2021
DOI: 10.2147/pgpm.s288918
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Genetic Polymorphism Effect on Warfarin–Rifampin Interaction: A Case Report and Review of Literature

Abstract: Warfarin–rifampin interaction has been reported since the 1970s. Due to rifampin’s strong induction of CYP2C9 , most cases could not attain the target international normalized ratio (INR) despite warfarin dose escalation. Genetic polymorphisms determine up to 50% of warfarin dose variability. A 38-year-old woman was started on warfarin and rifampin for cerebral venous sinus thrombosis and pulmonary tuberculosis. Over six weeks, the daily warfarin dose was increased from 3 to 10 mg to att… Show more

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Cited by 7 publications
(16 citation statements)
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“…Hamberg et al developed a PK-PD model for warfarin (Hamberg et al, 2007) respectively (Limdi et al, 2008;Fung et al, 2012). Furthermore, a recent clinical case report showed that a subject with CYP2C9 *3/*3 and VKORC1 GA mutations required a larger magnitude of warfarin dose adjustments while warfarin was treated together with rifampin (Salem et al, 2021), the conclusion of the case report is consistent with our findings to some extent. Thus, the impact of CYP2C9 genotype-dependent DDIs on the therapeutic outcomes of warfarin is ambiguous, which may warrant further investigations given the narrow therapeutic index of warfarin.…”
Section: Discussionsupporting
confidence: 91%
See 1 more Smart Citation
“…Hamberg et al developed a PK-PD model for warfarin (Hamberg et al, 2007) respectively (Limdi et al, 2008;Fung et al, 2012). Furthermore, a recent clinical case report showed that a subject with CYP2C9 *3/*3 and VKORC1 GA mutations required a larger magnitude of warfarin dose adjustments while warfarin was treated together with rifampin (Salem et al, 2021), the conclusion of the case report is consistent with our findings to some extent. Thus, the impact of CYP2C9 genotype-dependent DDIs on the therapeutic outcomes of warfarin is ambiguous, which may warrant further investigations given the narrow therapeutic index of warfarin.…”
Section: Discussionsupporting
confidence: 91%
“…Nonetheless, warfarin dosing remains challenging and a personalized medicine approach is not yet realized. Additional complications continue to be uncovered and a recent case report highlights the need for further investigations on the gene-DDIs of warfarin (Salem et al, 2021).…”
Section: Introductionmentioning
confidence: 99%
“…As a CYP2C9 inducer, rifampin can generate phenoconversion from a poor to a rapid metabolizing status 38–41 . Because almost all the previously reported warfarin‐rifampin interaction cases had not been genotyped, 24–34 carrying warfarin‐sensitizing CYP2C9/VKORC1 genotypes might stand as a hidden explanation for adequate responses to modest warfarin doses while concomitantly used with rifampin; due to minimal baseline dose requirements, as shown in the only genotyped case reported by the present authors 34 …”
mentioning
confidence: 49%
“…Most commonly, amiodarone, azole antifungals, phenytoin, rifampicin, trimethoprim/sulfamethoxazole, and the use of statins are included in warfarin maintenance dose algorithms. However, quantification of the effect of the interacting drug on warfarin dose is complicated and varies based on the interacting medication, genetic variants affecting the responsible metabolizing enzyme and other inter-individual variations [ 28 ]. For example, 30–50% warfarin dose reduction is recommended with amiodarone initiation, whereas a 25–33% reduction is recommended for fenofibrate [ 29 ].…”
Section: Resultsmentioning
confidence: 99%