Robenacoxib (Onsior) for Dogs: Dosage and Safe Use

Name: Robenacoxib (Onsior) for Dogs: Dosage and Safe Use
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

Robenacoxib for dogs dosage is not something you choose on your own. Your veterinarian calculates it from your dog's weight, the reason for treatment, and your dog's overall health, then decides whether an injection or a tablet is the right form. This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Robenacoxib is a prescription-only NSAID sold under the brand name Onsior, and it is approved for short-term pain and inflammation control in dogs [1][2].
The labeled oral dose range in dogs is 1 to 4 mg/kg once daily, and the labeled injectable dose is 2 mg/kg given under the skin [2].
Tablets come in fixed strengths, so your dog's dose is rounded to the nearest tablet size your vet selects. You should never split or combine tablets to hit a number on your own.
The labeled use period is a maximum of 3 days for postoperative pain and inflammation [1].
Never give robenacoxib with another NSAID, and never give it without telling your vet about every other medicine, supplement, or topical product your dog receives.

What Robenacoxib Is and What Veterinarians Use It For

Robenacoxib is a veterinary-approved nonsteroidal anti-inflammatory drug in the coxib group [2]. It has anti-inflammatory, anti-pain, and fever-reducing properties [2]. In the United States it is most familiar to owners as Onsior.

Vets use it to control postoperative pain and inflammation after orthopedic surgery, spaying (ovariohysterectomy), and castration [1]. The approved treatment window for those uses is a maximum of 3 days [1]. That short window matters. It reflects the safety data the drug was licensed on, and it is one reason vets often switch to a different long-term plan if your dog needs pain control beyond a few days.

Robenacoxib is also used as part of multimodal analgesia, meaning it is combined with other pain-relieving drugs instead of used alone. In one clinical study of dogs having elective orthopedic surgery, robenacoxib or meloxicam was given at the licensed dose, interval, and route alongside other pain management, and additional methadone was available when pain scores crossed a threshold [3]. That is the normal way vets think about this drug: one piece of a larger pain plan.

If your dog's pain is driven by allergies, itching, or a skin condition, robenacoxib is not the right tool. Those cases call for different drugs, and you can read about options in Dog Antihistamines for Allergies: Which Ones Are Safe? and Can You Give Your Dog Human Antihistamines? Safe Options and Doses.

How Robenacoxib Works

Robenacoxib selectively inhibits the COX-2 enzyme [2]. COX-2 is the isoform involved in producing prostaglandins that drive inflammation and pain. By blocking it, the drug reduces swelling, soreness, and fever.

The selectivity is the point. In laboratory testing, robenacoxib's COX-1 to COX-2 inhibition ratio was 129 to 1 in dogs, meaning it strongly prefers COX-2 over COX-1 [2]. COX-1 is the enzyme that helps protect the stomach lining and supports normal platelet function, so sparing it is generally better for the gut. That said, selective does not mean risk-free, and any NSAID can still cause gastrointestinal problems in a sensitive dog.

Two pharmacokinetic features explain how the drug behaves in your dog. First, robenacoxib is more than 98 percent bound to plasma proteins [2]. Second, it concentrates in inflamed tissue, so its clinical effect lasts longer than its blood level suggests [2]. The terminal half-life in blood is under 2 hours, yet once-daily dosing still produces clinical benefit [2]. In dogs, the drug leaves the body mainly through bile and feces, with about 65 percent of the dose excreted in bile [2]. A separate study measuring excretion found roughly 64.6 percent in feces and 35.4 percent in urine after intravenous dosing, and about 66.7 percent in feces and 33.3 percent in urine after oral dosing [4]. Both routes matter, which is why liver and kidney health are part of the prescribing decision.

Robenacoxib for Dogs Dosage: What Owners Need to Know

Who Decides the Dose

Your veterinarian decides. The labeled oral range in dogs is 1 to 4 mg/kg, and the labeled subcutaneous dose is 2 mg/kg [2]. Those are the numbers your vet works from, adjusted for your dog's weight and health status. You should not calculate a dose yourself from a tablet strength.

Tablets

Here is the practical problem with that search. A tablet strength is not a dose. The same tablet given to a 4 kg dog is 10 mg/kg, far above the labeled range. The tablet size only becomes meaningful once your vet pairs it with your dog's weight.

This is why your vet may send home a combination of tablet sizes, or a tablet plus a partial tablet, to land close to the target dose. Follow the label exactly. Do not substitute a different strength because it is what you have at home.

Injection

Robenacoxib injection for dogs is given subcutaneously, meaning under the skin, at 2 mg/kg [2]. This form is typically used in the clinic around surgery, when a dog is not yet eating or when a fast onset is useful. In the orthopedic surgery study described earlier, robenacoxib was administered at the licensed dose, interval, and route as part of the anesthetic and recovery protocol [3]. You will not be giving this injection at home.

Giving the Tablet

Robenacoxib tablets are usually given once daily [2]. Many dogs take them readily, and some owners hide them in a small amount of food. If your vet says to give it with food, follow that instruction. If your dog vomits the tablet shortly after taking it, call your vet before redosing. A second dose on top of a dose that may have been absorbed can push your dog over the intended amount.

Missed Dose

If you miss a dose, do not double up. Call your vet's office and ask how to handle it based on how late you are and how your dog is doing. For a short 3-day course, a missed dose is worth a phone call because the whole course is brief.

Storage and Handling

Keep the tablets in the original packaging, out of reach of children and other pets. Wash your hands after handling the medication, especially if you are pregnant or breastfeeding, and talk to your vet or pharmacist if you have questions about handling NSAIDs.

Side Effects: What to Watch For

Side effect	How common or serious	What to do
Vomiting, soft stool, reduced appetite	Common enough to watch for, usually mild	Stop the medication and call your vet the same day
Dark or tarry stool, blood in stool	Serious, possible gastrointestinal ulceration	Stop the medication and call your vet right away
Abdominal pain, hunched posture, restlessness	Serious	Call your vet right away
Lethargy, weakness, collapse	Serious	Treat as an emergency
Increased thirst and urination	Can signal kidney stress	Call your vet the same day
Yellow gums, eyes, or skin	Serious, possible liver problem	Treat as an emergency
Swelling, hives, difficulty breathing	Serious, possible allergic reaction	Treat as an emergency

NSAIDs as a class carry gastrointestinal risk, and that risk is the main reason vets ask about your dog's history before prescribing. If your dog has had stomach upset on another NSAID, say so. Your vet may choose a different drug or add stomach protection.

Who Should Not Take Robenacoxib

Robenacoxib is not right for every dog. Your vet will screen for the following before prescribing.

Dogs with active gastrointestinal ulcers or a history of NSAID-related stomach bleeding.
Dogs with kidney disease or dehydration. Because a meaningful share of the drug is cleared through urine, kidney function matters [4].
Dogs with liver disease. Bile is the main excretion route in dogs, accounting for about 65 percent of the dose [2].
Dogs with bleeding disorders or low platelet counts.
Dogs who are pregnant, breeding, or nursing, unless your vet specifically decides the benefit outweighs the risk.
Puppies below the labeled age and weight for the product.
Dogs already taking another NSAID, including aspirin, carprofen, meloxicam, deracoxib, firocoxib, or enflicoxib.

Drug Interactions

Tell your vet about every medication and supplement your dog takes. The most important interactions involve:

Other NSAIDs. Combining them raises the risk of stomach ulcers and kidney injury. If your dog is on deracoxib, for example, your vet needs to know before adding robenacoxib. General guidance on that drug is available from Pet Poison Helpline, which advises owners to follow their veterinarian's instructions on frequency and dose and to call with questions [5].
Corticosteroids such as prednisone or dexamethasone. These stack gastrointestinal risk with NSAIDs.
Diuretics and blood pressure medications, which can stress the kidneys when combined with an NSAID.
Anticoagulants and antiplatelet drugs.
Certain antibiotics and antifungals that affect liver enzymes. If your dog is on long-term antimicrobial therapy, kidney and liver function are already part of the picture, and you can read more in Renal Dosing Adjustments for Commonly Used Veterinary Antimicrobials.

If your dog takes an anti-seizure medication, that is a separate conversation with your vet, and dose and liver monitoring for those drugs is covered in Zonisamide Seizure Dogs: Modern Anti-Seizure Dose and Liver Safety.

Overdose and When to Call for Help

An overdose of robenacoxib can cause vomiting, stomach ulcers, kidney injury, and in severe cases, neurological signs. The risk rises with the size of the overdose and with how small your dog is.

If you think your dog ate extra tablets, or chewed through a bottle, act immediately. Do not wait for symptoms.

Call your veterinarian first. If your regular clinic is closed, call an emergency veterinary hospital. You can also call Pet Poison Helpline at (855)-764-7661 for guidance [5]. Have the following ready: your dog's weight, the tablet strength, how many tablets may have been eaten, and when it happened.

Do not induce vomiting unless a veterinarian tells you to. Do not give food, milk, or home remedies to try to dilute the drug.

Limitations and When to Contact a Veterinarian

This article gives general information. Your dog's individual case needs a veterinarian who can examine your dog, review bloodwork if needed, and set a dose.

Call your vet the same day if your dog vomits, has soft stool, eats less than usual, seems more tired than expected, or drinks and urinates more than normal.

Go to an emergency clinic now if you see dark or bloody stool, repeated vomiting, a swollen or painful belly, yellow gums or eyes, collapse, trouble breathing, or swelling of the face and muzzle.

Schedule a routine visit if the pain seems to be returning as the course ends, if you are unsure whether a dose was given, or if your dog needs pain control beyond the labeled 3-day window [1]. Longer treatment requires a fresh conversation about risks, monitoring, and alternatives.

Frequently Asked Questions

Can I give my dog robenacoxib without a prescription?

No. Robenacoxib is a prescription veterinary NSAID, and the dose depends on your dog's weight and health. Giving a tablet you obtained elsewhere, or reusing a leftover supply, can easily deliver too much or too little drug.

Is the injection stronger than the tablet?

They are different routes, not different strengths. The injection is given under the skin in the clinic, while tablets are given by mouth at home. Your vet picks the route based on timing, your dog's condition, and whether your dog is eating.

How long can my dog stay on robenacoxib?

The labeled use is a maximum of 3 days for postoperative pain and inflammation. If your dog needs pain control past that point, your vet will reassess and may switch to a different plan.

Can I give robenacoxib with other pain medications?

Only if your vet says so. Robenacoxib is often used as part of a multimodal plan, but the combination has to be chosen deliberately. Never add an over-the-counter pain pill, and never add a second NSAID.

What should I do if my dog seems fine after an overdose?

Call anyway. NSAID toxicity can develop over hours, and a dog who looks normal right after eating extra tablets can still get sick. Your vet or Pet Poison Helpline at (855)-764-7661 can advise on monitoring and treatment [5].

References

Pharmacokinetics of a Single Oral Dose of Robenacoxib in Hispaniolan Parrots (Amazona ventralis). Journal of avian medicine and surgery, 2025.
Pharmacology, safety, efficacy and clinical uses of the COX-2 inhibitor robenacoxib. Journal of veterinary pharmacology and therapeutics, 2022.
Intravenous paracetamol does not have significant opioid-sparing effects when used as part of a multimodal analgesic protocol in dogs undergoing elective orthopaedic surgery. The Veterinary record, 2026.
Determination of the route of excretion of robenacoxib (Onsior™) in cats and dogs: A pilot study. Journal of veterinary pharmacology and therapeutics, 2021.
Deracoxib for Dogs. Pet Poison Helpline.