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# Dextromethorphan (Dextromethorphan HBr)
## Overview
Dextromethorphan is a synthetic analog of codeine (levorphanol derivative) that acts as a cough suppressant by increasing the cough threshold in the medullary cough center. It lacks significant analgesic or addictive properties at therapeutic doses.
## Primary Indications
Symptomatic relief of non-productive cough associated with common cold or inhaled irritants.
## Adult Dosing
* **Immediate-release:** 10–20 mg every 4 hours or 30 mg every 6–8 hours as needed.
* **Extended-release:** 60 mg every 12 hours.
* **Maximum:** 120 mg/24 hours.
## Pediatric Dosing
* **4 to <6 years:** 2.5–5 mg every 4 hours or 7.5 mg every 6–8 hours (Max: 30 mg/24 hours).
* **6 to <12 years:** 5–10 mg every 4 hours or 15 mg every 6–8 hours (Max: 60 mg/24 hours).
* **≥12 years:** Same as adult dosing.
* **Note:** Use of OTC cough/cold products in children <4 years is generally discouraged due to lack of efficacy and safety concerns; consult local institutional protocols.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No formal dosage adjustments provided by the manufacturer, but use with caution in patients with severe hepatic impairment due to extensive first-pass metabolism.
## Contraindications
* Hypersensitivity to dextromethorphan.
* Concurrent use (or within 14 days) of Monoamine Oxidase Inhibitors (MAOIs).
* Patients with asthma or respiratory insufficiency (use caution, as suppression of the cough reflex may lead to mucus retention).
## Adverse Effects
* **Common:** Dizziness, drowsiness, nausea, vomiting, abdominal discomfort.
* **Serious:** Serotonin syndrome (especially with high doses or serotonergic agents), hallucinations, confusion, and potential for abuse/euphoria at supratherapeutic doses.
## Key Drug Interactions
* **MAOIs:** Risk of severe, potentially fatal serotonin syndrome (hypertension, hyperpyrexia, myoclonus).
* **SSRIs/SNRIs/TCAs:** Increased risk of serotonin syndrome.
* **CNS Depressants (Alcohol, Benzodiazepines):** May potentiate sedation.
* **CYP2D6 Inhibitors (e.g., Fluoxetine, Quinidine):** May significantly increase plasma concentrations of dextromethorphan, increasing the risk of adverse effects.
## Monitoring
* Frequency and severity of cough.
* Evidence of drug abuse or misuse.
* Signs of serotonin syndrome if used with serotonergic medications.
* Discontinue use if cough persists >7 days, is accompanied by high fever, rash, or persistent headache.
## Clinical Pearls
* Dextromethorphan is an NMDA receptor antagonist at high doses, leading to dissociative effects similar to phencyclidine (PCP) or ketamine.
* Often found in combination products (e.g., with acetaminophen, phenylephrine, or doxylamine); ensure patients check ingredient labels to avoid accidental overdose of other components, particularly acetaminophen.
* Clinical evidence for efficacy in acute cough is inconsistent; advise patients that it may not offer significant benefit over placebo for viral URI-associated cough.
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**Disclaimer:** This information is for educational purposes only. Always verify current prescribing information, dosing guidelines, and institutional protocols before administering or recommending medications. Consult a licensed healthcare provider for clinical decisions.
