Initiation of glucose‐lowering treatment decreases international normalized ratio levels among users of vitamin K antagonists: a self‐controlled register study. (29th December 2015)

• Record Type: Journal Article
• Authors: Stage, T. B.; Pottegård, A.; Henriksen, D. P.; Christensen, M. M. H.; Højlund, K.; Brøsen, K.; Damkier, P.
• Is Part Of: Journal of thrombosis and haemostasis. Volume 14:Number 1(2016:Jan.)
• Page Start: 129
• Page End: 133
• Publication Date: 2015-12-29
• Subjects: antidiabetic drugs -- drug interactions -- pharmacoepidemiology -- phenprocoumon -- warfarin; Thrombosis -- Periodicals; Hemostasis -- Periodicals; Blood coagulation disorders -- Periodicals; 616.1
• DOI: 10.1111/jth.13187
• Languages: English
• ISSNs: 1538-7933

Abstract

Abstract : Essentials It is not known if initiation of glucose‐lowering drugs alters the efficacy of vitamin K antagonists (VKA). We examined if glucose‐lowering drugs affected international normalized ratio (INR) in VKA‐treated patients. Upon initiating glucose‐lowering drugs, 51% of patients had INR values below the therapeutic window. Monitoring of INR levels should be intensified upon initiation of glucose‐lowering drugs. Summary: Background: It is not known whether initiation of antidiabetic treatment affects the effect of vitamin K antagonists (VKAs). It was previously shown that metformin affects the effect of one VKA, phenprocoumon. Objectives: The aim of this study was to determine if initiation of glucose‐lowering treatment affects the international normalized ratio (INR) and dose requirements of the anticoagulant VKAs warfarin and phenprocoumon. Patients/methods: We performed a self‐controlled retrospective register‐based study. A total of 118 patients commencing glucose‐lowering treatment while being treated with warfarin or phenprocoumon were included in the study. We compared INR, dose/INR and proportion of patients with at least one sub‐therapeutic INR measurement before and after initiation of glucose‐lowering treatment. Results: Initiation of glucose‐lowering treatment caused mean INR to decrease from 2.5 to 2.2 (decrease of −0.3 [95% CI: −0.1; −0.5]) and led to more than half of the patients having at least one sub‐therapeutic INR measurement. Six to 12 weeks later, the VKA dose/INR was increased by 11%, indicating a weakened effect of the VKA. Conclusion: Initiation of glucose‐lowering treatment reduces the anticoagulant effect of VKAs to an extent that is likely to be clinically relevant. This finding needs confirmation and mechanistic explanation.