Analgesic efficacy of an oral transmucosal spray formulation of meloxicam alone or in combination with tramadol in cats with naturally occurring osteoarthritis

Objective To evaluate the analgesic efficacy of meloxicam oral transmucosal spray (OTMS) alone and with tramadol in cats with osteoarthritis (OA). Study design Randomized, blinded study. Animals Fifteen geriatric cats weighing 4.5 +/- 1.0 kg. Methods Healthy cats with OA were randomly administered a placebo (every 12 hours orally) and meloxicam OTMS (approximately 0.05 mg kg(-1) every 24 hours) (group M, n = 7), or tramadol (3 mg kg(-1) every 12 hours orally) and meloxicam OTMS (group TM, n = 8) for 25 days. Evaluations performed before treatment (D0) and at week 3 (W3) consisted of peak vertical force, motor activity and response to mechanical temporal summation of pain (RMTS). Data were analyzed with mixed models and Fisher's exact test. Results Mean +/- standard deviation peak vertical force (percentage of body weight) increased significantly in both groups (p = 0.02), from 47.7 +/- 6.5% to 60.5 +/- 9.4% in group M, and from 51.8 +/- 5.0% to 64.1 +/- 6.5% in group TM, with no difference between groups. Motor activity increased in M (from 43 +/- 12 to 56 +/- 13; p = 0.02), but not in TM. The number of stimulations from RMTS increased in TM only. Cut-off values were reached in a larger number of cats (n = 5) in TM than M (n = 1) (p < 0.05). Gastrointestinal adverse effects were self-limiting in six cats, including five in TM. Conclusions and clinical relevance Meloxicam OTMS had similar effects on peak vertical force, motor activity and pain sensitization as previously reported for oral meloxicam in OA cats. The tramadol-meloxicam combination provided no evident benefit over meloxicam alone, except for central hypersensitivity (assessed with RMTS). Further assessment of the potential toxicity of the combination is required prior to clinical use. Gingival administration was well accepted overall.