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# Dextromethorphan/Guaifenesin (e.g., Delsym 12-Hour, Robitussin Chest Congestion) ## Overview Dextromethorphan is a cough suppressant. Guaifenesin is an expectorant, intended to thin mucus to make coughs more productive. Combination products are used for symptomatic relief of cough and chest congestion. ## Primary Indications * Cough associated with the common cold. * Chest congestion due to mucus. ## Adult Dosing * **Dextromethorphan 60 mg / Guaifenesin 600 mg extended-release liquid:** 10 mL every 12 hours. Do not exceed 20 mL in 24 hours. * Other formulations exist with varying strengths and dosing frequencies. Always consult the specific product label. ## Pediatric Dosing * **Dextromethorphan 60 mg / Guaifenesin 600 mg extended-release liquid:** * **12 years and older:** 10 mL every 12 hours. * **6 to under 12 years:** 5 mL every 12 hours. * **Under 6 years:** Safety and efficacy not established. Consult a pediatrician. ## Dose Adjustments No specific dose adjustments are routinely recommended for renal or hepatic impairment, but caution may be warranted. Consult product labeling and consider individual patient factors. ## Contraindications * Known hypersensitivity to dextromethorphan or guaifenesin. * Use with or within 14 days of MAO inhibitors. * Active ingredient in Robitussin Nighttime Cough is diphenhydramine. Dextromethorphan combination products may contain other active ingredients; always review the full list. ## Adverse Effects * **Common:** Dizziness, drowsiness, nausea, vomiting, stomach upset. * **Less Common/Serious:** Serotonin syndrome (especially with other serotonergic agents), respiratory depression (rare, typically with overdose or in susceptible individuals), abuse potential with dextromethorphan. ## Key Drug Interactions * **MAO Inhibitors:** Potentially fatal serotonin syndrome. * **Serotonergic Agents (e.g., SSRIs, SNRIs, triptans):** Increased risk of serotonin syndrome. * **CNS Depressants (e.g., alcohol, benzodiazepines):** Additive sedation and respiratory depression. * **CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine, quinidine):** May increase dextromethorphan levels, increasing risk of toxicity. ## Monitoring * Monitor for cough suppression and mucus clearance. * Assess for adverse effects, particularly drowsiness, dizziness, and signs of serotonin syndrome. ## Clinical Pearls * Extended-release formulations should not be crushed or chewed. * Dextromethorphan carries a risk of abuse and misuse, especially in adolescents. * Ensure adequate hydration to aid guaifenesin's expectorant effect. * If cough persists for more than 7 days, is accompanied by fever, rash, or persistent headache, discontinue use and consult a healthcare provider. *** *Disclaimer: This information is intended for educational purposes and does not substitute for professional medical advice. Always consult the most current prescribing information and your healthcare provider to ensure appropriate use and patient safety.*