Anticholinergics have long been linked to impaired cognition and falls risk, but (more recently) have also been linked to increased morbidity and mortality. Anticholinergics may also be a cause of constipation and urinary retention. The table below shows that anticholinergic effects are dose dependent (adapted from reference26). Of note is, however, that there is significant inter-individual variability regarding anticholinergic dose and manifestations of signs and symptoms of toxicity.
Table 4a: Anticholinergic effects
Atropine dose equivalent
Red, hot, dry
+++Mydriasis +++Blurred vision
+++ Tachycardia Fast and weak pulse
Ataxia Agitation Delirium Hallucinations Delusions Coma
Decreased gut motility
Hot and dry
Restlessness Fatigue Headache
++ Mouth dryness
+Mydriasis Blurred vision
+ Tachycardia Palpitations
+ Mouth dryness Thirst
Drugs with anticholinergic properties continue to be commonly prescribed to older people and those with mental illness, who are particularly susceptible to adverse effects, even at therapeutic doses. A recent study in NHS Tayside26 found that use of anticholinergics among older patients had increased to 24% in 2010, with 7% being classified as carrying a high anticholinergic drug burden.
How to assess and reduce the anticholinergic burden
Not all drugs with anticholinergic properties may individually put patients at risk of severe adverse effects. However, a wide range of commonly used drugs have anticholinergic properties and their effects may accumulate. A scale or table that lists the anticholinergic activity of commonly prescribed drugs can guide clinical decision-making to limit anticholinergic load. One such tool is the Anticholinergic Risk Scale (ARS), which was developed using 500 most prescribed medications.27 They ranked medication with anticholinergic potential on a scale of 0–3 (0. limited or none; 1. moderate; 2. strong; 3. very strong potential) based on information available on the dissociation constant for the muscarinic receptor and rates of anticholinergic adverse effects, i.e. based on in vitro data which may not always reflect in vivo effects.28 The scale may not always reflect in vivo actions however. The ARS has since been modified (subsequently referred to as mARS) to include newer medications with anticholinergic properties that are available in the United Kingdom (see table overleaf).28 Medications with moderate to severe anticholinergic effects according to other scales (Anticholinergic Burden Scale29 and Anticholinergic Drug Scale30) were added to the list. Medications identified as having significant anticholinergic properties in the BNF were also included and medications not available in the UK were excluded. The table overleaf also lists therapeutic alternatives with no or minimal anticholinergic effects.