Cilostazol-Induced Digoxin Toxicity Presenting as Accelerated Idioventricular Rhythm and Recurrent Syncope
Sameh Madanieh1, Drashti Desai1, Gianne Macedo Goedert1
1UCF College of Medicine, HCA Florida Healthcare GME Consortium, Orlando, Florida, USA.
Background:
Digoxin has a narrow therapeutic index, and toxicity may occur even with apparently normal serum levels, particularly when drug interactions alter its pharmacokinetics or pharmacodynamics.
Case Summary:
A 77-year-old man with atrial fibrillation and heart failure developed accelerated idioventricular rhythm (AIVR) after cilostazol was initiated for peripheral arterial disease. Serum digoxin appeared therapeutic, but the sample was drawn >30 hours postdose, outside the appropriate sampling window. Digoxin was discontinued and AIVR resolved completely.
Discussion:
Cilostazol potentiates digoxin toxicity via P-glycoprotein inhibition (reduced renal clearance) and PDE-3 inhibition (elevated cAMP, enhanced calcium influx). This interaction is frequently overlooked despite cilostazol being commonly coprescribed with digoxin in older patients with peripheral arterial disease and atrial fibrillation.
Take-Home Messages:
AIVR in a digoxin-treated patient should prompt toxicity evaluation regardless of serum levels. The cilostazol-digoxin interaction is under-recognized and warrants proactive monitoring when these agents are coprescribed.
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