1. Clinical Overview
A fixed-dose combination syrup used for the symptomatic relief of productive and non-productive cough associated with upper respiratory tract infections and allergies. Guaifenesin is an expectorant that thins and loosens mucus, Chlorpheniramine is a first-generation sedating antihistamine that reduces allergic symptoms and rhinorrhea, and Dextromethorphan is a centrally-acting antitussive that suppresses the cough reflex.
| Onset | Duration | Bioavailability |
|---|---|---|
| Guaifenesin: 30 minutes; Chlorpheniramine: 30-60 minutes; Dextromethorphan: 15-30 minutes. | Guaifenesin: 4-6 hours; Chlorpheniramine: 4-8 hours; Dextromethorphan: 5-6 hours. | Guaifenesin: ~100% (oral); Chlorpheniramine: ~25-50% (oral); Dextromethorphan: ~11% (extensive metabolizers), variable in poor metabolizers. |
2. Mechanism of Action
The combination works via three distinct mechanisms: 1) Guaifenesin enhances the output of respiratory tract fluid by reducing adhesiveness and surface tension, facilitating the removal of viscous mucus. 2) Chlorpheniramine competitively antagonizes histamine at the H1-receptor, reducing capillary dilation, edema, and secretions associated with allergic responses. 3) Dextromethorphan suppresses the cough reflex by acting on the sigma-1 receptor and NMDA receptor in the medullary cough center.
3. Indications & Uses
- Symptomatic relief of cough associated with common cold
- Symptomatic relief of allergic cough and bronchitis
- Relief of cough with thick, tenacious mucus in upper respiratory tract infections
4. Dosage & Administration
Adult Dosage: 10 ml (2 teaspoonfuls) every 6-8 hours. Maximum: 40 ml (4 doses) in 24 hours.
Administration: Shake the bottle well before use. Use the measuring cup/spoon provided. Can be taken with or without food. Maintain adequate hydration to aid Guaifenesin's expectorant action.
5. Side Effects
Common side effects may include:
- Drowsiness/sedation
- Dry mouth, nose, or throat
- Dizziness
- Gastrointestinal upset (nausea)
- Thickened bronchial secretions
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Monoamine Oxidase Inhibitors (e.g., Phenelzine, Selegiline) | Risk of severe serotonin syndrome, hyperpyrexia, death. | Contraindicated |
| Other CNS Depressants (Alcohol, Benzodiazepines, Opioids) | Additive sedation, respiratory depression, impaired psychomotor performance. | Major |
| Selective Serotonin Reuptake Inhibitors (SSRIs e.g., Fluoxetine) | Increased risk of serotonin syndrome with Dextromethorphan. | Major |
| Anticholinergic drugs (Tricyclic Antidepressants, Antipsychotics) | Additive anticholinergic effects (dry mouth, urinary retention, constipation). | Moderate |
| CYP2D6 Inhibitors (Quinidine, Paroxetine) | Increased Dextromethorphan levels, risk of toxicity. | Moderate |
| Sympathomimetics (Pseudoephedrine) | Chlorpheniramine may potentiate pressor effects. | Moderate |
7. Patient Counselling
- DO take with a full glass of water to help loosen mucus.
- DO use the measuring device provided; do not use a household spoon.
- DO inform your doctor if you are taking any other medicines.
- DO NOT exceed the recommended dose or frequency.
- DO NOT take with alcohol or other sedative medications.
- DO NOT drive or operate heavy machinery until you know how the medicine affects you.
- DO NOT use to treat a chronic cough due to smoking, asthma, or emphysema, or if cough is accompanied by excessive phlegm, without consulting a doctor.
8. Toxicology & Storage
Overdose: In adults: Extreme drowsiness, confusion, agitation, hallucinations, tachycardia, dilated pupils, dry skin/flushing, urinary retention, seizures, respiratory depression, coma. In children: Ataxia, hyperexcitability, hallucinations, convulsions, death from respiratory arrest.
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 use after the expiry date printed on the label. Discard any unused medicine safely.