Table 3: Oral Antihistamine Doses for Dogs

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Drug Name Dose
Hydroxyzine 2 mg/kg q 12 hr1
Cetirizine 1–2 mg/kg q 24 hr1
Chlorpheniramine 0.4 mg/kg q 12 hr2
Cyproheptadine 0.3–2 mg/kg q 12 hr2
Clemastine 0.05–1 mg/kg q 12 hr2
Loratadine 1 mg/kg q 12 hr2
Fexofenadine 5–15 mg/kg q 24 hr3
Amitriptyline 1–2 mg/kg q 12 hr2
Diphenhydramine 2–3 mg/kg q 12 hr2

Questionable efficacy if given orally4

  1. Bizikova P, Papich MG, Olivry T. Hydroxyzine and cetirizine pharmacokinetics and pharmacodynamics after oral and intravenous administration of hydroxyzine to healthy dogs. Vet Dermatol. 2008;19:348–57.
  2. Miller WH, Griffin GE, Campbell KL. Muller & Kirk’s Small Animal Dermatology. 7th ed. St. Louis:Elsevier;2013.
  3. Plevnik A, Kobal S, Domanjko-Petric A, et al. The efficacy of antihistamine fexofenadine versus methylprednisolone in the treatment of atopic dermatitis in dogs. Slov Vet Res. 2009;46:5–12.
  4. Banovic F, Denley T, Blubaugh A, et al. Effect of diphenhydramine and cetirizine on immediate and late-phase cutaneous allergic reactions in healthy dogs: a randomized, double-blinded crossover study. Vet Dermatol. 2020;31:256–e58.

The 2023 AAHA Management of Allergic Skin Diseases in Dogs and Cats Guidelines are generously supported by Hill’s Pet Nutrition, Merck Animal Health, and Zoetis.

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