Anticholinergics: theoretical and clinical overview

ABSTRACT

Introduction: Anticholinergics are a class of medicines that block the neurotransmitter, acetylcholine, in the brain and peripheral tissues. Medicines with anticholinergic activity are widely prescribed for and used by older people for various medical conditions. One-third to one-half of the medicines commonly prescribed for older people have anticholinergic activity. Several studies have reported anticholinergic burden to be a predictor of cognitive and functional impairments in older people.

Areas covered: This article exemplifies the theoretical and clinical aspects of medicines with anticholinergic activity, including pharmacology (definition of medicines that possess anticholinergic activity, antimuscarinic receptors, therapeutic and adverse effects), epidemiology, measures and effects of cumulative anticholinergic burden in older adults, and clinical recommendations. In addition, the gaps in the literature have been identified for future research.

Expert opinion: Many medicines that are commonly prescribed to older people have a degree of anticholinergic activity that can contribute to anticholinergic burden. Anticholinergic burden, measured in several ways that consider number, dose and/or degree of anticholinergic activity of medicines, has shown to be a predictor of adverse health and functional outcomes. The anticholinergic burden on older people should be minimised by avoiding, reducing dose and deprescribing medicines with anticholinergic activity where clinically possible.

KEYWORDS:

• Anticholinergic
• anticholinergic medicine
• antimuscarinic
• anticholinergic burden
• anticholinergic adverse effect
• acetylcholine
• older people
• muscarinic receptor
• anticholinergic risk scale
• anticholinergic mechanism
• anticholinergic overview
• anticholinergic activity

Article highlights

• Anticholinergic medicines work by antagonizing the effect of the neurotransmitter acetylcholine in the central nervous system and peripheral tissues, mainly by inhibiting the muscarinic receptors through competitive binding and results in reduced cholinergic neurotransmission.

• Medicines with anticholinergic activity can increase the risk of adverse effects (e.g. impaired physical activity, cognitive dysfunction) particularly in older people.

• Anticholinergic burden refers to the cumulative effect of taking one or more medicines with anticholinergic activity, and epidemiological studies have reported that 20–50% of older people are routinely exposed to medicines that possess anticholinergic activity.

• Numerous anticholinergic risk scales have been developed to quantify anticholinergic burden. These risk scales are designed to provide clinicians a practical tool to quantify anticholinergic-type adverse events in older people.

• Several gaps exist in the current literature on quantification of anticholinergic burden and associations with adverse outcomes.

• It is postulated that minimizing anticholinergic burden may result in improved short-term memory, confusion, behavior, and delirium together with an enhanced quality of life and daily functioning of older people.

This box summarizes key points contained in the article.

Declaration of interest

Mohammed Salahudeen is funded by a Doctoral Scholarship from the University of Otago, Dunedin, New Zealand. No sources of funding were specifically used to assist in the preparation of this article. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

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