# Zofran for Cats: Dosing, Frequency and Safety Can cats have Zofran? Yes, but only with a veterinarian's guidance. Ondansetron (the generic name for Zofran) is a prescription anti-nausea medicine that veterinarians use in cats, and the dose, frequency, and duration all depend on your cat's weight, condition, and other medications. Never give your cat a human Zofran tablet from your own medicine cabinet without talking to a veterinarian first. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Ondansetron is a prescription antiemetic (anti-vomiting drug) that veterinarians use in cats, and it is not available over the counter for pets. - Your veterinarian decides the dose based on your cat's weight and health, so there is no safe at-home dose you can calculate yourself. - In one controlled feline study, ondansetron was given at 0.22 mg/kg by injection to prevent vomiting after a sedative drug [1]. That number is a research dose, not a home dosing instruction. - How often and how long your cat takes ondansetron depends on the cause of the nausea and how your cat responds, and your vet will set the schedule. - Vomiting that lasts more than a day, comes with lethargy, or happens alongside a possible swallowed object needs a vet visit right away, because anti-nausea drugs can hide a serious problem [2]. ## What Is Zofran and What Do Veterinarians Use It For? Zofran is the brand name for ondansetron, a prescription medication that blocks serotonin signals in the body that trigger nausea and vomiting. In cats, veterinarians use it to settle nausea from many causes, including reactions to certain sedative and anesthetic drugs, gastrointestinal upset, kidney disease, pancreatitis, and chemotherapy. Ondansetron belongs to a group of drugs called serotonin receptor modulators. A large review of oral medications given to cats looked at this drug class, along with sedatives, anesthetics, and pain medications, and found that many of these oral drugs can be useful in cats when a veterinarian chooses them carefully [3]. That review focused on reducing fear and stress during handling, but it confirms that oral serotonin-modulating drugs are part of feline medicine. One important point: ondansetron treats the symptom of nausea, not the underlying disease. If your cat is vomiting because of a swallowed toy, a blocked intestine, or a toxin, the drug may quiet the vomiting while the real problem gets worse. A study of 537 dogs and cats with gastrointestinal foreign body obstruction found that pets given antiemetics waited longer for definitive care (3.2 days versus 1.6 days) and had longer hospital stays [2]. That is why veterinarians want to know why your cat is vomiting before reaching for any anti-nausea drug. ## How Ondansetron Works in Cats Ondansetron blocks 5-HT3 serotonin receptors in the gut and in the brain's vomiting center. When those receptors are blocked, the signals that tell your cat's body to vomit are muted. This is different from maropitant, another common antiemetic that works on a different receptor (NK-1). In a study of 64 cats, researchers compared ondansetron, maropitant, and metoclopramide for preventing vomiting caused by dexmedetomidine, a sedative. All three drugs significantly reduced retching and vomiting compared with a saline control [1]. That tells us ondansetron is a real, working antiemetic in cats, not a placebo. How fast it works depends on the route. An injection starts working quickly, which is why vets often use it in the hospital. An oral tablet has to be absorbed through the gut, and absorption varies. In dogs, oral ondansetron at 1 mg/kg had a bioavailability of only about 5 percent, meaning very little of the drug reached the bloodstream [4]. We do not have the same published number for cats, but this finding is a reminder that oral ondansetron may not always work as well as owners expect, especially in a cat who is already vomiting. ## Dosing Basics: Who Decides and How It Is Given ### Who decides the dose Your veterinarian does. There is no safe, universal dose of Zofran for cats that you can look up and use at home. The vet calculates the dose from your cat's body weight, the cause and severity of the nausea, kidney and liver function, and what other drugs your cat is taking. For context, the research dose used in one feline study was 0.22 mg/kg given by injection [1]. That is a study protocol, not a prescription for your cat. Do not use it to measure a dose at home. ### How it is given Ondansetron comes as an injection, an oral tablet, and an oral solution. In the hospital, your vet may give it by injection for fast relief. At home, you may be sent with tablets or a liquid. Some veterinarians use a specially compounded liquid or a transdermal gel, but these are made by a pharmacy and are not the same as a human tablet. If you are sent home with tablets, give them exactly as directed. Do not split, crush, or hide them in food unless your vet says it is okay, because some forms are bitter and some are designed to release slowly. If your cat refuses the pill, ask your vet about a liquid or a different anti-nausea option instead of forcing it. ### What to do about a missed dose If you miss a dose, give it when you remember, unless it is almost time for the next one. In that case, skip the missed dose and go back to the regular schedule. Never double up to make up for a missed dose. If you are unsure, call your vet's office and ask. ### How often can cats have Zofran? Your veterinarian sets the frequency, usually based on how long each dose controls the nausea and how your cat is doing. Some cats need it once a day, some need it more often, and some only need it for a short course. There is no single "correct" schedule that applies to every cat. Follow the label your vet gives you and do not stretch the interval or shorten it on your own. ### How long can cats take Zofran? That also depends on the cause. For a short bout of nausea after surgery or a sedative, a cat may take it for a day or two. For ongoing nausea from chronic kidney disease or cancer treatment, a vet may prescribe it for longer, with regular check-ins. Long courses need monitoring because the underlying disease still needs treatment. If you are managing other medications at home, our guide to [prescription medicine for cats](/knowledge/veterinary-medicine/clinical-methods/prescription-medicine-for-cats) covers how to store, measure, and give feline prescriptions safely. ## Side Effects of Ondansetron in Cats Most cats tolerate ondansetron well, but side effects can happen. The table below lists what to watch for. | Side effect | How common or serious | What to do | |---|---|---| | Sleepiness or mild sedation | Uncommon, usually mild | Note the time and how long it lasts. Call your vet if your cat is hard to wake. | | Drooling, lip licking, or nausea behaviors | Can happen, especially with bitter tablets | Stop forcing the pill and ask your vet about a liquid or injectable form. | | Constipation | Uncommon, mild | Mention it at your next visit if it lasts more than a day or two. | | Vomiting that continues despite the drug | Serious sign that the cause is not simple nausea | Call your vet the same day. Do not give another dose without advice. | | Trouble breathing, facial swelling, hives | Rare but serious allergic reaction | This is an emergency. Go to a vet or emergency clinic now. | | Weakness, collapse, or a very slow heart rate | Rare, serious | Emergency care now. | If your cat is vomiting and you are tempted to reach for a human medication, remember that many common human drugs are toxic to cats. Our article on [whether cats can have Tylenol](/knowledge/veterinary-medicine/toxicology-and-food-safety/can-cats-have-tylenol) explains why acetaminophen is dangerous, and [whether you can give your cat Benadryl](/knowledge/veterinary-medicine/pet-medication-guide/cat-benadryl-dosage-safety) covers another drug owners often ask about. ## Who Should Not Take Ondansetron and Drug Interactions Ondansetron is not right for every cat. Your veterinarian may avoid it or use it with extra caution if your cat: - Has a known allergy to ondansetron or similar drugs - Has severe liver disease, because the liver clears this drug - Is pregnant or nursing, since safety in breeding cats is not well established - Has a suspected gastrointestinal obstruction or a swallowed object, because masking vomiting can delay surgery [2] - Is already on other serotonin-affecting drugs, which can raise the risk of serotonin syndrome Drug interactions matter. Tell your vet about every medication, supplement, and herbal product your cat receives. Ondansetron can interact with other serotonin-active drugs, some antibiotics, some antifungals, and certain pain medications. Do not add any new drug, including over-the-counter products, without asking your vet first. If your cat takes a nonsteroidal anti-inflammatory drug for pain, our guide to [Onsior (robenacoxib) for cats](/knowledge/veterinary-medicine/calculators-clinical-tools/onsior-robenacoxib-for-cats-feline-nsaid-safe-dosing-protocol) explains how that class of drug is dosed and monitored. ## Overdose and When to Call a Veterinarian or Poison Control If your cat accidentally gets too much ondansetron, or chews into a bottle of human tablets, call for help right away. Do not wait for symptoms. - ASPCA Animal Poison Control Center: (888) 426-4435 - Pet Poison Helpline: (855) 764-7661 Both services may charge a consultation fee. Have the bottle or package with you so you can tell them the strength and how many tablets may have been eaten. Signs of overdose can include extreme sedation, agitation, tremors, a fast or irregular heartbeat, and vomiting. Your veterinarian may need to monitor your cat, give fluids, or treat symptoms directly. Never try to make your cat vomit at home. Do not give activated charcoal, milk, oil, or any home remedy unless a veterinarian or poison control tells you to. ## Limitations and When to Contact a Veterinarian Ondansetron can make your cat feel better, but it cannot tell you why your cat was sick in the first place. That is the biggest limitation. If the nausea is a symptom of something serious, the drug can hide it. Contact your veterinarian the same day if: - Your cat vomits more than two or three times in a day - Your cat refuses food or water for more than 12 to 24 hours - You see blood in the vomit or stool - Your cat seems painful in the belly when touched - The vomiting started after your cat may have eaten a toy, string, or object - Your cat is on ondansetron and the vomiting is not improving Go to an emergency clinic now if: - Your cat is collapsing, unresponsive, or having trouble breathing - Your cat's gums are pale, white, or blue - Your cat is having repeated, forceful vomiting with nothing coming up - You suspect an overdose or a toxin - Your cat is having a seizure Schedule a routine visit if: - The vomiting comes and goes over weeks - Your cat is losing weight - Your cat has chronic kidney disease, diabetes, or cancer and the nausea is not well controlled Every cat is different, and only a veterinarian who examines your cat can decide whether ondansetron is safe and appropriate. If you are unsure about anything on the label, call your vet's office before giving the next dose. ## Frequently Asked Questions ### Can I give my cat my own Zofran? No. Human Zofran tablets are not dosed for cats, and the strength in a single tablet can be far too high or too low for your pet. Even if a friend's cat took it, that does not make it safe for yours. Call your veterinarian for a prescription made for your cat. ### How often can cats have Zofran? Your veterinarian sets the schedule based on your cat's weight, the cause of the nausea, and how long each dose works. Some cats need it once daily, others more often, and some only for a short time. Follow the label exactly and do not change the timing on your own. ### How long can cats take Zofran? It depends on why your cat is nauseated. A short course may last a day or two after surgery or a sedative. For chronic conditions, a vet may prescribe it longer with regular rechecks. Long-term use should always come with monitoring of the underlying disease. ### What are the side effects of Zofran in cats? Most cats do fine, but sleepiness, drooling, and constipation can happen. Serious reactions like trouble breathing, swelling, or collapse are rare but need emergency care. If vomiting continues despite the drug, that is a sign to call your vet instead of give another dose. ### Can Zofran hide a serious problem in my cat? Yes. Anti-nausea drugs can quiet vomiting while an obstruction or other serious illness gets worse. One study found that pets with a gastrointestinal foreign body who received antiemetics waited longer for surgery and stayed in the hospital longer [2]. If your cat may have swallowed something, tell your vet before giving any anti-nausea medicine. ## Related Articles - [Can You Give Your Cat Benadryl? Dosage and Safety Guide](/knowledge/veterinary-medicine/pet-medication-guide/cat-benadryl-dosage-safety) - [Can I Give My Cat Melatonin? Safety, Dosage, and When to Avoid It](/knowledge/veterinary-medicine/vet-visit-decisions/can-i-give-my-cat-melatonin) - [Prescription Medicine For Cats](/knowledge/veterinary-medicine/clinical-methods/prescription-medicine-for-cats) - [Onsior Robenacoxib for Cats: Feline NSAID Safe Dosing Protocol](/knowledge/veterinary-medicine/calculators-clinical-tools/onsior-robenacoxib-for-cats-feline-nsaid-safe-dosing-protocol) - [Can Cats Have Tylenol?](/knowledge/veterinary-medicine/toxicology-and-food-safety/can-cats-have-tylenol) - [Mirtazapine Appetite Stimulant: Dose for Cats and Dogs Guide](/knowledge/veterinary-medicine/calculators-clinical-tools/mirtazapine-appetite-stimulant-dose-for-cats-and-dogs-guide) ## References 1. [The Effect of Maropitant, Ondansetron and Metoclopramide on Dexmedetomidine-Induced Vomiting in Cats](https://pubmed.ncbi.nlm.nih.gov/39792081/). Veterinary medicine and science, 2025. 2. [Delay of definitive care in cats and dogs with gastrointestinal foreign body obstruction following antiemetic administration: 537 cases (2012-2020)](https://pubmed.ncbi.nlm.nih.gov/37436922/). Journal of veterinary emergency and critical care (San Antonio, Tex. : 2001), 2023. 3. [Oral use of anxiolytic, sedative, and anaesthetic medications in domestic cats (Felis catus): A scoping review](https://pubmed.ncbi.nlm.nih.gov/42431357/). Veterinary journal (London, England : 1997), 2026. 4. [Bioavailability of Oral Ondansetron in Dogs: A Crossover Study](https://pubmed.ncbi.nlm.nih.gov/40924364/). Journal of veterinary pharmacology and therapeutics, 2026. ## Further Reading - [American Veterinary Medical Association: First Aid Tips for Pet Owners](https://www.avma.org/resources-tools/pet-owners/emergencycare/first-aid-tips-pet-owners) - [Merck Veterinary Manual: Cat Owners](https://www.merckvetmanual.com/cat-owners) - [Cornell Feline Health Center: Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information)