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Thank you for attending THSNA 2026. The virtual meeting is now closed.
Thank you for attending THSNA 2026. The virtual meeting is now closed.
Presentation Details
| Evaluating the indirect interaction between glucagon-like peptide receptor agonists and warfarin using real-world data Spencer J.Gilbert1, 2, 3, Sara R.Vazquez1, 2, Alexander Millar3, Ramkiran Gouripeddi3, Julio C.Facelli3, Daniel M.Witt1, 2. 1University of Utah College of Pharmacy, Salt Lake City, UT, USA.2University of Utah Health Thrombosis Service, Salt Lake City, UT, USA.3University of Utah Department of Biomedical Informatics, Salt Lake City, UT, USA |
Abstract
Background: The recent widespread adoption of glucagon-like peptide receptor agonists (GLP-1RAs) raises concerns about interactions with medications like warfarin, a vitamin K antagonist with a narrow therapeutic index and diet-dependent effectiveness. Because warfarin therapy requires regular monitoring of the international normalized ratio (INR) to ensure safe and effective anticoagulation, even modest shifts in vitamin K intake can have clinical consequences. While GLP-1RAs show no direct pharmacokinetic effects on warfarin, their predictable reduction in appetite and caloric intake may lower vitamin K consumption, potentially increasing warfarin variability. Detecting such indirect pharmacodynamic interactions requires large-scale Real World Data (RWD) to capture population-level trends. Objectives: To evaluate changes in time-in-therapeutic range (TTR) among warfarin patients in the 6 months before and after initiation of GLP-1RA therapy using RWD. Methods: This retrospective cohort study used RWD from the TriNetX US network, spanning earliest available records through November 12, 2024. Participants were selected for inclusion according to these criteria: 1) A warfarin prescription within 1 year before GLP-1RA initiation, or—if the prescription was within 90 days prior—a second warfarin prescription within the preceding year; 2) a post GLP-1RA initiation date warfarin prescription within 13 months; 3) a second GLP-1RA prescription within 90 days of the initial GLP-1RA prescription; 4) INR results available for at least 180 days before and after GLP-1RA initiation; and 5) an INR recheck frequency of no longer than 12 weeks for all INRs 180 days before and after GLP-1RA initiation. The primary outcome was percent change in TTR 180 days pre- and post-GLP-1RA initiation. Secondary outcomes included change in INR results and INR recheck frequency pre- and post-GLP-1RA initiation. Results: Of 53,943 patients with prescriptions for both warfarin and a GLP1-RA, 1,021 met inclusion criteria for this study. The mean change in TTR was ‑2.1% (95% CI ‑3.7% to ‑0.6%; p = 0.007), from 64.2% to 62.1% before and after GLP1-RA initiation, respectively. The mean change in time below therapeutic range was 0.8% (95% CI ‑0.6% to 2.1%; p = 0.248) from 19.7% to 20.5%. The mean change in time above therapeutic range was 1.3% (95% CI 0.07% – 2.6%; p = 0.039) from 16.1% to 17.5%. The mean change in INR value was 0.004 (95% CI ‑0.02 to 0.03; p = 0.790). The mean change in INR recheck frequency was -0.7 days (95% CI ‑1.4 to 0.0; p = 0.0499) from 19.6 days to 18.9 days. Conclusions: Overall, there was a modest decrease in TTR observed in patients on warfarin who initiated a GLP1-RA. This decrease in TTR lead to increased amounts of time participants spent both above and below the therapeutic INR range, which resulted in the overall mean INR value remaining unchanged across the population. These findings suggest that post GLP1-RA initiation clinicians should consider increasing INR recheck frequencies. Future analysis will assess whether these modest changes are uniform or if categories of individuals showing larger variations can be identified.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.