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Metformin use decreases the anticoagulant effect of phenprocoumon
Author(s) -
Wijnen J. C. F.,
Riet I. R.,
Lijfering W. M.,
Meer F. J. M.
Publication year - 2014
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.12578
Subject(s) - phenprocoumon , medicine , metformin , concomitant , anticoagulant , anticoagulant therapy , vitamin k , gastroenterology , warfarin , atrial fibrillation , insulin
Summary Background Anticoagulant therapy with vitamin K antagonists ( VKA s) is affected by interaction of the VKA s with a large number of other drugs. Although metformin is generally not considered to interact with VKA s, we observed a decrease in INR after starting metformin treatment in patients using the VKA phenprocoumon. Objectives To investigate the influence of metformin use on the dosage of phenprocoumon and INR in stably anticoagulated patients. Patients We used the database of the A nticoagulation C linic L eiden for this study. In a population of 369 patients screened, 27 consecutive patients using phenprocoumon were prescribed metformin during the study period (1 January 2007 to 1 March 2009), without use of other concomitant medications or medical interventions that could influence the INR . Results The mean phenprocoumon dosage increased from 2.13 to 2.37 mg per day within 6 weeks (mean increase, 0.23 mg; 95% CI , 0.12–0.34) and 2.49 mg per day within 3 months (mean increase, 0.36 mg; 95% CI , 0.24–0.48) after starting metformin. The mean INR decreased from 2.88 to 2.26 (mean decrease, 0.63; 95% CI , 0.41–0.85) within 6 weeks and 2.54 (mean decrease, 0.35; 95% CI , 0.24–0.48) within 3 months after starting metformin. Conclusions This study shows that clinicians should be aware that metformin treatment may lead to an increased optimal dosage of phenprocoumon.