Plasma steroid levels after intra-articular injection of prednisolone acetate in patients with rheumatoid arthritis.

Eight patients with rheumatoid arthritis received an intra-articular injection of either 50 mg or 100 mg of prednisolone acetate into the knee joint. After the injection plasma levels of prednisolone were measured by radioimmunoassay and plasma cortisol levels were estimated fluorimetrically. Peak prednisolone levels were reached at between 2 and 4 hours after the intra-articular injection at both dosage levels, though the peak was higher with the larger dose. The 50 mg dose did not have any effect on the plasma cortisol level at 24 or 48 hours, but there was some suppression of plasma cortisol levels for up to 48 hours after the 100 mg dose.