Last update:
08-Jul-2004

Physiological changes associated with aging can have a powerful effect on both the pharmacodynamic and the pharmacokinetic properties of prescribed drugs, including psychiatric drugs. Elderly patients are more sensitive to both the therapeutic and the toxic effects of drug regimens. Regarding the pharmacodynamic changes, there is substantial evidence indicating that the function of various neurotransmitter systems is altered by the aging process. Increase in body fat with a simultaneous decrease in total body water, decrement in liver mass and blood flow, as well as reduction of glomerular filtration, tubular function, and renal blood flow result in significant pharmacokinetic modifications. Chronic diseases, which are common in the elderly, further modify pharmacodynamic and pharmacokinetic effects, increasing the incidence and severity of adverse drug effects. Finally, polypharmacy, which is widespread among the elderly, is a very important problem when treating older people. Pharmacokinetic drug interactions can alter the body concentrations of one or more of them. There may also be drug interactions on a pharmacodynamic level. Prescribing drugs to elderly patients, who may be suffering from multiple diseases and taking other drugs, is often unavoidable. Physicians therefore, must employ specific principles to limit the potential dangers in such cases.

Key words: Elderly, Pharmacodynamic, Pharmacokinetic, Psychopharmacology.