Thromboprophylaxis in Patients Undergoing Orthopedic Surgeries; Comparison Between Rivaroxaban and Enoxaparin

The main objective is to reduce the incidence of venous thromboembolism (VTE) in orthopedic postoperative patients based on the potential benefit of using rivaroxaban as a monotherapy.

It is around efficacy and safety evaluation of using rivaroxaban as a monotherapy prophylactic agent in patients undergoing orthopedic surgeries taking into the account the reliable selection of patients most benefit.

Answering questions about additional cost benefit from the perceptive of the cost-effective analysis on extrapolating the results emerged to our university teaching hospital setting are going to be evaluating as well.

There is a Today consensus that patients undergoing high-risk surgery should receive prophylaxis against postoperative venous thromboembolism (VTE). A good example of that could be orthopedic surgeries which place patients at unnecessary increased risk of fatal pulmonary embolism. For many years, pharmacotherapy options have been recommended by the American College of Chest Physicians (ACCP) for postoperative thromboprophylaxis were low-molecular-weight heparins (LMWHs), fondaparinux, and warfarin. However, their limitations have been repeatedly demonstrated in a huge number of randomized controlled trials (RCTs).

Since its introduction, low-molecular-weight heparins (LMWHs) are still common used in practice as thromboprophylactic agent. But, they require subcutaneous administration which making it challenging for use in settings other than the inpatient one. Despite the lower incidence of low-molecular-weight heparins (LMWHs) induced heparin-induced thrombocytopenia (HIT) compared with unfractionated heparins (UFH) in the postoperative setting, the risk of LMWH induced HIT in patients treated for VTE still concerns many clinicians. In addition to its subcutaneous administration, fondaparinux is contraindicated in severe renal impairment patients (with creatinine clearance (CrCl) \<30 milliliter/minute) and those who have low body weight (\<50 kg; venous thromboembolism prophylaxis only). While available orally, Vitamin K antagonists (VKAs) like Warfarin have unpredictable pharmacologic effects requiring a wakeful monitoring. Warfarin is also a remarkable source of food and drug interactions. As a result, it is mandatory to search for novel drugs or at least to search for new indications of really existing drugs.

In July 2011, the Food and Drug Administration (FDA) approved an orally administered selective factor Xa inhibitor called Rivaroxaban for the prevention of deep vein thrombosis (DVT) after total hip replacement (THR) or total knee replacement (TKR) surgeries. According to the Regulation of Coagulation in Orthopedic Surgery to Prevent Deep Vein Thrombosis and Pulmonary Embolism (RECORD) trials, rivaroxaban demonstrated superiority to enoxaparin in reducing venous thromboembolism without significant increase of bleeding risk. Rivaroxaban is recommended to be used at a fixed dose of 10 mg daily, with or without food, for 35 days following THR or 12 days following TKR.

Although the US Food and Drug Administration (FDA) advisory committee has recommended approval of rivaroxaban, many questions have been raised on the Regulation of Coagulation in Orthopedic Surgery to Prevent Deep Vein Thrombosis and Pulmonary Embolism (RECORD) trials of rivaroxaban. Some may argue that dosing was inconsistent with the recommendations. Others went far to say that the duration of treatment was inconsistent and did vary with enoxaparin. In other words, it was somewhat short.

Results from the ORTHO-TEP registry on joint replacement arthroplasty (hip and knee) from Dresden, Germany and Xarelto® in the Prophylaxis of Postsurgical Venous Thromboembolism after Elective Major Orthopaedic Surgery of the Hip or Knee (XAMOS) study are in accordance with the conclusion of Regulation of Coagulation in Major Orthopedic surgery reducing the Risk of DVT and PE (RECORD) trials. A subset of countries that participated in XAMOS also included patients undergoing fracture-related orthopedic surgery.

Moreover, very few randomized clinical trials (RCTs) are powered to study side effects when comparing substances, and even large RCTs may be too small to reveal rare side effects. It seems difficult to compare safety data from trial to trial because there is no standardized definition of bleeding. One prospective study collecting data from the electronic health record at two institutions concluded that using of enoxaparin for venous thromboembolism prophylaxis following total hip arthroplasty (THA) and total knee arthroplasty (TKA) was associated with a lower rate of the primary outcome (any postoperative bleeding) compared with the use of rivaroxaban in a similar cohort of patients. However, it was a retrospective investigation with many limitations can be argued with regard to selection and change in practice guideline during the study period.

Finally, there is lack of literature data that define rivaroxaban as orthopedic postoperative thromboprophylactic agent rather than well-known indications (hip and knee replacements). It also is not plausible to accurately compare safety data with other injectable anticoagulants.

Eligibility Criteria:
Inclusion Criteria:

1. Undergo Orthopedic Surgery
2. Thromboprophylaxis Decision Taken
3. At least 18 years of age

Exclusion Criteria:

1. Planned intermittent pneumatic compression
2. A requirement for anticoagulant therapy that could not be stopped
3. Severe hypersensitivity reaction (eg, anaphylaxis) to rivaroxaban or enoxaparin.
4. Received another anticoagulant for more than 24 hours
5. Active bleeding or a high risk of bleeding
6. Thrombocytopenia associated with a positive test for antiplatelet antibody.
7. Warfarin associated international normalized ratio (INR) more than 1.5 on the day of the surgery
8. Conditions preventing bilateral venography
9. Intensive care unit (ICU) stay after surgery
10. Pregnant or breast-feeding
11. Creatinine clearance less than 30 ml per minute or acute renal failure before the surgery or at any point during the study period.
12. Moderate or Severe (Child Pugh B or C) hepatic Impairment or in patients with any hepatic disease associated with coagulopathy.
13. Concomitant use of drugs that are both P--glycoprotein inhibitors and moderate to strong cyp3a4 (ketoconazole, itraconazole, lopinavir/ritonavir, ritonavir, indinavir/ritonavir \& conivaptan)
14. Creatinine clearance (CrCl) 15 to 80 mL/min and concurrent use of P-glycoprotein inhibitors or moderate CYP3A4 inhibitors (eg, abiraterone acetate, diltiazem, dronedarone, erythromycin, verapamil)