Absorption of Chlormadinone Acetate and Norethindrone from In Situ Rat Gut

The GI absorption of chlormadinone acetate and norethindrone was studied in a rat in situ preparation. The data evaluated with respect to the absorption half-life in the ligated stomach and intestine suggest that chlormadinone acetate is absorbed slightly more rapidly than norethindrone and that both steroids are absorbed to a greater extent in the intestine. The effects of bile duct cannulation, ethanol, and exogenous bile salts were investigated. The presence of bile significantly altered the absorption and metabolism of chlormadinone acetate. Ethanol, which was used as the drug vehicle, did not improve or depress the absorption of either steroid. Tissue accumulation experiments indicated that the jejunum of the intestine and the pyloric and cardiac area of the stomach accumulate the steroids to a greater extent than other GI tissues. Both compounds exhibited biexponential absorption with significant membrane accumulation.