Persimmon-induced excessive anticoagulation in a patient with mechanical heart valves receiving warfarin therapy: A...

Warfarin is a widely used vitamin K antagonist requiring strict international normalized ratio monitoring due to its narrow therapeutic window. While the interaction between warfarin and vitamin K-rich foods is well known, limited data exist regarding the anticoagulant effects of persimmons, a fruit rich in various bioactive compounds.

A 51-year-old woman with a history of double mechanical valve replacement presented for routine follow-up. She reported no symptoms or changes in medication but had consumed unripe persimmons ("Dangam") daily for 2 weeks prior to a sudden elevation in coagulation parameters.

Routine laboratory testing revealed elevated prothrombin time and activated partial thromboplastin time without any signs of bleeding or other clinical abnormalities. The timing of the abnormal results suggested a possible food-drug interaction.

The patient was advised to discontinue persimmon intake immediately. Warfarin dosage was reduced from 4.25 to 3.5 mg without administering vitamin K supplementation. Coagulation parameters were monitored during this adjustment period.

Within 2 weeks, prothrombin time and activated partial thromboplastin time values returned to baseline. The patient remained stable on a slightly adjusted warfarin dose (3.25-3.9 mg), with no further abnormalities over the subsequent 3 years of follow-up. Over 9.5 years, she completed 63 visits with consistent international normalized ratio control.

This case highlights a potential food-drug interaction between persimmons and warfarin leading to excessive anticoagulation. The mechanism may involve more than vitamin K content alone, warranting further investigation. Physicians should consider dietary habits, including local or seasonal foods, in warfarin-treated patients presenting with unexpected coagulation changes.