Special considerations for geriatric therapeutic drug monitoring.

Numerous physiological changes during the normal aging process can potentially affect how drugs are handled by the body. Gastrointestinal changes include increased gastric pH, decreased intestinal motility, and decreased blood perfusion. Age-related changes in body composition and protein concentrations in plasma contribute to alterations in the distribution of drugs. Hepatic metabolism of drugs may be affected, and renal excretion via glomerular filtration or tubular secretion is diminished. The importance of each of these physiological changes in the elderly, as well as the contribution of multi-drug therapy and other external factors, is discussed.