Physo’s back: A case report and brief review of the safety of physostigmine in the management of antimuscarinic delirium

Antimuscarinic delirium is a commonly encountered condition. Physostigmine is an effective antidote with a well established safety profile, though use has waned following a supply shortage. Both antihistamines and atypical antipsychotics are frequently implicated in antimuscarinic delirium, and quetiapine in particular may cause prolonged symptoms. We present a case of delirium precipitated by quetiapine refractory to repeated physostigmine administration, highlighting both its safety of use and limitations. As physostigmine supply is renewed, clinicians should again become familiar with its applications, while acknowledging therapeutic limits and the necessity of adjuncts in the delivery of care in severe cases. • Quetiapine in overdose can cause severe and prolonged antimuscarinic delirium. • Physostigmine may need to be frequently re-dosed to effectively treat antimuscarinic delirium. • Even with frequent dosing, physostigmine has an excellent safety profile, and adverse events (clinically significant bradycardia, seizure) are rare.