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# Dextromethorphan/Guaifenesin
## Overview
Dextromethorphan is a cough suppressant. Guaifenesin is an expectorant that helps thin mucus. This combination is found in various over-the-counter formulations.
## Primary Indications
* Relief of cough associated with the common cold.
* Loosening of mucus associated with the common cold.
## Adult Dosing
Dosing varies significantly by product formulation. Always refer to the specific product labeling.
* **Dextromethorphan:** Typically 10 mg to 20 mg every 4 hours, or 30 mg every 6-8 hours. Maximum dose is generally 120 mg per 24 hours.
* **Guaifenesin:** Typically 200 mg to 400 mg every 4 hours. Maximum dose is generally 2400 mg per 24 hours.
Refer to specific product labeling for combined dosing, as strengths and frequencies differ.
## Pediatric Dosing
Dosing varies by age and product formulation. Consult specific product labeling for age-appropriate dosing. Many products are not recommended for children under 4 or 6 years of age.
* **Dextromethorphan:**
* **Ages 6-11 years:** 5 mg to 10 mg every 4 hours, or 15 mg every 6-8 hours. Maximum dose is generally 60 mg per 24 hours.
* **Ages 12 years and older:** Same as adult dosing.
* **Guaifenesin:**
* **Ages 6-11 years:** 100 mg to 200 mg every 4 hours. Maximum dose is generally 1200 mg per 24 hours.
* **Ages 12 years and older:** Same as adult dosing.
## Dose Adjustments
* **Hepatic Impairment:** Use with caution. Dextromethorphan is metabolized by the liver; impaired hepatic function may increase exposure. Specific dose adjustments are not well-established for OTC products; consider reduced frequency or dose.
## Contraindications
* Hypersensitivity to dextromethorphan or guaifenesin.
* Use within 14 days of initiating or discontinuing a monoamine oxidase inhibitor (MAOI) due to the risk of serotonin syndrome with dextromethorphan.
* Do not use for chronic cough (e.g., associated with asthma, emphysema, or persistent cough) unless directed by a healthcare provider.
## Adverse Effects
* **Common:** Nausea, vomiting, dizziness, drowsiness, headache.
* **Dextromethorphan Specific:** Potential for abuse and misuse, serotonin syndrome (especially with concomitant serotonergic agents), respiratory depression (at supratherapeutic doses).
* **Guaifenesin Specific:** Generally well-tolerated; rash and other allergic reactions are rare.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Contraindicated within 14 days of MAOI use due to risk of serotonin syndrome.
* **Serotonergic Agents (e.g., SSRIs, SNRIs, triptans, tramadol):** Increased risk of serotonin syndrome when used with dextromethorphan.
* **Central Nervous System (CNS) Depressants (e.g., alcohol, sedatives, benzodiazepines):** Additive CNS depression.
* **CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine, quinidine):** May increase dextromethorphan levels and risk of toxicity.
## Monitoring
* Monitor for effectiveness of cough suppression and mucus thinning.
* Monitor for adverse effects, particularly CNS effects and signs of serotonin syndrome.
* Assess for signs of drug misuse or abuse.
## Clinical Pearls
* Guaifenesin is most effective when adequate hydration is maintained.
* Dextromethorphan can cause dizziness; advise patients to avoid operating heavy machinery or driving until they know how it affects them.
* Be aware of combination products containing other active ingredients (e.g., decongestants, antihistamines, analgesics) which may have additional contraindications, interactions, and side effects.
* Dextromethorphan has a potential for abuse; counsel patients on appropriate use.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant literature before making clinical decisions. Dosing recommendations can vary based on specific product formulations and local protocols.*
