1. Clinical Overview
A fixed-dose combination (FDC) cough syrup/tablet providing comprehensive symptomatic relief of productive and dry cough associated with upper respiratory tract infections and allergic conditions. It combines an expectorant (Guaifenesin), a mucolytic (Bromhexine), an antihistamine (Chlorpheniramine), and a centrally-acting antitussive (Dextromethorphan). This combination is widely used in India for managing cough with congestion and allergic components, though its FDC status is under regulatory scrutiny.
| Onset | Duration | Bioavailability |
|---|---|---|
| Guaifenesin: 30 minutes; Bromhexine: 30-60 minutes; Chlorpheniramine: 30-60 minutes; Dextromethorphan: 15-30 minutes. | Guaifenesin: 4-6 hours; Bromhexine: 6-8 hours; Chlorpheniramine: 4-6 hours; Dextromethorphan: 5-6 hours. | Guaifenesin: ~100% (oral); Bromhexine: ~80% (oral); Chlorpheniramine: ~25-50% (oral); Dextromethorphan: ~11% (extensive metabolizers), variable. |
2. Mechanism of Action
This combination acts at multiple levels of the cough pathway. Guaifenesin increases respiratory tract fluid secretions and reduces mucus viscosity. Bromhexine depolymerizes mucopolysaccharide fibers in bronchial secretions and stimulates surfactant production. Chlorpheniramine competitively antagonizes histamine at H1 receptors, reducing allergic symptoms and providing mild anticholinergic drying effects. Dextromethorphan elevates the cough threshold in the central cough center in the medulla oblongata by acting as an NMDA receptor antagonist and sigma-1 agonist.
3. Indications & Uses
- Symptomatic relief of productive cough associated with common cold, acute bronchitis
- Symptomatic relief of dry, irritating cough with allergic rhinitis or post-nasal drip
4. Dosage & Administration
Adult Dosage: Syrup (typical strength per 5ml): Guaifenesin 50mg + Bromhexine 2mg + Chlorpheniramine Maleate 1mg + Dextromethorphan HBr 5mg. Dose: 5-10 ml three to four times daily. Tablet forms vary; follow specific brand instructions.
Administration: Take orally with or without food. Shake the syrup well before use. Use a measuring cup or spoon for accuracy. Maintain adequate hydration to aid expectorant action. Do not drive or operate machinery after taking.
5. Side Effects
Common side effects may include:
- Drowsiness, sedation
- Dry mouth, nose, or throat
- Dizziness
- Gastrointestinal upset (nausea, vomiting)
- Thickening of bronchial secretions (paradoxical)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Monoamine Oxidase Inhibitors (MAOIs) - Phenelzine, Tranylcypromine | Risk of severe serotonin syndrome, hyperpyrexia, death. | Contraindicated |
| Selective Serotonin Reuptake Inhibitors (SSRIs) - Fluoxetine, Paroxetine | Increased risk of serotonin syndrome with Dextromethorphan. | Major |
| Other CNS Depressants (Alcohol, Benzodiazepines, Opioids) | Additive CNS depression, sedation, respiratory depression. | Major |
| Anticholinergic drugs (Atropine, Tricyclic Antidepressants) | Enhanced anticholinergic side effects (dry mouth, urinary retention, confusion). | Moderate |
| Potassium Citrate, Sodium Citrate | Increased renal excretion of Guaifenesin, reducing effect. | Moderate |
| CYP2D6 Inhibitors (Quinidine, Bupropion) | Increased Dextromethorphan levels, increased side effects. | Moderate |
7. Patient Counselling
- DO take the exact dose as prescribed by your doctor.
- DO shake the syrup well before use.
- DO use a proper measuring device, not a household spoon.
- DO maintain good fluid intake to help loosen mucus.
- DO NOT exceed the recommended dose or frequency.
- DO NOT take with alcohol or other sedative medications.
- DO NOT drive or operate heavy machinery after taking this medicine.
- DO NOT give to children under 2 years of age.
8. Toxicology & Storage
Overdose: In adults: CNS depression (drowsiness, sedation, coma), respiratory depression, seizures, anticholinergic toxidrome (dry skin, hyperthermia, tachycardia, mydriasis, urinary retention, hallucinations). In children: Agitation, ataxia, hallucinations, nystagmus, respiratory depression, death.
Storage: Store at room temperature (15-30°C), protected from light and moisture. Keep the bottle tightly closed. Keep out of reach and sight of children. Do not freeze the syrup. Discard unused medicine after the expiry date.