Drug-nutrient interactions in the elderly.

Drug metabolism and efficacy may be affected simply by changing the diet of an elderly patient. For example, an increase in the protein content of the diet can affect the bioavailability of certain drugs and increase the rate of drug metabolism. All elderly patients receiving long-term drug therapies that cause diarrhea, with or without steatorrhea, should be monitored for evidence of hypokalemia, folate deficiency, and deficiencies of vitamins A and D.