1. Clinical Overview
Dextromethorphan Hydrobromide is a centrally-acting, non-opioid antitussive agent, widely used as a cough suppressant. It is the d-isomer of the codeine analog, levorphanol, but lacks significant analgesic, sedative, or respiratory depressant properties at therapeutic doses. It acts by elevating the threshold for coughing in the cough center of the medulla oblongata. In the Indian market, it is a mainstay in the management of non-productive (dry) cough associated with common cold, URTI, and bronchitis.
| Onset | Duration | Bioavailability |
|---|---|---|
| 15-30 minutes after oral administration. | Approximately 5-6 hours for immediate-release formulations; up to 12 hours for sustained-release preparations. | Approximately 11% due to extensive first-pass metabolism. |
2. Mechanism of Action
Dextromethorphan suppresses cough by a dual mechanism. Its primary action is agonist activity at sigma-1 receptors in the nucleus tractus solitarius of the medulla, which modulates the cough reflex. Its metabolite, dextrorphan, is a non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, which contributes to its antitussive and, at high doses, dissociative effects.
3. Indications & Uses
- Symptomatic relief of non-productive (dry) cough associated with the common cold
- Symptomatic relief of cough in upper respiratory tract infections (URTI)
4. Dosage & Administration
Adult Dosage: 10-20 mg (5-10 ml of 10mg/5ml syrup) every 4-6 hours. Maximum: 120 mg per day.
Administration: Shake the bottle well before use. Use the measuring cup or spoon provided. Can be taken with or without food. Do not use for more than 7 days for self-medication. If cough persists, consult a doctor.
5. Side Effects
Common side effects may include:
- Drowsiness
- Dizziness
- Nausea
- Gastrointestinal upset
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| MAO Inhibitors (e.g., Phenelzine, Selegiline, Linezolid) | Risk of life-threatening serotonin syndrome, hyperpyrexia, confusion. | Contraindicated |
| SSRIs/SNRIs (e.g., Fluoxetine, Sertraline, Venlafaxine) | Increased risk of serotonin syndrome. | Major |
| Other Serotonergic Drugs (Tramadol, Fentanyl, St. John's Wort) | Additive serotonergic effects, risk of serotonin syndrome. | Major |
| CNS Depressants (Alcohol, Benzodiazepines, Opioids) | Additive CNS depression, sedation, impaired psychomotor performance. | Major |
| CYP2D6 Inhibitors (Quinidine, Paroxetine, Bupropion) | Increased dextromethorphan levels, converting extensive metabolizers to poor metabolizers, increasing risk of side effects. | Moderate |
| CYP3A4 Inducers (Rifampicin, Carbamazepine, Phenytoin) | Decreased dextromethorphan levels, reduced efficacy. | Moderate |
7. Patient Counselling
- DO use the measuring device provided for accurate dosing.
- DO inform your doctor about all other medicines you are taking.
- DO NOT use for chronic cough associated with smoking, asthma, or emphysema.
- DO NOT use for cough with excessive mucus.
- DO NOT exceed the recommended dose or duration (7 days).
- DO NOT take with alcoholic beverages.
- DO NOT give to children under 2 years without doctor's advice.
8. Toxicology & Storage
Overdose: Nausea, vomiting, drowsiness, dizziness, blurred vision, nystagmus, ataxia, respiratory depression, stupor, coma, seizures (at very high doses), serotonin syndrome (if combined with other agents), hyperexcitability. Death is rare but possible with massive ingestion, especially in combination with other drugs.
Storage: Store at room temperature (15-30°C). Protect from light and moisture. Keep the bottle tightly closed. Keep out of reach of children. Do not freeze. Discard any unused medicine after the expiry date.