Comparison of 10-mg and 5-mg warfarin initiation nomograms in a South Indian population - An open label trial

Introduction: Early achievement of therapeutic INR leads to shorter hospital stay and lesser cost. Two warfarin initiation nomograms (10 mg nomogram and 5 mg nomogram) are widely used but it is not yet clear which one is better. They have been validated in the West but there are no studies from India. We undertook this study to compare the efficacy and safety of the 10 mg and 5 mg nomograms in the Indian population. Methods: 169 patients were enrolled between august 2014 to July 2016. Patients with venous thromboembolism or atrial fibrillation secondary to valvular heart disease were included. Patients were allocated to 10 mg or 5 mg nomogram as per the policy of the treating unit. Results: 52% of patients in the 10 mg nomogram achieved therapeutic INR by day 5 as compared to only 17% in the 5 mg nomogram (P = 0.022). The median time to achieve therapeutic INR was much shorter in the 10 mg nomogram (5 days vs 14 days, p = 0.018). Two patients in the 10 mg group (2.3%) and none in the 5 mg group had INR > 4 but they did not have any bleeding. Conclusion: The 10 mg nomogram achieved therapeutic INR significantly earlier with less INR measurements and appears safe. Indian patients require higher a dose of warfarin at initiation and maintenance as compared to other ethnic groups.