Gastrointestinal loss of galanthamine hydrobromide in rats in-situ

The disappearance kinetics of the acetylcholinesterase inhibitor galanthamine hydrobromide from the gastrointestinal tract of male Wistar rats, 200-250 g, in-situ has been examined. After 30 min the galanthamine loss was 16% in the stomach (pH 2), 54-85% in the duodenum and the successive small intestinal segments (pH 6.8), 43% in the colon and 76% in the rectum. Compared with the other segments, the disappearance rate was higher in the terminal ileum (0.38 x 10(-2) mg cm-1 min) and in the rectum (1.27 x 10(-2) mg cm-1 min). In the proximal jejunum, terminal ileum and rectum the disappearance rate was linearly dependent on the galanthamine dose (range 0.5-4 mg, 2-16 mg kg-1). The results suggest that when administered orally, rapid galanthamine absorption could be expected all over the gastrointestinal tract due mainly to the passive diffusion mechanism.