Antidote: physostigmine
Physostigmine is a cholinesterase inhibitor that prevents the breakdown of acetylcholine and increases its concentration in the body. It is the only intravenous anticholinesterase available. Physostigmine crosses the blood–brain barrier and its reversal of CNS anticholinergic effects (such as delirium) aids the initial diagnosis, particularly when the history is unclear. Treatment with physostigmine also enables ongoing treatment of delirium with an oral (rather than a parenteral) sedative.
Consult a clinical toxicologist when the toxin is not a pure anticholinergic drug (eg tricyclic antidepressant, antihistamine), because serious adverse effects (eg seizures, arrhythmias) have been reported with physostigmine use in this setting.
Administer physostigmine in a resuscitation area. Avoid physostigmine in patients with bradycardia and bronchospasm.
Use:
physostigmine 0.5 mg (child: 0.01 mg/kg up to 0.5 mg) intravenously, over 5 minutes. Repeat the dose after at least 15 minutes if there is no response or a partial response. Maximum dose is 2 mg (child: 1 mg) within any 60-minute period1. anticholinergic toxidrome - antidote
Additional doses are commonly required after 1 to 2 hours because physostigmine is short-acting.
If physostigmine is not available, use a parenteral sedative to control behavioural disturbance (see Sedation).