Long-Term Efficacy and Safety of Direct Oral Anticoagulants at Reduced Doses in the Secondary Prevention of Venous Thromboembolism and Post-Thrombotic Syndrome.

Background : Anticoagulation for venous thromboembolism (VTE) is required for at least three to six months; however, it is advisable to extend the duration in certain cases, in which case a reduced dose of Direct Oral Anticoagulants (DOACs) may be an option. Our objective was to investigate the efficacy and safety of reduced-dose DOACs in extended anticoagulation treatment compared to full doses. Methods and Results : This retrospective single-centre study included 185 patients treated with DOACs for at least 6 months who were divided into two groups: (1) the Full Dose (FD) group (n = 113) and (2) the Reduced Dose (RD) group (n = 72), which included patients treated with Apixaban at 2.5 mg bis in die (BID) and Rivaroxaban at 10 mg once daily (OD). Post-thrombotic syndrome (PTS) and its progression were evaluated. During an overall follow-up of 48.32 ± 29.49 months, no VTE occurred, and no patients experienced major bleeding; clinically relevant non-major bleeding occurred in three patients in each group (2.7% vs. 4.2% in FD vs. RD, respectively, p = 0.57). From baseline to follow-up, the prevalence of PTS was not significantly decreased in either group (FD: 54.9% vs. 51.3%, p = 0.29; RD 51.4% vs. 44.4%, p = 0.12); conversely, the Villalta score values were significantly decreased at the last follow-up (FD: 5.51 ± 4.18 vs. 5.51 ± 4.18, p < 0.001; RD 5.49 ± 4.06 vs. 5.11 ± 3.73, p = 0.006). Conclusion: In this real-world retrospective registry, very long-term extended anticoagulant therapy with DOACs at full or reduced doses showed comparable efficacy, safety, and impact on PTS progression. Larger studies are needed.