Rimadyl (Carprofen) for Dogs: Dosage Chart and Side Effects

Rimadyl is a brand name for carprofen, a prescription anti-inflammatory pain medicine for dogs. If your vet sent you home with "carprofen" instead of Rimadyl, your dog is getting the same active drug. The FDA approves a generic carprofen only after the maker shows it is bioequivalent to Rimadyl, meaning it is absorbed and acts in the body the same way.

Vets prescribe it for two jobs on the label: the pain and inflammation of osteoarthritis, and pain after soft tissue or orthopedic surgery. Most dogs do well on it. A small number have serious stomach, liver or kidney reactions, and that is where its rocky reputation comes from. Here is the FDA label dose as a chart and a weight calculator, plus the signs that mean stop and call, the bloodwork to expect, and what never to mix it with.

Is Carprofen the Same as Rimadyl?

Yes. Carprofen is the drug; Rimadyl is the original brand, now made by Zoetis and first approved by the FDA in 1996. Other companies sell carprofen through the FDA's generic pathway. In the FDA's approval summary for one generic carprofen tablet, the agency spells out the rule: the generic must be shown bioequivalent to Rimadyl, which already proved it was safe and effective when used according to its label.

In the US, carprofen is also sold as Novox, Vetprofen, Carprieve, Quellin, Levafen, Carprovet and Rovera, plus plain "carprofen" tablets. Flavors, tablet shapes and inactive ingredients can differ. Your vet's prescription is for carprofen, so do not swap products, or add a second one, without asking.

What Rimadyl Treats and How It Works

Carprofen is a nonsteroidal anti-inflammatory drug (NSAID), from the same chemical family as ibuprofen and naproxen (which are not safe for dogs).

NSAIDs block cyclooxygenase (COX), the enzyme that makes prostaglandins. Prostaglandins drive pain, swelling and fever, but they also protect the stomach lining, keep blood flowing to the kidneys and help platelets clot. Fewer prostaglandins means less pain, and it also explains the side effects.

You may read that Rimadyl "targets COX-2", the form of the enzyme tied to inflammation. In canine cell cultures it did favor COX-2, but the label says the clinical relevance has not been shown, and the Merck Veterinary Manual calls carprofen a weak COX inhibitor with an unclear exact mechanism. "COX-2 selective" is a lab finding, not a promise of zero stomach risk.

Carprofen reaches peak blood levels 1 to 3 hours after a dose. For arthritis, the owner information sheet says most dogs improve within a matter of days.

Osteoarthritis in brief

Osteoarthritis is the slow wearing down of the cartilage that cushions a joint, so the joint inflames and hurts. It has no cure, but pain control helps a dog stay active. Dogs with hip dysplasia or elbow dysplasia can develop it young. Signs owners notice:

• Limping, stiffness, or trouble getting up after lying down
• Reluctance to climb stairs, jump into the car or play
• Shorter walks, or lagging behind
• Muscle loss over the hips and back legs

Rimadyl eases the pain and inflammation. It does not repair the joint, and the label notes the pain may come back if the drug is stopped or not given as directed.

Rimadyl Dosage Chart for Dogs

The chart below shows the doses on the FDA-approved Rimadyl labels. It covers dogs only: Rimadyl is not approved for cats, so do not give it to a cat unless your vet prescribes it.

For information only. These are typical published dose ranges, not a prescription and not medically verified for your pet. Your veterinarian sets the dose after examining your pet. Never start, stop or change a medicine without their OK.

Only give what your vet prescribed, at the dose they set.

Why your prescription may not match the chart:

• The chart shows the full label amount. The label tells vets to use the lowest effective dose for the shortest time that controls the pain, so a lower dose is normal.
• Tablets come in 25, 75 and 100 mg, scored down the middle, and the label rounds doses to the nearest half tablet.
• The injection is given by the vet team at the same daily amount. The label notes that long-term use of the injectable has not been studied.

Too many tablets? Call your vet, the ASPCA Animal Poison Control Center at (888) 426-4435 or the Pet Poison Helpline at (855) 764-7661 right away.

Giving Rimadyl at home

Rimadyl can be given with or without food. The chewables are flavored and most dogs take them like a treat, so you can hand-feed one or put it on a little food. Watch that your dog eats the whole dose.

If you miss a dose, call your vet's office for what to do. Never give two doses together to catch up.

Who Should Not Take Rimadyl

The label says Rimadyl should not be given to a dog that has had an allergic reaction to carprofen. The owner information sheet adds dogs that reacted to aspirin or another NSAID (hives, facial swelling, red or itchy skin).

Your vet will weigh the risk more carefully, and may choose another option, if your dog:

• Has kidney, liver or heart disease, or past stomach or intestinal ulcers
• Is dehydrated, or takes a diuretic ("water pill")
• Has a bleeding disorder such as von Willebrand's disease
• Is younger than 6 weeks, pregnant, nursing or used for breeding (safety has not been established)
• Takes other medicines, including anything bought without a prescription

Dogs with arthritis are usually older, and the FDA points out they may have kidney or liver disease too. An NSAID can "unmask" a kidney problem that showed no signs before, the label warns, which is why the exam and blood tests come first.

Rimadyl and cats

Rimadyl is not approved for cats. Do not give it to a cat unless your vet prescribes it, and call your vet right away if a cat gets into the dog's tablets. Cats break down NSAIDs less efficiently than dogs and are especially sensitive to their side effects; only two NSAIDs are FDA-approved for cats (meloxicam as a single injection and robenacoxib for up to 3 days). The flavored chewables raise the odds: after they launched in 1999, the maker reported accidental overdoses in dogs and cats.

Rimadyl Side Effects: When to Stop and Call

In the label's field studies of dogs with arthritis, vomiting and diarrhea showed up about as often on Rimadyl as on a placebo. Serious reactions are uncommon, but they can come without warning and, rarely, have been fatal. The label says most dogs recovered when the signs were spotted early, the drug was stopped and the dog got veterinary care.

Stop Rimadyl and call your vet right away if you see:

• Eating less (or sometimes more), or vomiting
• Diarrhea, or black, tarry or bloody stool (see what stool color can mean)
• Yellow gums, skin or whites of the eyes (jaundice)
• Drinking or urinating more, or a change in urine color or smell
• Pale gums
• Lethargy, wobbliness, a seizure, aggression or other behavior change
• Red, scabby or itchy skin, facial swelling or hives

The FDA's memory aid for owners is BEST: Behavior changes, Eating less, Skin redness and scabs, Tarry black stool, diarrhea or vomiting.

Call now (emergency vet or poison line) if your dog vomits blood, passes black tarry stool and seems weak or pale, has a seizure or collapses, or has eaten more tablets than prescribed:

• ASPCA Animal Poison Control: (888) 426-4435
• Pet Poison Helpline: (855) 764-7661

Both lines may charge a fee. To report a suspected reaction, Zoetis lists 1-888-963-8471 on the label. Keep the bottle out of reach of every pet in the house.

Bloodwork and Monitoring

The label asks vets to consider baseline blood tests before starting any NSAID and to repeat them periodically. The FDA tells owners to ask about baseline tests before long-term use, and how often to recheck.

Schedules vary with the dog. One common plan for long-term use is baseline blood and urine tests, a recheck of liver and kidney values 2 to 4 weeks after starting, then every 3 to 6 months. The early recheck has a reason: the FDA notes that most NSAID-related liver damage happens within the first three weeks.

What the tests look for:

• Liver: carprofen can cause rare, unpredictable liver reactions, some serious. About a quarter of the liver reports listed on the label after approval involved Labrador Retrievers, although Merck notes a true breed risk has not been proven. More on elevated liver enzymes in dogs.
• Kidneys: prostaglandins help keep blood flowing to the kidneys when blood pressure drops, for example during anesthesia or dehydration, and NSAIDs can reduce that flow. Know the signs of kidney failure in dogs, such as drinking and urinating more.
• Blood counts: rare reactions include anemia from bleeding or from the immune system attacking red blood cells or platelets.

Between visits, you are the monitor. Keep the side-effect list handy and mention any change at each recheck.

Never Mix Rimadyl With These

• Another NSAID: aspirin, deracoxib, firocoxib, meloxicam, grapiprant or a second carprofen brand.
• Steroids: prednisone, dexamethasone and similar drugs. An NSAID plus a steroid raises the risk of stomach ulcers.
• Human painkillers: never give ibuprofen (Advil, Motrin) or naproxen (Aleve); Merck notes dogs are much more sensitive than people to ibuprofen's stomach and intestinal side effects. Acetaminophen (Tylenol) is not an NSAID, but it can damage a dog's liver and is fatal to cats.

When a dog switches from one NSAID to another, or from a steroid to an NSAID, the label tells vets to allow a washout period in between. A dog that reacted badly to one NSAID may react to another. Tell your vet about everything your dog takes, including flea products and supplements.

Arthritis Care Beyond Rimadyl

Some arthritis pain needs more than an NSAID, and Merck notes NSAIDs are often combined with other pain relievers for severe pain. Your vet may build a plan that includes:

• Weight control. Extra weight loads sore joints; the owner information sheet tells owners to discuss weight and exercise with the vet.
• Regular, gentle exercise such as leash walks and swimming, which keep muscle without pounding the joints.
• Physical therapy. Animal physical therapy uses joint mobilization, stretching, massage and modalities such as laser, heat, cold and TENS to ease pain.

• Other medicines. Gabapentin and amantadine are used off-label alongside an NSAID for nerve-type or long-standing pain. Your vet decides whether, which and how much.
• Acupuncture, which some vets offer for chronic arthritis and spinal pain.
• Joint supplements such as omega-3 fatty acids. Supplements are not FDA-approved drugs and quality varies, so ask your vet which ones they trust.

Other NSAIDs for Dogs

If Rimadyl does not suit your dog, the FDA lists these currently marketed NSAIDs approved for dogs, all prescription only:

Grapiprant works differently: it blocks one prostaglandin receptor (EP4) instead of the COX enzyme. It still needs monitoring.

No NSAID is approved for over-the-counter sale for dogs; the FDA warns that one sold without a prescription is an unapproved animal drug, checked by nobody for safety or quality. Full labels and client information sheets are on the NSAID Labels page of Animal Drugs @ FDA.

Why Rimadyl Became Controversial

Rimadyl was approved for dogs in 1996 and was soon used in a great many dogs. Rare reactions in that many dogs added up to a lot of reports, and in December 1999 the FDA's Center for Veterinary Medicine published an update addressing the high number of reports in dogs on Rimadyl.

In a March 2000 letter to veterinarians, sent as part of an ongoing effort with the FDA, Pfizer put the reported rate of possible adverse events in 1998 at about 0.18% of treated dogs, roughly 2 in 1,000. The letter announced a plain-language owner information sheet for every bottle and warned about accidental overdoses with the new chewables. Today every oral NSAID approved for dogs comes with a Client Information Sheet; if you did not get one, ask for it.

The risk was real, and every NSAID carries it. Merck puts carprofen's reported adverse events at about 2 per 1,000 treated dogs, and not every reaction gets reported. The safeguards that came out of it still protect your dog: an exam and baseline bloodwork, the lowest dose that works, rechecks, no mixing with other NSAIDs or steroids, and stopping at the first warning sign.

The Bottom Line

For a dog limping through every walk, carprofen can be the difference between getting up to greet you and staying on the bed. For a dog with hidden kidney or liver disease, or one on the wrong combination of drugs, it can do real harm. You and your vet make that call together, and you revisit it at each recheck. Your share of the job is to give exactly the dose prescribed, keep the bottle away from pets, watch for the warning signs and keep the follow-up appointments.

Originally written by Dr. Kaylee Ferreira. Updated by the I Love Veterinary editorial team.

Sources

• FDA / DailyMed: Rimadyl Caplets (carprofen) label and Dog Owner Information sheet, Zoetis
• FDA / DailyMed: Rimadyl Chewable Tablets (carprofen) label, Zoetis
• FDA / DailyMed: Rimadyl Sterile Injectable (carprofen) label, Zoetis
• Merck Veterinary Manual: Nonsteroidal Anti-inflammatory Drugs in Animals
• FDA: Get the Facts about Pain Relievers for Pets
• FDA: Controlling Pain and Inflammation in Your Dog with Nonsteroidal Anti-Inflammatory Drugs
• FDA: Freedom of Information Summary, ANADA 200-703, Carprofen Tablets (generic of Rimadyl)
• Pfizer Animal Health: Letter to veterinarians on Rimadyl, March 9, 2000 (FDA CVM document, archived)
• DailyMed: Carprofen products listed in the US
• VCA Animal Hospitals: Carprofen
• ASPCA Animal Poison Control Center
• Pet Poison Helpline

This article is for general information and is not a substitute for advice from your veterinarian.