Cetirizine: veterinary dose and monograph

At a glance

Drug class

Veterinary drug

Also known as

Zyrtec, Alerid

Species with doses

Dogs, Cats and Horses

General dose range

0.5–1 mg/kg PO q24h — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Canine atopic dermatitis / allergic pruritus (adjunct)
• Feline allergic / eosinophilic dermatitis
• Urticaria, mild allergic reactions

Cetirizine 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

• Allergic pruritus: Plumb’s p.245: atopic dermatitis 1 mg/kg PO once daily (Cook 2004); allergic dermatitis 1 mg/kg q12h (Hillier 2004); 0.5–1 mg/kg or 5–10 mg per dog once or twice daily. Papich 5e: 2 mg/kg q12h PO.

Cats

• Allergic / eosinophilic dermatitis: Papich 5e: 1 mg/kg daily PO — most commonly 5 mg per cat. Plumb’s p.245: 5 mg per cat once daily (Ashley 2009) or q12h for rhinosinusitis (Hawkins & Cohn); pruritus 2.5–5 mg per cat once daily. (2.5–5 mg per cat ≈ 0.5–1 mg/kg for a 5 kg cat.)

Horses

• Allergic disease (urticaria, pruritus, RAO adjunct): Papich 5e and Plumb’s p.245 (Olsen 2008): 0.2–0.4 mg/kg PO q12h, based on equine PK/PD data.

Contraindications

Significant renal impairment (reduce frequency — renally cleared). Hypersensitivity. Use plain cetirizine — avoid combination products containing pseudoephedrine.

Adverse effects

• Generally minimal — occasional mild sedation
• Hypersalivation / vomiting in cats (taste)
• Rare GI upset

Drug interactions

• Minimal — limited hepatic metabolism and few cytochrome-P450 interactions
• Mildly additive sedation with other CNS depressants
• Avoid combination products containing pseudoephedrine

Pregnancy and lactation

Considered relatively low-risk among antihistamines; use only if needed.

Monitoring

• Pruritus / lesion response over a 1–2 week trial
• Renal function in impairment (renally cleared — extend the dosing interval)

Toxicity and overdose

Wide safety margin; overdose mainly causes sedation (occasionally restlessness), and hypersalivation in cats from the bitter taste.

Management: Supportive; no specific antidote needed. Monitor for sedation and manage symptomatically.

Clinical pearls

• Once-daily and minimally sedating — a practical antihistamine to trial for steroid-sparing in mild atopy
• Antihistamine response is individual; trial for 1–2 weeks before deciding it has failed
• Use plain cetirizine only — combination Zyrtec-D contains pseudoephedrine, which is toxic to pets

Mechanism of action

Second-generation H1-antihistamine (a carboxylated metabolite of hydroxyzine). Selectively and peripherally blocks histamine H1 receptors with minimal blood-brain-barrier penetration, giving an antipruritic / anti-allergic effect with little sedation, plus mild anti-eosinophil activity.

Formulations and products

• Cetirizine 10 mg tablet
• Cetirizine 1 mg/mL syrup
• Alerid — 5 / 10 mg tablet; 1 mg/mL syrup, Tablet / syrup (human-label)
• Cetzine — 10 mg tablet; 1 mg/mL syrup, Tablet / syrup (human-label)

Storage

Store at 15–30 °C, dry.

Before you use this dose

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.

Other hormones, emergency drugs, supplements and other drugs

• Calcium Borogluconate (IV Calcium)
• Calcium EDTA (Calcium Disodium Edetate)
• Carbimazole
• Carboplatin
• Chlorambucil
• Chlorpheniramine Maleate
• Clenbuterol
• Clomipramine

Frequently asked questions