Evaluation of the four mg warfarin initiation dose in patients with cardiovascular disease

Background: Warfarin is the most widely used oral anticoagulant for the prevention of stroke in patients with cardiovascular disease. In Indonesia, validation of the initiation dose of warfarin has never been carried out. Objective: To evaluate the efficacy and safety of 4 mg warfarin initiation dose in achieving therapeutic targets. Methods: It was a prospective observational study involving hospitalised and ambulatory patients administered a 4 mg warfarin initiation dose between days one and three. On day four, the INR was measured for three to seven days. Subsequently, the initiation dose was adjusted to the therapeutic INR. The INR level was measured every seven days until patients achieved therapeutic INR twice. Results: A total of 14 patients were included in this study, with a mean age of 62 years. The most common indication for using warfarin was non-valvular atrial fibrillation (85.7%), with a CHA2DS2-VASc score between one and three and a HAS-BLED score ranging from zero to two. The median time to achieve therapeutic INR was 22.2 days, and the predictive value of the day four INR for determining the maintenance dose had an r2= 0.77. Conclusions: The initiation dose of 4 mg warfarin effectively achieved therapeutic INR within an acceptable time.