Prescribing in older people

Abstract

About a fifth of the population in the United Kingdom is 60 years or older, 1 yet people in this age group receive 59% of dispensed prescriptions and account for more than half of NHS drug costs.2 Older people often have several coexisting medical problems and take multiple drugs. Increasing age is associated with changes in pharmacokinetics and pharmacodynamics, so prescribing in this age group can be problematic. 3Many randomised controlled trials involving older patients focus on managing a single disease state, such as hypertension or osteoporosis, but people in this age group often have many interacting conditions and are taking many drugs, so guidance on their treatment often has to be based on consensus and involves extrapolating data derived from healthier patients. This review highlights some of the difficulties in prescribing in older patients and offers guidance for appropriate prescribing. Sources and selection criteriaWe searched the National Library for Health, PubMed, and Embase databases using the keywords "elderly" and "prescribing", including synonyms by the MeSH or major descriptor headings. Our search was limited to studies undertaken in humans that were published in English during the past five years. We displayed abstracts of interest using Abstract Plus before obtaining the full text of articles of interest. In addition, we searched the Cochrane Library and our own personal archives of references What physiological changes occur with ageing? Pharmacokinetic and pharmacodynamic changes With age the body undergoes several changes that can affect the distribution, metabolism, and excretion of drugs. These changes included a reduction in renal clearance, liver size, and lean body mass. 4 Hepatic enzyme activity and serum albumin may also be reduced in the presence of chronic disease. The most clinically important of these changes is the reduction in renal clearance, which results in reduced excretion of water soluble drugs. This is especially important for drugs with a narrow therapeutic window (ratio of desired effect to toxic effect), such as digoxin, lithium, and gentamicin.As well as changes in pharmacokinetics, older people are also more sensitive to the effects of some drugs, especially those that act on the central nervous system, such as benzodiazepines, which are associated with an increase in postural sway and risk of falls. Multiple pathology and polypharmacyPolypharmacy is common in older people-around 20% of people over 70 take five or more drugs. 5 In the past decade, the average number of items prescribed to people aged 60 and over has almost doubled from 21.2 to 40.8 items for each person each year. 6 Previously, polypharmacy implied inappropriate prescribing, but this is not necessarily true, because all of the prescribed drugs may have an appropriate indication.