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# Dextromethorphan (Commonly found in "D-Cold" products)
## Overview
Dextromethorphan (DXM) is a synthetic dextrorotatory analog of levorphanol that acts as a centrally acting cough suppressant (antitussive). It elevates the cough threshold in the medulla oblongata. It is frequently combined with antihistamines, decongestants, and analgesics in over-the-counter (OTC) multi-symptom "cold" medications.
## Primary Indications
Symptomatic relief of non-productive cough associated with the common cold, bronchitis, 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 per 24 hours.
## Pediatric Dosing
* **Children 6–12 years:** 5–10 mg every 4 hours or 15 mg every 6–8 hours (Max: 60 mg per 24 hours).
* **Children 4–6 years:** 2.5–5 mg every 4 hours or 7.5 mg every 6–8 hours (Max: 30 mg per 24 hours).
* **Children <4 years:** Generally not recommended due to lack of efficacy and safety concerns; dosing should follow specific product labeling or pediatric physician guidance.
## Dose Adjustments
* **Hepatic Impairment:** Reduce dose or increase dosing interval in patients with significant hepatic impairment, as DXM is extensively metabolized in the liver.
* **Renal Impairment:** No specific adjustment required, but use caution.
## Contraindications
* Hypersensitivity to dextromethorphan.
* Concomitant use with MAO inhibitors (MAOIs within the last 14 days) due to the risk of serotonin syndrome.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, drowsiness, nausea, vomiting, stomach pain.
* **Serious:** Serotonin syndrome (when combined with serotonergic agents), confusion, visual hallucinations, and potential for abuse/dependence at supratherapeutic doses.
## Key Drug Interactions
* **MAOIs:** Absolute contraindication; can lead to hypertensive crisis and fatal serotonin syndrome.
* **SSRIs/SNRIs/TCAs:** Increased risk of serotonin syndrome.
* **CNS Depressants (Alcohol, Opioids, Sedatives):** Enhanced CNS depression (drowsiness/respiratory depression).
* **CYP2D6 Inhibitors (e.g., fluoxetine, quinidine):** May increase plasma concentrations of DXM.
## Monitoring
* Monitor frequency and severity of cough.
* Assess for signs of misuse or toxicity (e.g., tachycardia, hypertension, altered mental status).
* Observe for signs of serotonin syndrome (tremor, hyperreflexia, hyperthermia).
## Clinical Pearls
* **Multi-symptom risk:** Many "Cold" products contain acetaminophen; monitor total daily dose to prevent accidental hepatic toxicity.
* **Efficacy:** Evidence for over-the-counter antitussives in acute pediatric cough is limited; hydration and honey (if >1 year old) are often advised as first-line supportive care.
* **Abuse:** DXM is often abused (known as "robo-tripping") for its dissociative effects at high doses; pharmacy staff should screen for suspicious purchase patterns.
* **Persisting Symptoms:** Patients should be advised to seek medical evaluation if the cough persists for >7 days or is accompanied by high fever, rash, or persistent headache.
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**Educational Disclaimer:** This information is for educational purposes only. Always verify current prescribing information, local clinical protocols, and manufacturer labeling before administering any medication. Clinical judgment should be used based on the individual patient profile.
