02 - General principles

General principles

The Maudsley® Prescribing Guidelines in Psychiatry, Fifteenth Edition. David M. Taylor, Thomas R. E. Barnes and Allan H. Young. © 2025 David M. Taylor. Published 2025 by John Wiley & Sons Ltd. General principles in prescribing in older adults General principles The pharmacokinetics and pharmacodynamics of most drugs are altered to an important extent in older people. These changes in drug handling and action must be taken into account if treatment is to be effective and adverse effects minimised. Older people often have a number of concurrent illnesses and may require treatment with several drugs. This leads to a greater chance of problems arising because of drug interactions and a higher rate of drug-­induced problems in general.1 It is reasonable to assume that all drugs are more likely to cause adverse effects in older patients than in younger patients (Box 6.1). How drugs affect the ageing body (altered pharmacodynamics) As we age, control over reflex actions such as blood pressure and temperature regulation is reduced. Receptors may become more sensitive. This results in an increased incidence and severity of adverse effects. For example, drugs that decrease gut motility are more likely to cause constipation (e.g. anticholinergics and opioids) and drugs that affect blood pressure are more likely to cause falls (e.g. tricyclic antidepressants [TCAs] Chapter 6 Prescribing in older people Box 6.1  Reducing drug-­related risk in older people Adherence to the following principles will reduce drug-­related morbidity and mortality: ■ ■Use drugs only when absolutely necessary ■ ■Avoid, if possible, drugs that block α1 adrenoceptors, have anticholinergic adverse effects, are very sedative, have a long half-­life or are potent inhibitors of hepatic metabolising enzymes ■ ■Start with a low dose and increase slowly but do not undertreat. Some drugs still require the full adult dose ■ ■Try not to treat the adverse effects of one drug with another drug. Find a better-­tolerated alternative ■ ■Keep therapy simple; that is, once-daily administration whenever possible