Plasma prednisolone levels after administration of prednisolone-21-phosphate as a retention enema in colitis.

A competitive protein-binding assay was used to measure plasma prednisolone levels after administration of prednisolone-21-phosphate retention enemas to seven patients with colitis. Prednisolone appeared in the plasma of all patients after the enema, and concentrations rose to a peak within three hours. In five of the patients plasma prednisolone levels were also measured after the same dose of prednisolone by mouth. Although in individual patients the plasma levels achieved by enema were often quite different from those achieved by mouth, overall the levels achieved by each mode of administration were of a similar order. These findings suggest that 20 mg prednisolone given by retention enema may well exert a systemic effect.