What is the effect of P-glycoprotein on drug movement in the GI tract?

What is the effect of P-glycoprotein on drug movement in the GI tract?

• A. Pumps the drug into capillaries, increasing absorption
• B. Pumps the drug back into the gut, reducing absorption
• C. Degrades the drug in the lumen
• D. Promotes diffusion into the bloodstream

Answer: (B)

P-glycoprotein is an efflux transporter located on the apical (lumen-facing) surface of intestinal epithelial cells. It uses ATP to pump a wide range of drugs from inside the enterocytes back into the gut lumen, which reduces the amount of drug that reaches the bloodstream after oral dosing. This action lowers oral bioavailability because the drug is actively moved out of the cells and back into the intestinal lumen rather than into the capillaries. It doesn’t degrade the drug in the lumen, nor does it promote diffusion into the bloodstream; its net effect is to limit absorption by ejecting the drug back into the gut.

P-glycoprotein is an efflux transporter located on the apical (lumen-facing) surface of intestinal epithelial cells. It uses ATP to pump a wide range of drugs from inside the enterocytes back into the gut lumen, which reduces the amount of drug that reaches the bloodstream after oral dosing. This action lowers oral bioavailability because the drug is actively moved out of the cells and back into the intestinal lumen rather than into the capillaries. It doesn’t degrade the drug in the lumen, nor does it promote diffusion into the bloodstream; its net effect is to limit absorption by ejecting the drug back into the gut.