Why are anticholinergic adverse effects problematic?

Anticholinergics have long been recognised as causing symptoms such as dry mouth, constipation and urinary retention. Exposure to anticholinergic medication has more recently been linked to impaired cognition and physical decline. There may also be an association with falls, and increased mortality and cardiovascular events. The table below shows that anticholinergic effects are dose dependent,¹²⁸ but there is significant inter-individual variability regarding anticholinergic dose and manifestations of signs and symptoms of toxicity.

Therefore, it is essential to take a person-centred approach when reviewing medications with anticholinergic side effects, to understand the individual’s perspective and experience as the impact will vary depending on individual sensitivity. At the time of writing this there is currently no commonly accepted measure of cumulative anticholinergic burden.¹²⁹

The table below sets out the potential anticholinergic effects that an individual may experience.¹²⁸ The table shows that anticholinergic effects can be dose dependent noting there can be significant individual variability.¹²⁸ 

Please note that the table may need to be scrolled horizontally or vertically in order to view all information, depending on your device. Turn mobile devices to landscape view.

Anticholinergic effects

Atropine dose equivalent	Digestive tract	Urinary tract	Skin	Eyes	Cardiovascular	CNS
10mg	Decreased gut motility	Urinary retention	Red, hot, dry	+++ Mydriasis  +++ Blurred vision	+++ Tachycardia Fast and weak pulse	Ataxia Agitation Delirium Hallucinations Delusions Coma
5mg	Decreased gut motility	Urinary retention	Hot and dry	++ Mydriasis	++ Tachycardia	Restlessness Fatigue Headache
2mg	++ Mouth dryness	-	-	+ Mydriasis Blurred vision	+  Tachycardia Palpitations	-
1mg	+ Mouth dryness Thirst	-	-	Mydriasis	Tachycardia	-
0.5mg	Mouth dryness	-	Anhidrosis	-	-	-

Key: + indicates increasing degree of symptoms

– indicates no occurrence

Medicines with anticholinergic properties continue to be commonly prescribed to older people and those with mental health conditions, who are particularly susceptible to adverse effects, even at therapeutic doses.

 

Anticholinergic burden principles

• Anticholinergic effect of medications vary greatly between individuals
• Anticholinergic effect of multiple medications are cumulative
• The comparative degree of anticholinergic medications are based partly on clinical evidence and partly on pharmacological theory