1. Clinical Overview
A fixed-dose combination oral liquid containing an ethanolamine-derivative antihistamine (Diphenhydramine), an expectorant (Ammonium Chloride), and an alkalizing agent/expectorant (Sodium Citrate). Primarily used for symptomatic relief of cough associated with upper respiratory tract infections, allergic conditions, and common cold. Diphenhydramine provides antitussive and sedative effects, Ammonium Chloride acts as an expectorant by irritating the gastric mucosa to stimulate respiratory tract secretions, and Sodium Citrate helps to alkalinize urine and loosen bronchial secretions.
| Onset | Duration | Bioavailability |
|---|---|---|
| Diphenhydramine: 15-30 minutes; Ammonium Chloride/Sodium Citrate: Expectorant effect within 1-2 hours. | Diphenhydramine: 4-6 hours; Overall symptomatic relief: 6-8 hours. | Diphenhydramine: ~40-60% (extensive first-pass metabolism); Ammonium Chloride: Rapidly and nearly completely absorbed; Sodium Citrate: Well absorbed. |
2. Mechanism of Action
The combination works synergistically: Diphenhydramine suppresses the cough reflex center in the medulla (central antitussive action) and blocks histamine at H1 receptors, reducing allergic symptoms and post-nasal drip. Ammonium Chloride acts as a gastric irritant, stimulating vagal afferents from the gastric mucosa, which reflexively increases the output of respiratory tract fluid (bronchial secretions), lowering viscosity. Sodium Citrate, upon metabolism to bicarbonate, alkalinizes the urine and blood, and also helps to loosen tenacious mucus by increasing the pH of respiratory secretions.
3. Indications & Uses
- Symptomatic relief of dry, non-productive cough associated with common cold and upper respiratory tract infections
- Allergic cough and cough associated with allergic rhinitis
- Cough with tenacious mucus where expectoration is difficult
4. Dosage & Administration
Adult Dosage: 10 ml (2 teaspoonfuls) three to four times daily. Maximum: 40 ml per day.
Administration: Shake the bottle well before use. Use the measuring cup or spoon provided. Can be taken with or without food. Taking with food may reduce gastric irritation from Ammonium Chloride. Maintain adequate fluid intake to aid expectoration.
5. Side Effects
Common side effects may include:
- Drowsiness, sedation, somnolence
- Dry mouth, nose, and throat
- Dizziness
- Gastrointestinal discomfort, nausea
- Thickened bronchial secretions (paradoxical)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Alcohol, Benzodiazepines, Opioids, other CNS Depressants | Additive CNS depression, increased sedation, impaired psychomotor performance. | Major |
| Monoamine Oxidase Inhibitors (MAOIs) - e.g., Phenelzine, Selegiline | Increased anticholinergic and CNS depressant effects; risk of hypertensive crisis. | Contraindicated |
| Anticholinergic drugs (e.g., Atropine, Tricyclic Antidepressants, Antipsychotics) | Enhanced anticholinergic side effects (dry mouth, urinary retention, constipation, blurred vision). | Major |
| Drugs excreted in alkaline urine (e.g., Amphetamines, Quinidine, Flecainide) | Sodium Citrate alkalinizes urine, decreasing renal excretion of these drugs, potentially increasing their toxicity. | Moderate |
| Drugs excreted in acidic urine (e.g., Salicylates, Phenobarbital) | Alkalinization may increase their excretion. | Moderate |
| Potassium-sparing diuretics, ACE inhibitors, ARBs, Potassium supplements | Risk of hyperkalemia, especially with Sodium Citrate (if potassium salt is used). | Moderate |
| Topiramate, Acetazolamide | Increased risk of kidney stone formation (alkaline urine). | Moderate |
7. Patient Counselling
- DO take the exact dose as prescribed by your doctor.
- DO shake the bottle well before each use.
- DO use the measuring device provided with the syrup.
- DO maintain adequate fluid intake unless contraindicated.
- DO report if cough persists for more than 5-7 days or is accompanied by fever, rash, or persistent headache.
- DONT drive, operate heavy machinery, or engage in hazardous activities while taking this medicine and for at least 8-12 hours after the last dose.
- DONT consume alcohol or other sedative medications.
- DONT take it for insomnia unless specifically advised by your doctor.
- DONT give to children below 2 years of age without medical advice.
8. Toxicology & Storage
Overdose: Anticholinergic Toxidrome: Severe CNS depression (coma) or stimulation (hallucinations, seizures), hyperthermia, flushing, dry skin/mucous membranes, mydriasis, tachycardia, hypertension followed by hypotension, urinary retention, respiratory depression, cardiac arrhythmias. In children: Paradoxical excitation, ataxia. Electrolyte imbalance (hyper/hypokalemia, metabolic alkalosis/acidosis) from other components.
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.