Dog · Canis lupus familiaris · typical adult weight 2.00–80.00 kg
Diphenhydramine is dosed at 0.5–1 mg/kg IM, IV Single dose or q8h in dogs, per Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.437 (2026-08-01). — Plumb's 10th ed (held) printed p.410, Diphenhydramine monograph spanning p.409-411; page located 2026-08-05 from the book's own running heads, and carries this exact dose under the matching species heading. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207 CORRECTED 2026-08-13: served 2-4 mg/kg by the IM route against a printed parenteral range of 0.5-1. Plumb's 10th ed, Diphenhydramine monograph, corpus p.437, DOGS, Antihistamine (extra-label): "b) 0.5 - 1 mg/kg IV or IM every 6 to 8 hours". The 1-2 mg/kg figure on the same page is the ORAL regimen and does not govern this row. The served range was 2-8x the printed parenteral figure.. Diphenhydramine is used in dogs for Acute allergic reaction, pre-chemotherapy, Antihistamine — allergic pruritus and allergic reactions (angioedema, urticaria, insect bite hypersensitivity, atopic dermatitis, anaphylaxis, mast cell tumors, vaccine or transfusion reactions). Routes documented in dogs: IM, IV, PO. A typical adult dog weighs 2.00–80.00 kg. ExoticRx lists 2 cited dose rules for Diphenhydramine in dogs, drawn from published veterinary references. Verify against current literature before clinical use.
US trade names: Benadryl
| Route | Dose | Frequency | Duration | Indication | Evidence | Source |
|---|---|---|---|---|---|---|
| IM, IV | 0.5–1 mg/kg | Single dose or q8h | Acute | Acute allergic reaction, pre-chemotherapy | Moderate | Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.437 (2026-08-01). — Plumb's 10th ed (held) printed p.410, Diphenhydramine monograph spanning p.409-411; page located 2026-08-05 from the book's own running heads, and carries this exact dose under the matching species heading. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207 CORRECTED 2026-08-13: served 2-4 mg/kg by the IM route against a printed parenteral range of 0.5-1. Plumb's 10th ed, Diphenhydramine monograph, corpus p.437, DOGS, Antihistamine (extra-label): "b) 0.5 - 1 mg/kg IV or IM every 6 to 8 hours". The 1-2 mg/kg figure on the same page is the ORAL regimen and does not govern this row. The served range was 2-8x the printed parenteral figure. |
| PO | 1–2 mg/kg | q8-12h | As needed | Antihistamine — allergic pruritus and allergic reactions (angioedema, urticaria, insect bite hypersensitivity, atopic dermatitis, anaphylaxis, mast cell tumors, vaccine or transfusion reactions) | Moderate | Verified against Plumb's Veterinary Drug Handbook, 10th Ed, p.437 (2026-08-01). — Plumb's 10th ed (held) printed p.410, Diphenhydramine monograph spanning p.409-411; page located 2026-08-05 from the book's own running heads, and carries this exact dose under the matching species heading. — SOURCE EDITION: Plumb's Veterinary Drug Handbook — ISBN 9781394172207, https://openlibrary.org/isbn/9781394172207 — Plumb's Veterinary Drug Handbook, 10th ed (held), Diphenhydramine monograph, printed p.410 (corpus PDF p.437), DOGS/CATS: "Antihistamine (eg, adjunctive treatment of allergic pruritus or reactions, including angioedema […]" [INDICATION NARROWED 2026-08-12, two readers — the motion-sickness heading on the same page is printed at q8h, and no sedative dose is printed.] CORRECTED 2026-08-13: served 2-4 mg/kg against a printed PO ceiling of 2. Plumb's 10th ed, Diphenhydramine monograph, corpus p.437, DOGS, Antihistamine (extra-label): "a) 1 - 2 mg/kg PO every 8 to 12 hours". The same page prints a separate parenteral regimen, "b) 0.5 - 1 mg/kg IV or IM every 6 to 8 hours", which governs the IM row rather than this one. |
Every held source for this drug and species, as printed. Where they differ, both are shown — the choice is yours, not ours.
| Dose (mg/kg) | Route | Source | As printed |
|---|---|---|---|
| 2–4 | PO | BSAVA Small Animal Formulary, 10th ed — Part A (Canine and Feline)p.146 | 2-4 mg/kg p.o. q6-8h. |
| 1–2 | PO | BSAVA Small Animal Formulary, 10th ed — Part A (Canine and Feline)p.146 | 1-2 mg/kg p.o. q8-12h |
| 2.2 | PO | Papich Saunders Handbook of Veterinary Drugs, 4th edp.280 | • 2.2 mg/kg q8-12h PO, IM, or SQ. • 2-4 mg/kg q6-8h PO. |
| 2–4 | PO | Papich Saunders Handbook of Veterinary Drugs, 4th edp.280 | • 2.2 mg/kg q8-12h PO, IM, or SQ. • 2-4 mg/kg q6-8h PO. |
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Competitive antagonist at histamine H1 receptors. Also has anticholinergic, anti-motion sickness, and mild sedative properties.
Sedation common (first-generation). Anticholinergic effects (dry mouth, urinary retention). Ensure product does not contain xylitol or pseudoephedrine. Dogs and cats. Less effective than second-gen antihistamines for pruritus.
Species-specific contraindications and adverse-reaction reports for dogs may differ from canine / feline reference data — consult the primary citations listed with each rule.
Diphenhydramine dose ranges in dogs, with cited source references: IM, IV 0.5–1 mg/kg Single dose or q8h; PO 1–2 mg/kg q8-12h. Reference ranges from cited sources — verify against current literature before clinical use.
Documented routes for Diphenhydramine in dogs: IM, IV, PO.
Cited course lengths for Diphenhydramine in dogs include: Acute; As needed. Duration depends on the indication — match it to the specific dose rule in the table above.
Diphenhydramine is indicated in dogs for: Acute allergic reaction, pre-chemotherapy, Antihistamine — allergic pruritus and allergic reactions (angioedema, urticaria, insect bite hypersensitivity, atopic dermatitis, anaphylaxis, mast cell tumors, vaccine or transfusion reactions).
These are general warnings for Diphenhydramine across species; consult the dog dosing table above for species-specific guidance. Sedation common (first-generation). Anticholinergic effects (dry mouth, urinary retention). Ensure product does not contain xylitol or pseudoephedrine. Dogs and cats. Less effective than second-gen antihistamines for pruritus.
Why a species-specific page? Diphenhydramine pharmacokinetics differ across species: dose ranges, intervals, and route preferences are not interchangeable. Cross-extrapolation from canine doses is unsafe in dogs — the rules above are the citations specific to this species, not generic recommendations.
Sourced from published veterinary references; awaiting credentialed clinical reviewer. See our editorial process. Reference only — not veterinary advice.
| 1 |
| IV |
| Papich Saunders Handbook of Veterinary Drugs, 4th edp.280 |
| For large dogs, this is equivalent to • 1 mg/kg q8h IV or IM. |
Figures are transcribed from the cited page or table of each held edition and are shown for reference only. They are not dose recommendations, they do not feed the calculator, and none has been reviewed by a veterinarian.