use with barbiturates.
- griseofulvin
phenobarbital decreases levels of griseofulvin by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- haloperidol
haloperidol, phenobarbital. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Risk of hyperthermia if haloperidol admin. during barbiturate withdrawal.
- ibuprofen
phenobarbital will decrease the level or effect of ibuprofen by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
- ibuprofen IV
phenobarbital will decrease the level or effect of ibuprofen IV by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
- imatinib
phenobarbital will decrease the level or effect of imatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- imipramine
phenobarbital, imipramine. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- isocarboxazid
isocarboxazid increases levels of phenobarbital by decreasing metabolism. Minor/Significance Unknown. Theoretical interaction.
- isradipine
phenobarbital will decrease the level or effect of isradipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- itraconazole
phenobarbital will decrease the level or effect of itraconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
phenobarbital decreases levels of itraconazole by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown. - ketoconazole
phenobarbital will decrease the level or effect of ketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
phenobarbital decreases levels of ketoconazole by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown. - L-methylfolate
L-methylfolate decreases levels of phenobarbital by increasing metabolism. Minor/Significance Unknown.
phenobarbital decreases levels of L-methylfolate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown. - lansoprazole
phenobarbital will decrease the level or effect of lansoprazole by affecting hepatic enzyme CYP2C19 metabolism. Minor/Significance Unknown.
- levocarnitine
phenobarbital decreases levels of levocarnitine by unspecified interaction mechanism. Minor/Significance Unknown.
- levoketoconazole
phenobarbital will decrease the level or effect of levoketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
phenobarbital decreases levels of levoketoconazole by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown. - levothyroxine
phenobarbital decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.
- linezolid
linezolid increases levels of phenobarbital by decreasing metabolism. Minor/Significance Unknown. Theoretical interaction.
- liothyronine
phenobarbital decreases levels of liothyronine by increasing metabolism. Minor/Significance Unknown.
- lofepramine
phenobarbital, lofepramine. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- loratadine
phenobarbital will decrease the level or effect of loratadine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.
- losartan
phenobarbital will decrease the level or effect of losartan by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
- maprotiline
phenobarbital, maprotiline. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- meloxicam
phenobarbital will decrease the level or effect of meloxicam by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
- methazolamide
methazolamide, phenobarbital. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Increased risk of anticonvulsant induced osteomalacia.
- methsuximide
methsuximide decreases effects of phenobarbital by pharmacodynamic antagonism. Minor/Significance Unknown.
- metyrapone
phenobarbital decreases effects of metyrapone by unspecified interaction mechanism. Minor/Significance Unknown.
- miconazole vaginal
phenobarbital decreases levels of miconazole vaginal by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- montelukast
phenobarbital will decrease the level or effect of montelukast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- nettle
nettle increases effects of phenobarbital by pharmacodynamic synergism. Minor/Significance Unknown. (High dose nettle; theoretical interaction) May enhance CNS depression.
- nimodipine
phenobarbital will decrease the level or effect of nimodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- nitrendipine
phenobarbital will decrease the level or effect of nitrendipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- nortriptyline
phenobarbital, nortriptyline. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- onabotulinumtoxinA
phenobarbital decreases effects of onabotulinumtoxinA by pharmacodynamic antagonism. Minor/Significance Unknown.
- ondansetron
phenobarbital will decrease the level or effect of ondansetron by affecting hepatic enzyme CYP1A2 metabolism. Minor/Significance Unknown.
- oxcarbazepine
phenobarbital decreases levels of oxcarbazepine by increasing metabolism. Minor/Significance Unknown.
- oxybutynin
phenobarbital will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- paclitaxel
phenobarbital will decrease the level or effect of paclitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- paclitaxel protein bound
phenobarbital will decrease the level or effect of paclitaxel protein bound by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- pancuronium
phenobarbital decreases effects of pancuronium by pharmacodynamic antagonism. Minor/Significance Unknown.
- pantoprazole
phenobarbital will decrease the level or effect of pantoprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- parecoxib
phenobarbital will decrease the level or effect of parecoxib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- phenelzine
phenelzine increases levels of phenobarbital by decreasing metabolism. Minor/Significance Unknown. Theoretical interaction.
- phenytoin
phenobarbital decreases levels of phenytoin by increasing metabolism. Minor/Significance Unknown. Phenobarbital may occasionally not change or even increase (via competitive inhibition) phenytoin levels.
- pimozide
phenobarbital will decrease the level or effect of pimozide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- pioglitazone
phenobarbital will decrease the level or effect of pioglitazone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- piroxicam
phenobarbital will decrease the level or effect of piroxicam by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
- posaconazole
phenobarbital decreases levels of posaconazole by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- procarbazine
procarbazine increases levels of phenobarbital by decreasing metabolism. Minor/Significance Unknown. Theoretical interaction.
- propafenone
phenobarbital will decrease the level or effect of propafenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- protriptyline
phenobarbital, protriptyline. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- pyridoxine
pyridoxine decreases levels of phenobarbital by increasing metabolism. Minor/Significance Unknown.
- pyridoxine (Antidote)
pyridoxine (Antidote) decreases levels of phenobarbital by increasing metabolism. Minor/Significance Unknown.
- quinine
phenobarbital will decrease the level or effect of quinine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- rabeprazole
phenobarbital will decrease the level or effect of rabeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- ramelteon
phenobarbital will decrease the level or effect of ramelteon by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
phenobarbital will decrease the level or effect of ramelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. - rapacuronium
phenobarbital decreases effects of rapacuronium by pharmacodynamic antagonism. Minor/Significance Unknown.
- riluzole
phenobarbital will decrease the level or effect of riluzole by affecting hepatic enzyme CYP1A2 metabolism. Minor/Significance Unknown.
- rocuronium
phenobarbital decreases effects of rocuronium by pharmacodynamic antagonism. Minor/Significance Unknown.
- rose hips
phenobarbital decreases levels of rose hips by increasing elimination. Minor/Significance Unknown.
- sage
phenobarbital and sage both increase sedation. Minor/Significance Unknown.
sage decreases effects of phenobarbital by pharmacodynamic antagonism. Minor/Significance Unknown. Theoretical interaction; some species of sage may cause convulsions. - saxagliptin
phenobarbital will decrease the level or effect of saxagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- selegiline transdermal
selegiline transdermal increases levels of phenobarbital by decreasing metabolism. Minor/Significance Unknown. Theoretical interaction.
- serdexmethylphenidate/dexmethylphenidate
serdexmethylphenidate/dexmethylphenidate increases effects of phenobarbital by decreasing metabolism. Minor/Significance Unknown.
- Siberian ginseng
Siberian ginseng increases effects of phenobarbital by pharmacodynamic synergism. Minor/Significance Unknown. May enhance CNS depression.
- succinylcholine
phenobarbital decreases effects of succinylcholine by pharmacodynamic antagonism. Minor/Significance Unknown.
- sufentanil
phenobarbital will decrease the level or effect of sufentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- sulfamethoxazole
phenobarbital will decrease the level or effect of sulfamethoxazole by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
- thioridazine
thioridazine decreases levels of phenobarbital by unspecified interaction mechanism. Minor/Significance Unknown.
- thyroid desiccated
phenobarbital decreases levels of thyroid desiccated by increasing metabolism. Minor/Significance Unknown.
- tiagabine
phenobarbital decreases levels of tiagabine by increasing metabolism. Minor/Significance Unknown.
- tibolone
phenobarbital decreases levels of tibolone by increasing metabolism. Minor/Significance Unknown. Theoretical interaction.
- tolbutamide
phenobarbital will decrease the level or effect of tolbutamide by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.
- topiramate
phenobarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.
- tranylcypromine
tranylcypromine increases levels of phenobarbital by decreasing metabolism. Minor/Significance Unknown. Theoretical interaction.
- trazodone
phenobarbital, trazodone. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- trimipramine
phenobarbital, trimipramine. Other (see comment). Minor/Significance Unknown. Comment: Barbiturates may increase adverse effects, including respiratory depression, produced by toxic doses of TCAs. With therapeutic doses of TCAs, barbiturates increase metabolism and decrease blood concentrations of TCAs.
- valproic acid
valproic acid increases levels of phenobarbital by unspecified interaction mechanism. Minor/Significance Unknown.
- vecuronium
phenobarbital decreases effects of vecuronium by pharmacodynamic antagonism. Minor/Significance Unknown.
- vinblastine
phenobarbital will decrease the level or effect of vinblastine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- vincristine
phenobarbital will decrease the level or effect of vincristine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- vincristine liposomal
phenobarbital will decrease the level or effect of vincristine liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- vinorelbine
phenobarbital will decrease the level or effect of vinorelbine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- zaleplon
phenobarbital will decrease the level or effect of zaleplon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- ziprasidone
phenobarbital will decrease the level or effect of ziprasidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- zolpidem
phenobarbital will decrease the level or effect of zolpidem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- zonisamide
phenobarbital will decrease the level or effect of zonisamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
Adverse Effects
Frequency Not Defined
IV
- Respiratory depression
Common
- Ataxia
- Dizziness
- Drowsiness
- Dysarthria
- Fatigue
- Headache
- Irritability
- Nystagmus
- Paresthesia restlessness
- Vertigo
- Geriatric patients: Excitement, confusion, depression
- Pediatric patients: Paradoxical excitement/hyperactivity
Less Common
- Mental dullness
- Constipation
- Diarrhea
- Nausea
- Vomiting
- Megaloblastic (folate-deficiency) anemia
Uncommon
- Rash
- Hypocalcemia
- Hepatotoxicity
Rare
- Stevens-Johnson syndrome
- Rickets
- Osteomalacia
Warnings
Contraindications
Hypersensitivity
Porphyria
Intra-arterial or subcutaneous administration
Severe hepatic impairment
Dyspnea or airway obstruction
History of sedative hyponotic addiction
Nephritic patients (large doses)
Pregnancy/lactation
Cautions
Commercial injection is highly alkaline and may cause tissue necrosis if given SC or if it extravasates (if happens, treat with application of moist heat and injection of 0.5% procaine)
May render oral contraceptives ineffective
Paradoxical responses may occur, especially in pediatric patients and patients experiencing acute or chronic pain
May cause CNS depression, causing physical and mental impairment; caution patient about performing tasks that require mental alertness
May cause respiratory depression, especially with intravenous administration; use caution in patients with respiratory disease and status asthmaticus
Withdraw therapy gradually; abrupt discontinuation, may increase seizure frequency
Use caution in patients with severe anemia, patients experiencing depression, cardiac disease, hemodynamically unstable patients, hyperthyroidism, renal impairment, hypoadrenalism, and in patients with diabetes
May mask important symptoms when used in patients with acute or chronic pain; use caution
Pregnancy & Lactation
Pregnancy category: D
Lactation: Do not nurse
Pregnancy Categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk. C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done. D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk. X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist. NA: Information not available.Pharmacology
Mechanism of Action
Depresses sensory and motor cortex, cerebellum
Antiseizure activity occurs primarily where GABA mediates neurotransmission
Hypnotic effects of barbiturates result from activity at GABA receptor in the polysynaptic midbrain reticular formation (controls CNS arousal)
Off-label use for hyperbilirubinemia: Phenobarbital induces glucuronyl transferase and hepatic bilirubin-binding Y-protein to lower serum bilirubin concentrations
Absorption
Bioavailability: 70-90%
Onset: 5 min (IV)
Duration: 4-6 hr (IV/IM)
Peak plasma time: 8-12 hr
Therapeutic plasma concentration: 10-40 mcg/mL; may require 3-4 weeks of treatment to achieve therapeutic levels
Distribution
Protein bound: 20-45%
Metabolism
Metabolized by hepatic oxidative hydroxylation
Metabolites: Inactive
Enzymes induced: CYP1A2, CYP2B6, CYP2C19, CYP2C9/10, CYP3A4
Elimination
Half-life: 50-140 hr
Excretion: Urine (major)
Administration
IV Incompatibilities
Additive: Chlorpromazine, ephedrine, hydralazine, hydrocortisone Na-succinate, hydroxyzine, insulin, levorphanol, meperidine, morphine, norepinephrine, pentazocine, procaine, prochlorperazine, promazine, promethazine, streptomycin, vancomycin
Syringe: Hydromorphone, ranitidine, sufentanil
Y-site: Amphotericin B cholSO4
IV Compatibilities
Solution: Dextrose Ringer, dextrose LR, dextrose saline, Ringer, LR, NS, ½ NS, Na-lactate 1/6 M, D5W, D10W
Additive: Amikacin, aminophylline, CaCl2, Ca-gluconate, colistimethate, dimenhydrinate, meropenem, polymyxin B, thiopental, verapamil
Syringe: Caffeine, heparin
Y-site: Doxapram, enalaprilat, fentanyl, fosphenytoin gatifloxacin, hydromorphone (may be incompatible at high concentrations of both), levofloxacin, linezolid, meropenem, methadone, morphine SO4, propofol, sufentanil
IV Preparation
Sezaby
- Determine number of vials to be reconstituted based on patient’s weight and recommended dose
- Aseptically reconstitute lyophilized powder in vial using 10 mL of 0.9% NaCl
- Swirl vial gently until contents are completely dissolved
- Reconstituted solution contains 100 mg/10 mL (10 mg/mL)
- Inspect visually for particulate matter and discoloration before administration; solution should appear clear, colorless, and free from visible particulate matter
- Discard if solution is discolored or contains foreign particles
IV Administration
Slow injection at <60 mg/min
May be given IM into large muscle but not SC
Commercial injection is highly alkaline and can cause local tissue necrosis
Sezaby
- Administer IV over 15 minutes
Stability
Store intact vials at room temperature, protected from light
Sezaby
-
Unopened vials in original cartons
- 20-25ºC (68-77ºF); excursions permitted to 15-30ºC (59-86ºF)
-
Reconstituted solution
- If not administered immediately, place vial back in original carton to protect from light
- Store at either room temperature (20-25ºC [68-77ºF]) for up to 8 hr, OR
- Refrigerate at 2-8ºC (36-46ºF) for up to 24 hr
- Discard any unused portion after recommended storage duration
Images
BRAND | FORM. | UNIT PRICE | PILL IMAGE |
---|---|---|---|
phenobarbital oral - | 100 mg tablet | ![]() | |
phenobarbital oral - | 16.2 mg tablet | ![]() | |
phenobarbital oral - | 97.2 mg tablet | ![]() | |
phenobarbital oral - | 32.4 mg tablet | ![]() | |
phenobarbital oral - | 97.2 mg tablet | ![]() | |
phenobarbital oral - | 64.8 mg tablet | ![]() | |
phenobarbital oral - | 16.2 mg tablet | ![]() | |
phenobarbital oral - | 16.2 mg tablet | ![]() | |
phenobarbital oral - | 97.2 mg tablet | ![]() | |
phenobarbital oral - | 64.8 mg tablet | ![]() | |
phenobarbital oral - | 20 mg/5 mL (4 mg/mL) elixir | ![]() | |
phenobarbital oral - | 64.8 mg tablet | ![]() | |
phenobarbital oral - | 32.4 mg tablet | ![]() | |
phenobarbital oral - | 100 mg tablet | ![]() | |
phenobarbital oral - | 16.2 mg tablet | ![]() | |
phenobarbital oral - | 97.2 mg tablet | ![]() | |
phenobarbital oral - | 15 mg tablet | ![]() | |
phenobarbital oral - | 32.4 mg tablet | ![]() | |
phenobarbital oral - | 16.2 mg tablet | ![]() | |
phenobarbital oral - | 32.4 mg tablet | ![]() | |
phenobarbital oral - | 64.8 mg tablet | ![]() | |
phenobarbital oral - | 32.4 mg tablet | ![]() | |
phenobarbital oral - | 64.8 mg tablet | ![]() | |
phenobarbital oral - | 97.2 mg tablet | ![]() | |
phenobarbital oral - | 15 mg tablet | ![]() | |
phenobarbital oral - | 97.2 mg tablet | ![]() | |
phenobarbital oral - | 64.8 mg tablet | ![]() | |
phenobarbital oral - | 32.4 mg tablet | ![]() | |
phenobarbital oral - | 15 mg tablet | ![]() | |
phenobarbital oral - | 16.2 mg tablet | ![]() | |
phenobarbital oral - | 97.2 mg tablet | ![]() | |
phenobarbital oral - | 100 mg tablet | ![]() | |
phenobarbital oral - | 60 mg tablet | ![]() | |
phenobarbital oral - | 30 mg tablet | ![]() | |
phenobarbital oral - | 64.8 mg tablet | ![]() | |
phenobarbital oral - | 30 mg tablet | ![]() | |
phenobarbital oral - | 30 mg tablet | ![]() | |
phenobarbital oral - | 64.8 mg tablet | ![]() | |
phenobarbital oral - | 64.8 mg tablet | ![]() | |
phenobarbital oral - | 97.2 mg tablet | ![]() | |
phenobarbital oral - | 97.2 mg tablet | ![]() | |
phenobarbital oral - | 20 mg/5 mL (4 mg/mL) elixir | ![]() | |
phenobarbital oral - | 100 mg tablet | ![]() | |
phenobarbital oral - | 20 mg/5 mL (4 mg/mL) elixir | ![]() | |
phenobarbital oral - | 15 mg tablet | ![]() | |
phenobarbital oral - | 15 mg tablet | ![]() | |
phenobarbital oral - | 15 mg tablet | ![]() | |
phenobarbital oral - | 60 mg tablet | ![]() | |
phenobarbital oral - | 30 mg tablet | ![]() |
Copyright © 2010 First DataBank, Inc.
Patient Handout
phenobarbital oral
PHENOBARBITAL - ORAL
(fee-no-BARB-ih-tall)
COMMON BRAND NAME(S): Luminal
USES: This medication is used alone or with other medications to control seizures. Controlling and reducing seizures lets you do more of your normal daily activities, reduces your risk of harm when you lose consciousness, and lessens your risk for a possibly life-threatening condition of frequent, repeated seizures. Phenobarbital belongs to a class of drugs known as barbiturate anticonvulsants/hypnotics. It works by controlling the abnormal electrical activity in the brain that occurs during a seizure. This medication is also used for a short time (usually no more than 2 weeks) to help calm you or help you sleep during periods of anxiety. It works by affecting certain parts of the brain to cause calming.
HOW TO USE: Take this medication by mouth with or without food as directed by your doctor, usually once daily at bedtime for seizure control. Take with food or milk if stomach upset occurs. If you are using the liquid form of this medication, measure the dose carefully using a special measuring device/cup. Do not use a household spoon because you may not get the correct dose.Dosage is based on your medical condition, phenobarbital blood levels, and response to treatment. The dosage in children may also be based on weight.Your doctor may direct you to start this medication at a low dose and gradually increase your dose to prevent side effects such as drowsiness and dizziness. Follow your doctor's instructions carefully. Do not take more or less of this drug than prescribed.It may take several weeks to reach the best dose for you and completely control your seizures. This medication works best when the amount of drug in your body is kept at a constant level. Take it at the same time(s) each day.Do not stop taking this medication (and other anticonvulsant medications) without consulting your doctor. Your seizures may worsen or cause a very severe seizure that is difficult to treat (status epilepticus) when this drug is suddenly stopped.If you suddenly stop using this medication, you may have withdrawal symptoms (such as anxiety, hallucinations, twitching, trouble sleeping). Withdrawal from phenobarbital can be severe and include seizures and (rarely) death. To help prevent withdrawal, your doctor may lower your dose slowly. Withdrawal is more likely if you have used phenobarbital for a long time or in high doses. Tell your doctor or pharmacist right away if you have withdrawal.Though it helps many people, this medication may sometimes cause addiction. This risk may be higher if you have a substance use disorder (such as overuse of or addiction to drugs/alcohol). Take this medication exactly as prescribed to lower the risk of addiction. Ask your doctor or pharmacist for more details.When this medication is used for a long time for anxiety or to help you sleep, it may not work as well. Phenobarbital should only be used for a short time for anxiety or sleep. Talk with your doctor if this medication stops working well.Tell your doctor if your anxiety or seizure control worsens (such as the number of seizures increases).
SIDE EFFECTS: Dizziness, drowsiness, excitation, headache, tiredness, loss of appetite, nausea, or vomiting may occur as your body adjusts to the medication. If any of these effects last or get worse, notify your doctor or pharmacist promptly.Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.A small number of people who take anticonvulsants for any condition (such as seizure, bipolar disorder, pain) may experience depression, suicidal thoughts/attempts, or other mental/mood problems. Tell your doctor right away if you or your family/caregiver notice any unusual/sudden changes in your mood, thoughts, or behavior including signs of depression, suicidal thoughts/attempts, thoughts about harming yourself.Tell your doctor right away if you have any serious side effects, including: staggering walk/clumsiness, double vision, fainting, slow heartbeat, severe tiredness/weakness, pale skin.Get medical help right away if you have any very serious side effects, including: slow/shallow breathing.A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: fever, swollen lymph nodes, rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.In the US -Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
PRECAUTIONS: Before taking phenobarbital, tell your doctor or pharmacist if you are allergic to it; or to other barbiturates (such as primidone, secobarbital); or to other anti-seizure medications (such as carbamazepine, fosphenytoin, oxcarbazepine, phenytoin); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.Before using this medication, tell your doctor or pharmacist your medical history, especially of: certain hormone problems (adrenal disease such as Addison's disease), liver problems, kidney problems, lung disease (such as sleep apnea, chronic obstructive pulmonary disease-COPD), mental/mood disorders (such as depression, thoughts of suicide), personal or family history of a substance use disorder (such as overuse of or addiction to drugs/alcohol), personal/family history of a certain blood disorder (porphyria), certain vitamin deficiencies (folic acid, vitamin K).This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Avoid alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).The liquid form of this product may contain alcohol or sugar. Caution is advised if you have diabetes, alcohol dependence, liver disease, or any other condition that requires you to limit/avoid these substances in your diet. Ask your doctor or pharmacist about using this product safely.Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).Older adults may be more sensitive to the side effects of this drug, especially drowsiness and dizziness. However, this drug can often cause excitement or confusion instead of drowsiness in older adults. Drowsiness, confusion, and dizziness can increase the risk of falling.Children may be more sensitive to the side effects of the drug. This drug can often cause excitement instead of drowsiness in young children.During pregnancy, this medication should be used only when clearly needed. It may harm an unborn baby. Newborn babies of mothers who use this medication late in pregnancy may have symptoms such as slow/shallow breathing, nonstop crying, shaking, or trouble feeding. However, since untreated seizures are a serious condition that can harm both a pregnant woman and her unborn baby, do not stop taking this medication unless directed by your doctor. If you are planning pregnancy, become pregnant, or think you may be pregnant, discuss with your doctor right away the benefits and risks of using this medication during pregnancy. Since birth control pills, patches, implants, and injections may not work if taken with this medication (see also Drug Interactions section), discuss reliable forms of birth control with your doctor.This medication passes into breast milk and may cause excessive sleepiness or feeding problems in the nursing infant. Consult your doctor before breast-feeding.
DRUG INTERACTIONS: Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.Some products that may interact with this drug include: darunavir, etravirine, orlistat, rilpivirine.Other medications can affect the removal of phenobarbital from your body, which may affect how phenobarbital works. Examples include St. John's wort, among others.This medication can speed up the removal of other medications from your body, which may affect how they work. Examples of affected drugs include artemether/lumefantrine, asunaprevir, atazanavir, cobicistat, lurasidone, ranolazine, sofosbuvir, sorafenib, voriconazole, certain calcium channel blockers such as felodipine/nimodipine, among others.This medication may decrease the effectiveness of hormonal birth control such as pills, patch, or ring. This could cause pregnancy. Discuss with your doctor or pharmacist if you should use reliable backup birth control methods while using this medication. Also tell your doctor if you have any new spotting or breakthrough bleeding, because these may be signs that your birth control is not working well.The risk of serious side effects (such as slow/shallow breathing, severe drowsiness/dizziness) may be increased if this medication is taken with other products that may also cause drowsiness or breathing problems. Tell your doctor or pharmacist if you are taking other products such as opioid pain or cough relievers (such as codeine, hydrocodone), alcohol, marijuana (cannabis), other drugs for sleep or anxiety (such as alprazolam, lorazepam, zolpidem), muscle relaxants (such as carisoprodol, cyclobenzaprine), or antihistamines (such as cetirizine, diphenhydramine).Check the labels on all your medicines (such as allergy or cough-and-cold products) because they may contain ingredients that cause drowsiness. Ask your pharmacist about using those products safely.Phenobarbital is very similar to primidone. Do not use medications containing primidone while using phenobarbital.
OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe tiredness/dizziness, inability to wake up, very slow breathing rate.
NOTES: Do not share this medication with others. Sharing it is against the law.For long-term use, lab and/or medical tests (such as phenobarbital blood levels, blood counts, liver/kidney function) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.
MISSED DOSE: If you are taking this medication to prevent seizures and miss a dose, take it as soon as you remember unless it is almost time for the next dose. In that case, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.
STORAGE: Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.
MEDICAL ALERT: Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).
Information last revised June 2023. Copyright(c) 2023 First Databank, Inc.
IMPORTANT: HOW TO USE THIS INFORMATION: This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.
Formulary
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