Pharmacokinetics of rimexolone after intra-articular administration

The pharmacokinetics of rimexolone were investigated after intra-articular injection into the knee joints of patients with rheumatoid arthritis. After a single dose of 40 mg rimexolone the drug could be detected in plasma over 3 months. The suspension dissolves in the synovia very slowly and provides a sustained release of the steroid in the joint. Pharmacokinetic analysis was performed on the assumption that the disposition of rimexolone after intra-articular administration is absorption limited ("flip-flop-case"). Dose linearity was studied in a range from 40 to 200 mg. Total body clearance averaged 106 L/h and was independent of dose. The mean residence time of rimexolone in the knee joint is very long and averaged 25 days. It could be shown that the mean residence time of different glucocorticoids correlates well with the duration of their clinical effectiveness.