According to the Merck Veterinary Manual’s antihistamine dosages table, the recommended dosage of diphenhydramine is 2–4 mg/kg, IM, PO, or SC, q 8–12 h as needed. This means that pet parents should ...

It is also available as an intramuscular or IV (intravenous, into a vein) injection. Doxylamine and diphenhydramine belong to the same class of drugs and share the exact mechanism of action. Both are ...