3.11 : 载体介导运输

Carrier-mediated transport facilitates the movement of lipid-insoluble drugs via membrane-spanning transporters.

As drug concentration increases during transport, absorption rates initially rise but eventually plateau because carrier proteins become saturated.

Carrier-mediated transport has two subtypes: facilitated diffusion and active transport.

Facilitated diffusion involves drug transport along their concentration gradient without using energy.

In contrast, active transport requires ATP to transport drugs against their concentration gradient.

There are two types of transporters. Uptake transporters, like amino acid transporters,  move drugs like methyldopa and gabapentin into the blood, increasing their absorption.

Efflux transporters, such as  P-glycoprotein, remove drugs back to the GI lumen, lowering their absorption.