DEXTROMETHORPHAN POLISTIREX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DEXTROMETHORPHAN POLISTIREX (DEXTROMETHORPHAN POLISTIREX).
Dextromethorphan polistirex is an NMDA receptor antagonist and sigma-1 receptor agonist. It inhibits serotonin reuptake and acts on the brain stem cough center to elevate the threshold for coughing.
| Metabolism | Hepatic via CYP2D6 (O-demethylation to dextrorphan, active metabolite). Also undergoes N-demethylation via CYP3A4. Polymorphic metabolism (poor metabolizers at risk of toxicity). |
| Excretion | Renal: ~45% as unchanged drug and metabolites (dextrorphan conjugates); fecal: <2%; biliary: minimal |
| Half-life | Terminal half-life: 13–19 hours; clinical context: extended-release formulation due to polistirex complex; time to steady-state: ~3 days |
| Protein binding | ~50% bound; primarily to albumin |
| Volume of Distribution | Vd: ~5–6 L/kg; clinical meaning: extensive tissue distribution, including CNS |
| Bioavailability | Oral (polistirex): approximately 50–60% (first-pass metabolism reduces systemic availability) |
| Onset of Action | Oral (polistirex): 15–30 minutes; clinical effect: antitussive action within 30–60 minutes |
| Duration of Action | Duration: 8–12 hours; clinical note: sustained-release formulation provides prolonged cough suppression |
| Molecular Weight | 370.48 |
30-60 mg orally every 12 hours; not to exceed 120 mg in 24 hours.
| Dosage form | SUSPENSION, EXTENDED RELEASE |
| Renal impairment | No specific dosing adjustment provided for dextromethorphan polistirex; use with caution in severe renal impairment (CrCl < 30 mL/min) due to potential accumulation of metabolites. |
| Liver impairment | No specific dosing adjustment provided; use with caution in severe hepatic impairment (Child-Pugh class C) due to reduced clearance. |
| Pediatric use | Children 6-12 years: 15-30 mg orally every 12 hours; not to exceed 60 mg in 24 hours. Children 2-5 years: 7.5-15 mg orally every 12 hours; not to exceed 30 mg in 24 hours. Not recommended under 2 years. |
| Geriatric use | Elderly patients may be more sensitive to anticholinergic effects; use the lowest effective dose and monitor for adverse effects such as sedation and dizziness. |
| 1st trimester | Limited human data; animal studies have not shown teratogenicity. Use only if benefit outweighs risk. |
| 2nd trimester | No known increased risk of major malformations; however, use with caution due to limited data. |
| 3rd trimester | Avoid use near term due to potential respiratory depression in neonates. |
Clinical note
Comprehensive clinical and safety monograph for DEXTROMETHORPHAN POLISTIREX (DEXTROMETHORPHAN POLISTIREX).
| Placental transfer | Dextromethorphan crosses the placenta; fetal concentrations may be similar to maternal. |
| Breastfeeding | Dextromethorphan is excreted into breast milk in small amounts; however, typical maternal doses are unlikely to cause adverse effects in infants. Monitor for sedation or respiratory depression. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Concurrent use or within 14 days of monoamine oxidase inhibitors (MAOIs)Known hypersensitivity to dextromethorphan or any component of the formulation
| Precautions | Do not use with MAOIs or within 14 days of stopping MAOIs, Risk of serotonin syndrome when used with serotonergic drugs, Caution in patients with G6PD deficiency, hepatic impairment, or chronic cough associated with smoking, asthma, or emphysema, QT prolongation risk at supratherapeutic doses, Misuse potential with high doses causing dissociative effects |
| Food/Dietary | Avoid grapefruit and grapefruit juice as they may alter metabolism. Take with or without food; food does not significantly affect absorption. |
Loading safety data…
| Lactation Rating |
| L2 (Safer) |
| Teratogenic Risk | No well-controlled studies in pregnant women. Animal studies have not shown evidence of fetal harm. Based on limited human data, risk of major congenital malformations is low. Avoid use in first trimester due to theoretical risk based on weak NMDA antagonism. |
| Fetal Monitoring | Monitor for maternal sedation, dizziness, and respiratory depression. Fetal monitoring not routinely required unless maternal overuse or toxicity suspected. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies have not shown impairment of fertility. |
| Clinical Pearls | Dextromethorphan polistirex is an extended-release formulation allowing twice-daily dosing. Its antitussive effect lasts up to 12 hours. Caution in patients with asthma or COPD as it may reduce mucociliary clearance. Avoid concurrent use with MAOIs due to risk of serotonin syndrome. Not effective for chronic cough and should not be used for more than 7 days. |
| Patient Advice | Do not crush or chew the extended-release capsules or suspension; swallow whole or shake suspension well before use. · Do not exceed recommended doses; may cause drowsiness, avoid driving or operating machinery. · Discontinue use and consult healthcare provider if cough persists more than 7 days or is accompanied by fever, rash, or headache. · Avoid alcohol and other CNS depressants as they may increase sedation. · Inform healthcare provider if you are taking MAOIs (e.g., for depression, Parkinson's) or SSRIs to avoid serotonin syndrome. · Keep out of reach of children; overdose can be fatal. |