Treatment of opioid-induced delirium with acetylcholinesterase inhibitors: a case report.

A 55-year-old woman with advanced ovarian cancer and severe pain developed hypoactive delirium after an increase in her opioid dosage. Myoclonus and delirium improved dramatically with the intravenous injection of the acetylcholinesterase inhibitor physostigmine, and this improvement was maintained during the administration of donepezil, an oral medication with similar pharmacodynamic properties. Evidence for a disorder of cholinergic neurotransmission in opioid-induced delirium is discussed, as is the rationale for treatment with acetylcholinesterase inhibitors and other cholinomimetic agents.