Which statement describes a pharmacokinetic interaction affecting gastric emptying?

• A. Drugs altering the rate of gastric emptying, modulating the rate of absorption of another drug.
• B. A drug inhibits hepatic enzymes.
• C. A drug alters the pH of the stomach.
• D. A drug displaces another from plasma proteins.

Answer: (A)

The concept here is that pharmacokinetic interactions can change how fast a drug is absorbed by altering gastric emptying. If one drug speeds up or slows the stomach’s emptying, the other drug reaches the small-intestine absorption sites sooner or later, changing the rate of absorption and the time to peak concentration. This is why the statement describing a drug that changes gastric emptying and thereby modulates how quickly another drug is absorbed is the best fit.

For example, a prokinetic medicine can speed gastric emptying, making another drug absorbed more quickly, whereas an agent that slows gastric emptying delays absorption. In contrast, inhibiting hepatic enzymes affects metabolism, changing clearance but not gastric emptying. Altering stomach pH changes dissolution and absorption in different ways but not the gastric emptying rate itself. Displacing a drug from plasma proteins changes distribution, not the rate at which it leaves the stomach.