Rivaroxaban: new drug. After hip or knee replacement surgery: LMWH is safer.

(1) The standard anticoagulant therapy for prevention of thrombosis after hip or knee replacement surgery is subcutaneous injection of a low-molecular-weight heparin, such as enoxaparin; (2) Rivaroxaban is an oral factor-Xa inhibitor anticoagulant approved for use in these indications in the European Union; (3) Four double-blind controlled trials in more than 12 000 patients undergoing hip or knee replacement surgery failed to show that rivaroxaban was any more effective than enoxaparin on relevant clinical outcomes; there was no reduction in mortality, nor in the incidence of pulmonary embolism and symptomatic deep venous thrombosis; (4) In the selected populations enrolled in these trials, the bleeding risk was similar in the rivaroxaban and enoxaparin groups. However, it is possible that very underweight or overweight patients have an increased bleeding risk with rivaroxaban; (5) More information is needed on the nephrotoxicity of rivaroxaban, and a risk of mitochondrial toxicity cannot be ruled out. Post-marketing studies also need to focus on the consequences of wound seepage, which is more frequent with rivaroxaban. (6) Rivaroxaban is metabolized by the cytochrome P450 isoenzyme CYP 3A4 and binds to P-glycoprotein, hence a high risk of pharmacokinetic interactions; (7) Rivaroxaban has the advantage of being an oral treatment that does not require laboratory monitoring. However, it seems best to monitor renal function. It should also be noted that there is no effective antidote if severe bleeding occurs; (8) In practice, for frail elderly patients, who are often polymedicated, it seems more prudent to continue using low-molecular-weight heparin, a drug with which we have more experience.