Dosing & Uses
Dosage Forms & Strengths
tablet
- 15mg
capsule
- 15mg
gel, oral
- 7.5mg/5mL
liquid, oral
- 7.5mg/5mL
- 10mg/5mL
- 15mg/5mL
syrup, oral
- 5mg/5mL
- 7.5mg/5mL
- 10mg/5mL
- 15mg/5mL
- 20mg/15mL
liquid, extended release
- 30mg/5mL
lozenge
- 5mg
- 7.5mg
- 15mg
strip, oral
- 7.5mg
Cough
Liquid and syrup: 10-20 mg PO q4hr OR 30 mg q6-8hr
Gel: 30 mg PO q6-8hr; not to exceed 120 mg/24hr
Extended release: 60 mg PO q12hr; not to exceed 120 mg/24hr
Lozenges: 5-15 mg PO q1-4hr; not to exceed 120 mg/day
Strips: 30 mg PO q6-8hr; not to exceed 120 mg/day
Dosing considerations
- Abuse potential much lower than codeine
- About 15-30 mg dextromethorphan equal to 8-15 mg codeine as an antitussive
Dosage Forms & Strengths
tablet
- 15mg
capsule
- 15mg
- 25mg
gel, oral
- 7.5mg/5mL
syrup
- 5mg/5mL
- 7.5mg/5mL
- 10mg/5mL
- 15mg/5mL
- 20mg/15mL
liquid, extended release
- 30mg/5mL
lozenge
- 5mg
- 7.5mg
- 15mg
strip, oral
- 7.5mg
Cough
<4 years
- Prescription only
Extended release
- 4-6 years: 15 mg PO twice daily; not to exceed 30 mg/24hr
- 6-12 years: 30 mg PO twice daily; not to exceed 60 mg/24hr
- >12 years: 60 mg PO q12hr; not to exceed 120 mg/24hr
Liquid/Syrup
- 4-6 years: 7.5 mg q6-8hr (not to exceed 30 mg/day)
- 6-12 years: 15 mg PO q6-8hr; not to exceed 60 mg/24hr
- 12 years: 10-20 mg PO q4hr or 30 mg q6-8hr not to exceed 120 mg/24hr
Gel
- >12 years: 30 mg PO q6-8hr; not to exceed 120 mg/24hr
Lozenges
- 6-12 years: 5-10 mg q1-4hr; not to exceed 60 mg/day
- >12 years: 5-15 mg PO q1-4hr; not to exceed 120 mg/day
Strips
- 6-12 years: 15 mg PO q6-8hr; not to exceed 60 mg/day
- >12 years: 30 mg PO q6-8hr; not to exceed 120 mg/day
Dosing considerations
Interactions
Interaction Checker
No Results

Contraindicated
Serious - Use Alternative
Significant - Monitor Closely
Minor

Contraindicated (7)
- isocarboxazid
isocarboxazid and dextromethorphan both increase serotonin levels. Contraindicated.
- phenelzine
phenelzine and dextromethorphan both increase serotonin levels. Contraindicated.
- procarbazine
procarbazine and dextromethorphan both increase serotonin levels. Contraindicated. Combination is contraindicated within 2 weeks of MAOI use.
- rasagiline
rasagiline and dextromethorphan both increase serotonin levels. Contraindicated. Risk of psychosis episodes or bizarre behavior.
- safinamide
dextromethorphan, safinamide. Other (see comment). Contraindicated. Comment: Coadministration of MAOIs and dextromethorphan has been reported to cause episodes of psychosis or bizarre behavior.
- selegiline
selegiline and dextromethorphan both increase serotonin levels. Contraindicated.
- tranylcypromine
tranylcypromine and dextromethorphan both increase serotonin levels. Contraindicated.
Serious - Use Alternative (34)
- amitriptyline
amitriptyline and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- amoxapine
amoxapine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- buspirone
buspirone and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- citalopram
citalopram and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug. Combination may increase risk of serotonin syndrome or neuroleptic malignant syndrome-like reactions.
- clomipramine
clomipramine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- desipramine
desipramine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- desvenlafaxine
dextromethorphan and desvenlafaxine both increase serotonin levels. Avoid or Use Alternate Drug.
- doxepin
doxepin and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- duloxetine
duloxetine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
duloxetine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug. - escitalopram
escitalopram and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- fluoxetine
fluoxetine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
fluoxetine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug. - fluvoxamine
fluvoxamine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- grapefruit
grapefruit will increase the level or effect of dextromethorphan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- imipramine
imipramine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- levomilnacipran
levomilnacipran and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- linezolid
linezolid and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug. Linezolid may increase serotonin as a result of MAO-A inhibition. If linezolid must be administered, discontinue serotonergic drug immediately and monitor for CNS toxicity. Serotonergic therapy may be resumed 24 hours after last linezolid dose or after 2 weeks of monitoring, whichever comes first.
- lofepramine
lofepramine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- lorcaserin
dextromethorphan and lorcaserin both increase serotonin levels. Avoid or Use Alternate Drug.
- maprotiline
maprotiline and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- memantine
memantine, dextromethorphan. Either increases toxicity of the other by pharmacodynamic synergism. Contraindicated.
- meperidine
dextromethorphan and meperidine both increase serotonin levels. Avoid or Use Alternate Drug.
- methylene blue
methylene blue and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug. Methylene blue may increase serotonin as a result of MAO-A inhibition. If methylene blue must be administered, discontinue serotonergic drug immediately and monitor for CNS toxicity. Serotonergic therapy may be resumed 24 hours after last methylene blue dose or after 2 weeks of monitoring, whichever comes first.
- milnacipran
milnacipran and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- nefazodone
nefazodone and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- nortriptyline
nortriptyline and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- paroxetine
paroxetine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
paroxetine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug. - protriptyline
protriptyline and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- selegiline transdermal
selegiline transdermal and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- sertraline
sertraline and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- St John's Wort
dextromethorphan and St John's Wort both increase serotonin levels. Avoid or Use Alternate Drug.
- trazodone
trazodone and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- trimipramine
trimipramine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.
- venlafaxine
venlafaxine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.
venlafaxine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug. - vilazodone
dextromethorphan, vilazodone. Either increases toxicity of the other by serotonin levels. Avoid or Use Alternate Drug. Concomitant therapy should be discontinued immediately if signs or symptoms of serotonin syndrome emerge and supportive symptomatic treatment should be initiated. .
Monitor Closely (61)
- 5-HTP
5-HTP and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.
- abiraterone
abiraterone increases levels of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Avoid coadministration of abiraterone with substrates of CYP2D6. If alternative therapy cannot be used, exercise caution and consider a dose reduction of the CYP2D6 substrate.
- almotriptan
almotriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.
- amphetamine
amphetamine, dextromethorphan. Either increases effects of the other by serotonin levels. Use Caution/Monitor. Monitor for signs and symptoms of serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability, mental status changes) when amphemtamines are coadministered with dextromethorphan. .
- aripiprazole
dextromethorphan, aripiprazole. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- artemether/lumefantrine
artemether/lumefantrine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- asenapine
dextromethorphan, asenapine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- bupropion
bupropion will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- cariprazine
dextromethorphan, cariprazine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- clobazam
clobazam will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Lower doses of drugs metabolized by CYP2D6 may be required when used concomitantly.
- clozapine
dextromethorphan, clozapine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- cocaine topical
cocaine topical and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.
- desvenlafaxine
desvenlafaxine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Desvenlafaxine inhibits CYP2D6; with higher desvenlafaxine doses (ie, 400 mg) decrease the CYP2D6 substrate dose by up to 50%; no dosage adjustment needed with desvenlafaxine doses <100 mg
- dexfenfluramine
dexfenfluramine and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.
- dextroamphetamine
dextroamphetamine, dextromethorphan. Either increases effects of the other by serotonin levels. Use Caution/Monitor. Monitor for signs and symptoms of serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability, mental status changes) when amphemtamines are coadministered with dextromethorphan. .
- dextroamphetamine transdermal
dextromethorphan, dextroamphetamine transdermal. Either increases effects of the other by serotonin levels. Modify Therapy/Monitor Closely. Initiate with lower doses and monitor for signs and symptoms of serotonin syndrome, particularly during initiation or dosage increase. If serotonin syndrome occurs, discontinue dextroamphetamine transdermal and concomitant serotonergic drug(s).
dextroamphetamine transdermal, dextromethorphan. Either increases effects of the other by serotonin levels. Use Caution/Monitor. Monitor for signs and symptoms of serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability, mental status changes) when amphemtamines are coadministered with dextromethorphan. . - dihydroergotamine
dextromethorphan and dihydroergotamine both increase serotonin levels. Modify Therapy/Monitor Closely.
- dihydroergotamine intranasal
dextromethorphan and dihydroergotamine intranasal both increase serotonin levels. Modify Therapy/Monitor Closely.
- eletriptan
eletriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.
- ergotamine
dextromethorphan and ergotamine both increase serotonin levels. Modify Therapy/Monitor Closely.
- fenfluramine
dextromethorphan and fenfluramine both increase serotonin levels. Modify Therapy/Monitor Closely.
fenfluramine, dextromethorphan. Either increases effects of the other by serotonin levels. Use Caution/Monitor. Coadministration with drugs that increase serotoninergic effects may increase the risk of serotonin syndrome. - fluphenazine
dextromethorphan, fluphenazine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- frovatriptan
frovatriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.
- gepirone
gepirone and dextromethorphan both increase serotonin levels. Use Caution/Monitor. Monitor for symptoms of serotonin syndrome when gepirone is used gepirone with other drugs that may affect the serotonergic neurotransmitter systems. If serotonin syndrome occurs, consider discontinue gepirone and/or concomitant serotonergic drug.
- haloperidol
dextromethorphan, haloperidol. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- iloperidone
dextromethorphan, iloperidone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- isoniazid
dextromethorphan and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.
- L-tryptophan
dextromethorphan and L-tryptophan both increase serotonin levels. Modify Therapy/Monitor Closely.
- letermovir
letermovir increases levels of dextromethorphan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- lithium
dextromethorphan and lithium both increase serotonin levels. Modify Therapy/Monitor Closely.
- loxapine
dextromethorphan, loxapine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- loxapine inhaled
dextromethorphan, loxapine inhaled. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- lsd
dextromethorphan and lsd both increase serotonin levels. Modify Therapy/Monitor Closely.
- lumefantrine
lumefantrine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- lurasidone
dextromethorphan, lurasidone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- mirtazapine
dextromethorphan and mirtazapine both increase serotonin levels. Modify Therapy/Monitor Closely.
- molindone
dextromethorphan, molindone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- morphine
dextromethorphan and morphine both increase serotonin levels. Modify Therapy/Monitor Closely.
- naratriptan
naratriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.
- olanzapine
dextromethorphan, olanzapine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- paliperidone
dextromethorphan, paliperidone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- panobinostat
panobinostat will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Panobinostat can increase the levels and effects of sensitive CYP2D6 substrates or those with a narrow therapeutic index CYP2D6.
- pazopanib
pazopanib increases levels of dextromethorphan by decreasing metabolism. Use Caution/Monitor.
- peginterferon alfa 2b
peginterferon alfa 2b, dextromethorphan. Other (see comment). Use Caution/Monitor. Comment: When patients are administered peginterferon alpha-2b with CYP2D6 substrates, the therapeutic effect of these drugs may be altered. Peginterferon alpha-2b may increase or decrease levels of CYP2D6 substrate.
- pentazocine
dextromethorphan and pentazocine both increase serotonin levels. Modify Therapy/Monitor Closely.
- perphenazine
dextromethorphan, perphenazine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- pimavanserin
dextromethorphan, pimavanserin. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- pimozide
dextromethorphan, pimozide. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- quetiapine
dextromethorphan, quetiapine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- quinidine
quinidine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
- risperidone
dextromethorphan, risperidone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- rizatriptan
rizatriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.
- rolapitant
rolapitant will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Monitor for adverse reactions when unable to avoid coadministration with narrow therapeutic index CYP2D6 substrates.
- SAMe
dextromethorphan and SAMe both increase serotonin levels. Modify Therapy/Monitor Closely.
- sumatriptan
sumatriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.
- sumatriptan intranasal
sumatriptan intranasal and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.
- thiothixene
dextromethorphan, thiothixene. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- tramadol
dextromethorphan and tramadol both increase serotonin levels. Modify Therapy/Monitor Closely.
- trifluoperazine
dextromethorphan, trifluoperazine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- ziprasidone
dextromethorphan, ziprasidone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).
- zolmitriptan
zolmitriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.
Minor (22)
- amiodarone
amiodarone will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- asenapine
asenapine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- celecoxib
celecoxib will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- chloroquine
chloroquine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- cimetidine
cimetidine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- darifenacin
darifenacin will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- diphenhydramine
diphenhydramine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- dronedarone
dronedarone will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- haloperidol
haloperidol will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- imatinib
imatinib will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- maraviroc
maraviroc will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- marijuana
marijuana will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- nilotinib
nilotinib will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- parecoxib
parecoxib will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- perphenazine
perphenazine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- propafenone
propafenone will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- quinacrine
quinacrine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- ranolazine
ranolazine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- ritonavir
ritonavir will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- sertraline
sertraline will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- thioridazine
thioridazine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
- tipranavir
tipranavir will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
Adverse Effects
Common
Nausea
Vomiting
Constipation
Drowsiness
Dizziness
Sedation
Confusion
Nervousness
Warnings
Contraindications
Concurrent nonselective MAO inhibitors: Serotonin syndrome
Cautions
Do not take for persistent or chronic cough associated with smoking, asthma, or emphysema, or if it is accompanied by excessive phlegm unless directed by a healthcare provider; may slow respiration rate
Hallucinations, confusion, agitation, hyper-reflexia, shivering, myoclonus, and tachycardia may occur
Caution in children younger than 6 years
Not for OTC use in children <4 years
Use caution in patients who are sedated, debilitated or confined to supine position
Pregnancy & Lactation
Pregnancy category: C
Lactation: Not known if excreted in breast milk; use caution
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
Acts on cough center in medulla; decreases sensitivity of cough receptors and interrupts cough impulse transmission
Derivative of levorphanol
Absorption
Onset: 15-30 min
Duration: ≤6 hr
Time to peak: 2-3hr
Metabolism
Hepatic P450 enzyme CYP2D6
Elimination
Half-life: 2-4hr (extensive metabolizers); 24 hr (poor metabolizers)
Excretion: Urine
Pharmacogenomics
CYP2D6 substrate
Approximately 7-10% of Caucasians and 3-8% of African Americans lack the capacity to metabolize CYP2D6 substrates and are classified as poor metabolizers
Genetic testing laboratories
- Genotyping tests for CYP2D6 variants are commercially available through the following companies:
- Applied Biosystems (http://www.appliedbiosystems.com/)
- GenPath Diagnostics (http://www.genpathdiagnostics.com/)