Dextromethorphan (Dextromethorphan Hydrobromide)
Also sold as: Alex, Dextol, Benylin DM, Robitussin DM, Kofarest DX, D-Meth
Pregnancy
Cat C
Lactation
Caution
Schedule
OTC
Forms
Tablet/Capsule 10mg, 15mg +4
Indications
- Suppression of non-productive (dry) cough
- Cough due to minor throat and bronchial irritation
- Symptomatic relief of cough in common cold and influenza
- Cough associated with allergic rhinitis (post-nasal drip component)
Adult Dosing
Non-productive cough (immediate release)
10–30mg every 4–8 hours as needed
Every 4–8 hours; maximum 120mg/day
Do NOT use for productive (wet/chesty) cough — suppressing a productive cough may worsen respiratory infections. Use only for dry, irritating cough.
Non-productive cough (extended-release)
60mg twice daily
BD; maximum 120mg/day
Extended-release formulation for sustained overnight cough suppression
Pediatric Dosing
Not recommended for children under 6 years — risk of toxicity and seizures. Strict OTC labelling: no use in children <12 years in some countries.
Renal Dose Adjustment
| CrCl / eGFR | Dose Adjustment |
|---|---|
| Mild–moderate renal impairment | No specific adjustment required; use with caution |
| Severe renal impairment | Use with caution — active metabolite (dextrorphan) may accumulate |
Hepatic Adjustment
CYP2D6 is the primary metabolising enzyme. Poor metabolisers (5–10% of Caucasians; fewer in Asians) have significantly higher dextromethorphan levels. Use lower doses in hepatic impairment and suspect CYP2D6 poor metabolisers.
Pregnancy & Lactation
Pregnancy: Category C
Conflicting data. Some epidemiological studies suggest possible risk of neural tube defects and omphalocele in first trimester with high-dose use. Use only when benefit clearly outweighs risk. Avoid in first trimester where possible. Non-pharmacological measures preferred.
Lactation: Caution
Limited human data. Likely present in breast milk at low levels. Monitor infant for sedation. Short-term use at standard doses probably compatible with breastfeeding but data insufficient.
Top Drug Interactions
| Interacting Drug | Effect | Severity |
|---|---|---|
| Serotonergic drugs: SSRIs (fluoxetine, sertraline, paroxetine), SNRIs, MAO inhibitors, tramadol, linezolid, triptans | SEROTONIN SYNDROME — potentially life-threatening: agitation, hyperthermia, muscle rigidity, clonus, tachycardia. Dextromethorphan inhibits serotonin reuptake. Combination with MAOIs is ABSOLUTELY CONTRAINDICATED. | Major |
| Strong CYP2D6 inhibitors (fluoxetine, paroxetine, quinidine, bupropion) | Markedly increase dextromethorphan plasma levels (>5-fold) by blocking CYP2D6 metabolism. Dramatically increases toxicity and hallucination risk. | Major |
| MAO inhibitors (phenelzine, tranylcypromine, isocarboxazid, selegiline) | Risk of serotonin syndrome and hypertensive crisis — CONTRAINDICATED. Allow 14 days after stopping MAOI before starting dextromethorphan. | Major |
| CNS depressants (opioids, benzodiazepines, alcohol) | Additive CNS depression; increased sedation and impaired psychomotor function | Moderate |
| Amiodarone / Terbinafine (CYP2D6 inhibitors) | Inhibit CYP2D6, increasing dextromethorphan toxicity risk — hallucinations, agitation, dissociation | Moderate |
| Quinidine | Potent CYP2D6 inhibitor — used therapeutically to increase DXM levels (Nuedexta for pseudobulbar affect) but at usual doses causes toxicity | Major |
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Side Effects
Common
- Drowsiness / dizziness (dose-dependent)
- Nausea
- Vomiting
- Stomach discomfort
- Headache
- Constipation
Serious / Discontinue If
- Serotonin syndrome (especially with SSRIs/MAOIs — potentially fatal)
- Hallucinations and dissociation at high doses (deliberate misuse/overdose)
- Respiratory depression (overdose)
- Psychosis (rare, at high doses)
- Anaphylaxis (rare)
Contraindications
- Concurrent MAO inhibitor use (or within 14 days of stopping)
- Productive (wet/chesty) cough — suppressing mucociliary clearance worsens outcome
- Known hypersensitivity to dextromethorphan
- Children <6 years (OTC; <4 years by most guidelines)
Available Indian Brands
| Brand | Manufacturer | Price (approx) |
|---|---|---|
| Alex Syrup | Glenmark Pharmaceuticals | 100 mL ₹72 |
| Dextol DX | Alkem Laboratories | 100 mL ₹58 |
| Kofarest DX | Franco-Indian Pharmaceuticals | 100 mL ₹65 |
| Benylin DM | Johnson & Johnson India | 100 mL ₹85 |
| Robitussin DM | Pfizer India | 100 mL ₹78 |
| Coscopin DX | East India Pharmaceutical | 100 mL ₹55 |
Monitoring Required
- Cough duration — if cough persists >2 weeks, reassess for underlying cause (TB, asthma, ACE inhibitor cough, malignancy)
- Serotonin syndrome signs in patients on SSRIs/SNRIs
- Level of consciousness and respiratory rate in elderly
- Productive vs non-productive cough assessment before prescribing
Patient Counseling Points
- IMPORTANT: Use only for DRY, non-productive cough. Do NOT use if you are coughing up phlegm or sputum.
- Do not use with antidepressants (especially SSRIs, MAOIs) without checking with your doctor — serious drug interaction risk.
- Do not give to children under 6 years — it can cause serious harm.
- Do not exceed the recommended dose — high doses cause hallucinations and can be dangerous.
- If cough persists beyond 2 weeks, see a doctor — this medicine treats symptoms, not the cause.
- Avoid alcohol and sedative medications while using dextromethorphan.
- Do not use for asthma, COPD, or chronic bronchitis without medical advice.
- This is OTC but not without risks — read the label carefully and follow dosing instructions.
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Clinically reviewed by: Dr. Meera Krishnamurthy, MD (General Medicine), Christian Medical College Vellore
Last reviewed: 2026-03-15
References
- FDA Drug Safety Communication: Use caution with dextromethorphan-containing products. 2010.
- Schroeder K, Fahey T. Over-the-counter medications for acute cough in children and adults in ambulatory settings. Cochrane Database Syst Rev. 2004.
- Indian Pharmacopoeia Commission. Dextromethorphan Hydrobromide monograph. IP 2022.
- CIMS India Drug Database 2025 — Dextromethorphan
- Taylor CP et al. Pharmacology of dextromethorphan: Relevance to dextromethorphan/quinidine (Nuedexta®). Pharmacol Ther. 2016;164:170–182.