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Ondansetron

Prescription

5-HT3 receptor antagonist (antiemetic)

Last reviewed 19 Apr 2026 · PetCare.AI Editorial Team

Species

Dog, Cat

Brands

3 available

Interactions

2 documented

Formulations

Mechanism of action

Selectively blocks serotonin (5-HT3) receptors in the chemoreceptor trigger zone and vagal afferents, preventing nausea and vomiting

At a glance

Class

5-HT3 receptor antagonist (antiemetic)

Schedule

Prescription

Storage

Store below 25°C, protect from light

Dosing

🐕

Dog

Acute vomiting / chemotherapy-induced nausea

Dose

0.5–2 mg/kg

Route

IV, PO

Frequency

BID-TID

Max dose

16 mg/dose; 48 mg/day

Duration: 1-3 days

🐈

Cat

Acute vomiting

Dose

0.5–1 mg/kg

Route

IV, PO

Frequency

BID-TID

Max dose

4 mg/dose; 12 mg/day

Duration: 1-3 days

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

💊

Tablet — 2

Strength

4mg

Available in India

Strength

8mg

Available in India

💉

Injectable — 1

Strength

2mg/mL

Available in India

💊

Oral disintegrating tablet — 1

Strength

4mg

Available in India

Storage

Store below 25°C, protect from light

Safety

Absolute contraindications — do not use

Known hypersensitivity
Rare

Use with caution

Hepatic impairment
Hepatically metabolised — reduce dose in liver disease
Concurrent serotonergic drugs
Theoretical serotonin syndrome risk

Adverse effects

Common

Constipation

Headache (presumed)

Serious

QT prolongation (IV, high dose)

Serotonin syndrome (with concurrent serotonergic drugs)

Monitoring parameters

Vomiting frequencyHydration statusECG if concurrent QT-prolonging drugs

Educational reference only

Interactions

Major — 1

Apomorphine

major

Ondansetron (5-HT3 antagonist with some D2 activity) antagonizes apomorphine's emetic effect. If antiemetic given before apomorphine, emesis may fail.

Management: Do NOT give antiemetics before apomorphine when emesis is indicated. If emesis needed after antiemetic administration, use different emetic method.

Moderate — 1

Tramadol

moderate

5-HT3 antagonism by ondansetron may partially block tramadol's serotonin-mediated analgesic component.

Management: Clinical significance debated. Monitor pain scores if using both. Consider alternative analgesic if control inadequate.

Educational reference only

Brands

International

Zofran

GSK

India

Emeset

Cipla

Ondem

Alkem

FAQs

Frequently asked questions

›What is Ondansetron?

Ondansetron is a 5-ht3 receptor antagonist (antiemetic) used in pets. Selectively blocks serotonin (5-HT3) receptors in the chemoreceptor trigger zone and vagal afferents, preventing nausea and vomiting

›What is Ondansetron used for in pets?

Ondansetron is used in veterinary medicine for: Acute vomiting / chemotherapy-induced nausea; Acute vomiting.

›What is the Ondansetron dose for dogs?

For dogs, Ondansetron is typically dosed as follows — Acute vomiting / chemotherapy-induced nausea: 0.5–2 mg/kg IV/PO BID-TID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›What is the Ondansetron dose for cats?

For cats, Ondansetron is typically dosed as follows — Acute vomiting: 0.5–1 mg/kg IV/PO BID-TID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›What are the side effects of Ondansetron?

Common: Constipation, Headache (presumed). Serious (call your vet immediately): QT prolongation (IV, high dose), Serotonin syndrome (with concurrent serotonergic drugs).

›Does Ondansetron need a prescription?

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

›When should Ondansetron not be used?

Do not use Ondansetron if: Known hypersensitivity.

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