Rivaroxaban compared with standard thromboprophylaxis after major orthopaedic surgery: co‐medication interactions

AIM: The aim of the present study was to analyse concomitant drug use and its association with outcome in patients (N = 17 701) receiving rivaroxaban or standard of care (SOC) for the prevention of venous thromboembolism after major orthopaedic surgery in the non‐interventional, phase IV XAMOS (Xarelto® in the prophylaxis of post‐surgical venous thromboembolism after elective major orthopaedic surgery of hip or knee) study. METHODS: Concomitant drug use was at the discretion of the treating physician. Prespecified co‐medications of interest were cytochrome P450 (CYP) 3A4/P‐glycoprotein inhibitors/inducers, platelet aggregation inhibitors (PAIs) and nonsteroidal anti‐inflammatory drugs (NSAIDs). Crude event incidences were compared between rivaroxaban and SOC groups. RESULTS: CYP3A4/P‐glycoprotein inhibitor/inducer use was infrequent, in contrast to PAI (~7%) and NSAID (~52%) use. Rivaroxaban was associated with a lower incidence of overall symptomatic thromboembolic events compared with SOC, regardless of co‐medication use. In both treatment groups, PAI users, with higher age and prevalence of cardiovascular co‐morbidities, had similar higher (>7‐fold) incidences of symptomatic arterial but not venous thromboembolic events compared with non‐users. NSAID use had no influence on thromboembolic events. However, odds ratios (ORs) for major bleeding events (European Medicines Agency definition) were higher in NSAID users compared with non‐users in rivaroxaban [OR = 1.50; 95% confidence interval (CI) 1.06, 2.13] and SOC (OR = 1.70; CI 1.16, 2.49) groups. In PAI users, ORs for major bleeding events were no different from those of non‐users in both the rivaroxaban (OR = 1.49; CI 0.84, 2.65) and SOC (OR = 1.46; CI 0.82, 2.62) groups. CONCLUSIONS: Use of NSAIDs in XAMOS was frequent and associated with a higher frequency of bleeding events in patients receiving rivaroxaban or SOC, although the benefit–risk profile of rivaroxaban compared with SOC was maintained.