Delirium anticholinergic drugs

Most of the anticholinergic drugs which cause delirium have prominently antimuscarinic actions. However, nicotinic receptors are also present in the brain. Mecamylamine, a nicotinic receptor antagonist which penetrates the brain to some extent, has produced delirium (Paykel et al., 1982). Furthermore, general (inhalational) anaesthetics, which by definition decrease arousal, target nicotinic receptors among others (Chapter 9). Conversely, nicotine itself increases arousal and selective attention (Ashton, 1992b). 

The adverse effects of the anticholinergic drugs are due to their antimuscarinic effects in other systems (e.g., cycloplegia, dry mouth, urinary retention, and constipation). Confusion, delirium, and hallucinations may occur at higher doses. 

The incidence of delirium in elderly subjects (over 65 years old) taking lithium does not appear to be higher than in those who are taking valproate (233). Among 5360 subjects with a mood disorder who had taken lithium or valproate in the previous year, the incidence of delirium with valproate was very similar to that of lithium (4.1 versus 2.8 cases/100 person years HR = 1.36 95% Cl = 0.94, 1.97). Both of these rates were significantly lower than the rates observed with the anticholinergic drug benzatropine. 

Rebound psychosis or delirium or both have been reported after withdrawal of clozapine (207-212). Clozapine withdrawal has also been associated with nausea, vomiting, diarrhea, headache, restlessness, agitation, and sweating (213,214), which occur as the result of cholinergic rebound and which may respond to anticholinergic drugs (215), and with dystonias and dyskinesias. Delirium and the return of dyskinetic movements can occur within days after clozapine withdrawal. 

A 39-year-old man who was a recreational user of alcohol and cocaine presented with agitation, hallucinations, and delirium. He had a dry flushed skin, tachycardia, dilated, minimally reactive pupils, urinary retention, and absent bowel sounds. He was treated with intravenous fluids and a sedative. There were cocaine metabolites in the urine. Reanalysis of a urine sample by thin layer chromatography confirmed the presence of the anticholinergic drug atropine. 

Itil, T., Fink, M. (1966). Anticholinergic drug-induced delirium experimental modification, quantitative EEG and behavioral correlations. J. Nerv. Ment. Dis. 143 492-507. 

Heiser JF, Gillin JC. The reversal of anticholinergic drug-induced delirium and coma with physostigmine. Amer /Psychiatry. 1971 127 1050. 

Drugs with anticholinergic effects may cause delirium but also tachycardia, urinary retention, constipation, dry mouth and blurred vision... 

Geriatric Considerations - Summary Alkaloids from the belladonna plant contain 3 potent anticholinergics and offer no advantage over other available drugs. Belladonna alkaloids possess potent anticholinergic effects and can cause dry mouth, blurred vision, delirium, confusion, psychosis, and increased risk of falls. This compound has no role in treating the older adult. 

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