Medication Safety
Issue 14 2024
Anticholinergic burden
Anticholinergic burden: Knowing the score
What is anticholinergic burden?
Acetylcholine (ACh) is a neurotransmitter which regulates several involuntary body functions, including the cardiovascular and respiration systems, involuntary smooth muscle and glandular secretions. Its effects on the brain include a significant role in alertness, memory and learning.
Medicines with anticholinergic effects are used to treat conditions such as overactive bladder, chronic obstructive pulmonary disease and irritable bowel syndrome. However, anticholinergic effects are often an unintended side-effect of medications prescribed for other conditions.
Anticholinergic burden (ACB) is the cumulative effect of taking one or more medications that have anticholinergic properties. In people aged 65 years and over, ACB has been associated with an increased risk of falls, decline in cognitive function and memory, and higher mortality rates. Studies have shown that increases in polypharmacy have also contributed to increasing ACB as a result of prescribing multiple medications with low ACB scores.
Older adults are more sensitive to the anticholinergic effects of medications due to a reduction in ACh receptors and age-related physiological changes eg. reduced renal and hepatic function and increased blood brain barrier permeability.
Anticholinergic Rating scales- Interpreting ACB scores
Many scales have been developed to measure anticholinergic burden, however there is variance across tools in how the burden of anticholinergic activity was assigned. Hence, scoring of anticholinergic properties of the same medicines
across different tools can be different. No one scale is the gold standard.
A combined ACB score of 3 or greater using the ACB calculator has been demonstrated to increase risk of confusion and falls. These increased risks have been suggested as the mechanisms responsible for the reported association between greater/raised ACB score and increased mortality.
For a comparison of anticholinergic effects of medicines taken from the ACB calculator, please see the table overleaf. This list is not exhaustive.
Recommendations to minimise anticholinergic burden
• Avoid prescribing anticholinergic medicines in old and frail patients whenever possible.
• Medication reviews are recommended to identify and decrease ACB score. Consider switching to lower risk alternative medications for ACB scores of 3 or greater. Gradual discontinuation of anticholinergic medications may be required to avoid withdrawal effects such as nausea, sweating, agitation, confusion and urinary urgency.
• Avoid medications with an ACB score of 3 whenever possible.
• Be aware of the cumulative effects of medications with a lower ACB score.
• Avoid prescribing anticholinergic medicines with cholinesterase inhibitors (donepezil, galantamine and rivastigmine).
Useful resources
• NMIC Bulletin Vol.30 No. 3 Use of medicines with anticholinergic activity
• ACB Calculator
• Medichec (AEC Scale)
• Choice and Medication Patient Information Leaflet.
Comparison of anticholinergic effects of medicines taken from the ACB calculator (List is not exhaustive)
Therapeutic
Antidepressants Duloxetine, Trazadone
Venlafaxine, Sertraline, Citalopram, Mirtazapine
Antipyschotics Paliperidone Aripiprazole, Risperidone
Antiemetics Domperidone, Ondansetron
Urinary antispasmodics Mirabegron
Antihistamines
Gastric acid suppressants Famotidine, Esomeprazole
Prochloperazine
Cetirizine, Loratadine
Omeprazole, Pantoprazole
Amitriptyline, Clomipramine, Nortripyline, Paroxetine, Dosulepin
Quetiapine, Olanzapine, Clozapine, Chloropromazine
Cyclizine
Oxybutynin, Tolterodine, Solifenacin
Chlorphenamine, Promethazine
Written by Margaret Brooks, Ita Fitzgerald and Elaine Lee,
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