Late breaking clinical trials

Background: Several studies have compared different vitamin K antagonists with regard to the quality of treatment. The results were mostly in favour of longer acting vitamin K antagonists. These were mainly comparisons of warfarin or phenprocoumon with acenocoumarol, while only one small randomised study compared warfarin with phenprocoumon. Objective: The aim of our study was to investigate whether treatment with warfarin leads to a better anticoagulant control than phenprocoumon. Methods: We conducted a randomised controlled trial at the Leiden Anticoagulation Clinic, the Netherlands among patients initiating anticoagulant therapy and patients who were already using the vitamin K antagonist acenocoumarol. All patients were randomised to treatment with either warfarin or phenprocoumon. We compared the quality of anticoagulant treatment with warfarin to treatment with phenprocoumon. Follow-up was 6 months. Primary outcome measure was the percentage of time spent within therapeutic ranges. From March 1st 2004 to September 2008 all patients have been included. The trial is registered in the ISRCTN register (identifier ISRCTN60446748). Results: Five hundred and four patients were included, 243 (48.2%) patients who initiated anticoagulant therapy and 261 (51.8%) patients who were already using acenocoumarol. More men than women participated (352, 69.8% vs. 152, 30.2%), mean age was 65.4 years (standard deviation 12.3). By randomisation 250 patients were assigned to treatment with warfarin and 254 patients to phenprocoumon. Equal number of initiating and switching patients were treated with warfarin (121 initiating, 129 switchers) and phenprocoumon (122 initiating, 132 switchers). Overall, mean percentage of time spent within the therapeutic ranges for patients treated with warfarin was 74.6% vs. 65.3% for patients treated with phenprocoumon (Diff 9.3; 95%CI 5.8–12.8). The difference in time in therapeutic range was mainly seen in switchers; 78.3% in warfarin treated patients versus 57.6% in phenprocoumon patients (Diff 20.7; 95%CI 16.3–25.1), whereas no difference was seen in patients initiating therapy; phenprocoumon 73.3%, warfarin 70.5% (Diff 2.7, 95%CI 2.4–7.7). After excluding the first 6 weeks of follow up the results did not change, although the time spent in therapeutic range in patient initiating therapy became higher (77.1% vs. 78.5%). Conclusions: Overall, treatment with warfarin led to a better anticoagulant control compared to treatment with phenprocoumon. Disclosure of interest: none declared.