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# Dextromethorphan/Guaifenesin ## Overview Dextromethorphan is a cough suppressant. Guaifenesin is an expectorant. This combination is used to relieve cough and thin mucus. ## Primary Indications Symptomatic relief of cough due to minor throat and bronchial irritation associated with the common cold. ## Adult Dosing * **Dextromethorphan 10 mg / Guaifenesin 100 mg per 5 mL:** 10 mL to 20 mL every 4 hours as needed. Maximum daily dose is 120 mL. * **Dextromethorphan 20 mg / Guaifenesin 200 mg per 10 mL:** 10 mL every 4 hours as needed. Maximum daily dose is 40 mL. * **Dextromethorphan 15 mg / Guaifenesin 100 mg tablet/capsule:** 1 to 2 tablets/capsules every 4 hours as needed. Maximum daily dose is 8 tablets/capsules. Specific dosing may vary based on the product formulation and local protocol. ## Pediatric Dosing * **Dextromethorphan 10 mg / Guaifenesin 100 mg per 5 mL:** * 6 to under 12 years: 5 mL to 10 mL every 4 hours as needed. Maximum daily dose is 60 mL. * 2 to under 6 years: 2.5 mL to 5 mL every 4 hours as needed. Maximum daily dose is 30 mL. * Under 2 years: Safety and efficacy not established. Consult a pediatrician. * **Dextromethorphan 20 mg / Guaifenesin 200 mg per 10 mL:** * 6 to under 12 years: 5 mL every 4 hours as needed. Maximum daily dose is 20 mL. * 2 to under 6 years: Dosing not recommended for this strength or formulation in children under 6 years. Consult a pediatrician. * Under 2 years: Safety and efficacy not established. Consult a pediatrician. * **Dextromethorphan 15 mg / Guaifenesin 100 mg tablet/capsule:** * 6 to under 12 years: 1 tablet/capsule every 4 hours as needed. Maximum daily dose is 4 tablets/capsules. * Under 6 years: Consult a pediatrician. ## Dose Adjustments No specific dose adjustments are typically required for renal or hepatic impairment, but caution and monitoring are advised due to potential for accumulation and increased side effects. ## Contraindications * Hypersensitivity to dextromethorphan or guaifenesin. * Concurrent use with MAO inhibitors or within 14 days of discontinuing MAO inhibitors (due to dextromethorphan). * Use in children under 2 years for liquid formulations unless directed by a physician. ## Adverse Effects * **Dextromethorphan:** Drowsiness, dizziness, nausea, vomiting, constipation. Higher doses can cause confusion, hallucinations, respiratory depression, and serotonin syndrome. * **Guaifenesin:** Nausea, vomiting, stomach pain, dizziness. ## Key Drug Interactions * **MAO Inhibitors:** Risk of severe hypertension or serotonin syndrome with dextromethorphan. * **SSRIs, SNRIs, TCAs, Opioids, Triptans, Buspirone, Tramadol:** Increased risk of serotonin syndrome with dextromethorphan. * **CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine, quinidine):** May increase dextromethorphan levels and toxicity. * **CNS Depressants (e.g., alcohol, benzodiazepines, opioids):** Additive sedative effects. ## Monitoring * Assess cough and sputum production. * Monitor for adverse effects, particularly drowsiness, dizziness, and signs of serotonin syndrome (agitation, confusion, rapid heart rate, hallucinations, fever). ## Clinical Pearls * Dextromethorphan can be a drug of abuse; counsel patients on appropriate use. * Encourage adequate fluid intake to help thin mucus when using guaifenesin. * If cough persists for more than 7 days, is accompanied by fever, rash, or persistent headache, discontinue use and consult a healthcare provider. * Be aware of combination products that may contain other active ingredients (e.g., decongestants, antihistamines, analgesics) and their associated risks and interactions. *** **Disclaimer:** This information is for educational purposes only and does not constitute medical advice. Always verify current prescribing information and consult with a qualified healthcare provider before making any treatment decisions.