Final answer:
Food in the stomach delays the absorption and decreases the maximum drug level for orally administered drugs due to the secretion of digestive juices stimulated by the food and the competition for absorption resources.
Step-by-step explanation:
The presence of food in the stomach delays absorption and decreases the maximum drug level achieved for orally administered drugs. When food is in the stomach, it stimulates cells in the stomach wall to secrete digestive juices through mechanical and chemical stimuli. This not only affects the digestion process but also affects drug absorption, as the presence of food can compete for absorption or alter the conditions in the gastrointestinal tract that could influence drug dissolution and uptake. While villi and microvilli in the small intestine work to increase absorption rates by expanding the surface area for nutrient uptake, the initial presence of food in the stomach generally results in a delayed and reduced peak concentration of the drug in the bloodstream. Therefore, the correct answer is D. delays; decreases.