Changed pharmacokinetics under the influence of age.

Age significantly affects therapeutics in both general and specific ways. In newborns and in infants various physiological processes are still developing, whereas in elderly there may be decreased efficiency or capacity of physiological processes. Unexpected or 'idiosyncratic' responses to drugs in the very old or in the very young often can be explained by age-related changes in absorption, distribution, metabolism, end-organ responsiveness and excretion. Adolescence is often associated with rapid growth and changing body composition. Special problems with adolescents are poor compliance and drug abuse. Adults show a rather stable pharmacokinetic profile, although the cardiac output diminishes and the peripheral resistance increases about 1% annually. Exposure to enzyme-inducing agents (nicotine, cimetidine) influences the pharmacokinetic parameters of both adolescents and adults.