🌿 Antihistamine / Anxiolytic

Hydroxyzine Dosage for Dogs Calculator

Accurate hydroxyzine HCl and pamoate dosing for dogs — covering allergic pruritus, anxiety, and pre-anaesthetic sedation with tablet and syrup calculations.

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Veterinary supervision recommended. Hydroxyzine causes CNS depression and anticholinergic effects. Use with caution in dogs with glaucoma, urinary retention, cardiac arrhythmias, or concurrent CNS depressants.

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About Hydroxyzine (Atarax / Vistaril)

Drug Class

First-Generation H₁ Antihistamine — Anxiolytic and Antipruritic

Mechanism of Action

Hydroxyzine competitively blocks peripheral H₁ histamine receptors, reducing allergic itch and urticaria. It also has CNS activity (crosses blood-brain barrier readily), producing sedation and mild anxiolytic effects. Anticholinergic properties contribute to drying effects and sedation.

Primary Uses in Dogs

Allergic pruritus (atopic dermatitis, contact allergy), urticaria, insect-bite hypersensitivity, mild situational anxiety, and as adjunct to immunotherapy in allergic dogs.

Dosing Quick Reference

Indication Dose Frequency
Allergic pruritus 1–2.5 mg/kg q8–12h PO
Acute urticaria 2.2 mg/kg q8h PO/IM
Anxiety 1–2 mg/kg q8h PRN PO

Common Side Effects

  • Sedation (dose-dependent)
  • Dry mouth, reduced tear production
  • Urinary retention (anticholinergic)
  • Excitability or hyperactivity (paradoxical, rare)
  • Constipation

Monitoring

Check tear production (Schirmer tear test) with prolonged use — anticholinergic effects can reduce tear production and worsen dry eye.

⚠️ Use cautiously in dogs with glaucoma, urinary obstruction, prostate hypertrophy, or thyroid disease. Hydroxyzine potentiates CNS depressants (opioids, sedatives). Tolerance to antihistamine effects can develop with continuous use — consider cycling therapy.

What Is Hydroxyzine?

Hydroxyzine is a first-generation H1-receptor antihistamine with significant anxiolytic and sedative properties, derived from piperazine. It is used in dogs for allergic pruritus (atopic dermatitis, contact/food allergy), anxiety management, pre-anaesthetic sedation, and as an adjunct in motion sickness. Its anxiolytic effects are mediated partly through histamine H1 blockade and serotonin receptor interactions in the CNS.

Available as hydroxyzine HCl (Atarax): 10 mg, 25 mg, 50 mg tablets and 10 mg/5 mL syrup; hydroxyzine pamoate (Vistaril): 25 mg, 50 mg, 100 mg capsules. The HCl salt is most commonly used in veterinary practice.

Clinical Applications

  • Allergic pruritus / atopic dermatitis: Primary antipruritic use
  • Anxiety / noise phobia: Mild-moderate anxiolytic effect
  • Pre-anaesthetic sedation: Reduces induction agent requirement
  • Motion sickness: Adjunct antiemetic effect

How to Use This Calculator

  1. Enter your dog’s body weight in kg or lbs
  2. Select the indication (determines dosing protocol)
  3. Choose your available tablet or syrup strength
  4. Click Calculate to see dose and frequency

🧮 Hydroxyzine Dose Calculator

Hydroxyzine Dosing Result

References

  1. Plumb DC. Plumb’s Veterinary Drug Handbook, 9th ed. Wiley-Blackwell; 2018.
  2. Papich MG. Saunders Handbook of Veterinary Drugs, 4th ed. Elsevier; 2016.
  3. Rosychuk RAW, Bloom P. The clinical approach to the pruritic dog. Vet Clin North Am Small Anim Pract. 1999;29(6):1373-1395.