Plasma prednisolone studies in rheumatic patients.

Prednisolone concentration in plasma after a daily maintenance steroid dose was monitored in 83 patients with rheumatic diseases. Although no restrictions were imposed on the intake of food or drink, plasma drug levels tended to peak at 1 h after the ingestion of the standard tablets, whereas intestinal absorption of the enteric-coated preparation was found to be most unpredictable. A profound individual variation was observed in plasma prednisolone concentrations, and neither total nor unbound drug levels showed any consistent relationship with the size of the prednisolone dose or the control of the disease activity. The basal cortisol production was suppressed in one-third of the patients. There is no support from this study for the concept of an 'optimum therapeutic range' of plasma prednisolone for the treatment of rheumatic disease.