Meloxicam, an NSAID used to manage osteoarthritis, achieves maximal plasma concentrations 4.5 hours after oral administration, is highly plasma protein bound, and has an elimination half-life of 24 hours in dogs. Previous studies have shown preferential accumulation and persistence of meloxicam in inflamed joints of rats and humans. This study in dogs investigated the concentration of meloxicam in the synovial fluid of inflamed joints versus noninflamed joints 24 hours after dosing. Eight dogs were treated with 0.2 mg/kg of oral meloxicam on day 1 and 0.1 mg/kg on day 2. On day 3, inflammation was experimentally generated using a reversible induced synovitis model of uric acid salt. Four dogs had synovitis induced in the left stifle and 4 dogs had the same procedure in the right stifle. Synovial fluid was collected 8 hours after the sodium urate injection, which corresponded to 24 hours after the last administration of meloxicam. Control samples were collected from the stifles that were not injected with uric acid.Meloxicam concentration (ng/mL) in the inflamed joint was greater than that in the control joint in each individual animal. The mean meloxicam concentration in inflamed joints was 391 ng/mL and 246 ng/mL in control joints.

Results of this study are similar to those found in other species. Acidic NSAIDs combined with the acidic environment of inflammatory sites can result in higher concentrations in inflamed body compartments. NSAIDs are still the mainstay of treating arthritis as part of a multimodal approach to the disease.—Patricia Thomblison, DVM,MS

Preferential accumulation of meloxicam in inflamed synovial joints of dogs. Johnston L, Narbe R. VET REC 170:207, 2012.