Cerenia vs ondansetron for vomiting in dogs and cats
Cerenia (maropitant) is an FDA-approved veterinary medicine for vomiting in dogs and cats and motion sickness in dogs. Ondansetron is a human anti-nausea medicine vets use off-label, which a regular pharmacy can fill. Vomiting can signal a serious problem, so both are used with a vet’s diagnosis.
Updated October 4, 2026
At a glance
- Approval
- Cerenia
- FDA-approved for dogs and cats
- Ondansetron
- Human medicine used off-label
- How often
- Cerenia
- Once a day
- Ondansetron
- Two or three times a day
- Motion sickness
- Cerenia
- Approved for dogs
- Ondansetron
- Not a usual use
- Where to fill
- Cerenia
- Through your vet
- Ondansetron
- A regular pharmacy can fill it
- Forms
- Cerenia
- Tablets and injection
- Ondansetron
- Tablets, dissolving tablets, liquid
Cerenia maropitant | Ondansetron Zofran | |
|---|---|---|
| Approval | FDA-approved for dogs and cats | Human medicine used off-label |
| How often | Once a day | Two or three times a day |
| Motion sickness | Approved for dogs | Not a usual use |
| Where to fill | Through your vet | A regular pharmacy can fill it |
| Forms | Tablets and injection | Tablets, dissolving tablets, liquid |
How they differ
Maropitant blocks a vomiting signal in the brain and lasts a day per dose, which makes it convenient and the usual first choice. Ondansetron blocks a different signal and is particularly useful for nausea, for example with chemotherapy or kidney disease, and is sometimes combined with maropitant.
Find the cause first
Vomiting can come from something minor or from a blockage, pancreatitis, poisoning or organ disease. Anti-nausea medicine can hide warning signs, so a vet should examine a pet with repeated vomiting, blood in vomit, a swollen belly, lethargy or a suspected swallowed object.
Motion sickness
For car sickness in dogs, Cerenia tablets are given ahead of travel as your vet directs, after a light meal. Ondansetron is not usually used for travel.
Safety
Maropitant can cause drooling or reduced appetite, and is used with care in very young puppies and pets with liver disease. Ondansetron is generally well tolerated but interacts with some serotonin-affecting medicines. Use only the forms your vet specifies.
Cost
Ondansetron is an inexpensive human generic, so filling it at a regular pharmacy can save money. Cerenia comes through your vet or a veterinary pharmacy.
Giving tablets and keeping notes
Hiding a tablet in a small treat or pill pocket helps, unless your vet has said to withhold food. Keep a note of each vomiting episode, including the time and what came up, to share with your vet if it continues.
Questions for your vet
- What is likely causing the vomiting?
- Which medicine suits my pet’s condition?
- Which signs mean I should come back straight away?
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Sources
Written by the Script Unlock editorial team from the sources above. It is general information, not advice for you or your pet; your vet decides which medicine is right.
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.