Low Molecular Weight Heparin
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More Specific Terms
Introduction
Indications
- treatment of uncomplicated DVT
- prophylaxis against thrombosis after total knee or hip replacement in patients who did not receive spinal anesthesia Advantages over heparin:
- long 1/2 life
- more predictable anticoagulant effect
- less thrombocytopenia
- no need to monitor aPTT
- Disadvantages: expensive
Contraindications
- recent spinal or epidural anesthesia
- morbid obesity
- hypersensitivity to heparin or porcine proteins
- history of heparin-induced thrombocytopenia
- GI disease/ bleed within 2 weeks
- high-dose NSAID therapy
- current CNS insult ( stroke, spinal cord injury, neurosurgery)
- renal failure, creatinine clearance < 20 mL/min
Dosage
- QD or BID dosing
- overlap with warfarin therapy, discontinue when INR is therapeutic for 2 consecutive days
- discontinue for 12 hours prior to surgery [6] Protocol: (prior to starting LMW heparin)
- laboratory
- complete blood count ( platelets)
- PT/ aPTT
- history of hemorrhage
Pharmacokinetics
- bioavailability is 90% following SC administration
- different preparations have different activity & different 1/2life
- elimination is prolonged with renal insufficiency
Monitor
- NOT necessary in non- pregnant patients
- anti- factor Xa activity
- most LMW heparins do not prolong aPTT [4] Adverse reactions:
- major & minor bleeding
- fever
- pain
- necrosis at the site of injection
- elevation in serum transaminases
- thrombocytopenia (less than heparin)
- nausea
- peripheral edema
- confusion
Drug-interactions
- high dose NSAIDs or glucocorticoids
- in combination with spinal anesthesia associated with:
- spinal hematoma
- neurologic injury
- permanent paralysis
Mechanism-of-action
- binds to antithrombin III ( AT3) accelerating the rate AT3 neutralizes activated clotting factors
- has higher anti factor Xa/anti factor IIa than does heparin
- may diminish mortality in cancer patients, possibly via inhibition of angiogenesis [4]
- * see dalteparin for comparison of different LMW heparins.
More General Terms
Additional Terms
Internet Database
PubChem: 772
References
- Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998 - not on National VA formulary
- Kaiser Permanente Northern California Regional Drug Formulary, 1998
- Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
- Journal Watch 25(10):84, 2005 Klerk CP, Smorenburg SM, Otten HM, Lensing AW, Prins MH, Piovella F, Prandoni P, Bos MM, Richel DJ, van Tienhoven G, Buller HR. The effect of low molecular weight heparin on survival in patients with advanced malignancy. J Clin Oncol. 2005 Apr 1;23(10):2130-5. Epub 2005 Feb 7. PMID: [1]
- Lee AY, Rickles FR, Julian JA, Gent M, Baker RI, Bowden C, Kakkar AK, Prins M, Levine MN. Randomized comparison of low molecular weight heparin and coumarin derivatives on the survival of patients with cancer and venous thromboembolism. J Clin Oncol. 2005 Apr 1;23(10):2123-9. Epub 2005 Feb 7. PMID: [2] - UpToDate 14.1 [3]
- O'Donnell MJ, Kearon C, Johnson J, Robinson M, Zondag M, Turpie I, Turpie AG. Brief communication: Preoperative anticoagulant activity after bridging low-molecular-weight heparin for temporary interruption of warfarin. Ann Intern Med. 2007 Feb 6;146(3):184-7. PMID: [4]
