Improvement in delirium and visuospatial function after rivastigmine in antimuscarinic toxicity: a case report

Treatment of antimuscarinic toxicity has become more difficult in the United States due to an ongoing national shortage of physostigmine. Rivastigmine has emerged as an alternative, off-label therapy due to its similar mechanism of action as a reversible, centrally-acting acetylcholinesterase inhibitor. We present a case of a diphenhydramine overdose where the patient exhibited classic central antimuscarinic delirium characterized by inattention, floccillation, and deficits in spatial planning manifested by the inability to properly draw a clock. These symptoms rapidly resolved after treatment with oral rivastigmine.