TableĀ 1

Symptoms of anticholinergic syndrome

Red as a beetCompensating for the loss of sweat leads to excessive vasodilation of the skin to maximise heat loss
Dry as a boneMuscarinic action causes sweat glands to activate, therefore, anticholinergics cause anhidrosis (absence of sweat)
Hot as a hareThe removal of the normal thermal haemostasis mechanisms often results in high fever
Blind as a batPupillary constriction and accommodation rely on muscarinic receptors, therefore, anticholinergics cause pupillary dilation and blurry vision
Mad as a hatterThe loss of central nervous system muscarinic receptor action can lead to a range of symptoms from anxiety, delirium, visual hallucinations through to seizures and coma
Full as a drumBoth the detrusor muscle and urinary sphincter are under muscarinic control and therefore anticholinergics will lead to a decreased signal to urinate and an increase in urinary retention
Non-mnemonicLoss of muscarinic receptors means there is unopposed sympathetic action on the heart, giving tachycardia. There is also slowing (or complete absence) of bowel sounds