# Cerenia for Cats: Side Effects and Dosing Basics Most cats handle Cerenia well, and the side effects owners notice most often are sleepiness, drooling, and mild stomach upset. Serious reactions are uncommon but possible, especially with the injectable form. This guide covers what Cerenia does, how dosing works, which cats should not take it, and the signs that mean you should call your veterinarian. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Cerenia (maropitant) is a prescription anti-vomiting medicine for cats, given as a tablet or an injection by your veterinarian. - The dose is calculated from your cat's weight and health status, so never guess or reuse a dose from another pet. - Common side effects include sleepiness, drooling, and mild digestive changes. These usually pass. - Pain or a reaction at the injection site, collapse, or severe lethargy after an injection needs same-day veterinary attention. - Call your veterinarian or a poison control hotline right away if your cat gets too much Cerenia or the wrong medicine. ## What Cerenia Is and What Veterinarians Use It For Cerenia is the brand name for maropitant citrate. It is a prescription medication labeled for treating vomiting in dogs and cats [1]. Veterinarians use it to stop acute vomiting, to prevent vomiting before surgery or travel, and to control nausea that comes with many illnesses. Vomiting in cats has a long list of causes. Hairballs, eating something spoiled, kidney disease, pancreatitis, and reactions to other medicines can all trigger it. Cerenia treats the vomiting itself. It does not fix the underlying cause, which is why your veterinarian will still want to examine your cat and may run blood work or imaging. Cerenia comes in two forms. The tablet is given by mouth, usually with a small amount of food. The injectable form is given under the skin or into a vein by a veterinarian. Some compounding pharmacies also make a transdermal gel that is rubbed on the inner ear, and one small study of eight cats found that a compounded transdermal product given once daily helped manage vomiting [2]. Compounded products are not the same as the FDA-approved drug, so ask your veterinarian before using one. Cerenia is not the only medicine that can cause side effects in cats. If your cat takes other prescriptions, our guides to [gabapentin side effects in cats](/knowledge/veterinary-medicine/pet-medication-guide/gabapentin-side-effects-cats) and [seizure medication side effects in cats](/knowledge/veterinary-medicine/pet-medication-guide/seizure-medication-side-effects-cats) cover what to watch for with those drugs. ## How Cerenia Works Cerenia blocks a receptor in the brain and gut called the NK-1 receptor. Substance P, a chemical the body releases during nausea, normally docks at this receptor and triggers the vomiting reflex. Cerenia occupies the receptor so substance P cannot attach, which quiets the signal that leads to vomiting [1]. Because it works on a specific receptor, Cerenia is different from older anti-nausea drugs that act on other pathways. That specificity is one reason it is often effective when other medicines are not. A 2026 systematic review and meta-analysis pooled five controlled feline studies and found that maropitant cut the risk of vomiting compared with control, with a risk ratio of 0.20 (95% confidence interval 0.08 to 0.55) [3]. In plain terms, cats given maropitant vomited far less often than cats that did not receive it. Cerenia also appears to slow the movement of the stomach and small intestine. A study in healthy adult dogs found that a 1 mg/kg subcutaneous dose significantly decreased the rate of peristalsis in the stomach and jejunum without changing intestinal diameter or wall thickness [1]. That slowed movement may explain why some cats seem quieter or less interested in food after a dose. This finding comes from dogs, so it may or may not apply the same way to cats. ## Cerenia for Cats Dosage: The Basics ### Who decides the dose Your veterinarian does. The dose depends on your cat's weight, the reason for treatment, and whether the medicine is given by mouth or by injection. There is no single dose that fits every cat, and the label dose for one species or condition does not transfer to another. Never split a tablet meant for a dog and give it to your cat. Never give a leftover dose from a previous illness without checking first. Cats metabolize drugs differently than dogs, and a dose that is safe for one cat may be too much for another. ### How it is given Tablets are usually given by mouth, often with a small amount of food to reduce drooling and stomach upset. If your cat refuses food, ask your veterinarian whether the tablet can be given directly or whether an injection is a better option. Injections are given in the clinic. The injectable form is typically dosed once daily, and many cats need only one or two injections before switching to tablets at home. Your veterinarian will decide how long your cat stays on the medicine based on how the vomiting responds. ### 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 your regular schedule. Do not double up to make up for a missed dose. If you are unsure, call your veterinary clinic and ask. ## Cerenia for Cats Side Effects: What Owners Actually See Most reactions are mild and short lived. The table below covers what owners report and what to do about each one. | Side effect | How common or serious | What to do | |---|---|---| | Sleepiness or quiet behavior | Common and usually mild | Let your cat rest. Call your vet if it lasts more than a day or your cat will not eat or drink. | | Drooling or lip smacking after a pill | Common and usually mild | Give the tablet with a small amount of food. Do not force a second pill if the first was spit out. Call your vet for guidance. | | Vomiting that continues despite treatment | Uncommon but important | Call your vet the same day. Ongoing vomiting can mean the underlying cause is not controlled. | | Pain, swelling, or hair loss at the injection site | Uncommon | Call your vet. Injection site reactions should be checked, especially if the area is warm or growing. | | Severe lethargy, collapse, or trouble breathing | Rare but serious | Treat as an emergency. Go to a veterinary hospital now. | | Signs of an allergic reaction such as facial swelling, hives, or difficulty breathing | Rare but serious | Emergency care now. | Diarrhea is a question many owners ask about. Cerenia is used to stop vomiting, and some cats develop looser stools while they are on it or because of the illness being treated. If diarrhea is mild and your cat is otherwise bright, mention it at your next visit. If diarrhea is severe, bloody, or paired with vomiting that will not stop, call your veterinarian the same day. Cats with ongoing digestive or urinary signs may need a broader workup, and our article on [cat urinary tract infection side effects](/knowledge/veterinary-medicine/clinical-methods/cat-urinary-tract-infection-side-effects) explains what those signs can look like. ### Cerenia injection reaction in cats The injectable form can sting. Some cats vocalize, pull away, or act sore at the injection site. This is usually brief. More serious injection reactions are rare but include marked sleepiness, wobbliness, and swelling or pain at the site that gets worse over the following days. If your cat had an injection today and seems much more sedated than expected, or if the injection site looks angry, call the clinic that gave it. If your cat collapses, has trouble breathing, or has swelling around the face, go to an emergency hospital right away. ## Who Should Not Take Cerenia and What Interacts With It Cerenia is not right for every cat. Tell your veterinarian about all medicines, supplements, and conditions before your cat gets a dose. Cats with liver disease need extra caution. Maropitant is processed by the liver, so a cat with liver problems may clear the drug more slowly. Your veterinarian may adjust the dose or choose a different medicine. Cats with heart disease or certain neurologic conditions may also need a different plan. Young kittens and pregnant or nursing cats are usually not given Cerenia unless the veterinarian decides the benefit clearly outweighs the risk. Drug interactions matter. Because Cerenia can slow stomach and intestinal movement [1], it may change how quickly other oral medicines are absorbed. If your cat takes heart medication, seizure medication, or other daily drugs, tell your veterinarian so timing can be planned. Cats on multiple medicines are at higher risk for interactions. Our guide to [cat allergy medication side effects](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/cat-allergy-medication-side-effects) is a useful companion read if your cat takes more than one prescription. ## Overdose and When to Call for Help An overdose can cause excessive sleepiness, wobbliness, vomiting, or a slow heart rate. Signs may not appear for an hour or more, so do not wait to see what happens. If you think your cat swallowed extra tablets, chewed a pill bottle, or received too much injectable medicine, call your veterinarian or an animal poison control hotline immediately. Have the product name, the strength, and your best estimate of how much your cat got. Do not induce vomiting unless a veterinarian tells you to. Some cats vomit poorly from common induction methods, and forcing the issue can cause harm [4][5]. If your cat is unresponsive, having trouble breathing, or cannot stand, skip the phone call and go straight to the nearest emergency veterinary hospital. ## Limitations and When to Contact a Veterinarian No article can tell you whether your specific cat is having a normal reaction or a problem. Only a veterinarian who examines your cat can do that. Use the timing below as a guide. **Call the same day** if your cat is sleepier than expected, refuses food or water for more than 12 hours, keeps vomiting after treatment, has diarrhea that is worsening, or has a sore or swollen injection site. **Go to an emergency hospital now** if your cat collapses, has trouble breathing, has facial swelling or hives, has a seizure, or cannot be woken up. **Bring it up at a routine visit** if your cat had mild drooling with pills, seemed tired for a few hours after a dose, or had soft stools that have since resolved. Keep a simple log of doses and any symptoms you notice. That record helps your veterinarian decide whether to continue, adjust, or stop the medicine. ## Frequently Asked Questions ### How long do Cerenia side effects last in cats? Most mild effects, like sleepiness and drooling, fade within a few hours to a day. If your cat still seems off after 24 hours, or if new signs appear, call your veterinarian. Long-lasting or worsening symptoms are not expected and should be checked. ### Can I give my cat Cerenia for diarrhea? No, Cerenia is an anti-vomiting medicine, not a diarrhea treatment. Diarrhea in cats has different causes and different treatments. If your cat has diarrhea, have your veterinarian evaluate it instead of reaching for a leftover anti-nausea pill. ### Is Cerenia safe to give every day? Many cats receive it daily for a short course, and some receive it longer under veterinary supervision. The safe duration depends on your cat's condition, liver health, and response to treatment. Your veterinarian will set the schedule and decide when to stop. ### What should I do if my cat vomits right after taking Cerenia? Call your veterinarian before giving another dose. You may not know how much of the tablet was absorbed, and repeating the dose could lead to too much medicine. Your vet may recommend an injection instead or a different plan. ### Can Cerenia be used in kittens? Kittens are usually not given Cerenia unless a veterinarian decides it is necessary. Their bodies handle drugs differently than adult cats, and dosing is less predictable. Ask your veterinarian before giving any anti-nausea medicine to a kitten. ## Related Articles - [Cat Urinary Tract Infection Side Effects](/knowledge/veterinary-medicine/clinical-methods/cat-urinary-tract-infection-side-effects) - [Cat Allergy Medication Side Effects: What to Watch For](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/cat-allergy-medication-side-effects) - [What Are the Side Effects of Apoquel for Cats?](/knowledge/veterinary-medicine/pet-medication-guide/apoquel-side-effects-cats) - [What Are the Side Effects of Seizure Medication in Cats?](/knowledge/veterinary-medicine/pet-medication-guide/seizure-medication-side-effects-cats) - [What Are the Side Effects of Gabapentin for Cats?](/knowledge/veterinary-medicine/pet-medication-guide/gabapentin-side-effects-cats) - [Cat Prednisolone for Allergies: Side Effects and Safe Use](/knowledge/veterinary-medicine/skin-allergy-and-ear-care/cat-prednisolone-allergies) - [Cerenia and Restlessness in Cats: Side Effects](/knowledge/veterinary-medicine/pet-medication-guide/cerenia-restlessness-cats) - [Cerenia Tablets for Cats: Forms, Doses, and Limits](/knowledge/veterinary-medicine/pet-medication-guide/cerenia-tablets-cats-forms-doses) - [Maropitant (Cerenia) for Cats: Appetite and Dosing](/knowledge/veterinary-medicine/pet-medication-guide/maropitant-cerenia-for-cats) ## References 1. [Maropitant Citrate Administration Significantly Decreases the Rate of Peristalsis in the Stomach and Jejunum and Does Not Significantly Alter Intestinal Diameter or Intestinal Wall Thickness in Healthy Adult Dogs](https://pubmed.ncbi.nlm.nih.gov/42083426/). Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 2026. 2. [Evaluation of the efficacy of transdermal administration of maropitant in managing vomiting in cats](https://pubmed.ncbi.nlm.nih.gov/36589400/). Open veterinary journal, 2022. 3. [Receptor-Targeted Antiemetic Strategies in Cats: A Systematic Review and Intervention-Specific Meta-Analysis](https://pubmed.ncbi.nlm.nih.gov/42599757/). Veterinary medicine and science, 2026. 4. [Evaluation of different doses of medetomidine for the induction of emesis in cats](https://pubmed.ncbi.nlm.nih.gov/41017076/). Journal of feline medicine and surgery, 2025. 5. [Inducing emesis in Australian dogs and cats: agents, adverse effects and antiemetic administration](https://pubmed.ncbi.nlm.nih.gov/40326551/). Australian veterinary journal, 2025. ## 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)