Veterinary drug · Drug monograph

Loratadine: veterinary dose and monograph

Loratadine is a veterinary drug. A second-generation, NON-SEDATING H1-antihistamine — used for allergic conditions (allergic dermatitis/pruritus, urticaria, allergic rhinitis) where drowsiness is undesirable. Indications include allergic pruritus / atopic dermatitis (adjunct; individual response); urticaria / allergic skin reactions; allergic rhinitis / mild allergic signs where non-sedating antihistamine is wanted. This monograph lists 3 reference doses for dogs and cats, each with route, frequency and source.

At a glance

Drug class: Veterinary drug
Also known as: Claritin, Lorfast, Alaspan
Species with doses: Dogs and Cats
General dose range: 0.25–1.1 mg/kg PO q24h or divided q12h — check the species tables for the indication
Routes: PO
Last reviewed: 1 October 2026

Indications

Allergic pruritus / atopic dermatitis (adjunct; individual response)
Urticaria / allergic skin reactions
Allergic rhinitis / mild allergic signs where non-sedating antihistamine is wanted

Loratadine 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

Loratadine doses for dogs
Indication	Dose	Route	Frequency	Duration
Antihistamine	0.25–1.1 mg/kg	PO	q24h or divided q12h	—

Antihistamine: Plumb’s 10e p.777 (extra-label): anecdotal doses range from 0.25–1.1 mg/kg PO once daily or divided twice daily. Practically: small dogs 5 mg/dog once daily; medium dogs 10 mg/dog once daily; large dogs 10 mg/dog twice daily (per dog, NOT per kg). Papich 5e has no loratadine monograph.

Cats

Loratadine doses for cats
Indication	Dose	Route	Frequency	Duration
Antihistamine (per kg)	0.5 mg/kg	PO	q24h	—
Antihistamine (per cat)	2.5–5 mg/cat	PO	q24h	—

Antihistamine (per kg): Plumb’s 10e p.778 (extra-label): anecdotal 0.5 mg/kg PO once daily. Papich 5e has no loratadine monograph.
Antihistamine (per cat): Plumb’s 10e p.778 (extra-label): anecdotal 2.5–5 mg per cat (NOT mg/kg) PO once daily.

Contraindications

Combination products containing PSEUDOEPHEDRINE/decongestants (toxic to pets — avoid). Known hypersensitivity. Significant hepatic impairment (hepatically metabolised). Use plain loratadine only.

Species-specific warnings

Dogs: Avoid "loratadine-D"/decongestant combination products — the pseudoephedrine component is toxic (agitation, tachycardia, hypertension, hyperthermia). Use plain loratadine only.

Adverse effects

Non-sedating (minimal drowsiness) — its main advantage
Occasional GI upset
Modest/variable antipruritic efficacy
Anticholinergic effects minimal (2nd-generation)

Drug interactions

CYP3A4/2D6 inhibitors (ketoconazole, macrolides): may raise loratadine levels
CNS depressants: minimal additive effect (non-sedating)
Avoid pseudoephedrine-containing combination products (pet toxicity)
May suppress allergy skin-test reactions — withdraw before intradermal testing

Pregnancy and lactation

Limited veterinary data; considered relatively low-risk but use only if needed.

Monitoring

Pruritus response over a 1–2 week trial (individual)
Confirm the product is PLAIN loratadine (no pseudoephedrine)
Withdraw before intradermal allergy testing

Toxicity and overdose

Wide safety margin; overdose is usually limited to mild GI upset (and, at high doses, possible mild CNS/cardiac effects). The important toxicity risk is really from PSEUDOEPHEDRINE in combination "loratadine-D" products — pseudoephedrine causes serious agitation/tachycardia/hypertension in dogs and cats.

Management: Supportive; no specific antidote. For a pseudoephedrine-containing combination ingestion, treat the sympathomimetic toxicosis (decontaminate, sedation with acepromazine/phenothiazine, manage tachycardia/hypertension/hyperthermia). Plain loratadine overdose is generally mild.

Clinical pearls

A non-sedating, once-daily antihistamine — useful when first-generation antihistamines' drowsiness is a problem, though antipruritic efficacy in atopy is modest and individual (worth a 1–2 week trial)
CRUCIAL: dispense PLAIN loratadine — many human "loratadine-D/decongestant" products contain PSEUDOEPHEDRINE, which is toxic to dogs and cats
Stop antihistamines before intradermal allergy testing (they blunt reactions)
Not a substitute for steroids/oclacitinib/lokivetmab in significant atopic dermatitis — best as an adjunct or for mild disease

Mechanism of action

A selective peripheral H1-receptor antagonist that blocks histamine-mediated pruritus, vasodilation and wheal formation. Being a second-generation antihistamine it poorly crosses the blood–brain barrier (little central H1 blockade → minimal sedation) and has negligible anticholinergic activity. Its active metabolite (desloratadine) contributes to a long duration, allowing once-daily dosing.

Formulations and products

10 mg tablet
Syrup 1 mg/mL (5 mg/5 mL)
Claritin / Lorfast — 10 mg tablet; 5 mg/5 mL syrup, Tablet / syrup (human-label)

Storage

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

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.

Frequently asked questions

What is the dose of Loratadine for dogs?

Reference doses for Loratadine in dogs: 0.25–1.1 mg/kg PO q24h or divided q12h (Antihistamine). Confirm against the label and the patient before use.

What is the dose of Loratadine for cats?

Reference doses for Loratadine in cats: 0.5 mg/kg PO q24h (Antihistamine (per kg)); 2.5–5 mg/cat PO q24h (Antihistamine (per cat)). Confirm against the label and the patient before use.

When should Loratadine not be used?