The small intestine, despite its alkaline environment, is better suited for drug absorption than the stomach because of its larger surface area, longer transit time, and thinner lining. Acidic drugs may remain unionized in the stomach, which typically would favor absorption. However, the stomach's smaller surface area and thicker mucus layer make it harder for drugs to cross into the bloodstream there.
In contrast, the small intestine’s extensive surface area, thin epithelial lining, and rich blood supply enhance absorption, even if acidic drugs become ionized. The video further explains why acidic drugs are better absorbed in the small intestine.
