title: Rectal and oral absorption of methylprednisolone acetate.
abstract: Rectal absorption of methylprednisolone acetate and oral absorption of methylprednisolone and methylprednisolone acetate were investigated in a single-dose 3-way crossover study of 12 normal male volunteers. The median value of bioavailability (relative to oral dose) of methylprednisolone acetate based on unchanged methylprednisolone plasma levels was 14.2% after rectal administration, suggesting that the drug exerts its therapeutic effect topically rather than systemically. In contrast, the median of total radioactivity in urine (as a percentage of rectal dose) was 34.3% (range, 4.52% to 58.8%), suggesting partial bacterial metabolism in the rectum prior to absorption. Mean bioavailability (relative to oral administration of methylprednisolone acetate) of methylprednisolone after oral administration was 89.9%, indicating somewhat better systemic availability of the ester than the alcohol. The average apparent elimination rate constant for methylprednisolone after oral administration of both ester and alcohol was 0.290 hr-1, corresponding to a half-life of 2.39 hr.
mesh_terms: D000042:Absorption; D000284:Administration, Oral; D000328:Adult; D001682:Biological Availability; D002851:Chromatography, High Pressure Liquid; D004733:Enema; D005243:Feces / Q000032:analysis; D006801:Humans; D008297:Male; D008775:Methylprednisolone / Q000008:administration & dosage / Q000378:metabolism*; D011239:Prednisolone / Q000097:blood / Q000652:urine
chemical_list: D011239:Prednisolone; D008775:Methylprednisolone