Merck Manual

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Antihistamine Dosages

Antihistamine Dosages

Drug

Dosage

Diphenhydramine

2–4 mg/kg, bid-tid

Hydroxyzine

0.5–2 mg/kg, tid-qid

Clorpheniramine

Cats: 2–4 mg, bid

Dogs <20 kg: 4 mg, tid

Dogs >20 kg: 8 mg, tid; 0.25–0.5 mg/kg, tid

Cyproheptadine

0.25–0.5 mg/kg, tid; 1.1 mg/kg, bid

Terfenadine

5 mg/kg, bid

Clemastine

Cats: 0.05 mg/kg, bid

Dogs: 0.1 mg/kg, bid

Trimeprazine

1 mg/kg, bid

Cetirizine

Dogs: 1 mg/kg or 10–20 mg per dog, once or twice daily

Cats: 1 mg/kg or 5 mg per cat, once or twice daily

Fexofenadine

Dogs: 2–5 mg/kg, once or twice daily

Cats: 10–15 mg per cat, once or twice daily