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Low Molecular Wt Heparins / Enoxaparin (Lovenox)

- Discussion: 
    - for treatment of DVT / PE;
    - hypercoagulable states
    - coagulation pathway 
    - anti-Xa to anti IIa ratio for enoxaparin is about 3 to 1 where as unfractionated heparin  has a ratio of 1 to 1;
            - hence LMWH has a greater inhibitory effect on factor Xa and has a lesser effect on thrombin; 
            - in contrast, arixtra inhibits anti-thrombin;  
    - labs:

            - because LMWH have minimal effect on thrombin, there is minimal elevation of the PTT
    - prophylactic dosage:
            - subcutaneous enoxaparin 40 mg SQ q24hrs or 30 mg every 12 hours;
            - onset of activity occurs after about 3 hours;
            - it is advised to delay administration of Lovenox for 12-24 hours following surgery;
            - renal excretion is the main route of removal, and therefore dose reduction is required w/ significant renal dysfunciton; 
    - DVT treatment dosage: (lovenox dosage calculator)
            - 1 mg/kg q12 hour with normal renal function;
            - DVT treatment

- Outcomes:
    - in a THR study by Colwell et al (1999), the overall rate of throboembolic disease was 3.6% for patients receiving lovenox versus 3.7 % for
           patients receiving adjusted dose coumadin;
           - rate of clinically significant bleeding was 0.9%;
           - lovenox was continued only for the length of the hospitalization which averaged about 7 days;
    - Breddin, et al. 2001:
           - SQ administration of a low-molecular-weight heparin, reviparin, twice a day for one week, or SQ administration of reviparin once a day for 4 weeks. 
           - of the patients receiving unfractionated heparin, 40.2 percent (129 of 321) had thrombus regression, as compared with 53.4 percent (175 of 328) of the patients
                   receiving reviparin twice daily and 53.5 % (167 of 312) of the patients receiving reviparin once daily; 
           - in acute deep-vein thrombosis, reviparin regimens are more effective than unfractionated heparin in reducing the size of the thrombus;
           - reviparin is also more effective than unfractionated heparin for the prevention of recurrent thromboembolism and equally safe;
           - references:
                   - Effects of a Low-Molecular-Weight Heparin on Thrombus Regression and Recurrent Thromboembolism in Patients with Deep-Vein Thrombosis
                   - A Randomized Controlled Trial of a Low-Molecular-Weight Heparin (Enoxaparin) to Prevent Deep-Vein Thrombosis in Patients Undergoing Elective Hip Surgery
                   - Failure of the American College of Chest Physicians-1A protocol for lovenox in clinical outcomes for thromboembolic prophylaxis.
                   - Comparison of Enoxaparin and Warfarin for the Prevention of Venous Thromboembolic Disease After Total Hip Arthroplasty. Evaluation During Hospitalization and Three Months After Discharge 

- Complications:
     - heparin induced thrombocytopenia 
             - thrombocytopenia and platlet dysfunction seems to occur less often than w/ unfractionated herapin; 
                    - Thrombocytopenia and Intra-cerebral Complications Associated with Low-Molecular-Weight Heparin Treatment in Patients Undergoing Total Hip Replacement. A Report of Two Cases. 

 Low-molecular-weight heparin compared with warfarin for prophylaxis of deep-vein thrombosis in patients who are operated on for fracture of the hip. A prospective, randomized trial.

Prevention of deep-vein thrombosis and pulmonary embolism after total hip replacement. Comparison of low-molecular-weight heparin and unfractionated heparin.

Prevention of deep-vein thrombosis after elective hip surgery. A randomized trial comparing low molecular weight heparin with standard heparin.

Dihydroergotamine/heparin in the prevention of deep vein thrombosis after total hip replacement. A controlled, prospective, randomized multicenter trial

The thromboprophylactic effect of a low-molecular-weight heparin (Fragmin) in hip fracture surgery. A placebo-controlled study.

Benefit-to-harm ratio of thromboprophylaxis for patients undergoing major orthopaedic surgery. A systematic review.

Patient-reported treatment satisfaction with oral rivaroxaban versus standard therapy in the treatment of acute symptomatic deep-vein thrombosis.

Incidence of neuraxial haematoma after total hip or knee surgery: RECORD programme (rivaroxaban vs. enoxaparin).

Elective hip and knee arthroplasty and the effect of rivaroxaban and enoxaparin thromboprophylaxis on wound healing.

Concomitant use of medication with antiplatelet effects in patients receiving either rivaroxaban or enoxaparin after total hip or knee arthroplasty.

Cost-effectiveness of rivaroxaban in the prevention of venous thromboembolism: a Canadian analysis using the Ontario Ministry of Health Perspective.

Cost and outcomes associated with rivaroxaban vs enoxaparin for the prevention of postsurgical venous thromboembolism from a US payer's perspective.

Oral rivaroxaban for symptomatic venous thromboembolism.

Oral rivaroxaban for the prevention of symptomatic venous thromboembolism after elective hip and knee replacement.