Measurement of plasma prednisolone in man.

1. A modification of the competitive protein binding assay for prednisolone described by English, Chakraborty & Marks (1974) is presented. 2. Addition of pg quantities of [3H]-prednisolone following oral dosage with prednisone or prednisolone. 3. Mean plasma half-life and peak plasma concentrations in patients with respiratory disease seen following prednisolone administration agree well with previous studies in healthy volunteers performed by other workers using competitive protein binding and radioimmunoassay techniques. 4. A considerable inter-patient variation in bioavailability after a standard dose of prednisolone (20 mg) was noted.