Chlorpheniramine Maleate: veterinary dose and monograph

At a glance

Drug class

Veterinary drug

Also known as

Anistamin, Avilin, Avil, Chlor-Trimeton

Species with doses

Dogs, Cats, Cattle, Horses and Ferrets

General dose range

0.2–0.5 mg/kg IM q8–12h — check the species tables for the indication

Routes

IM, PO

Last reviewed

1 October 2026

Indications

• Allergic dermatitis / urticaria
• Anaphylactic shock (adjunct after adrenaline)
• Rhinitis, photo-dermatitis, tail eczema (horses)
• Pruritus, serum sickness, transport-induced oedema
• Pulmonary emphysema (horses, adjunct)

Chlorpheniramine Maleate 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

• Atopy / urticaria: Papich 5e and Plumb’s p.260: 4–8 mg per dog PO q8–12h, not exceeding 0.5 mg/kg q12h; pruritus trial 0.2–0.8 mg/kg PO 2–3 times daily (Rosychuk; Marsella). Injectable use follows the product label.

Cats

• Atopy / pruritus: Papich 5e: 2 mg per cat q12h PO. Plumb’s p.260: 2–4 mg per cat q12–24h (Hnilica; Rosychuk); pruritus 2–4 mg twice daily (Messinger) or 0.5–2 mg 2–3 times daily (Marsella); mild sedation 1–4 mg q12–24h (Overall). Bitter — capsule or mask the taste.

Cattle

• Allergic reactions / urticaria: 5–10 mL of Anistamin 10 mg/mL per adult cow. Dose per Indian product label (Anistamin); Papich 5e states no large-animal dose has been reported and Plumb’s 10e (pp.251–253) gives no cattle dose. Label dose 0.2–0.5 mg/kg IM q8–12h. Follow the product label withdrawal.

Horses

• Histamine-related pruritus (e.g. insect-bite hypersensitivity): Plumb’s 10e p.252 (extra-label): adjunctive treatment and prevention of histamine-related pruritic conditions such as insect-bite hypersensitivity — 0.25 mg/kg PO every 12 hours. A pharmacokinetic study found a single 0.5 mg/kg PO dose less efficacious than other antihistamines. No injectable horse dose is given; Papich 5e reports no large-animal dose.

Goats

• No reference dose for this species: No goat chlorpheniramine dose appears in Papich 5e (no large-animal dose reported) or Plumb’s 10e (pp.251–253 dose dogs, cats, horses, birds and ferrets only), and the previous row had no source.

Sheep

• No reference dose for this species: No sheep chlorpheniramine dose appears in Papich 5e (no large-animal dose reported) or Plumb’s 10e (pp.251–253 dose dogs, cats, horses, birds and ferrets only), and the previous row had no source.

Pigs

• No reference dose for this species: No pig chlorpheniramine dose appears in Papich 5e (no large-animal dose reported) or Plumb’s 10e (pp.251–253 dose dogs, cats, horses, birds and ferrets only), and the previous row had no source.

Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

• Allergic reactions / urticaria: 5–10 mL of Anistamin 10 mg/mL per adult cow. Dose per Indian product label (Anistamin); Papich 5e states no large-animal dose has been reported and Plumb’s 10e (pp.251–253) gives no cattle dose. Label dose 0.2–0.5 mg/kg IM q8–12h. Follow the product label withdrawal.

Ferrets

• Pruritus / allergic disease: Plumb's p.260 (Williams 2000): 1–2 mg/kg PO 2–3 times a day.

Contraindications

Hypersensitivity. Caution with concurrent CNS depressants. Narrow-angle glaucoma. Urinary retention.

Species-specific warnings

Dogs: 0.2–0.5 mg/kg IM q8–12h or 4–8 mg PO q8–12h. Sedation expected.

Cats: 2 mg per cat PO q12h. Watch for paradoxical excitement.

Horses: Transport oedema / photo-dermatitis: 0.2 mg/kg IM. Tail-rub eczema: 0.2 mg/kg IM q8–12h.

Cattle: Pheniramine combinations (Avilin) widely used in cattle. Withdrawal: 7 d slaughter / 2 d milk.

Adverse effects

• Sedation / drowsiness
• Anticholinergic — dry mouth, mydriasis, ileus
• Excitement / paradoxical reaction (cats)

Drug interactions

• CNS depressants (opioids, alpha-2 agonists, anaesthetics, alcohol): ADDITIVE sedation
• Anticholinergic drugs (atropine, tricyclic antidepressants): additive anticholinergic effects (urinary retention, ileus, mydriasis)
• MAO inhibitors (selegiline): potentiate anticholinergic effects
• Beta-blockers: blunted bronchodilator response in asthma / anaphylaxis
• Epinephrine: COMPLEMENTARY in anaphylaxis (epi first, antihistamine second-line)
• Phenytoin / phenobarbital: induce hepatic metabolism — may reduce antihistamine effect

Pregnancy and lactation

Generally considered safe at therapeutic doses. Crosses placenta in low amounts. FDA Category B (human). Used widely in pregnant animals for allergic reactions, transport oedema.

Monitoring

• Sedation depth — usually mild
• Cats: paradoxical excitement — switch to alternative if observed
• Urinary output (anticholinergic retention)
• Withdrawal periods: cattle 7 d slaughter / 2 d milk (pheniramine combinations — Avilin)
• Clinical response to allergic reaction — typically within 30–60 min
• Adjunct to epinephrine for anaphylaxis, NEVER monotherapy

Toxicity and overdose

Sedation is the most common side effect — usually mild. Anticholinergic: dry mouth, mydriasis, urinary retention, ileus. Cats: PARADOXICAL EXCITEMENT possible at higher doses — switch to alternative antihistamine if observed. Overdose: severe anticholinergic syndrome — mydriasis, tachycardia, hyperthermia, agitation, seizures, coma. Pheniramine combinations: similar profile.

Management: No specific antidote. Supportive: IV fluids, diazepam 0.5 mg/kg IV for excitement / seizures, active cooling for hyperthermia, beta-blocker (esmolol) for tachyarrhythmias. Activated charcoal if recent ingestion. Physostigmine 0.02 mg/kg IV slow can reverse central anticholinergic effects but rarely needed and risks cholinergic crisis.

Clinical pearls

• Allergic dermatitis / urticaria: 0.2–0.5 mg/kg IM or 4–8 mg per dog PO q8–12h
• Cat atopy / pruritus: 2 mg per cat PO q12h — first-line first-generation antihistamine in cats
• Anaphylaxis adjunct: 0.2–0.5 mg/kg IM/IV AFTER epinephrine (0.01 mg/kg IM) + corticosteroid (dexamethasone 0.5 mg/kg IV)
• Transport oedema (horses): 0.2 mg/kg IM single dose
• Photo-dermatitis (cattle): 0.2 mg/kg IM q8–12h
• Cats with paradoxical excitement on chlorpheniramine: switch to cetirizine (1 mg/kg PO q24h) or cyproheptadine (1.1 mg/kg PO q12h)
• For chronic atopy: second-generation non-sedating antihistamines (cetirizine, fexofenadine) may be preferred
• NEVER alone for anaphylactic shock — epinephrine is first-line, antihistamine is supportive

Mechanism of action

First-generation alkylamine H1 histamine receptor antagonist (with some pheniramine combination formulations sharing the same class). Competitively blocks H1 receptors → reduces histamine-mediated vasodilation, smooth muscle contraction, and pruritus. Crosses blood-brain barrier (vs newer non-sedating antihistamines) — sedation is the predominant side effect. Also has weak anticholinergic and mild sedative properties. Useful adjunct (NOT primary) for type I hypersensitivity / anaphylaxis — epinephrine is the first-line.

Formulations and products

• Anistamin 10 mg/mL (Intas, 50 / 100 mL)
• Avilin 22.75 mg/mL pheniramine maleate (MSD, 10 / 33 mL)
• Anistamin (Intas (Neovet)) — Chlorpheniramine maleate 10 mg/mL, Injection
• Avilin VET (MSD Animal Health) — Pheniramine maleate 22.75 mg/mL, Injection
• CPM-Sure (Assure Biotech, Jagadhri (HR)) — 10 mg/mL, Injection

Storage

Tablets: 15–25 °C, dry, protected from light. Injection: 15–25 °C, protect from light. Multidose vial: discard 28 days after broaching. Pheniramine combinations: per product label.

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.

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• Carbimazole
• Carboplatin
• Cetirizine
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• Clenbuterol
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• Clopidogrel
• Cloprostenol

Frequently asked questions