Characterization of osteoarthritis in cats and meloxicam efficacy using objective chronic pain evaluation tools

This study aimed to characterize osteoarthritis (OA)-related chronic pain and disability in experimental cats with naturally occurring OA. Peak vertical ground reaction force (PVF), accelerometer-based motor activity (MA) and the von Frey anesthesiometer-induced paw withdrawal threshold were used to define OA and to test the efficacy of meloxicam. A diagnosis of OA was based on radiographic and orthopedic examinations. Cats with OA (n = 39) and classified as non-OA (n = 6) were used to assess the reliability and sensitivity of the parameters to assess OA over 3 weeks while being administered placebo medication. A randomised parallel design study was then used to investigate the effects on OA of daily oral meloxicam treatment for 4 weeks at different dose rates (0.025 mg/kg, n = 10 mg/kg; 0.04 mg/kg, n = 10; 0.05 mg/kg, n = 9), compared to cats administered a placebo (n = 10).The test-retest repeatability for each tool was good (intra-class correlation coefficient ⩾0.6). The PVF and the von Frey anesthesiometer-induced paw withdrawal threshold discriminated OA (P < 0.05). Meloxicam did not add to the PVF improvement observed in placebo-treated cats during the treatment period (adj-P ⩽ 0.01). The 0.025 and the 0.05 mg/kg meloxicam-treated cats experienced a higher night-time (17:00-06:58 h) MA intensity during the treatment period compared to the placebo period (adj-P = 0.04, and 0.02, respectively) and this effect was not observed in the placebo group. The high allodynia rate observed in the 0.04 mg/kg meloxicam-treated group may explain the lower responsiveness to the drug. The von Frey anesthesiometer-induced paw withdrawal threshold demonstrated no responsiveness to meloxicam. The results from this study indicated that daily oral meloxicam administration for 4 weeks provided pain relief according to night-time MA.