DRUG PROBLEMS IN THE GERIATRIC PATIENT

response in man. However there has been little emphasis in the pharmacy literature to specific drug problems and considerations in the elderly. Such information is avail-able but is widely scattered throughout the medical literature. Age and Factors Affecting Drug Action Variables influencing the quantity and duration of drug available at the receptor site include absorption, tissue localization, metabolism, and excretion.1 Age-related biokinetic changes may be postulated, but be-cause of the variety of changes, the final direction and magnitude of changes are difficult to predict.2 ABSORPTION Advancing age is accompanied by some impairment of both active and passive absorption. Decreased phos-phorylation in the intestinal mucosa delays the active absorption of galactose, and the passive absorption of xylose undergoes a 40 percent decrease from the ages of 18 to 40 to 70 to 80. Related changes include altera-tions in gastric emptying times, intestinal motility, in-testinal blood flow, less absorbing cells, and a decrease of basal and maximal hydrochloric acid output which in turn alters the degree of solubility and state of ionization of drugs.3'5 TRANSPORTATION Total systemic perfusion decreases with age.4 Al-though there is no significant age change in blood and plasma volume per unit of body weight, " cardiac output decreases about 1 percent per year from age 19 to 86.T A smaller proportion of the remaining blood flow enters the liver and kidney.'1 TISSUE LOCALIZATION Highly lipid soluble compounds may become highly localized in body fats. This becomes an important deter