Absorption, Metabolism and Excretion of 6α-Methylprednisolone-3H, 21-acetate Following Oral and Intramuscular Administrations in the Dog

Abstract

The absorption, excretion and metabolism of 6α-methylprednisolone-³H, 21-acetate has been studied in dogs following oral and intramuscular administration of a crystalline suspension of the labeled steroid. In 3 dogs after 48 hr from 25 to 31% of the radioactivity initially present in an oral dose of 9.3 mg of steroid was recovered in urine and 44 to 52% in feces. Fecal excretion also predominated in a second group of 4 dogs which received an intramuscular injection of 18.5 mg of the labeled steroid. In this case, however, absorption and excretion occurred at a much slower rate, and after 45 days from 25 to 34% of the initial radioactivity was recovered in urine and 27 to 52% appeared in feces. The administered 6α-methylprednisolone-³H, 21-acetate was metabolized to a considerable extent in dogs and the urine was found to contain 6 amethyl- 11β, 17a, 20β, 21-tetrahydroxy-l,4-pregnadiene-3-one (the major metabolite), 6αmethyl-11β, 17α, 20α, 21-tetrahydroxy-l,4-pregnadiene-3-one, 6α-methyl-17α, 20β, 21-trihydroxy-l,4-pregnadiene-3,ll-dione and 6α-methylprednisolone in addition to several more polar metabolites which have not been identified. Unchanged 6α-methylprednisolone, 21-acetate and several unidentified nonpolar metabolities were found to be present in the feces. (Endocrinology76: 852, 1965)