warfarin

A Retrospective Cohort Study on The Anticoagulation Control of Patients Receiving Warfarin in Queen Elizabeth Hospital (QEH) Sabah

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    Abstract

    Warfarin is a vitamin K antagonist (VKA) with a narrow therapeutic window prescribed to prevent thromboembolic events. Time in therapeutic range (TTR) is the most recognised way to measure anticoagulation quality over time. High TTR correlates with reduced thromboembolic events and low TTR with increased complications. Objective: To evaluate anticoagulation quality for patients receiving warfarin at Queen Elizabeth Hospital. Method: A retrospective observational population study was conducted on patients reviewed under the Warfarin Medication Therapy Adherence Clinic (MTAC) from April 2016 to April 2017. Data was collected using a data collection form. Patients who were on warfarin treatment for at least 6 months or at least 5 visits for those newly started with warfarin were included in the study. The primary outcome was the time in therapeutic range (TTR) of 1.8-3.2, calculated using the Rosendaal method. Results: 150 patients on warfarin with 1765 clinic visits were evaluated. Most were male (56%), and the mean age was 61.33±13.47. The prevalent indication observed was nonvalvular atrial fibrillation, which accounted for 110 patients (73.3%) of the total. The overall mean TTR (1.8-3.2) was 80.6±20.2%. The wrong/missed warfarin dose was the main reason the International Normalised Ratio (INR) was out of range (150/851 episodes, 17.6%). Hospitalisation rendered most patients defaulting clinic visits (10/34 episodes, 29.4%) and was predominantly non-warfarin related (27/37 episodes, 19 patients). There was a single episode of major bleeding (1 patient). Conclusion: A high average TTR was achieved in patients taking warfarin at our institution. Wrong/missed doses and inconsistent diet were the main reasons for INR being out of range. However, the primary reason for INR being out of range remains unknown. A total of 37 cases of hospitalisation were reported, and 72.9% of them were non-warfarin related. No mortality was recorded.

    Warfarin – Fenofibrate Interaction: Hospital Kuala Lumpur Experience

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      Abstract

      Case reports in western populations reported that fenofibrate enhances the anticoagulatory effect of warfarin. We are reporting ten cases of warfarin-fenofibrate interaction among Malaysian patients’ cases that were managed at the anticoagulation clinic of Hospital Kuala Lumpur. Patients taking warfarin and micronized fenofibrate 145mg daily concurrently between the year 2014 to 2018 were identified in May 2018. Ten active patients were included, and the relevant data were retrieved retrospectively. All patients received warfarin for stroke prevention in atrial fibrillation (AF), with a target international normalised ratio (INR) of 2 to 3. No dose adjustment was done upon initiation of fenofibrate. Warfarin doses were adjusted to achieve the targeted range but fenofibrate was not discontinued. Eight patients had INR levels above the target range when INR being reassessed between 20 to 62 days after initiation of fenofibrate. Their weekly warfarin doses were between 17.5mg-46.5mg. Baseline INR ranged between 1.6 -3.1. Percentage of dose reduction ranged between 5%-60%. Four of the patients were on other concurrent interacting medications such as statin and levothyroxine. Only one patient, whose case was with an INR 3.1 before initiation of fenofibrate, required admission for hematoma (INR 12). Two patients had INR within the target range, and INR were assessed at 14 and 21 days after fenofibrate initiation. Their weekly warfarin doses were between 24.5mg and 26.5mg while baseline INR was 2.8 and 1.9 respectively. Interaction between fenofibrate and warfarin may increase INR among Malaysian patients, thus close monitoring of INR is warranted. Empirical warfarin dose reduction may be considered upon initiation of this drug combination for patients with AF. The next INR reassessment date should be arranged not later than three weeks after initiation of fenofibrate.