Opposite effects of metoclopramide and propantheline on intestinal absorption of imipramine in rats.

Intraperitoneally administered metoclopramide (MCP) markedly increased the serum concentration of imipramine (IPM) soon after oral administration. In contrast, intraperitoneally administered propantheline (PPT) slightly decreased the serum concentration. The administration of these two drugs had no significant effect on the serum concentration of IPM after intravenous bolus administration. It was concluded from pharmacokinetic analyses and gastric emptying experiments that the administration of MCP markedly increased the rate of IPM absorption by counteracting the gastric emptying delayed by IPM, but that the administration of PPT slightly decreased the rate of IPM absorption by strengthening the gastric emptying also delayed by IPM.