الفهرس 
الملخص العربىOnly 14 pages are availabe for public view
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Abstract
Aging is the progressive loss of function accompanied by decreasing fertility and increasing mortality and disability. Theories that try to explain aging lie in one of two categories; evolutionary theories focusing on the way nature selected for the occurrence of aging and mechanistic theories that consider aging as either a programmed or random event.
Aging affects pharmacokinetics in many ways. Absorption is generally well preserved in old age but age-related changes in gastric pll, gastrointestinal motility, regional blood How and subcutaneous fat can affect it. Vd is also liffected by the age-related reduced muscle mass and the relative increase in body fat together with reduced plasma albumin and increased uraeid giycoprotein. As for. drug metabolism, Phase 2 hepatic metabolism is less affected by aging than phase 1. However, in \itro estimation of microsomal en/yme activity revealed more or less normal activity, which is not the condition for in vivo tests. This can be explained by the reduced oxygen delivery to hepatocyte with aging that inhibits oxidative reactions. Renal drug elimination is reduced due to reduced renal blood How together with age-related changes in renal tubular efflux, and influx transporters.
Aging affects also pharmacodynamics by altering receptor sensitivity or post receptor events together with the changes in neurotransmitters and ion channel activity. Homeostasis in the aged is reduced and so they can’t adjust body temperature, blood pressure or electrolyte balance rapidly.
The aforementioned changes are to be kept in consideration when prescribing drugs to elderly patients and the doses and routes of administration should be adjusted accordingly.
Many interventions have been proposed to delay aging including caloric restriction, hormonal replacement therapy, stem cell therapy, gene manipulations, dnu’,s and hormcsis. However, not all of them are believed to be effective in humans. To the best of our knowledge, no single intervention is known to stop or prevent aging in human as yet.