The elderly (individuals over 65 years of age) constitute more than 13% of the population. This figure is increasing steadily and is expected to reach 50 million by the year 2020. This segment of our society is the most highly drug-treated and accounts for about 25% of prescription drugs dispensed. The average Medicare patient in an acute-care hospital receives approximately 10 different drugs daily, and this translates into a higher incidence of adverse drug reactions in geriatric patients than in the general population.
Chronological aging may not necessarily be an accurate index of biological aging, which is the result of many genetic and environmental factors. While most 20-year-olds have a similar response to a given drug, it is difficult to predict the response among 80-year-olds. A clear relationship between the appearance of untoward effects to drugs and aging has been demonstrated only for about 10 drugs. For some 90 other drugs in common clinical use, age alone was not a major determinant of clinical toxicity. It is apparent that an increase in life span is accompanied by an increase in chronic illnesses such as hypertension, congestive heart failure, arthritis, and diabetes. The pharmacological management of these conditions, especially when the same person has several diseases, becomes increasingly complex.
Age-related alterations in pharmacokinetics (absorption, distribution, metabolism, and excretion) have received considerable attention. Thus, physiological changes in elderly patients, when taken together, may contribute to impairments in drug clearance in this segment of the population (Table 6.5).
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