Competitively blocks histamine H1 receptors, reducing allergic symptoms including pruritus, urticaria, and oedema; crosses the blood-brain barrier causing sedation
At a glance
Class
First-generation antihistamine (H1 receptor antagonist)
Storage
Store below 25°C, protect from light
Dosing
Allergic pruritus / urticaria
Max dose
16 mg/dose; 48 mg/day
Duration: As needed; may use long-term
Acute allergic reaction (adjunct to adrenaline)
Duration: Acute; follow with oral dosing BID for 3-5 days
Allergic pruritus / eosinophilic dermatitis
Max dose
4 mg/dose; 8 mg/day
Duration: As needed
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet.
Find a vet near you →Safety
Urinary retention / prostatic hypertrophy
Anticholinergic effects worsen urinary retention
Glaucoma
Anticholinergic effects may increase intraocular pressure
Concurrent CNS depressants
Additive sedation
Adverse effects
Common
Sedation/drowsiness
Dry mouth
Urinary retention
Serious
CNS excitation (paradoxical, especially cats)
Seizures (overdose)
Pruritus scoreSedation levelUrination
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet.
Find a vet near you →Interactions
No documented interactions.
FAQs
Frequently asked questions
›What is Chlorpheniramine?
Chlorpheniramine is a first-generation antihistamine (h1 receptor antagonist) used in pets. Competitively blocks histamine H1 receptors, reducing allergic symptoms including pruritus, urticaria, and oedema; crosses the blood-brain barrier causing sedation
›What is Chlorpheniramine used for in pets?
Chlorpheniramine is used in veterinary medicine for: Allergic pruritus / urticaria; Acute allergic reaction (adjunct to adrenaline); Allergic pruritus / eosinophilic dermatitis.
›What is the Chlorpheniramine dose for dogs?
For dogs, Chlorpheniramine is typically dosed as follows — Allergic pruritus / urticaria: 0.2–0.5 mg/kg PO BID-TID; Acute allergic reaction (adjunct to adrenaline): 0.2–0.5 mg/kg IM/SC Single dose. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What is the Chlorpheniramine dose for cats?
For cats, Chlorpheniramine is typically dosed as follows — Allergic pruritus / eosinophilic dermatitis: 1–2 mg/cat PO BID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What are the side effects of Chlorpheniramine?
Common: Sedation/drowsiness, Dry mouth, Urinary retention. Serious (call your vet immediately): CNS excitation (paradoxical, especially cats), Seizures (overdose).
›Does Chlorpheniramine need a prescription?
Chlorpheniramine is available over the counter. Even so, you should consult your veterinarian before giving any medication to your pet.
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet.
Find a vet near you →References
References
The PetCare.AI drug reference is built from 13 authoritative sources cited across 580 drug monographs.
Textbooks & handbooks — 5
- Plumb's Veterinary Drug Handbook
- Withrow & MacEwen's Small Animal Clinical Oncology
- Merck Veterinary Manual
- NRC Nutrient Requirements of Dogs and Cats
- Veterinary Pharmacology and Therapeutics (Riviere & Papich)
Clinical guidelines & consensus — 4
- ASPCA Animal Poison Control Center Guidelines
- AAHA Diabetes Management Guidelines
- ASPCA Poison Control Guidelines
- RECOVER CPR Guidelines
Journals & peer-reviewed studies — 2
- EPIC Study (J Vet Intern Med 2016)
- JVIM FAT CAT Study
Regulatory & approvals — 1
- CDSCO Veterinary Drug Approval Registry (1969–2026)
Databases — 1
- Washington State University VCPL MDR1 Database