Case report: delirium due to a diltiazem-fentanyl CYP3A4 drug interaction.

INTRODUCTION

Fentanyl and diltiazem are frequently used medications. Diltiazem inhibits cytochrome P450 3A4 isoenzymes. This can suppress fentanyl metabolism.

METHOD: We present a case of delirium after coadministration of fentanyl and diltiazem.

DISCUSSION: Cautious use is warranted while concomitantly administering fentanyl and diltiazem as this can potentiate fentanyl toxicity. Other 3A4 inhibitors include ketoconazole, erythromycin, nefazodone, ritonavir, delavirdine, aprepitant and imatinib. Psychosomatic medicine psychiatrists, pain and palliative care physicians and cardiologists in particular should be aware of this interaction.