Dabigatran: new drug. Continue to use heparin, a better-known option

Abstract

(1) The standard anticoagulant for preventing thromboembolic events after hip or knee replacement surgery is a subcutaneous low-molecular-weight heparin such as enoxaparin; (2) Dabigatran, a specific thrombin inhibitor, was recently licensed for oral prophylaxis in this setting, as dabigatran etexilate (mesilate), a prodrug; (3) The clinical evaluation of dabigatran in this indication is based on two comparative double-blind trials with similar protocols, comparing dabigatran 150 mg or 220 mg/day versus enoxaparin in 3494 patients undergoing hip replacement surgery and 2101 patients undergoing knee replacement surgery. The results were virtually identical: compared with enoxaparin, dabigatran did not reduce overall mortality (almost zero in the different groups), the frequency of symptomatic pulmonary embolism (almost zero in the different groups), or the frequency of symptomatic deep venous thrombosis (0.1% to 1.2%); (4) There was no difference between the groups with respect to the frequency of severe bleeding (about 1.5%), hepatic disorders (about 4%), or acute coronary events (a few cases). But dabigatran was associated with surgical wound seepage in 7% of patients, versus 4.7% with enoxaparin; (5) The anticoagulant effect of dabigatran, and therefore the frequency of haemorrhage, increases with age and in cases of renal failure. However, clinical trials included relatively few elderly patients and/or patients with renal failure, who nonetheless represent a large proportion of the candidates for hip or knee replacement; (6) Dabigatran becomes more potent when combined with P-glycoprotein inhibitors or with drugs that impair renal function. Combination with other antithrombotic drugs should be avoided. (7) Dabigatran is administered orally, while enoxaparin requires daily subcutaneous injections. Dabigatran therapy does not necessitate laboratory monitoring, while the platelet count must be monitored with enoxaparin. There is no known antidote for dabigatran overdose; (8) In summary, for the prevention of venous thromboembolic events after orthopaedic surgery, it is better to continue to use heparins, at least pending more thorough evaluation of dabigatran.