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# Dextromethorphan (DXC) ## Overview Dextromethorphan is a synthetic dextrorotatory isomer of levorphanol. It acts centrally on the medulla oblongata to elevate the cough threshold. It lacks analgesic, addictive, or respiratory depressant properties at therapeutic doses. ## Primary Indications Symptomatic relief of non-productive cough associated with common cold, bronchitis, or inhaled irritants. ## Adult Dosing * **Immediate-release:** 10–20 mg every 4 hours or 30 mg every 6–8 hours. * **Extended-release:** 60 mg every 12 hours. * **Maximum:** 120 mg per 24 hours. ## Pediatric Dosing * **Children 6–12 years:** 5–10 mg every 4 hours or 15 mg every 6–8 hours. Maximum 60 mg/24 hours. * **Children 4–6 years:** 2.5–5 mg every 4 hours or 7.5 mg every 6–8 hours. Maximum 30 mg/24 hours. * *Note: Use is generally discouraged in children <4 years due to lack of evidence and risk of adverse events; check local institutional protocols/labeling restrictions.* ## Dose Adjustments * **Hepatic Impairment:** Reduce dose or increase dosing interval in patients with severe hepatic impairment; monitor for toxicity. * **Renal Impairment:** No specific adjustments provided by manufacturer, but monitor for accumulation. ## Contraindications * Hypersensitivity to the drug. * Concurrent use of MAO inhibitors (MAOIs) or within 14 days of discontinuing MAOI therapy (risk of serotonin syndrome). ## Adverse Effects * **Common:** Dizziness, drowsiness, nausea, vomiting, abdominal discomfort. * **Rare/Serious:** Serotonin syndrome (when combined with serotonergic agents), abuse/dependency (at supratherapeutic doses), hallucinations/psychosis. ## Key Drug Interactions * **MAOIs:** Fatal hyperpyrexia, coma, and death. * **SSRIs/SNRIs/TCAs:** Increased risk of serotonin syndrome. * **CNS Depressants:** Additive sedation with alcohol, opioids, or benzodiazepines. * **CYP2D6 Inhibitors (e.g., fluoxetine, quinidine):** May increase dextromethorphan plasma concentrations. ## Monitoring * Monitor for symptom relief and duration of cough (do not use for >7 days). * Assess for excessive sedation or altered mental status. * Evaluate for potential misuse or dependence in populations with history of substance use disorder. ## Clinical Pearls * Dextromethorphan is structurally related to codeine but acts as an NMDA receptor antagonist at high doses, leading to dissociative effects similar to ketamine or PCP. * Not indicated for productive cough or chronic cough (e.g., smoking, emphysema, asthma). * Formulations often contain combination ingredients (acetaminophen, antihistamines, decongestants); always check labels to prevent accidental overdose of secondary components. *** **Educational Disclaimer:** This information is for educational purposes only. Clinical practice varies by institution and jurisdiction. Always verify the most current prescribing information via official FDA-approved labeling (e.g., DailyMed) or clinical decision support tools (e.g., Lexicomp, UpToDate) before prescribing or administering medication.