API

Cetirizine (10mg/ml)

Drug classification

Antihistamine; second-generation selective H1 receptor antagonist.

Dosage form

Oral drops solution containing cetirizine 10 mg per milliliter.

API strength per dosage

Dose

Cetirizine drops (10 mg/mL) dosing varies by age: children 2–6 years typically receive 2.5 mg once daily (max 5 mg/day); children 6–12 years, 5–10 mg once daily; adults and children ≥12 years, 10 mg once daily. In renal or hepatic impairment, use half the usual dose. Always follow local prescribing guidelines.

Mechanism of action

Cetirizine, the active ingredient in Zyrtec Drops, is a selective antagonist of peripheral histamine H1 receptors. By blocking H1 receptors, cetirizine inhibits the effects of histamine, reducing symptoms such as sneezing, itching, and rhinorrhea associated with allergic reactions, without significant central nervous system penetration.

Indications

Treatment of Allergic conditions

Side effects

Sleepiness Fatigue Vomiting Dryness in mouth Headache Constipation

Pregnancy category

Cetirizine should be used during pregnancy only if clearly needed; limited human data suggest low risk, but consult a healthcare provider before use.

Precautions

Renal or hepatic impairment, elderly patients, risk of drowsiness, avoid alcohol, monitor for allergic reactions, caution in epilepsy, assess for urinary retention, monitor response in children, avoid exceeding recommended dose, discontinue if hypersensitivity occurs.

Contraindications

Hypersensitivity to cetirizine, hydroxyzine, or any excipients; severe renal impairment (creatinine clearance <10 mL/min); history of severe hypersensitivity reactions to piperazine derivatives.