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Physostigmine and Anticholinergic Toxidrome - #PHARMFAX

Updated: Jul 31, 2023

Physostigmine is a reversal agent for anticholinergic toxicities.


Physostigmine is a reversal agent for anticholinergic toxicities. By inhibiting acetylcholinesterase, increased acetylcholine becomes available at the synapses. As a tertiary amine, it readily crosses the blood brain barrier to reverse the effects of antimuscurinic poisonings.

Severe ingestions present with agitation and delirium. Benzodiazepines are often used first-line for undifferentiated agitation, but it does not address the source of the symptoms. Theres also the risk of oversedation with excessive doses.

Physostigmine has been associated with a quicker time to control of anticholinergic-induced delirium in comparison to benzodiazepines.

It is dosed at 0.5 to 2 mg and may be repeated every 10 to 30 minutes as needed. Physostigmine has a short half life with a duration of an hour. Severe ingestions will require repeat doses or continuous infusion. Administer no faster than 1 mg/min to minimize risks of bradycardia, respiratory distress, and seizures.

Future availability is questionable given the manufacturer shut down recently. Thats unfortunate because physostigmine is an awesome drug to see effectively treat anticholinergic-induced delirium.

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