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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
4

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

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

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.

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.

References

References

Textbooks & handbooks

  • Plumb, D.C. Plumb's Veterinary Drug Handbook. 10th ed., Wiley-Blackwell, 2023.
  • Vail, D.M., Thamm, D.H., & Liptak, J.M. (eds.). Withrow & MacEwen's Small Animal Clinical Oncology. 6th ed., Saunders/Elsevier, 2020.
  • Riviere, J.E., & Papich, M.G. (eds.). Veterinary Pharmacology and Therapeutics. 10th ed., Wiley-Blackwell, 2018.
  • National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press, Washington DC, 2006.
  • The Merck Veterinary Manual. Merck & Co., Online edition. https://www.merckvetmanual.com/

Clinical guidelines & consensus

  • Fletcher, D.J., Boller, M., Brainard, B.M., et al. "RECOVER Evidence and Knowledge Gap Analysis on Veterinary CPR." Journal of Veterinary Emergency and Critical Care, 2012;22(S1):S102–S131.
  • American Animal Hospital Association. 2018 AAHA Diabetes Management Guidelines for Dogs and Cats. AAHA Press.

Journals & peer-reviewed studies

  • Hogan, D.F., Fox, P.R., Jacob, K., et al. "Secondary prevention of cardiogenic arterial thromboembolism in the cat: The FAT CAT study." Journal of Veterinary Cardiology, 2015;17(Suppl 1):S306–S317.
  • Boswood, A., Häggström, J., Gordon, S.G., et al. "Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study — A Randomized Clinical Trial." Journal of Veterinary Internal Medicine, 2016;30(6):1765–1779.
  • ASPCA Animal Poison Control Center. Toxicology and Poison Management Guidelines. American Society for the Prevention of Cruelty to Animals. https://www.aspca.org/pet-care/animal-poison-control

Regulatory & approvals

  • Central Drugs Standard Control Organisation (CDSCO), Government of India. Veterinary Drug Approval Registry, 1969–2026. Directorate General of Health Services. https://cdsco.gov.in/

Databases

  • Washington State University, College of Veterinary Medicine. Veterinary Clinical Pharmacology Laboratory (VCPL) — MDR1 Multidrug Sensitivity Database. https://vcpl.vetmed.wsu.edu/
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 →