Abstract 16326: Poor Understanding and Compliance Among AF Patients on Warfarin Who Use Herbal and Dietary Supplements
Background: The majority of commonly used herbal and drug supplements (HDS) interact with warfarin, exposing patients to risk of thromboembolism and/or bleed. It is unknown if patients that use HDS have more understanding of warfarin, which would minimize the interaction risk to which they are exposed.
Methods: A 52-item questionnaire related to knowledge of warfarin was administered in a face-to-face interview to 100 patients with AF. This study examined (1) general knowledge of warfarin therapy, (2) warfarin compliance, and (3) adverse outcomes associated with warfarin use in patients that use HDS (n=35) compared to those who do not (n=65). Patients were followed longitudinally to examine the incidence of stroke, bleeding, and blood transfusion after warfarin therapy was initiated.
Results: Stroke risk factors included hypertension (57%), heart failure (36%), age >75 years (33%), diabetes (22%), and prior stroke/transient ischemic attack (29%). There were no significant differences in baseline demographics based upon HDS use. HDS patients more often reported that they did not take warfarin (6% vs. 3%, p=0.54), skipped doses of warfarin (34% vs. 17%, p=0.06), and doubled doses of warfarin (3% vs. 0%, p=0.18). HDS patients were less aware of potential HDS-warfarin interactions (47% vs. 54%, p=0.35) and of how to interpret a supplement facts label (54% vs. 57%, p=0.79). Dietary knowledge was similar between both groups, with each group scoring poorly across a broad spectrum of food products. Significantly more strokes occurred in the non-HDS patients (5% vs. 17%, p=0.04). In contrast, HDS patients had higher rates of unexplained bleeding (23% vs. 17%, p=0.52 hematuria/blood in stool) and nonoperative need for blood transfusions (14% vs. 10%, p=0.47).
Discussion: AF patients that use HDS are less compliant with warfarin and less aware of potential risks related to supplement use. These patients had higher bleeding rates on warfarin. Due to these complicating factors, physicians should ask warfarin patients about HDS use and improve education to minimize bleeding risk and increase drug understanding and compliance.
- © 2010 by American Heart Association, Inc.