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Cyproheptadine

Prescription

Antihistamine / Appetite Stimulant / Serotonin Antagonist

Last reviewed 21 Apr 2026 · PetCare.AI Editorial Team

Species

Dog, Cat

Brands

1 available

Interactions

2 documented

Formulations

Mechanism of action

First-generation antihistamine with potent H1-receptor antagonism and serotonin (5-HT2) antagonism. The antiserotonin properties underlie its appetite-stimulating effects and utility in serotonin syndrome.

At a glance

Class

Antihistamine / Appetite Stimulant / Serotonin Antagonist

Schedule

Prescription

Storage

Store at room temperature below 30°C, protect from moisture

Dosing

🐕

Dog

Used for allergic conditions, serotonin syndrome, and feline urethral spasm

Dose

0.3–2 mg/kg

Route

Frequency

q8–12h (antihistamine); as needed (serotonin syndrome)

🐈

Cat

Excellent appetite stimulant in anorexic cats

Dose

1–2 mg/cat

Route

Frequency

q8–24h

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 →

Formulations

💊

Other — 2

Strength

—

Strength

—

Storage

Store at room temperature below 30°C, protect from moisture

Safety

Monitoring parameters

Body weight with long-term useSigns of anticholinergic excess

Educational reference only

Interactions

Moderate — 2

Fluoxetine

moderate

Cyproheptadine is a 5-HT2 serotonin antagonist. It directly opposes the serotonergic effects of SSRIs, potentially reducing antidepressant/behavioral efficacy. However, this property is therapeutically useful for treating serotonin syndrome.

Management: Not typically combined for behavioral indications (antagonistic). However, cyproheptadine is the TREATMENT for serotonin syndrome caused by SSRIs — keep available as rescue.

Tramadol

moderate

Cyproheptadine antagonizes serotonin receptors, potentially reducing tramadol's serotonin-mediated analgesic component.

Management: May reduce tramadol analgesic efficacy. Monitor pain control. Useful as serotonin syndrome antidote if tramadol toxicity occurs.

Educational reference only

Brands

Other markets

Periactin

FAQs

Frequently asked questions

›What is Cyproheptadine?

Cyproheptadine is a antihistamine / appetite stimulant / serotonin antagonist used in pets. First-generation antihistamine with potent H1-receptor antagonism and serotonin (5-HT2) antagonism. The antiserotonin properties underlie its appetite-stimulating effects and utility in serotonin syndrome.

›What is Cyproheptadine used for in pets?

Cyproheptadine is used in veterinary medicine for: Used for allergic conditions, serotonin syndrome, and feline urethral spasm; Excellent appetite stimulant in anorexic cats.

›What is the Cyproheptadine dose for dogs?

For dogs, Cyproheptadine is typically dosed as follows — Used for allergic conditions, serotonin syndrome, and feline urethral spasm: 0.3–2 mg/kg PO q8–12h (antihistamine); as needed (serotonin syndrome). Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›What is the Cyproheptadine dose for cats?

For cats, Cyproheptadine is typically dosed as follows — Excellent appetite stimulant in anorexic cats: 1–2 mg/cat PO q8–24h. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›Does Cyproheptadine need a prescription?

Yes. Cyproheptadine is a prescription medication and should only be administered under veterinary supervision.

Educational reference only

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