Intestinal absorption, demethylation, and enterohepatic circulation of imipramine.

The intestinal absorption and metabolism of single oral doses of imipramine (ip) have been studied in man by portal catheterization. The concentration of ip and the formed desipramine (dmi) was followed in blood-plasma obtained from the portal and cubital veins. The absorption of ip seemed to be completed 80 min after the administration of the drug. There was no sign of demethylation of ip during the passage across the intestinal wall. Evidence was found of an enterohepatic circulation of both ip and dmi.