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Changes in the effectiveness of drugs in elderly people
Many physiological variables change their performance with age. This results in an altered effectiveness of drugs due to changes in both pharmacokinetic and pharmacodynamic characteristics. A reduction in oxidative metabolism yields higher absorption of drugs known to undergo extensive first-pass metabolism, the increase in fatty tissue a higher volume of distribution particularly relevant for drugs with low lipophilicity, the decrease in excretion calls for lower steady state dosages. On the other hand sensitivity for drug effects increases with age: CNS is more sensitive to sedative drug effects, circulation reacts more sensitive to drug effects lowering blood pressure, loss of feedback mechanisms in metabolism may cause hypoglycemia. Consequently elderly people are endangered by falls. Early symptoms of adverse drug effects include weakness, dementia, somnolence, depression, loss of appetite, and dehydration. Moreover, drugs may aggravate pre-existing comorbidity, such as renal insufficiency by NSAIDs. Therefore the reasons for initiation drug therapy have to be evaluated especially carefully in elderly patients, the less drugs the better, prescription schemes have to be simple and understandable.