The absorption pathways of drugs in suppositories: The main absorption pathways of drugs in rectal administration suppositories are:
① The drug enters the liver through the superior rectal vein and the portal vein, undergoes metabolism, and then enters the human circulation through the liver.
② The drug passes through the inferior rectal and anal veins, bypasses the liver through the internal iliac vein, and directly enters the systemic circulation through the inferior vena cava, exerting a systemic effect.
③ The drug is absorbed through the rectal lymphatic system.