Published: 4 June 2020

Publications

Anticholinergic burden – a cause of adverse reactions for older patients

Prescriber Update 41(2): 35–36
June 2020

Medicines with anticholinergic effects

Anticholinergic medicines (also called antimuscarinic medicines) antagonise the effect of the neurotransmitter acetylcholine on muscarinic (M1–M5) receptors in the central and peripheral nervous system^1–3.

Medicines with anticholinergic activity are used to treat a wide range of conditions. The anticholinergic effect may be intended (eg, hyoscine for gastrointestinal muscle spasm, oxybutynin, benzatropine, procyclidine) or unintended (eg, tricyclic antidepressants, sedating antihistamines, clozapine, olanzapine, chlorpromazine).

Many commonly used medicines such as warfarin, metoprolol, furosemide, venlafaxine and loratadine have weak anticholinergic effects, which may be inconsequential when used alone but have an additive effect when used in combination⁴.

Undesirable anticholinergic effects

Peripheral anticholinergic effects include constipation, dry mouth, dry eyes, blurred vision (mydriasis), tachycardia and urinary retention. Central nervous system effects include agitation, confusion, delirium, hallucinations and cognitive impairment³. Consequential effects include problems such as tooth decay, falls or gastrointestinal obstruction.

Problems with anticholinergics in older patients

Older patients are more susceptible to adverse reactions associated with anticholinergic medicines. Effects such as cognitive impairment, dizziness and blurred vision increase the risk of falls in older patients,⁴ and may increase the risk of hospitalisation and limit their ability to perform activities of daily living^3,5,6. Combined use of sedative and anticholinergic medicines further increases the risk of falls and cognitive impairment in the older patients and should be avoided^7,8.

Recent studies suggest a possible association between the use of strong anticholinergic medicines and a risk of dementia^2,9,10. Further investigation is needed to confirm the association¹¹. Nevertheless, these data provide further need for caution in the use of these medicines.

Minimising risk

When prescribing medicines for older patients, it is important to consider the overall ‘anticholinergic burden’ (ie, the combined anticholinergic effect of all the medicines a patient is taking). Where clinically possible, aim to reduce the anticholinergic burden by avoiding, reducing, or deprescribing medicines with anticholinergic activity^1–4.

It may be possible to replace certain medicines with alternatives that do not have anticholinergic properties¹¹. If an anticholinergic medicine is unavoidable, start treatment at a low dose and increase slowly to the lowest effective dose¹².

References

1. Nishtala PS, Salahudeen MS and Hilmer SN. 2016. Anticholinergics: theoretical and clinical overview. Expert Opinion on Drug Safety 15(6): 753–68. DOI: 10.1517/14740338.2016.1165664 (accessed 19 April 2020).
2. Richardson K, Fox C, Maidment I, et al. 2018. Anticholinergic drugs and risk of dementia: case-control study. BMJ 361:k1315. DOI: 10.1136/bmj.k1315 (accessed 20 April 2020).
3. Ruxton K, Woodman RJ and Mangoni AA. 2015. Drugs with anticholinergic effects and cognitive impairment, falls and all-cause mortality in older adults: A systematic review and meta-analysis. British Journal of Clinical Pharmacology 80(2): 209–20. DOI: 10.1111/bcp.12617 (accessed 20 April 2020).
4. Green AR, Reifler LM, Bayliss EA, et al. 2019. Drugs contributing to anticholinergic burden and risk of fall or fall-related injury among older adults with mild cognitive impairment, dementia and multiple chronic conditions: A retrospective cohort study. Drugs Aging 36(3): 289–97. DOI: 10.1007/s40266-018-00630-z (accessed 20 April 2020).
5. Campbell NL, Perkins AJ, Bradt P, et al. 2016. Association of anticholinergic burden with cognitive impairment and health care utilization among a diverse ambulatory older adult population. Pharmacotherapy 36(11): 1123–31. DOI: 10.1002/phar.1843 (accessed 20 April 2020).
6. Fox C, Smith T, Maidment I, et al. 2014. Effect of medications with anti-cholinergic properties on cognitive function, delirium, physical function and mortality: a systematic review. Age and Ageing 43(5): 604–15. DOI: 10.1093/ageing/afu096 (accessed 21 April 2020).
7. BPAC NZ. 2018. Stopping Medicines in Older People: The Flip Side of the Prescribing Equation 30 November 2018. URL: bpac.org.nz/2018/stopping.aspx (accessed 20 April 2020).
8. Jamieson HA, Nishtala PS, Scrase R, et al. 2018. Drug burden and its association with falls among older adults in New Zealand: A national population cross-sectional study. Drugs & Aging 35(1): 73–81. DOI: 10.1007/s40266-017-0511-5 (accessed 21 April 2020).
9. Coupland CAC, Hill T, Dening T, et al. 2019. Anticholinergic drug exposure and the risk of dementia: A nested case-control study. JAMA Internal Medicine 179(8): 1084–93. DOI: 10.1001/jamainternmed.2019.0677 (accessed 21 April 2020).
10. Gray SL, Anderson ML, Dublin S, et al. 2015. Cumulative use of strong anticholinergics and incident dementia: a prospective cohort study. JAMA Internal Medicine 175(3): 401–7. DOI: 10.1001/jamainternmed.2014.7663 (accessed 20 April 2020).
11. Gray SL and Hanlon JT. 2018. Anticholinergic drugs and dementia in older adults. BMJ 361: k1722. DOI: 10.1136/bmj.k1722 (accessed 19 April 2020).
12. Therapeutic Goods Administration. 2013. Anticholinergics and cognitive impairment. Medicines Safety Update 4(3): 94. URL: tga.gov.au/publication-issue/medicines-safety-update-volume-4-number-3-june-2013 (accessed 22 April 2020).