Rifampicin, a P-gp inducer, has what effect on the absorption of other substances?

Rifampicin, a P-gp inducer, has what effect on the absorption of other substances?

• A. Increased absorption
• B. Reduced absorption
• C. No effect
• D. Variable effect

Answer: (B)

P-glycoprotein in the intestinal lining acts as an efflux pump, pushing drugs back into the gut lumen as they try to cross into the bloodstream. When rifampicin induces P-gp, it increases both the amount of this transporter and its activity. With more P-gp available, a greater portion of a orally administered substrate is pumped back into the gut, reducing the amount that actually gets absorbed. This lowers the drug’s oral bioavailability and can affect systemic exposure, especially for drugs that are good P-gp substrates. The induction effect develops with continued rifampicin use and may reverse after stopping it. Hence, the absorption of other substances that are P-gp substrates is generally reduced.

P-glycoprotein in the intestinal lining acts as an efflux pump, pushing drugs back into the gut lumen as they try to cross into the bloodstream. When rifampicin induces P-gp, it increases both the amount of this transporter and its activity. With more P-gp available, a greater portion of a orally administered substrate is pumped back into the gut, reducing the amount that actually gets absorbed. This lowers the drug’s oral bioavailability and can affect systemic exposure, especially for drugs that are good P-gp substrates. The induction effect develops with continued rifampicin use and may reverse after stopping it. Hence, the absorption of other substances that are P-gp substrates is generally reduced.