Drug-Induced Delirium from a Suspected Drug-Drug Interaction between Promethazine and Ketorolac

Case: An 18 year old female with no psychiatric history experiences delirium following the administration of promethazine and ketorolac which resolves following the discontinuation of both medications. The pathophysiology of druginduced delirium has not been well established and is thought to be multifactorial. Delirium has been independently associated with both promethazine and ketorolac through different mechanisms. The objective of this case report is to describe a suspected synergistic drug-drug interaction between promethazine and ketorolac presenting as drug-induced delirium. Conclusion: There appears to be a synergistic drug-drug interaction between promethazine and ketorolac presenting as acute drug-induced delirium. Clinicians should consider withdrawing both medications should psychiatric adverse effects appear or are exacerbated when promethazine and ketorolac are used concomitantly.