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Aims: Adherence to the generally complex regimen of coumarin derivatives is vital in order to keep patients in the adequate International Normalized Ratio range. Patients' beliefs about medicines are associated with the level of therapy adherence. Our first aim was to assess beliefs about coumarins. Secondly, we compared the beliefs about coumarins with the beliefs about other cardiovascular drugs., Methods: The Beliefs about Medicines Questionnaire was used to assess medication beliefs. The questionnaire was completed by new users of coumarins indicated for venous thromboembolism or atrial fibrillation. A necessity score and a concerns score were calculated for all patients. The analyses were repeated for users of antihypertensive drugs or statins (not using coumarins)., Results: Three hundred and twenty patients were included in the analysis of the beliefs about coumarins. The mean necessity score was 15.3, the concerns score 12.3 and the necessity-concerns differential 3.0. Patients with venous thromboembolism (n = 71) had higher necessity scores than patients with atrial fibrillation (n = 249; 16.8 vs. 14.9, P < 0.001). The mean necessity score in 493 users of other cardiovascular drugs was 16.1, the concerns score 13.5 and the necessity-concerns differential 2.6. The necessity score was higher in chronic cardiovascular drug users (n = 192) than in new users (n = 301; 17.9 vs. 14.9, P < 0.001)., Conclusions: Coumarin users score higher on the necessity scale than on the concerns scale, which is also the case in users of other cardiovascular drugs. Patients with atrial fibrillation have a less positive attitude towards these drugs than patients with venous thromboembolism, and could therefore benefit more from specific attention., (© 2014 The British Pharmacological Society.)

Coumarin derivatives, such as warfarin, acenocoumarol and phenprocoumon are frequently prescribed oral anticoagulants to treat and prevent thromboembolism. Because there is a large inter-individual and intra-individual variability in dose-response and a small therapeutic window, treatment with coumarin derivatives is challenging. Certain polymorphisms in CYP2C9 and VKORC1 are associated with lower dose requirements and a higher risk of bleeding. In this review we describe the use of different coumarin derivatives, pharmacokinetic characteristics of these drugs and differences amongst the coumarins. We also describe the current clinical challenges and the role of pharmacogenetic factors. These genetic factors are used to develop dosing algorithms and can be used to predict the right coumarin dose. The effectiveness of this new dosing strategy is currently being investigated in clinical trials., (© 2013 The British Pharmacological Society.)