These units are the smallest structures still capable of performing the specific physiological activities characteristic of the organ of which they are a part (e.g. The most consistent is the time-related loss of functional units. Although an all-encompassing definition of ageing is not possible, several characteristics are recognized. Ageing is the effect of these underlying changes and not the cause. Ageing is not a single entity but a collective term representing the sum of cumulative local effects at the molecular, cellular and tissue level. Moreover, the interindividual variability in the physiological responses increases with age. This limits the average life expectancy to about 85 years, maximum life span to around 122 years, and lowers the ability to cope with external stresses. This review focuses on the main age-related physiological changes affecting different organ systems and their implications for pharmacokinetics and pharmacodynamics of drugs.Īgeing is the progressive accumulation of more or less random changes. Pharmacokinetic changes include a reduction in renal and hepatic clearance and an increase in volume of distribution of lipid soluble drugs (hence prolongation of elimination half-life) whereas pharmacodynamic changes involve altered (usually increased) sensitivity to several classes of drugs such as anticoagulants, cardiovascular and psychotropic drugs.
Important pharmacokinetic and pharmacodynamic changes occur with advancing age. The reduced homeostatic ability affects different regulatory systems in different subjects, thus explaining at least partly the increased interindividual variability occurring as people get older. Therefore, there may be a failure to maintain homeostasis under conditions of physiological stress. Advancing age is characterized by impairment in the function of the many regulatory processes that provide functional integration between cells and organs.