Dabigatran etexilate for the prophylaxis of venous thromboembolism after hip or knee replacement rationale for dose regimen

A 12 month review of a modified protocol using low dose Dabigatran Etexilate in postoperative thromboembolic prophylaxis in joint replacement surgery

Background

Venous Thrombo-embolic disease is currently a hot topic especially in the UK. 25,000 patients per year die of Pulmonary Emboli (PE) in the United Kingdom (UK). Hip and knee arthroplasty surgery is associated with an increased rate of deep vein thrombosis (DVT) and pulmonary embolus (PE). The National Institute for Clinical Excellence (NICE) guidelines introduced in January 2010 recommended use of subcutaneous heparin or an oral anticoagulant (Dabigatran or Rivaroxiban) for 10-14 days post knee and 28-35 days post hip arthroplasty. In our unit we were keen on the advantages of an oral anticoagulant post arthroplasty in terms of patient compliance, and avoiding the need for self administered injection in the community.

Methods

We analysed all the notes, blood results and imaging of patients undergoing total hip or knee arthroplasty and present 1 year’s data using a regime of subcutaneous Dalteparin whilst an inpatient, followed by discharge on oral Dabigatran at a low dose (150 mg once daily).

Results

There were 337 patients over 1 year with hip and knee arthroplasty, with a 1.19% rate of DVT with no PEs and 1 death due to an unrelated cause. There was a transfusion rate of 11.57% with 1.19% patients taken back to theatre for evacuation of haematomas. There were no reported adverse effects of Dabigatran.

Conclusion

Our treatment protocol is a novel practical approach for VTE prophylaxis in hip and knee replacement patients. This approach shows promising data but no definitive evidence to warrant wide-spread use of this new regime. This data can act as a foundation for larger randomised clinical trials.

Preoperative versus postoperative initiation of thromboprophylaxis following major orthopedic surgery: safety and efficacy of postoperative administration supported by recent trials of new oral anticoagulants

In European countries, low-molecular-weight heparin is generally initiated preoperatively for thromboprophylaxis in hip or knee replacement surgery. The objective of this review is to compare pre- and postoperative thromboprophylaxis strategies using available evidence, and discuss the challenges and issues that arise. Surgery is the first step in the process of thrombus formation, but thrombosis is not an instant process and the formation and growth of the thrombus can take several days or weeks. Hence, it may be possible to stop this process if thromboprophylaxis is initiated after surgery. Meta-analyses or systematic reviews comparing pre- and postoperative initiation of therapy have found no consistent differences in efficacy and similar safety (bleeding rates) between the two strategies. The recently available oral anticoagulant dabigatran etexilate provides thromboprophylaxis when administered postoperatively and is as safe as preoperative enoxaparin. Further support for the use of postoperative oral thromboprophylaxis in hip or knee replacement surgery has been provided by the phase III clinical trials of rivaroxaban and apixaban versus preoperative enoxaparin. Postoperative thromboprophylaxis offers the opportunity to change management practices in Europe. As postoperative initiation may have a clinical benefit in some settings (e.g. for neuraxial anesthesia) and practical advantages (e.g. allowing same-day admission), it is a worthwhile thromboprophylactic strategy for hip or knee replacement surgery.

Pharmacology, pharmacokinetics, and pharmacodynamics of dabigatran etexilate, an oral direct thrombin inhibitor

Dabigatran etexilate is a novel, oral reversible direct thrombin inhibitor that is rapidly absorbed and converted to its active form, dabigatran. Dabigatran has been shown to be a potent, competitive, and reversible inhibitor of thrombin, inhibiting both thrombin activity and generation. Studies in healthy volunteers and in patients undergoing orthopedic surgery indicate that dabigatran has a predictable pharmacokinetic profile, allowing for a fixed-dose regimen without the need for coagulation monitoring. In healthy volunteers, peak plasma concentrations of dabigatran are reached approximately 2 hours after oral administration. The elimination half-life is 12 to 14 hours, with clearance predominantly occurring via renal excretion of unchanged drug. Dabigatran is not metabolized by cytochrome P450 isoenzymes, has no interactions with food, and also has a low potential for drug-drug interactions. The pharmacokinetic profile of dabigatran is consistent across a broad range of different patient populations and is unaffected by gender, body weight, ethnic origin, obesity, and mild-to-moderate hepatic impairment. Small differences in dabigatran pharmacokinetics associated with age are attributable to variation in renal function. Dabigatran etexilate produces a predictable pharmacodynamic effect and requires no coagulation monitoring. It has been approved in the European Union (EU) and Canada for prophylaxis of thromboembolism in patients undergoing total knee or hip arthroplasty. Ongoing clinical trials are investigating its use in the treatment of venous thromboembolism, prevention of stroke in patients with nonvalvular atrial fibrillation, and treatment of thromboembolic complications, following acute coronary syndromes.