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Subtherapeutic INR due to warfarin interaction with smokeless tobacco
Author(s) -
Nicolas Diala,
Elmouhayyar Christopher,
Nicolas Samar,
Talj Juliana,
Hattar Laith,
Alhudairy Maad
Publication year - 2020
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/jth.15057
Subject(s) - smokeless tobacco , warfarin , medicine , pharmacology , tobacco use , environmental health , atrial fibrillation , population
We report an interesting case of warfarin resistance and subtherapeutic international normalized ratio (INR) in the setting of chronic smokeless tobacco use. A 33‐year‐old white male with a mechanical mitral valve failed to achieve therapeutic INR despite being on warfarin doses of up to 30 mg by mouth daily. The patient admits to chewing tobacco daily for the past 16 years. While evaluating potential causes of subtherapeutic INR, nonadherence, drug interactions, genetic polymorphisms, and dietary factors were considered. Subtherapeutic INR may be due to increased exposure to vitamin K from chewing tobacco. Tobacco is rich in vitamin K, and its chronic use may have caused the failure to attain a therapeutic INR. To our knowledge, there is only one other case of warfarin resistance resulting from smokeless tobacco described in published literature.