Pharmacokinetic adaptations can alter absorption when food or drug interactions are present.

• A. True
• B. False
• C. They only alter distribution
• D. They only alter metabolism

Answer: (A)

The key idea is that absorption, the initial step of pharmacokinetics, can be changed by both what you eat and by other drugs taken together. Food can modify how a drug dissolves and leaves the stomach, changing how much actually gets into the bloodstream. For example, meals can alter gastric pH, delay or speed up gastric emptying, and affect the solubility of certain drugs; some medicines form complexes with minerals in food that reduce absorption, while others dissolve better in the fed state due to increased bile and solubilization.

Drug interactions in the gut can also hinder or enhance absorption. Transport proteins in the intestinal lining, like P-glycoprotein, can pump drugs back into the gut lumen, lowering absorption, while inhibitors or inducers of these transporters or of intestinal enzymes can increase or decrease the amount absorbed.

Because all of these factors can influence how much drug actually reaches systemic circulation, absorption can indeed be altered by food and by drug interactions.