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# Dextromethorphan/Guaifenesin
## Overview
Dextromethorphan is a cough suppressant, and guaifenesin is an expectorant.
## Primary Indications
* Symptomatic relief of cough and chest congestion associated with the common cold.
## Adult Dosing
* **Dextromethorphan:** 10 mg to 20 mg by mouth every 4 hours, OR 30 mg by mouth every 6 to 8 hours.
* **Guaifenesin:** 200 mg to 400 mg by mouth every 4 hours.
* **Combination Products:** Dosing varies by product; refer to specific product labeling. Common doses include dextromethorphan 10-20 mg and guaifenesin 200-400 mg every 4-6 hours.
* Maximum dose for dextromethorphan is generally 120 mg in 24 hours. Maximum dose for guaifenesin is typically 2400 mg in 24 hours.
## Pediatric Dosing
* **Dextromethorphan:**
* 6 to 12 years: 5 mg to 10 mg by mouth every 4 hours, OR 15 mg by mouth every 6 to 8 hours. Maximum dose 60 mg in 24 hours.
* Under 6 years: Dosing is not recommended by many guidelines due to risk of adverse effects and lack of proven efficacy. Consult product labeling and consider age-appropriate alternatives.
* **Guaifenesin:**
* 6 to 12 years: 100 mg to 200 mg by mouth every 4 hours. Maximum dose 1200 mg in 24 hours.
* Under 6 years: Dosing varies by product; consult specific labeling. Many products are not recommended for children under 6 years.
* **Combination Products:** Dosing varies significantly by product and age. **Always refer to specific product labeling for pediatric dosing recommendations.**
## Dose Adjustments
* No specific dose adjustments are typically required for renal or hepatic impairment, but caution is advised, and lower doses may be considered.
## Contraindications
* Hypersensitivity to dextromethorphan or guaifenesin.
* Use with or within 14 days of MAO inhibitors (for dextromethorphan).
* Concurrent use of certain antidepressants (SSRIs, SNRIs, tricyclic antidepressants) and other drugs that increase serotonin levels due to the risk of serotonin syndrome (for dextromethorphan).
* Children under 4 years of age for combination cough and cold products, per FDA recommendations.
## Adverse Effects
* **Dextromethorphan:** Dizziness, drowsiness, nausea, vomiting, confusion, hallucinations (rare at therapeutic doses).
* **Guaifenesin:** Nausea, vomiting, dizziness, headache.
## Key Drug Interactions
* **Dextromethorphan:**
* MAO inhibitors: Risk of hypertensive crisis.
* SSRIs, SNRIs, tricyclic antidepressants, buspirone, fentanyl, lithium, tramadol, St. John's wort: Increased risk of serotonin syndrome.
* CYP2D6 inhibitors (e.g., quinidine, fluoxetine, paroxetine, sertraline): May increase dextromethorphan levels, increasing risk of toxicity.
* Alcohol and CNS depressants: Additive sedative effects.
* **Guaifenesin:** Generally considered to have minimal significant drug interactions.
## Monitoring
* Monitor for efficacy (cough suppression, thinning of mucus).
* Monitor for adverse effects, particularly CNS effects with dextromethorphan.
* Monitor for signs and symptoms of serotonin syndrome if used with serotonergic agents.
## Clinical Pearls
* Dextromethorphan is an NMDA receptor antagonist and sigma-1 receptor agonist.
* Guaifenesin works by increasing respiratory tract fluid secretions, which helps to loosen mucus in the airways.
* Combination products can be convenient but may lead to over-treatment or inappropriate dosing of individual components. Assess the patient's specific needs before recommending.
* Adequate hydration is important for guaifenesin's efficacy.
* Avoid concomitant use of other medications containing dextromethorphan to prevent overdose.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always verify current prescribing information, drug interactions, and patient-specific factors before making treatment decisions.*
