# Hydroxyzine: veterinary dose and monograph

> Hydroxyzine is a veterinary drug. First-generation (sedating) H1-antihistamine widely used in dogs for ALLERGIC PRURITUS (atopic dermatitis, urticaria) and as a mild anxiolytic/sedative — it tends to be one of the more effective antihistamines for canine itch. Indications include allergic pruritus — atopic dermatitis, urticaria, insect-bite reactions; mild sedation / anxiolysis; adjunct antihistamine in allergic/anaphylactoid management. This monograph lists 5 reference doses for dogs, cats, horses, birds and ferrets, each with route, frequency and source.

Source: https://vetmasterji.com/drugs/hydroxyzine · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Veterinary drug
- **Also known as:** Atarax, Hydroxyzine HCl/pamoate, Hyzine
- **Species with doses:** Dogs, Cats, Horses, Birds and Ferrets
- **General dose range:** 2 mg/kg PO q8h — check the species tables for the indication
- **Routes:** PO
- **Last reviewed:** 1 October 2026

## Indications

- Allergic pruritus — atopic dermatitis, urticaria, insect-bite reactions
- Mild sedation / anxiolysis
- Adjunct antihistamine in allergic/anaphylactoid management
- Pre-treatment to reduce histamine-related reactions

## Hydroxyzine dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Hydroxyzine doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Allergic pruritus / mild sedation | 2 mg/kg | PO | q8h | — |

- Allergic pruritus / mild sedation: Papich 5e: 2 mg/kg q8–12h IM or PO. Plumb’s p.629: 2.2 mg/kg PO three times daily (Gershwin; Paradis; White); flea allergy 2 mg/kg q8h. Response is individual — trial 1–2 weeks.

### Cats

*Hydroxyzine doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Allergic pruritus | 1–2 mg/kg | PO | q8–12h | — |

- Allergic pruritus: Plumb’s p.629: 1–2 mg/kg or 5–10 mg per cat PO q8–12h (Messinger; Hnilica); recurrent idiopathic LUTD 5–10 mg per cat q12h (Lane). Papich 5e: effective doses not established in cats — cetirizine is an alternative.

### Horses

*Hydroxyzine doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Allergic dermatitis / urticaria | 0.5–1 mg/kg | PO | q12h | — |

- Allergic dermatitis / urticaria: Plumb's p.630 (Robinson 1992): 0.5–1 mg/kg IM or PO twice daily; pamoate salt 0.67 mg/kg PO q12h. ARCI Class 2 — observe competition withdrawal.

### Birds

*Hydroxyzine doses for birds*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Pruritus / feather picking | 2 mg/kg | PO | q8–12h | — |

- Pruritus / feather picking: Plumb’s p.629: 2 mg/kg PO q8h or 1.5–2 mg per 4 oz of drinking water daily (Hillyer 1994); 2 mg/kg PO q12h (Siebert 2003). Adjust to limit drowsiness.

### Ferrets

*Hydroxyzine doses for ferrets*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Allergic pruritus | 2 mg/kg | PO | q8h | — |

- Allergic pruritus: Plumb's p.630 (Williams 2000): 2 mg/kg PO three times daily.

## Contraindications

Glaucoma, urinary retention, GI obstruction (anticholinergic). Significant cardiac disease (QT effects at high dose). Pregnancy (early — teratogenic in some studies). Concurrent CNS depressants (additive sedation). Known hypersensitivity.

## Adverse effects

- Sedation, lethargy
- Anticholinergic effects (dry mouth, urinary retention, constipation)
- Occasional paradoxical excitement
- GI upset

## Drug interactions

- CNS depressants (sedatives, opioids, anaesthetics): additive sedation
- Anticholinergics: additive (urinary retention, ileus)
- QT-prolonging drugs: caution at high doses
- May suppress allergy skin-test reactions — withdraw before intradermal testing

## Pregnancy and lactation

Avoid in early pregnancy (teratogenicity reported in some studies); otherwise limited data.

## Monitoring

- Pruritus response over a 1–2 week trial
- Sedation / anticholinergic effects
- Withdraw before intradermal allergy testing

## Toxicity and overdose

Overdose causes pronounced sedation or paradoxical excitation, anticholinergic signs (mydriasis, tachycardia, urinary retention, ileus), and at high doses tremor/seizures and QT effects. Generally a wide margin for ordinary dosing.

Management: No specific antidote. Supportive — manage sedation/excitation, IV fluids; control seizures with benzodiazepines; monitor for anticholinergic complications (bladder, ileus) and cardiac rhythm at high doses. Decontaminate large recent ingestions.

## Clinical pearls

- Often the more effective antihistamine for canine allergic itch — worth a 1–2 week trial, but responses are individual
- Its active metabolite is cetirizine, which is why both work for allergic skin disease
- Sedation is common (and sometimes useful) — warn owners; anticholinergic effects can cause urinary retention
- Stop antihistamines before intradermal allergy testing (they blunt the reactions)
- Not a replacement for steroids/oclacitinib in severe atopy — best for mild disease or as an adjunct

## Mechanism of action

Competitively blocks peripheral H1 histamine receptors, reducing histamine-mediated pruritus, vasodilation and wheal formation. As a first-generation antihistamine it crosses the blood–brain barrier (central H1 blockade → sedation) and has anticholinergic activity. Its metabolite cetirizine provides additional, less-sedating antihistamine effect.

## Formulations and products

- 10 mg tablet
- 25 mg tablet
- Syrup 2 mg/mL (10 mg/5 mL)
- Atarax — 10 / 25 mg tablet; 10 mg/5 mL syrup, Tablet / syrup (human-label)
- Hyzine — 10 / 25 mg tablet, Tablet (human-label)

## Storage

Tablets/syrup: 15–30 °C, dry, protect from light.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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## Frequently asked questions

### What is the dose of Hydroxyzine for dogs?

Reference doses for Hydroxyzine in dogs: 2 mg/kg PO q8h (Allergic pruritus / mild sedation). Confirm against the label and the patient before use.

### What is the dose of Hydroxyzine for cats?

Reference doses for Hydroxyzine in cats: 1–2 mg/kg PO q8–12h (Allergic pruritus). Confirm against the label and the patient before use.

### What is the dose of Hydroxyzine for horses?

Reference doses for Hydroxyzine in horses: 0.5–1 mg/kg PO q12h (Allergic dermatitis / urticaria). Confirm against the label and the patient before use.

### When should Hydroxyzine not be used?

Glaucoma, urinary retention, GI obstruction (anticholinergic). Significant cardiac disease (QT effects at high dose). Pregnancy (early — teratogenic in some studies). Concurrent CNS depressants (additive sedation). Known hypersensitivity.

### What are the side effects of Hydroxyzine in animals?

Sedation, lethargy; Anticholinergic effects (dry mouth, urinary retention, constipation); Occasional paradoxical excitement; GI upset.

## Sources

- Plumb's Veterinary Drug Handbook
- Merck Veterinary Manual, 11th edition
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.