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# Arsil (Dextromethorphan + Guaifenesin) ## Overview Arsil is a combination product typically containing **dextromethorphan hydrobromide** (an antitussive/cough suppressant) and **guaifenesin** (an expectorant). It is indicated for the temporary relief of coughs due to minor throat and bronchial irritation associated with the common cold or inhaled irritants. ## Primary Indications * Temporary relief of cough. * Loosening of bronchial secretions (mucus) to make coughs more productive. ## Adult Dosing * **Standard Formulation:** 10–20 mg (dextromethorphan) / 200–400 mg (guaifenesin) every 4 hours, or 30 mg / 600 mg every 6–8 hours. * **Maximum Dose:** Do not exceed 120 mg of dextromethorphan per 24 hours. ## Pediatric Dosing * **12 years and older:** Same as adult dosing. * **6 to <12 years:** 5–10 mg (dextromethorphan) / 100–200 mg (guaifenesin) every 4 hours. Maximum: 60 mg dextromethorphan/24 hours. * **Under 6 years:** Generally not recommended unless directed by a pediatrician. * *Note:* Always follow the specific concentration and labeling provided by the manufacturer for the chosen formulation. ## Dose Adjustments * **Renal/Hepatic Impairment:** No specific adjustment guidelines exist; however, use with caution in patients with severe impairment. * **Geriatric:** Start at the low end of the dosing range due to potential for increased sensitivity to CNS effects. ## Contraindications * Hypersensitivity to dextromethorphan, guaifenesin, or any excipients. * **MAOI Therapy:** Concurrent use or use within 14 days of monoamine oxidase inhibitors (MAOIs) due to the risk of serotonin syndrome. ## Adverse Effects * **Common:** Dizziness, drowsiness, nausea, vomiting, or stomach pain. * **Severe:** Serotonin syndrome (if taken with serotonergic agents), or confusion/hallucinations if taken in supra-therapeutic doses (dextromethorphan abuse). ## Key Drug Interactions * **Serotonergic Agents (SSRIs, SNRIs, TCAs):** Increase risk of serotonin syndrome. * **MAOIs:** Absolute contraindication. * **CNS Depressants (Alcohol, Opioids, Sedatives):** May potentiate sedative effects. * **CYP2D6 Inhibitors (e.g., Fluoxetine, Quinidine):** May increase plasma concentrations of dextromethorphan. ## Monitoring * Monitor for symptom resolution. * Discontinue use and consult a provider if the cough persists for >7 days, recurs, or is accompanied by fever, rash, or persistent headache. * Observe for signs of drug-seeking behavior or abuse in high-risk populations. ## Clinical Pearls * **Hydration:** Guaifenesin is most effective when taken with a full glass of water to help thin secretions. * **Product Selection:** Many OTC combination products have different active ingredient concentrations; always verify the *mg per mL* or *mg per tablet* before dosing. * **Efficacy:** Evidence for cough suppressants in acute cough is often modest; focus on hydration and environmental control. * **Caution:** Do not use for persistent or chronic cough (e.g., related to smoking, asthma, or emphysema) unless directed by a physician. *** **Educational Disclaimer:** This information is for educational purposes and does not substitute for professional medical judgment. Always verify current prescribing information, institutional protocols, and local drug product labeling before administering any medication.