Are worries about long-term use of robenacoxib in arthritic cats warranted?

Osteoarthritis (OA) is a common problem in feline patients, especially in those that are senior and geriatric. Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used in many other species for relief from OA because of their analgesic and anti-inflammatory effects. Currently in the United States there are no NSAIDs approved for long-term use in cats. Long-term use of meloxicam is approved in Europe but is strongly discouraged in the U.S. because of concerns about renal damage. Robenacoxib (Onsior-Elanco) is currently approved in the U.S. for use of up to three days' duration for postoperative pain. It is reported to have good safety in cats, but there are currently no studies looking at safe usage in cats with OA, until now.

What they did

The authors recruited 194 cats from 26 different veterinary hospitals across the country that had a confirmed radiographic diagnosis of OA and a history of impaired activity for at least 12 weeks. Cats with existing endocrine, cardiac or chronic kidney disease (CKD) were not excluded from the study. On day one of the study a physical examination, complete blood count, serum chemistry profile, urinalysis and thyroid screen were performed. The cats were then randomly assigned to either a control group that received a placebo or a treatment group. The treatment group was administered 6-mg robenacoxib tablets at a minimum dose of 1 mg/kg every 24 hours with a dosage range for participants of 1 to 2.4 mg/kg every 24 hours. After 28 days, the blood screening was repeated. Repeat physical examinations were performed on days 14 and 28. A follow-up phone call was made on day 42 for an update on how the cats were doing post-study.

What they found

At the end of the study, no clinically relevant safety-related differences were found between the placebo and treatment groups. Twenty-one clinically serious adverse events were reported between the two groups. A clinically serious adverse event was defined as one that required medical intervention. However, the adverse events were relatively evenly divided between the groups (13 reports from 10 cats in the placebo group and eight reports from eight cats in the treatment group). No deaths or euthanasia occurred during the study. Even more interestingly, 40 cats were identified as having CKD and randomized, almost evenly, into the placebo (n = 22) and treatment (n= 18) groups. There were no significant differences between the groups for change in blood urea nitrogen and creatinine concentrations during the study. International Renal Interest Society (IRIS) scores for 87.5% of the cats in both groups did not change.

Takeaways

Robenacoxib was well-tolerated when given to cats for one month. No clinically detectable evidence of damage to liver, gastrointestinal tract or kidneys was found. Of particular interest is the lack of changes in the CKD group. The weakness of the study was the relatively small number of participants which may not accurately identify the likelihood of rare but serious adverse events. The authors caution that the study has only a 95% power to detect such side effects and that further study is recommended in a larger group to detect such potential rare adverse events.

King JN, King S, Budsberg SC, et al. Clinical safety of robenacoxib in feline osteoarthritis: results of a randomized, blinded, placebo-controlled clinical trial. J Feline Med Surg 2016;18(8):632-642.

Link to abstract: http://www.ncbi.nlm.nih.gov/pubmed/26058587