pharmacokinetics of tiaprofenic acid in normal rabbits and rabbits subjected to joint immobilisation in a previous study tiaprofenic acid ta was administered daily over a 30day period at 5 and 10 mgkg of body weight subcutaneously sc to animals with arthritis induced by immobilisation the 10 mgkg dose exacerbated the loss of proteoglycan from joint cartilage but the 5 mgkg dose showed protective effects on articular cartilage these results led us to investigate the concentration of ta achieved in synovial fluid of both the immobilised and nonimmobilised rabbit joints after single sc doses of 5 or 10 mgkg the halflives of elimination of ta from the synovial fluids of the immobilised joints were 127 and 107 h after the 5 and 10 mg doses respectively and 066 and 039 h in the nonimmobilised contralateral joints clearances from synovial fluid to plasma were found to be 041 and 055 mlhkg from the immobilised joints after the 5 and 10 mg doses respectively and 011 and 025 mlhkg from the nonimmobilised contralateral joints the peak concentration of ta achieved in synovial fluid of immobilised knee joints after a single sc injection of 10 mgkg was approximately two times greater than the concentrations achieved after administration of 5 mgkg by the same route and two to six times greater than the levels achieved after oral administration of ta at 600 mgday in humans