Characteristics and Clinical Implications of the Pharmacokinetic Profile of Ibuprofen in Patients with Knee Osteoarthritis

Background and Objective Ibuprofen is a non-selective cyclo-oxygenase (COX)-1/COX-2 inhibitor used to treat pain conditions and inflammation. Limited data have been published concerning the pharmacokinetic profile and clinical effects of ibuprofen in patients with osteoarthritis (OA). In this paper we compared the pharmacokinetic and clinical profile of ibuprofen (at a dosage of from 800 mg/day to 1800 mg/day) administered in patients affected by severe knee OA. Methods Ibuprofen was administered for 7 days to patients who were scheduled to undergo knee arthroplasty due to OA. After 7 days, the ibuprofen concentration in plasma and synovial fluid was measured through both high-performance liquid chromatography (HPLC)-UV and gas chromatography-mass spectroscopy (GC/MS), while clinical effects were evaluated through both visual analogue scale (VAS) and Western Ontario and McMaster Universities (WOMAC) scores. The Naranjo scale and the WHO causality assessment scale were used for estimating the probability of adverse drug reactions (ADRs). The severity of ADRs was assessed by the modified Hartwig and Siegel scale. Results Ibuprofen showed a dose-dependent diffusion in both plasma and synovial fluid, which was related to the reduction of pain intensity and improvement of health status, without the development of ADRs. Conclusion Ibuprofen at higher dosages can be expected to provide better control of OA symptoms as a result of higher tissue distribution.