Therapeutic effects of drug-nutrient interactions in the elderly.

The elderly are the major drug users both because they need specific prescription drugs for control of chronic diseases and because they make excessive use of over-the-counter (OTC) drugs. Therapeutic drugs that are required may be discontinued because the individuals suffer side effects or because the drug is ineffective. Adverse drug reactions in the elderly may result from drug overuse or misuse, slowed drug metabolism or elimination secondary to aging or to age-related chronic disease, intake of alcohol, food-drug incompatibilities, or nutrient-drug interactions. The timing of drug intake in relation to food intake is an important determinant of therapeutic efficacy in the elderly. Food-drug interactions in the gastrointestinal tract may reduce drug absorption. Enteral formula feeding may also interfere with drug absorption. Conversely, absorption of certain drugs (e.g., thiazides) may be promoted by meal-induced slowing of gastric emptying time. Therapeutic diet prescription can influence drug responses in the elderly because the protein composition of the diet influences the rate of drug metabolism. Nutrient depletion secondary to the effect of drugs may be recognized as an important and often avoidable type of adverse drug reaction.