This case highlights a potential drug interaction between aspirin and residual warfarin leading to elevated INR and hemoptysis.
Potential bleeding risk warrants INR monitoring with aspirin-warfarin coadministration; hypothesis-generating case report leaves open causal confirmation.
An 80-year-old female with a history of hypertension and atrial fibrillation had been receiving warfarin anticoagulant therapy and had stably maintained an international normalized ratio (INR) within the 2.0-3.0 range. Due to dental extractions, she was prescribed aspirin (100 mg/day) as an alternative therapy to warfarin. Three days later, the patient complained of hemoptysis without obvious inducement and the INR was 3.51. The aspirin was immediately discontinued and intravenous vitamin K was administered. Hemoptysis did not reappear and the INR returned to the normal limits. According to the Drug Interaction Probability Scale, a causal relationship between aspirin and warfarin and an increased INR value is possible.
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Song et al. (2015) studied this question.
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