Prednisolone pharmacokinetics in patients with rheumatoid arthritis, polymyalgia rheumatica and asthma.

The pharmacokinetic profile of a single 10 mg oral dose of prednisolone was studied in three groups of six patients with rheumatoid arthritis (RA), polymyalgia rheumatica (PMR) and bronchial asthma (BA) who were already receiving steroid therapy. A fourth group of age and sex-matched normal controls was also studied. Kinetic parameters (including elimination half-life, area under the plasma concentration curve, apparent volume of distribution and total body clearance) were similar for all four groups but there was considerable inter-subject variability. The correlations between these kinetic parameters and age, body weight and serum albumin were poor. The results suggest that any differences in the effects of corticosteroids in these inflammatory diseases are unlikely to be due to pharmacokinetic factors. The duration of steroid therapy and the reduction in patient mobility would appear to be more likely explanations for the reduction in bone mass observed in patients with RA.