Reinitiation of Anticoagulation After Temporary Withdrawal of Vitamin K Antagonist (DOSIDO)

It is not known how to best restart warfarin after temporary withdrawal. Participants will be randomized to two groups. Group 1 will restart warfarin at their usual maintenance dose, group 2 will restart warfarin at double their maintenance dose for two days followed by their usual maintenance dose. The main outcome parameter will be the number of patients who are back in therapeutic INR (international normalized ratio) range 4, and 9 days after restarting anticoagulation with warfarin. Thromboembolic and/or bleeding events will be recorded as additional parameters. These data will be collected by a standardized telephone interview at 1 month. In addition, the investigators will evaluate a possible prothrombotic state by measuring the potential of thrombin generation and D-dimers in the subset of patients visiting HHS-General Hospital for their INR tests.

We will investigate if it is feasible to use double maintenance dose for the first two administrations of vitamin K antagonists when these drugs were temporarily interrupted and thus keep the time of an increased risk of thromboembolism and duration of "bridging" at a minimum. The control group will consist of patients who resume vitamin K antagonists at their usual maintenance dose. The aim of the study is to establish how to best restart anticoagulation with vitamin K antagonists after temporal withdrawal of these drugs. The main outcome parameter will be the proportion of patients who are back to a therapeutic international normalized ratio (INR) ratio at certain days after restarting vitamin K antagonists. Two additional parameters will be evaluated: Firstly, bleeding and thromboembolic complications will be reported and secondly, a possible prothrombotic state, measured as an elevation of D-dimer, at the initiation of anticoagulation will be evaluated.

Re-initiation with warfarin at twice the usual maintenance dose the first 2 days, then maintenance dose.

Proportion of patients with INR 2.0-3.0 on Day 5 or Day 10 (day of invasive procedure defined as Day 1)

Quantitative D-dimer and Thrombin Generation performed in a subset at day of procedure, day 5 and 10 to identify abnormal rise.

Inclusion Criteria: Current treatment with warfarin Need for temporary interruption for invasive procedure or surgery Exclusion Criteria: Need for post-operative hospitalization more than one day Participation in another clinical trial No consent given

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Schulman S, Hwang HG, Eikelboom JW, Kearon C, Pai M, Delaney J. Loading dose vs. maintenance dose of warfarin for reinitiation after invasive procedures: a randomized trial. J Thromb Haemost. 2014 Aug;12(8):1254-9. doi: 10.1111/jth.12613. Epub 2014 Jun 25.