A Cost-Effectiveness Model Comparing Rivaroxaban and Dabigatran Etexilate with Enoxaparin Sodium as Thromboprophylaxis after Total Hip and Total Knee Replacement in the Irish Healthcare Setting

Abstract

Background: It has been estimated that major orthopaedic surgery has the highest risk of venous thromboembolism (deep vein thrombosis and pulmonary embolism) when compared with other surgery. Two new orally active anticoagulants have recently become licensed in Ireland for the primary prevention of venous thromboembolism in adult patients undergoing elective total hip replacement (THR) or total knee replacement (TKR). Rivaroxaban (Xarelto®) is a direct factor Xa inhibitor and dabigatran etexilate (Pradaxa®) is a prodrug of the active compound dabigatran, which inhibits thrombin. Objective: To evaluate the cost effectiveness of rivaroxaban and dabigatran etexilate compared with enoxaparin sodium for the prophylaxis of venous thromboembolism in patients undergoing elective THR and TKR in the Irish healthcare setting. Methods: The evaluation was conducted from the Irish health-payer perspective. A static decision-tree model was developed with a 180-day post-surgery time horizon. Separate models for the disease states THR and TKR were run to accommodate the different venous thromboembolism risks associated with each procedure. Outcome measures were QALYs and life-years gained (LYG). Costs were valued in ®, year 2008 values. One-way sensitivity analysis of all probabilities in the model was performed. A probabilistic sensitivity analysis using second-order Monte Carlo simulation was performed to determine the probability of cost effectiveness at a €45 000 per QALY threshold. Results: In the THR base-case model, rivaroxaban dominated both dabigatran etexilate and enoxaparin sodium. The incremental cost-effectiveness ratios for dabigatran etexilate relative to enoxaparin were €23 934 per LYG and €17 835 per QALY. In the TKR base-case model, rivaroxaban dominated both dabigatran etexilate and enoxaparin sodium. Dabigatran etexilate also dominated enoxaparin sodium. In the one-way sensitivity analysis, the THR model was robust to all but four probability variations; the TKR model was robust to all variations. At a cost-effectiveness threshold of €45 000 per QALY, the probability that rivaroxaban was the most cost-effective strategy after THR was 39%, followed by dabigatran etexilate at 32% and enoxaparin sodium at 29%. The probability that rivaroxaban was the most cost-effective strategy after TKR was 46%, followed by dabigatran etexilate at 30% and enoxaparin sodium at 24%. Conclusion: Base-case analysis indicates that when both rivaroxaban and dabigatran etexilate are compared with enoxaparin sodium, rivaroxaban is the less costly and more effective option after THR and TKR. Probabilistic sensitivity analysis indicates that rivaroxaban is the most cost-effective strategy at a cost-effectiveness threshold of €45 000 per QALY; however, there is uncertainty regarding this strategy being more cost effective than dabigatran etexilate when both are compared with enoxaparin sodium.