This is a fixed-dose combination of an antihistamine (Diphenhydramine) and an acidifying agent (Citric Acid). Diphenhydramine is a first-generation ethanolamine-class H1-antihistamine with pronounced sedative, antiemetic, and anticholinergic properties. Citric Acid is used to acidify urine, which can enhance the excretion of certain substances and may provide symptomatic relief in urinary discomfort. In the Indian context, this combination is primarily marketed for the symptomatic relief of cough associated with the common cold and upper respiratory allergies, leveraging the antitussive and sedative effects of Diphenhydramine. It is important to note that the use of first-generation sedating antihistamines like diphenhydramine for cough in children is controversial and not recommended by many guidelines due to risk-benefit concerns.
Adult: 10-20 ml syrup, every 4-6 hours. Maximum: 80 ml in 24 hours. OR as directed by physician. Typical strength: Diphenhydramine HCl 12.5 mg + Citric Acid 50 mg per 5 ml.
Note: 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 GI upset. Maintain adequate hydration.
Diphenhydramine competitively antagonizes histamine at the H1 receptor, reducing allergic symptoms. Its antitussive action is central, mediated by suppression of the cough reflex in the medulla, though the exact mechanism is not fully elucidated. It also possesses strong antimuscarinic (drying) and sedative effects due to its ability to cross the blood-brain barrier. Citric Acid, upon absorption and metabolism, can increase the acidity of urine. In the context of this combination, it is theorized to provide a soothing effect on the urinary tract and potentially aid in mild diuresis, though its primary role in a cough formulation is adjunctive and not strongly pharmacologically synergistic.
Pregnancy: Category B (US FDA). Diphenhydramine crosses the placenta. Use only if clearly needed, especially in third trimester (risk of neonatal anticholinergic effects). Avoid during lactation as it is excreted in breast milk and may cause sedation/irritability in the infant.
Driving: STRONGLY DISCOURAGED. Impairs alertness, reaction time, and motor coordination. Do not operate machinery for at least 6-8 hours after a dose.
| Alcohol, Benzodiazepines, Opioids | Potentiation of CNS depression, increased risk of sedation, respiratory depression, and impaired psychomotor performance. | Major |
| MAO Inhibitors (Phenelzine, Tranylcypromine) | Increased anticholinergic and CNS depressant effects; risk of hypertensive crisis. | Contraindicated |
| Other Anticholinergics (Atropine, TCAs, Antipsychotics) | Additive anticholinergic side effects (dry mouth, constipation, urinary retention, confusion). | Major |
| CNS Stimulants (Amphetamines) | Diphenhydramine may counteract the stimulant effect. | Moderate |
| Antihypertensives | Diphenhydramine may potentiate the hypotensive effect. | Moderate |
Same composition (Citric Acid (NA) + Diphenhydramine (NA)), different brands: