chapter  101
Principles of Pharmacokinetics and Pharmacodynamics
Pages 16

Absorption Absorption refers to the transfer of a drug from its site of delivery into the circulation.This commonly occurs by diffusion across plasma membranes with carriermediated transfer or active transport recognized for certain drugs.P-glycoprotein encoded by the multidrug resistance-1 (MDR1) gene is an important drug transporter that acts as an efflux pump and limits drug absorption in enterocytes by causing transport of the drug back into the intestinal lumen subsequent to its absorption by passive diffusion.