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# Dextromethorphan/Guaifenesin (Various Formulations) ## Overview Dextromethorphan is a cough suppressant, and guaifenesin is an expectorant. These ingredients are commonly combined in various over-the-counter (OTC) formulations for symptomatic relief of cough and chest congestion. ## Primary Indications * Symptomatic relief of cough due to minor throat and bronchial irritation. * Helps loosen phlegm (mucus) and thin bronchial secretions to make coughs more productive. ## Adult Dosing Dosing varies significantly by specific product formulation (e.g., immediate-release, extended-release, liquids, tablets). Always consult the product label for specific dosing instructions. **General guidelines (consult product label for exact amounts):** * **Dextromethorphan:** Typically 10-30 mg every 4-12 hours. Maximum daily dose generally 120 mg. * **Guaifenesin:** Typically 200-400 mg every 4 hours or 600-1200 mg every 12 hours for extended-release formulations. Maximum daily dose generally 2400 mg. ## Pediatric Dosing Dosing varies significantly by specific product formulation and age. **Use with extreme caution in children under 4 years old.** Many products are not recommended for use in children under 6 or 12 years old without physician guidance. Always consult the product label or a pediatrician. **General guidelines (consult product label for exact amounts and age restrictions):** * **Children 6 to under 12 years:** Half the adult dose is often recommended, but specific product instructions must be followed. * **Children 4 to under 6 years:** Dosing is highly specific to the product and manufacturer. Consult a pediatrician. * **Children under 4 years:** Generally not recommended for OTC use. ## Dose Adjustments No specific dose adjustments are typically required for renal or hepatic impairment when used at recommended OTC dosages for short durations. However, caution is advised in patients with severe impairment. ## Contraindications * Hypersensitivity to dextromethorphan or guaifenesin. * Use within 14 days of an MAOI or within 2 weeks of stopping an MAOI (for dextromethorphan). * Certain formulations may be contraindicated in children under a specific age (refer to product labeling). ## Adverse Effects * **Dextromethorphan:** Dizziness, drowsiness, confusion, nausea, vomiting. High doses can cause euphoria, hallucinations, respiratory depression, and CNS effects. * **Guaifenesin:** Nausea, vomiting, dizziness, headache, rash. ## Key Drug Interactions * **Monoamine Oxidase Inhibitors (MAOIs):** Concomitant use with dextromethorphan can lead to serotonin syndrome, characterized by agitation, confusion, rapid heart rate, high blood pressure, muscle rigidity, and fever. * **Selective Serotonin Reuptake Inhibitors (SSRIs) / Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs):** Increased risk of serotonin syndrome when combined with dextromethorphan. * **CNS Depressants (e.g., alcohol, benzodiazepines, opioids):** Additive sedative effects. * **CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine, quinidine):** Can increase dextromethorphan plasma concentrations, potentially leading to toxicity. ## Monitoring * Monitor for effectiveness in suppressing cough and loosening phlegm. * Monitor for adverse effects, particularly CNS effects with dextromethorphan. * Monitor for signs of serotonin syndrome if concomitant serotonergic agents are used. ## Clinical Pearls * Dextromethorphan is an NMDA receptor antagonist and sigma-1 receptor agonist. * Guaifenesin works by increasing the volume and reducing the viscosity of secretions in the trachea and bronchi. * Product formulations vary widely in concentration and dosing frequency. **Always read and follow the specific product label directions.** * These products are for symptomatic relief only and do not treat the underlying cause of the cough or congestion. * Consult a healthcare professional if cough persists for more than 7 days, is accompanied by fever, rash, or persistent headache, or if significant side effects occur. * Be aware of the potential for abuse of dextromethorphan-containing products, especially in adolescents. *** **Disclaimer:** This information is for educational purposes only and does not substitute for professional medical advice. Always verify current prescribing information with the official drug labeling or consult a healthcare provider before making any treatment decisions.