Geneesmiddelopname: Factoren die de opname in de maagdarmkanaal beïnvloeden

Absorption of an orally administered drug is influenced by various factors.

Weakly acidic drugs are more likely to be absorbed from the stomach, where they are predominantly nonionized.

In comparison, absorption from the upper intestine, which contains ionized drugs, may be low. 

In reality, the stomach's mucous layer makes diffusion difficult. It's smaller surface area compared to the intestine further reduces the rate of absorption from the stomach.

The intestinal villi provide a larger surface area, which coupled with a higher blood flow, leads to higher drug absorption.

If food is in the stomach, drugs may be poorly absorbed as they form complexes with food constituents.

Food also delays gastric emptying, that is, the movement of drugs into the small intestine, which slows down intestinal absorption.

Rapid movement of the gut contents during diarrhea further slows down drug absorption.

Also, the gut epithelium comprised of the P-glycoprotein transporters often pumps the drugs back into the gut lumen. This reduces drug absorption into the blood.