Advancing age is characterized by impairment in the function of the many regulatory processes that provide functional integration between cells and organs. Therefore, there may be a failure to maintain homeostasis under conditions of physiolog ical stress. 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. Important pharmacokinetic and pharmacodynamic changes occur with advancing age. 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. This review focuses on the main age-related physiological changes affecting different organ systems and their implications for pharmacokinetics and pharmacodynamics of drugs.

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vitamin D supplementation, in fallers with vitamin D insufficiency, has a significant beneficial effect on functional performance, reaction time and balance, but not muscle strength. This suggests that vitamin D supplementation improves neuromuscular or neuroprotective function, which may in part explain the mechanism whereby vitamin D reduces falls and fractures.

ABSTRACT

There is widespread evidence both of the exclusion of older people from clinical research, and of under-recruitment to clinical trials. This review and opinion piece provides practical advice to assist researchers both to adopt realistic, achievable recruitment rates and to increase the number of older people taking part in research. It analyses 14 consecutive recently published trials, providing the number needed to be screened to recruit one older participant (around 3:1), numbers excluded (up to 49%), drop out rates (5-37%) and whether the planned power was achieved. The value of planning and logistics are outlined, and approaches to optimising recruitment in hospital, primary care and care home settings are discussed, together with the challenges of involving older adults with mental incapacity and those from minority groups in research. The increasingly important task of engaging older members of the public and older patients in research is also discussed. Increasing the participation of older people in research will improve the generalisability of research findings and inform best practice in the clinical management of the growing older population.