Background and Objectives: While non-vitamin K antagonist oral anticoagulants (NOACs) show better renal preservation than warfarin in nonvalvular atrial fibrillation (NVAF) patients, real-world evidence within Asian populations remains limited. This study compared the renal outcomes between NOACs and warfarin in Thai patients with NVAF. Materials and Methods: A retrospective cohort study was conducted among NVAF patients who received either NOACs or warfarin from two university hospitals in Thailand from January 2015 to December 2019. The primary outcome was a ≥30% decline in the estimated glomerular filtration rate (eGFR) with a doubling of the serum creatinine (SCr), while acute kidney injury (AKI) and incidence rate of stroke and systemic embolism event (SEE) were secondary outcomes. All outcomes of each NOAC versus the warfarin group were analyzed using Cox proportional hazards regression. Results: A total of 1456 patients were enrolled. During a follow-up period of 24 months, NOACs were associated with a lower risk of a ≥30% decline in the eGFR than warfarin after inverse probability of treatment weighting (IPTW) and multivariable adjustment (adjusted hazard ratio (aHR) of 0.67, 95% confidence interval [CI] 0.45–1.00, p = 0.050). No significant differences were observed between NOACs and warfarin regarding the doubling of SCr (aHR 0.64, 95% CI 0.24–1.72, p = 0.373) or AKI (aHR 0.69, 95% CI 0.41–1.17, p = 0.169), although a trend toward a lower risk was noted in the NOAC group. Similarly, a trend toward a lower risk of the incidence rate of ischemic stroke and SEE were observed in the NOAC group (aHR 0.49, 95% CI 0.22–1.10, p = 0.084). Conclusions: In real-world data, NOACs may be associated with a lower eGFR decline and lower doubling of SCr and AKI than warfarin. Additionally, NOACs may reduce the risk of ischemic stroke and SEE, supporting their potential benefit over warfarin in both renal and thromboembolic outcomes.

Warfarin is an oral anticoagulant commonly used to prevent thromboembolism. Its pharmacodynamics can be affected by interactions with other drugs and dietary supplements, although there is only limited information available on these interactions. One dietary supplement that has been associated with increased international normalized ratio (INR) levels, potentially leading to supratherapeutic levels, is fish oil. However, the data available on this interaction are not extensive. This case study focused on a sixty-nine years old Thai female who was prescribed warfarin at a weekly dose of 30 milligrams (maintaining an INR range of 2.5-3.5) to prevent thromboembolism resulting from atrial fibrillation (AF) following a mechanical valve replacement at the mitral position. The patient began taking fish oil supplements for a period of 2 months. After initiating the fish oil supplement in addition to the warfarin, the patient’s INR had increased from 2.94 to 4.13, although no bleeding symptoms were observed. When combining fish oil with warfarin, it is important for medical professionals to exercise caution and to monitor the INR levels in all cases to ensure safety and optimize efficacy. KEYWORDS warfarin, fish oil, dietary supplement