With the recognition that the aged constitute an increasing proportion of our patient population, attention is being directed toward understanding the epidemiology, pharmacology and toxicology of drug use in the elderly. As a group, elderly patients have more illness and inevitably take more medications than younger patients. Although not unique to geriatric medicine, medication errors and lack of comprehension of treatment plans are prevalent. These factors undoubtedly contribute to the increased incidence of adverse drug reactions in the elderly.
It is possible that age differences in pharmacokinetics may contribute importantly to the apparent increased ‘sensitivity’ of older persons to both the therapeutic and toxic effects of some drugs. For most drugs studied, such pharmacokinetic differences are generally consistent with age differences in body composition, protein binding, renal function and tissue perfusion. Aging is associated with a decrease in lean body mass and total body water, a decrease in serum albumin concentration, a decline in glomerular and tubular function in the kidney, and diminished cardiac output, liver blood flow and cerebral blood flow. Although some evidence suggests that hepatic metabolism of drugs is impaired with aging, it is increasingly clear that apparent effects of age on antipyrine metabolism may be more related to age differences in other factors, such as diet and smoking, than to age per se. For antipyrine, a model compound for the study of hepatic microsomal drug metabolising enzyme activity in man, biological variation seems to be much more important than any single non-genetic variable presently investigated. The few available studies suggest little effect of age on drug absorption, but more information is needed.
In addition to considering the epidemiology of drug use and the altered physiology in the elderly, this review attempts to provide an overview of what is known about the relationship of advanced age and the pharmacokinetics and pharmacodynamics of representative compounds from several groups of drugs. Although the response to isoprenaline (isoproterenol) and propranolol is impaired in the elderly, most studies seem to bear out the long held clinical impression that the elderly are generally more sensitive to drugs than younger individuals.
Finally, several general principles of drug use in a patient of any age are restated as guidelines for geriatric pharmacotherapy. Worthy of special consideration are ways of promoting compliance with prescribed therapy.