At the time this article was first published (2013) Onsior was a fairly new painkiller for pets. The active drug is robenacoxib. Before this drug became available in June 2012, a cat owner had little else to choose from when their cat was in need of drug therapy. You had Metacam, which has proven to be at the least unpredictable and at the worst deadly. Or you had Buprenorphine, a drug 30 times more powerful than morphine and in the opiate family.
THERE ARE MORE PAGES ON PAINKILLERS AFTER THE ARTICLE.
Onsior has a website that tells us more about the drug, which is classified as a NSAID (nonsteroidal anti-inflammatory drugs). It’s similar to Meloxicam and Celebrex used for pain management in people. Their company webpage states:
“Pain delays recovery, impacts negatively on a patient’s well-being, and disturbs the bond with its owner and also the veterinary team.”
Discussion and side-effects
The small, yeast-flavored 6 mg. tablets provide a full 24 hours of pain relief. It’s primary uses are for postoperative pain associated with orthopedic surgery, hysterectomy and castration in cats. Onsior reaches maximum concentration in only 30 minutes via the intestinal tract, and is eliminated from the blood within two to four hours via the biliary route.
Onsior is recommended only for three days. It’s usually given half an hour prior to surgery, then 24 hours later the cat gets a second dose, followed by the final dose 24 hours after the second dose. The drug is sold in a blister-pack holding three pills. The pills are around $3 each. For cats over 13 1/2 pounds, two tablets daily are required.
In a field study, the most commonly reported adverse reactions were surgical site bleeding, infected surgery sites, lethargy, vomiting, and appetite reduction. Onsior should not be used in cats that have a hypersensitivity to robenacoxib or known intolerance to NSAIDs. It also can’t be administered with any other NSAID or with corticosteroids.
The most common side effects are lethargy, vomiting, loss of appetite and increased bleeding time. Clinical studies on cats dosed up to 5 to 10 times the daily dose for 6 weeks to 6 months, reported no deaths and/or encountered clinical side effects resolved upon termination of medication.
Update on side effects as at 2021: The Onsior website says that this drug is safe and efficient for use up to a maximum of three days. The report that the most commonly reported adverse reactions were: surgical site bleeding, infected surgical sites, lethargy and loss of appetite. Other possible side-effects include vomiting, cystitis, haematuria, diarrhoea, hair loss, bruising, excoriation, cardiac arrest, ataxia, weakness. The chart below shows the prevalence of these side effects and a study conducted by the manufacturers of this drug. It is published online on their website.
Lorie Huston DVM – input
Lorie Huston DVM on Ingrid King’s website writes that as a 2011 Onsior had similar problems to Metacam in terms of kidney damage. She says that veterinarians at that time were cautiously optimistic but were fearful of the side effects. At that time Onsior was used more often in Europe than in the US. She also states that there were less side effects for Metacam when used in Europe than in the US. It was unclear as to why. The possibility is that veterinarians in the US use the drug inappropriately compared to that in Europe because they haven’t limited access to the proper educational materials about the drug.
VCA Hospitals – input
A large animal hospital chain, VCA hospitals, say (Rania Gollakner, BS DVM, MPH) that some parents are hypersensitive to robenacoxid and other NSAIDs and if so this drug can have the side effects mentioned above. It should not be used they save for patients who are dehydrated or have renal, heart or liver disease. Should not be administered with any other NSAID or corticosteroid. Pets should be monitored closely when given the drug. The administration of the drug should be stopped immediately if there are any adverse effects.
Chart on prevalence of side effects from Onsior field trial
I read several reviews where Onsior was used to treat arthritis in cats. This confused me, because the drug is marketed for short term use for mild to moderate pain. I don’t know how long-term use would eventually affect a cat. Especially since it takes years for some drug companies to warn the public about negative consequences. NSAIDS are notorious for causing gastrointestinal upset. Hopefully it won’t cause something medical to pop up five or ten years down the road.
Having rescued several injured cats, we’ve used all three drugs for pain management. Although Metacam didn’t cause any side effects, I was on edge after reading up on its negative reviews. Update December 1, 2021: since his article was written by Eliza in 2013 it’s come to my notice that the drug in Metacam, meloxicam, is under an FDA (Food and Drug Administration) warning online. They say in clear terms that repeated use of meloxicam and cats has been linked to acute renal failure and death. It’s been approved for one-time use in cats before surgery to control post-operative pain and inflammation. From my personal experience, I can say that I dislike this painkiller. I gave it to my now deceased male cat who had cancer behind his right eye to relieve pain and I think that it caused kidney damage to my horror. It hastened his death through euthanasia. I still regret approving its use.
Our cat Sealy was on liquid Buprenorphine after his two operations. Since it’s a narcotic, it left him quite drugged. Other than that, he experienced no side effects. He sat in his cage and stared at us, or he ate. It was clear he was on strong medication. Sealy was on the drug for several weeks, and we “weaned” him off of it, being an addictive opiate.
The Onsior was definitely the clear winner, used after spaying. No side effects at all and they drug appeared to do what it claimed it could do-reduce pain. No “zombie cat” from using this drug. It will be the drug of choice, should any of our cats require short term pain medication in the future.
Have any of the readers used Onsior? I’m curious whether it’s been prescribed for long-term use for pain. It would be rather expensive, should a cat need to stay on it for longer than the three-day recommendation.
- Updates by MikeB at Dec 1, 2021
Note: this page was first written in 2013 and upgraded and re-published on Dec 1 2021.