Prednisolone levels in the plasma and urine: a study of two preparations in man.

1. A competitive protein binding method was used to measure prednisolone and cortisol in blood and urine of volunteers given prednisolone by mouth (15 mg) in the standard tablet form and a fortnight later a regulated release formulation of prednisolone metasulphobenzoate containing an equivalent amount of prednisolone. 3. Plasma prednisolone levels rose rapidly after the standard tablet and more slowly after the regulated release form. The normal activity of the hypothalamic-pituitary-adrenal axis as measured by the 09.00 h plasma cortisol concentration was present 24 h after ingestion of the regulated release preparation. In contrast, the 09.00 h plasma cortisol level was reduced in subjects 24 h after receiving prednisolone in the standard tablet form.