General muscarinic agents toxicity

Blockade of thermoregulatory sweating may result in hyperthermia or atropine fever. This is the most dangerous effect of the antimuscarinic drugs in children and is potentially lethal in infants. Sweating, salivation, and lacrimation are all significantly reduced or stopped. Moderate tachycardia is common, and severe tachycardia or arrhythmias are common with large overdoses. In the elderly, important toxicities include acute angle-closure glaucoma and urinary retention, especially in men with prostatic hyperplasia. Constipation and blurred vision are common adverse effects in all age groups. CNS toxicity includes sedation, amnesia, and delirium or hallucinations; convulsions may also occur. Central muscarinic receptors are probably involved. Other drug groups with antimuscarinic effects, for example, tricyclic antidepressants, may cause hallucinations or delirium in the elderly, who are especially susceptible to antimuscarinic toxicity. At very high doses, intraventricular conduction may be blocked; this action is probably not mediated by muscarinic blockade and is difficult to treat. Dilation of the cutaneous vessels of the arms, head, neck, and trunk also occurs at these doses; the resulting “atropine flush” may be diagnostic of overdose with these drugs.