ArticleThe journal of Tehran Heart Center2023
A Case of Unexplained Warfarin Resistance: A Case Report and Literature Review.
Article in The journal of Tehran Heart Center, 2023. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 3 papers.
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Who cites it
3 citing papers in PubMed.
- Challenging Anticoagulation With Warfarin and Heparin Following Mechanical Mitral Valve Replacement in a Patient With Infective Endocarditis: A Case Report Highlighting Diagnostic Difficulties.Clinical case reports · 2026Article
- From warfarin resistance to warfarin overdose: an unusual case report.Drug metabolism and personalized therapy · 2026Article
- An Unlikely Culprit of Hospital-Acquired Warfarin Resistance: A Case Report and Review of Literature.International medical case reports journal · 2026Article
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Authors and funding
10 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Adjusting the exact warfarin dose has always been challenging since it has a narrow therapeutic window. Numerous factors, including poor drug compliance, drug-drug interactions, and malabsorption syndromes, affect the warfarin plasma concentration, leading to oversensitivity or resistance to warfarin. Patients who need more than 15 mg/d of warfarin for maintained anticoagulant effects are considered warfarin resistant. We describe a 62-year-old man referred to our center with bruising on his feet in June 2021. The patient had a history of valve replacement (mechanical prosthetic valves in 2013), hypothyroidism, and atrial fibrillation. He presented with warfarin resistance (first noticed in 2013) and did not reach the desired warfarin therapeutic effect despite receiving 60 mg of warfarin daily. Upon admission, the patient was on warfarin (100 mg/d) with an international normalized ratio (INR) of 1.5. He underwent laboratory and molecular genetic tests, which showed no mutation in the CYP2C9 and VKORC1, the genes associated with warfarin resistance. A stepwise diagnosis is required to identify the underlying cause. Assessing the patient's compliance, drug history, dietary habits, malabsorption diseases, and genetics may be necessary. We evaluated these possible reasons for resistance and found no correlation. The patient's warfarin intake was monitored closely to reach the INR therapeutic target of 3-3.5. He decided to leave the hospital with personal consent. He was discharged with a cardiologist referral and 24 warfarin tablets daily (120 mg/d) with an INR of 1.8. The patient was followed up 6 months and 2 years after discharge and was on the same daily dose of warfarin as at discharge, with no complications.
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