Update (June 11, 2026): Pooled Analysis Finds Robenacoxib Safety Comparable to Placebo in Cats with CKD

TL;DR

A pooled analysis of four randomized trials found robenacoxib was not associated with an increased risk of adverse events versus placebo in cats with chronic musculoskeletal disease, including a chronic-kidney-disease subgroup, though follow-up was short and severely affected cats were excluded.

What just dropped

This evidence update revisits King and colleagues, "Clinical safety of robenacoxib in cats with chronic musculoskeletal disease," in the Journal of Veterinary Internal Medicine (2021;35(5):2384-2394; DOI 10.1111/jvim.16148), an open-access pooled safety analysis that remains the key reference for the NSAID-in-feline-CKD question.

• The analysis pooled safety variables from four prospective, randomized, blinded clinical trials of robenacoxib (n equals 222) versus placebo (n equals 227); per the study, the drug was given orally once daily for 4 to 12 weeks.
• The number of cats with at least one adverse event was not significantly different (P equals .15): 47.8 percent with robenacoxib versus 41.0 percent with placebo; relative risk 1.15 (95 percent confidence interval 0.93 to 1.43).
• Serum creatinine was modestly higher during robenacoxib administration (plus 4.36 micromol/L, 95 percent confidence interval 0.21 to 8.50), but no related adverse clinical effects were detected.
• In the subgroup of 126 cats with evidence of chronic kidney disease, the relative risk of at least one adverse event (robenacoxib versus placebo) was 1.09 (95 percent confidence interval 0.78 to 1.52, P equals .61).

Context

Concern about renal injury has long limited NSAID use in cats, particularly those with chronic kidney disease, even though osteoarthritis and CKD frequently coexist in older cats and create a genuine analgesic dilemma. Robenacoxib is a highly COX-2 selective NSAID, and the question is whether that selectivity translates into an acceptable safety margin in this population. An independent clinician-grade summary of the same pooled analysis (EveryCat Health Foundation) reports the matching figures - 47.7 percent versus 41.0 percent of cats with at least one adverse event (P equals .15), relative risk 1.15, number needed to harm 14.8 - and notes no significant haematologic, urinary, or biochemical differences between groups, with emesis, anorexia, diarrhoea, and lethargy the most common events.

Both the primary analysis and the independent summary stress the same limitations: relatively short follow-up compared with the expected duration of osteoarthritis therapy, and exclusion of cats with severe or uncontrolled concurrent disease.

What this changes in the Robenacoxib (Onsior) evergreen

The robenacoxib pain page (https://www.thevoyage.ai/forvets/knowledge/robenacoxib-cats-dogs-pain) covers COX-2 selectivity and clinical efficacy. This update sharpens the safety section for the CKD-comorbid cat: in a pooled analysis of four RCTs, robenacoxib did not significantly raise the rate of adverse events versus placebo overall (RR 1.15) or in the 126-cat CKD subgroup (RR 1.09, 95 percent confidence interval 0.78 to 1.52). A small rise in serum creatinine occurred without related clinical effects. The practical caveats remain that follow-up was short and that cats with severe concurrent disease were excluded, so the data support cautious, monitored use rather than blanket reassurance. Dosing should follow the current product label.

References

1. King JN, Seewald W, Forster S, Friton G, Adrian DE, Lascelles BDX. Clinical safety of robenacoxib in cats with chronic musculoskeletal disease. Journal of Veterinary Internal Medicine. 2021;35(5):2384-2394. https://academic.oup.com/jvim/article/35/5/2384/8448563
2. EveryCat Health Foundation. Clinical safety of robenacoxib in cats with chronic musculoskeletal disease (summary of King et al. 2021). https://everycat.org/cat-health/clinical-safety-of-robenacoxib-in-cats-with-chronic-musculoskeletal-disease/

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Changelog

• 2026-06-11: First published.

Related reads

• Robenacoxib (Onsior) for Pain in Cats and Dogs: COX-2 Selectivity and Clinical Evidence
• Telmisartan (Semintra) for Proteinuria and Hypertension in Cats with CKD