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 |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for DEXTROMETHORPHAN POLISTIREX (DEXTROMETHORPHAN POLISTIREX).
| Breastfeeding | Limited data; excreted in human breast milk in low amounts (M/P ratio not established). Theoretical risk of CNS depression in infant. Use with caution, especially in neonates or preterm infants. Consider immediate-release formulations if necessary. |
| 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. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Concurrent use or within 14 days of MAOIs","Hypersensitivity to dextromethorphan or any component","Use in children under 2 years of age (OTC products)"]
| 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"] |
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| 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. |