The response to drug treatment seen in the elderly is very different to that seen with younger patients. Altered drug response in the elderly is often associated with changes in the body that result in modification to the pharmacokinetics of the drugs in older people. Absorption changes result from Morphological changes to the gastrointestinal mucosa. GI function changes have an effect on enzymatic breakdown, dissolution, and drug ionization which then leads to alterations in oral drug absorption. Intestinal absorption of some drugs is delayed due to reduction rate in gastric emptying. Another example is Elimination changes, which are caused by altered pharmacokinetics in renal function. Diminished renal and hepatic function can have a profound effect on the metabolic clearance and pharmacological effects of many drugs. This depends on the disease state, and drugs used. Reduced glomerular filtration rate, tubular secretion, and blood flow cause decreased elimination by the kidneys which in return increases the half-life of the drug. If dosage is not modified as needed, serious drug-related problems may occur. Distribution changes also occur in the elderly; these include alterations in body composition, cardiac output, lean body mass, and decrease in total body water. These changes could all result in toxic and pharmacologic effects. For example, alterations in protein binding such as less protein in the blood can result in more free drug in plasma. If the drug is protein bound Pharmacological or toxic effects may occur. Last but not least, Metabolism Changes in the elderly allow the drug to accumulate due to decreased clearance. This could lead to toxic levels in the blood. Blood flow/minute decreases 1% per a year from ages 35 to 75. Reduction in blood flow and enzyme activity causes a decline in liver metabolism.
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