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# Dextromethorphan (DM)
## Overview
Dextromethorphan is a cough suppressant that acts centrally on the cough center in the medulla.
## Primary Indications
* Symptomatic relief of cough.
## Adult Dosing
* **Oral:** Typically 10-20 mg every 4 hours as needed, or 30 mg every 6-8 hours as needed.
* **Maximum:** Generally 120 mg per 24 hours. Specific product formulations may have lower maximums.
## Pediatric Dosing
* **Ages 6 to under 12 years:** 5-10 mg every 4 hours as needed, or 15 mg every 6-8 hours as needed.
* **Ages 2 to under 6 years:** 2.5-5 mg every 4 hours as needed, or 7.5 mg every 6-8 hours as needed.
* **Under 2 years:** Safety and efficacy not established. Use is generally not recommended.
*Note: Specific dosing for pediatric patients is highly dependent on the product formulation and concentration. Always refer to the product labeling.*
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, but caution and reduced doses may be considered in severe impairment.
## Contraindications
* Known hypersensitivity to dextromethorphan.
* Use within 14 days of MAO inhibitor therapy (risk of serotonin syndrome).
* Use in children under 2 years of age.
## Adverse Effects
* Drowsiness, dizziness, confusion
* Nausea, vomiting, constipation
* Hallucinations, euphoria, dysphoria (especially at higher doses)
* Respiratory depression (rare at therapeutic doses, more common with overdose)
* Serotonin syndrome (rare, but increased risk with concomitant serotonergic agents)
## Key Drug Interactions
* **MAO Inhibitors:** Significant risk of serotonin syndrome.
* **Serotonergic Agents (SSRIs, SNRIs, triptans, etc.):** Increased risk of serotonin syndrome.
* **CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine, quinidine):** May increase dextromethorphan plasma concentrations, leading to increased adverse effects.
* **CYP3A4 Inhibitors (e.g., ketoconazole, ritonavir):** May increase dextromethorphan plasma concentrations.
## Monitoring
* Monitor for effectiveness in cough suppression.
* Monitor for adverse effects, particularly CNS effects and signs of serotonin syndrome.
## Clinical Pearls
* Dextromethorphan is available in numerous over-the-counter formulations, often combined with other ingredients (e.g., acetaminophen, decongestants, antihistamines). It is crucial to review the full ingredient list of combination products to avoid unintended drug exposure or interactions.
* Misuse or abuse of dextromethorphan, particularly in higher than recommended doses, can lead to significant psychotomimetic effects and is a public health concern.
* For persistent or severe cough, further evaluation is necessary to identify the underlying cause.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making therapeutic decisions. Product formulations and recommendations can vary.
