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# Dextromethorphan ## Overview Dextromethorphan is a centrally acting cough suppressant. ## Primary Indications Symptomatic relief of cough. ## Adult Dosing * **Oral:** 10 mg to 20 mg every 4 hours as needed, or 30 mg every 6-8 hours as needed. * **Maximum:** Typically 120 mg in 24 hours. ## Pediatric Dosing * **Ages 6-12 years:** 5 mg to 10 mg every 4 hours as needed, or 15 mg every 6-8 hours as needed. * **Ages 2-5 years:** 2.5 mg to 5 mg every 4 hours as needed, or 7.5 mg every 6-8 hours as needed. * **Under 2 years:** Use is generally not recommended due to potential for serious adverse effects; consult with a pediatrician. ## Dose Adjustments No specific dose adjustments are typically required for renal or hepatic impairment, but caution is advised. ## Contraindications * Hypersensitivity to dextromethorphan. * Use within 14 days of monoamine oxidase inhibitors (MAOIs). * Concurrent use with certain selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, linezolid, or other drugs that inhibit CYP2D6 or are serotonergic may increase the risk of serotonin syndrome. ## Adverse Effects * Dizziness, drowsiness, nausea, vomiting, constipation. * Potential for abuse and dependence. * High doses can cause hallucinations, confusion, and respiratory depression. * Serotonin syndrome when used with serotonergic agents. ## Key Drug Interactions * **MAOIs:** Risk of hypertensive crisis and serotonin syndrome. * **SSRIs, SNRIs, TCAs, triptans, linezolid, tramadol:** Increased risk of serotonin syndrome. * **CYP2D6 Inhibitors (e.g., quinidine, fluoxetine, paroxetine):** May increase dextromethorphan plasma concentrations, leading to increased adverse effects. * **Alcohol:** May potentiate CNS depressant effects. ## Monitoring * Monitor for cough effectiveness. * Assess for adverse effects, particularly CNS effects and signs of serotonin syndrome (agitation, hallucinations, rapid heart rate, fever, sweating, muscle stiffness, tremor, loss of coordination). ## Clinical Pearls * Dextromethorphan is often found in combination products; ensure no duplication of ingredients if prescribing or recommending. * The risk of serotonin syndrome is a significant concern with concomitant serotonergic medications. * Due to its potential for abuse, consider careful patient selection and appropriate duration of use. *** **Disclaimer:** This information is intended for clinical decision support and does not replace current prescribing information. Always consult the official product monograph and relevant literature before making any treatment decisions.