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# Dextromethorphan/Guaifenesin
## Overview
Dextromethorphan is a cough suppressant, and guaifenesin is an expectorant. This combination product is intended to relieve cough and thin mucus.
## Primary Indications
* Symptomatic relief of cough associated with the common cold.
* Aids in the loosening of mucus.
## Adult Dosing
* **Dextromethorphan:** Typically 10-20 mg every 4 hours, or 30 mg every 6-8 hours. Maximum 120 mg per 24 hours.
* **Guaifenesin:** Typically 200-400 mg every 4 hours. Maximum 2400 mg per 24 hours.
* **Combination Products:** Dosing varies widely by formulation. Always check the specific product label for the correct dosage of both active ingredients. For example, one common formulation is 10 mg dextromethorphan HBr and 600 mg guaifenesin every 12 hours.
## Pediatric Dosing
* **Dextromethorphan:**
* 6 to <12 years: 5-10 mg every 4 hours, or 15 mg every 6-8 hours. Maximum 60 mg per 24 hours.
* <6 years: Use is generally not recommended due to increased risk of adverse effects and lack of clear benefit. Consult a pediatrician.
* **Guaifenesin:**
* 6 to <12 years: 100-200 mg every 4 hours. Maximum 1200 mg per 24 hours.
* <6 years: Use is generally not recommended. Consult a pediatrician.
* **Combination Products:** Dosing varies widely. **Always consult product labeling or a pediatrician.** Combination products are often not recommended for children under 6 years of age.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustments are typically required for dextromethorphan or guaifenesin, but caution is advised, especially in severe impairment.
* **Hepatic Impairment:** Dextromethorphan undergoes hepatic metabolism. Caution and potential dose reduction may be considered in severe hepatic impairment.
## Contraindications
* Hypersensitivity to dextromethorphan or guaifenesin.
* Concurrent use of MAO inhibitors or within 14 days of discontinuing MAO inhibitors (for dextromethorphan).
* Use in children under 6 years of age for combination products is often contraindicated by manufacturers.
## Adverse Effects
* **Dextromethorphan:** Dizziness, drowsiness, nausea, vomiting, confusion, hallucinations (at high doses). Serotonin syndrome is a risk with co-administration of other serotonergic agents.
* **Guaifenesin:** Nausea, vomiting, dizziness, headache, rash.
## Key Drug Interactions
* **MAO Inhibitors:** Potentially life-threatening serotonin syndrome with dextromethorphan.
* **SSRIs, SNRIs, Tricyclic Antidepressants, Triptans, Opioids (tramadol, meperidine), Linezolid, St. John's Wort:** Increased risk of serotonin syndrome with dextromethorphan.
* **CNS Depressants (e.g., alcohol, benzodiazepines, sedatives):** Additive CNS depression.
## Monitoring
* Assess cough frequency and severity.
* Monitor for signs of adverse effects, particularly CNS effects with dextromethorphan.
* Monitor for signs of serotonin syndrome (agitation, confusion, rapid heart rate, sweating, tremors, muscle rigidity).
## Clinical Pearls
* Ensure the correct dosage of both dextromethorphan and guaifenesin is administered, as combination product strengths vary significantly.
* Dextromethorphan is an NMDA receptor antagonist and can cause dissociative effects at supratherapeutic doses.
* Guaifenesin's efficacy is debated; adequate hydration is crucial for its expectorant effect.
* Avoid in children under 6 years of age for combination products unless specifically directed by a healthcare provider.
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*This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and institutional protocols before administering any medication.*
