Pain relief in relation to tissue piroxicam concentrations in hip osteoarthritis.

Nine male and fourteen female hospital in-patients aged 45-82 years and suffering from advanced osteoarthritis participated in an open pharmacodynamic and pharmacokinetic study. After the clinical examination the patients were given piroxicam 30 mg daily for one to seven days before the elective hip joint operation. Drug effects were assessed by measuring the duration of morning stiffness and scoring pains at night and on motion. Concentrations of piroxicam were measured from serum and tissue (joint capsule, cartilage, cancellous bone) samples taken during the operation. Piroxicam concentrations in tissues were negligible on the first two days; measurable concentrations appeared from the third day on. They correlated to serum piroxicam levels but were much lower. Generally, the appearance of piroxicam in joint tissues coincided with the appearance of the analgesic effect of piroxicam. Skin samples from four patients showed piroxicam concentrations which were negligible or at least definitely lower than respective concentrations in serum. It is concluded that in patients with osteoarthritis the piroxicam concentrations in joint tissues are fairly low, and their correlation to the analgesic effect of piroxicam is not convincing.