Final answer:
Physiologic changes in the gastrointestinal tract of older adults, such as reduced surface area of the small intestine villi, decreased blood flow, and reduced function of enzymes and transporters, can reduce the absorption of drugs.
Step-by-step explanation:
As individuals age, there are several physiologic changes that occur in the gastrointestinal (GI) tract which can reduce the absorption of drugs. These changes include a decrease in the surface area of the small intestine villi, reduced blood flow to the GI tract, and a decrease in the function of enzymes and transporters involved in drug absorption.
Firstly, the villi in the small intestine decrease in size, which reduces the surface area available for absorption. This decrease in surface area limits the contact between drugs and the absorptive epithelial cells, making drug absorption less efficient.
Secondly, blood flow to the GI tract decreases with age. This reduced blood flow can limit the delivery of drugs to the GI tract for absorption.
Lastly, the function of enzymes and transporters involved in drug absorption can decline with age. Enzymes, such as cytochrome P450, and transporters, such as P-glycoprotein, are responsible for the metabolism and efflux of drugs in the GI tract. Reduced function of these enzymes and transporters can lead to decreased drug absorption.