Ondansetron
Zofran (human) · generic ondansetron
Ondansetron is a human anti-nausea drug that vets use in dogs and cats for vomiting from chemotherapy, kidney disease, pancreatitis and other causes, often when maropitant (Cerenia) is unavailable or not enough. It is a cheap generic that any pharmacy can fill.
What it is used for
Ondansetron blocks serotonin receptors in the gut and the brain’s vomiting centre. It is a standard anti-nausea drug for people on chemotherapy and after surgery, and vets use it in the same situations, as well as for the nausea of kidney failure, pancreatitis and inflammatory bowel disease. It works within an hour and is given two or three times a day; the dissolving tablets are useful for animals that will not swallow.
Cats absorb it poorly by mouth, so vets sometimes use higher doses or an injection in the clinic; dogs absorb it well. Side effects are uncommon; constipation and drowsiness are reported. It is often used alongside maropitant, which works on a different pathway, when one drug is not enough.
Safety points that differ from human use
- Vomiting that continues, or that contains blood, or an animal that cannot keep water down, needs the vet rather than another dose.
- Ondansetron has a mild effect on heart rhythm and is used cautiously with other drugs that do the same; tell the vet about everything the animal takes.
- The human orally disintegrating tablets contain sweeteners; have the pharmacist check for xylitol before giving them to a dog.
- Tablets (human)
- Orally disintegrating tablets (human; check sweeteners)
- Oral solution (human)
- Injection (clinic use)
- 4 and 8 mg tablets
- 4 and 8 mg disintegrating tablets
- Solution 4 mg per 5 mL
Why the cash price varies
Ondansetron tablets are a commodity generic that fell sharply in price after years as an expensive brand, but some pharmacies still quote it as if it were costly; the disintegrating tablets and the solution cost more. A quote from a second pharmacy usually corrects a high one.
How to pay less
- Ask the vet whether plain tablets would do rather than the disintegrating form or the liquid.
- Compare two pharmacies; the spread on this drug is wide.
- Ask whether a human anti-nausea drug is appropriate instead of a veterinary brand for your pet’s situation.
- Upload the prescription to Script Unlock so licensed pharmacies can quote. You pay the pharmacy directly.
Questions for your vet
- What is causing the vomiting, and is that being treated?
- Ondansetron, Cerenia or both for my pet?
- Plain tablets or the dissolving form?
- How often, and for how many days?
- Is it safe with my pet’s other medicines?
Rules on refills, transfers and controlled substances differ by state; see pharmacy rules by state.
How Script Unlock gets you a cash price for your pet’s ondansetron prescription
Prices on this site come from pharmacies responding to a real prescription. We do not publish estimated, average or "typical" prices, because none of those would be your price.
- 1You upload your prescription
A photo of your your pet’s ondansetron prescription prescription is enough. Nothing is sold on the site; you are asking pharmacies to quote.
- 2Licensed pharmacies respond
Pharmacies that Script Unlock has verified see the request and each can reply with its own cash price for your exact drug, strength and quantity.
- 3You choose and pay the pharmacy
You compare the responses, pick a pharmacy, and pay that pharmacy directly when you collect. Script Unlock never takes a patient payment and never sets the price.
Related pet medications
Sources
- Merck Veterinary Manual
- FDA Orange Book (approved generics and therapeutic equivalence)
- MedlinePlus drug information (National Library of Medicine)
- ASPCA Animal Poison Control
Written by the Script Unlock editorial team from the sources above. Not yet reviewed by a veterinarian or veterinary pharmacist. Last checked 2026-10-03. Nothing here replaces your vet\u2019s directions; doses for animals are set by weight and species.
Script Unlock is a marketplace that lets licensed pharmacies quote a cash price on your prescription. It does not prescribe, dispense or sell medication, does not process patient payments, and does not give medical advice. Always follow the instructions of your prescriber and pharmacist and read the medication guide supplied with your medicine.