# How Long Can a Cat Take Onsior? Safe Duration Explained How long can a cat take Onsior? For most cats, the answer is a maximum of 3 days. Onsior (robenacoxib) is approved in the United States only for short-term pain and inflammation control after surgery, and the label limits use to 3 consecutive days in cats. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Onsior is approved for a maximum of 3 days of treatment in cats, given once daily by mouth. - It is a nonsteroidal anti-inflammatory drug (NSAID) made for short-term surgical pain, not for long-term arthritis management. - Never give more than one dose per day, and never combine it with another NSAID or a steroid unless your veterinarian specifically directs it. - Stop the drug and call your veterinarian if your cat vomits, stops eating, becomes lethargic, or has diarrhea. - If you think your cat needs pain relief beyond 3 days, ask your veterinarian about other options instead of continuing Onsior on your own. ## What Is Onsior and What Is It Used For? Onsior is the brand name for robenacoxib, an NSAID approved for cats in the United States. Veterinarians use it most often to control pain and swelling in the days right after surgery, such as a spay, neuter, dental extraction, or orthopedic procedure. The approved use is short. The drug is not labeled for chronic conditions like osteoarthritis, even though arthritis pain is a common reason owners ask about longer treatment. When a cat needs pain control for weeks or months, veterinarians usually reach for a different drug or a different strategy. Onsior comes as a small flavored tablet. Many cats take it willingly, which makes it easier to give at home after a procedure. It also comes in an injectable form that veterinarians use in the clinic. ## How Onsior Works Onsior belongs to the NSAID family. It blocks cyclooxygenase enzymes, which are involved in producing prostaglandins. Prostaglandins drive pain, fever, and inflammation at the site of an injury or surgery. The same enzymes also help protect the stomach lining and support normal blood flow to the kidneys. That dual role is why NSAIDs relieve pain well but carry real risks, especially with longer use or in cats with kidney or liver problems. Onsior was designed to favor the COX-2 enzyme, which is more involved in inflammation. That selectivity is one reason it can be used safely in cats for a short window. It does not make the drug risk-free, and it does not change the 3-day limit. ## How Long Can a Cat Take Onsior? The Duration Explained Three days. That is the approved duration for oral Onsior in cats in the United States, and it is the number your veterinarian will most likely follow after a routine procedure. Why so short? Cats clear NSAIDs more slowly than dogs, and their kidneys and gastrointestinal tract are more vulnerable to prolonged NSAID exposure. The 3-day window covers the period of peak surgical pain while keeping cumulative risk low. If your cat had surgery and still seems painful on day 4, that is a conversation, not a refill. Call your veterinarian. They may examine your cat, adjust other pain medications, or choose a different drug class. Do not simply keep giving the tablets because they seem to help. Some veterinarians use NSAIDs off-label for longer periods in specific cats, with bloodwork monitoring and a clear plan. That decision belongs to your veterinarian, who knows your cat's kidney values, liver values, and overall health. It is not something to manage at home on your own. ## Dosing Basics ### Who decides the dose Your veterinarian calculates the dose from your cat's body weight and health status. Never guess a dose, split a tablet meant for a dog, or borrow medication from another pet. Dog NSAID products can be toxic to cats. ### How it is given Onsior is typically given by mouth once daily, with or without food. Some cats do better with a small treat or a bit of food right after the pill to settle the stomach. Follow the instructions on your cat's prescription exactly. ### 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. Never double up to catch up. ### What to do when the course ends When the 3 days are done, the course is done. If your cat still shows signs of pain, such as hiding, growling when touched, or refusing to move normally, contact your veterinarian. Ongoing pain needs a plan, and there are options beyond NSAIDs. If your cat stops eating during or after treatment, that alone is a reason to call. A cat that refuses food for more than a day or two needs veterinary attention, and you can read more about the timeline in [Cat Not Eating: How Long Is Too Long?](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-not-eating-how-long-too-long). Constipation from pain, dehydration, or reduced intake is another concern covered in [Cat Not Pooping: How Long Is Too Long?](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-not-pooping-how-long-too-long). ## Onsior Side Effects in Cats Most cats tolerate a 3-day course well. When problems happen, they usually involve the stomach, the kidneys, or the liver. Some cats also react at the site of an injection. | Side effect | How common or serious | What to do | |---|---|---| | Vomiting | Uncommon but important | Stop the drug and call your veterinarian the same day | | Diarrhea or soft stool | Uncommon | Stop the drug and call your veterinarian | | Reduced appetite or not eating | Uncommon, can be serious | Stop the drug and call your veterinarian the same day | | Lethargy or weakness | Uncommon, can be serious | Stop the drug and seek veterinary care promptly | | Stomach or intestinal ulcers, black tarry stool | Rare but serious | Emergency care now | | Kidney injury | Rare but serious, higher risk in cats with existing kidney disease or dehydration | Emergency care now | | Liver injury | Rare | Stop the drug and call your veterinarian | | Injection site reaction (swelling, pain) | Possible with the injectable form | Tell your veterinarian, most reactions are mild and short-lived | | Hiding, pacing, or behavior change | Can signal pain or a drug reaction | Call your veterinarian to sort out which | Pain itself can look like a side effect. A cat that hides after surgery may be painful, nauseated, or simply stressed. Your veterinarian can help you tell the difference. If your cat is not eating but otherwise seems normal, the guidance in [Cat Not Eating But Acting Normal: How Long Can You Wait?](/knowledge/veterinary-medicine/vet-visit-decisions/cat-not-eating-but-acting-normal) can help you decide how urgently to act. ## Who Should Not Take Onsior Onsior is not right for every cat. Your veterinarian will avoid it or use it with extra caution in cats with: - Existing kidney disease or a history of kidney problems - Liver disease - Stomach or intestinal ulcers, or a history of gastrointestinal bleeding - Bleeding disorders or low platelet counts - Dehydration, shock, or low blood pressure - A known allergy to NSAIDs - Pregnancy, breeding, or nursing Cats that are very young, very old, or already on multiple medications need a closer look before any NSAID is started. ### Drug interactions to know about Tell your veterinarian about everything your cat takes, including supplements and over-the-counter products. The biggest concerns are: - Other NSAIDs, including meloxicam and aspirin. Combining them raises the risk of ulcers and kidney injury. - Corticosteroids such as prednisolone or dexamethasone. Combining steroids with NSAIDs increases gastrointestinal risk. - Diuretics such as furosemide, and blood pressure medications such as ACE inhibitors. These can stress the kidneys when paired with an NSAID. - Blood thinners or drugs that affect clotting. - Certain antibiotics and antifungals that compete for the same liver enzymes. Some of these combinations are used deliberately in specific patients with monitoring. Most are avoided. Your veterinarian makes that call. ## Overdose and When to Call for Help An overdose means more than the prescribed amount, a double dose, or a cat eating the tablets from the bottle. Signs can include vomiting, drooling, stomach pain, weakness, collapse, black stool, or seizures. If you suspect an overdose, call your veterinarian or an animal poison control hotline right away. Do not wait for symptoms. Treatment is easier and safer when it starts early. If your cat is collapsed, having trouble breathing, or having a seizure, go to an emergency clinic now. ## Limitations and When to Contact a Veterinarian Call your veterinarian the same day if your cat vomits, has diarrhea, refuses food, seems painful, or acts unusually tired during or after the Onsior course. Go to an emergency clinic now if you see collapse, difficulty breathing, seizures, severe weakness, a swollen or painful abdomen, or black tarry stool. Schedule a routine visit if the 3-day course ends and your cat still shows signs of pain, or if you have questions about longer-term pain control. Ongoing pain deserves a real plan, not a repeated short course. Individual cases vary, and only your veterinarian can decide what is safe for your cat. ## Frequently Asked Questions ### Can I give Onsior to my cat for more than 3 days? No, not without direct instruction from your veterinarian. The approved duration is 3 days, and longer use raises the risk of stomach, kidney, and liver problems. If your cat still needs pain relief after that window, ask about other options. ### Is Onsior the same as Metacam or meloxicam? They are different drugs in the same NSAID family. Both control pain and inflammation, and both carry similar warnings about stomach and kidney risk. Never switch between them or combine them without veterinary guidance. ### Can I give Onsior with food? Yes, it can be given with or without food. A small amount of food or a treat afterward often helps if your cat has a sensitive stomach. Follow your veterinarian's specific instructions for your cat. ### What if my cat vomits after taking Onsior? Stop the medication and call your veterinarian. A single vomit may be minor, but vomiting can also be an early sign of stomach irritation or a more serious reaction. Your veterinarian can decide whether treatment should continue or change. ### Can Onsior be used for arthritis in cats? It is not approved for long-term arthritis treatment in cats. Some veterinarians use NSAIDs for chronic pain in selected cats with monitoring, but that is an individual medical decision. Ask your veterinarian what long-term plan fits your cat, since options like other drug classes, joint support, and environmental changes may work better. ### Does my cat need bloodwork before starting Onsior? Often, yes, especially for older cats or cats with any history of kidney or liver problems. Bloodwork gives your veterinarian a baseline and helps catch problems that would make an NSAID unsafe. Ask whether testing is recommended for your cat. ### What happens if I miss a dose? Give it when you remember unless the next dose is almost due, then skip it and resume your normal schedule. Never give two doses at once. If you are unsure, call your veterinarian's office for guidance. ## Related Articles - [Cat Not Eating: How Long Is Too Long?](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-not-eating-how-long-too-long) - [Cat Not Pooping: How Long Is Too Long?](/knowledge/veterinary-medicine/digestive-and-urinary-care/cat-not-pooping-how-long-too-long) - [Cat Not Eating But Acting Normal: How Long Can You Wait?](/knowledge/veterinary-medicine/vet-visit-decisions/cat-not-eating-but-acting-normal) - [How Long Can A Cat Safely Go Without Urinating](/knowledge/veterinary-medicine/toxicology-and-food-safety/how-long-can-a-cat-safely-go-without-urinating) - [Cat Hissing at New Kitten: How Long Will It Last?](/knowledge/veterinary-medicine/anxiety-and-behavior-support/cat-hissing-at-new-kitten) - [How Long Can A Cat Go Without Peeing Before It Is Dangerous](/knowledge/veterinary-medicine/symptom-guides/how-long-can-a-cat-go-without-peeing-before-it-is-dangerous) - [How Long Can a Cat Stay on Steroids? Duration and Risks](/knowledge/veterinary-medicine/pet-medication-guide/how-long-cat-stay-on-steroids) - [How Long Can a Cat Stay on Prednisolone? Long-Term Risks](/knowledge/veterinary-medicine/pet-medication-guide/how-long-cat-prednisolone) - [How Long Can a Cat Take Mirataz? Duration and Safety](/knowledge/veterinary-medicine/pet-medication-guide/how-long-cat-mirataz) ## References ## 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) - [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare) - [American Veterinary Medical Association: Resources for Pet Owners](https://www.avma.org/resources-tools/pet-owners)