Purpose: Warfarin monitoring of the international normalized ratio (INR) within a narrow range is assessed by time in therapeutic range (TTR). This study evaluates whether glucagon-like peptide-1 (GLP-1) agonists impact TTR in stable patients.
Methods: This retrospective cohort study included adult patients managed at an anticoagulation clinic at the University of Pennsylvania Health System who were on stable warfarin therapy and initiated a GLP-1 agonist between January 2023 and September 2025. Patients required ≥3 values and documented targets in 6-month pre/post periods. Exclusions included unstable therapy, insufficient data, anticoagulant changes, or therapy discontinuation. The primary endpoint was change in TTR from baseline to 6 months post-initiation. Secondary endpoints included percentage of INRs within range, frequency of warfarin dose interventions, bleeding events, and weight change at 6 months. Data was collected via electronic records and REDCap. The primary endpoint was analyzed using a Wilcoxon signed-rank test; secondary endpoints were summarized descriptively.
Results: A total of 52 patients were included. Median TTR decreased from 91.6% pre-initiation to 86.6% post-initiation (p=0.107), which was not statistically significant. Few bleeding events were observed (n=2). Patients experienced a significant reduction in weight at 6 months (mean change −7.3 kg, p<0.001). Data on INR within range and dose interventions showed variability, but no clear pattern of increased instability.
Conclusion: Initiation of GLP-1 agonists in stable warfarin patients was not associated with a statistically significant change in TTR, though a numerical decline was observed. Concurrent use is well tolerated, with minimal bleeding events and significant weight loss. Findings suggest that safe warfarin therapy may be maintained with GLP-1 initiation, though close INR monitoring remains prudent. Larger studies are needed to further clarify this relationship.
