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Pharmacodynamics: changes in homeostatic mechanisms, receptor and target organ sensitivity in the elderly.

Response to drugs in the elderly may be accentuated or modified by age related changes in homeostatic mechanisms such as postural control, orthostatic circulatory responses, thermoregulation, visceral muscle function and higher cognitive function. Changes in specific receptor and target organ responses have also been described. beta-Adrenoceptor-mediated effects are apparently attenuated by a reduction in high affinity binding sites and altered post receptor mechanisms resembling desensitization. alpha 2-Adrenoceptor and cholinergic effects may also be attenuated though there is no evidence for altered alpha 1-adrenoceptor sensitivity. The effects of age on sensitivity to benzodiazepines, calcium channel blocking agents, angiotensin converting enzyme inhibitors, anticoagulants and cardiac glycosides are also discussed. There is a major requirement for further work in this field.