Which of the following is a pharmacokinetic mechanism affecting absorption?

• A. A drug inhibits hepatic enzymes.
• B. A drug alters gastric pH to modify absorption.
• C. Drugs altering the rate of gastric emptying.
• D. Drugs altering the pH of the stomach or intestine, interfering with disintegration, dissolution, and absorption.

Answer: (D)

Absorption hinges on the drug dissolving in GI fluids and then crossing the intestinal lining. The pH of the stomach and intestines strongly affects solubility and ionization, which in turn governs how well a drug disintegrates and dissolves. When a drug alters the pH in these regions, it can directly change the rate and extent of dissolution and thus absorption. This direct link between GI environment, dissolution, and absorption is why changing gastric or intestinal pH to interfere with disintegration and dissolution best describes a pharmacokinetic mechanism affecting absorption.

Inhibiting hepatic enzymes affects metabolism after absorption, not the absorption step itself. Altering gastric emptying changes the timing of when the drug reaches absorption sites, affecting rate and peak time rather than the fundamental dissolution/absorption process.