From the Guidelines
Low molecular weight heparin (LMWH) in acute myocardial infarction (MI) is recommended to be administered subcutaneously, typically twice daily, with the most commonly used LMWH being enoxaparin, administered at a dose of 1 mg/kg subcutaneously every 12 hours. This recommendation is based on the findings of the 2014 AHA/ACC guideline for the management of patients with non-ST-elevation acute coronary syndromes, which suggests that LMWHs have a molecular weight approximately one third that of unfractionated heparin (UFH) and have balanced anti-Xa and anti-IIa activity 1. The ESSENCE trial, which compared enoxaparin with UFH in patients with unstable angina or non-Q-wave MI, found a significant 17% risk reduction in the primary end point of death, MI, or recurrent angina at 14 days with LMWH 1.
The administration of LMWH should take into account the patient's renal function, with a reduced dose of 1 mg/kg once daily recommended for patients with impaired renal function (creatinine clearance <30 mL/min) to prevent bleeding complications 1. The treatment duration typically continues throughout hospitalization and may extend for up to 8 days or until revascularization occurs. Before administration, clinicians should check for contraindications including active bleeding, severe thrombocytopenia, or recent stroke.
Some key points to consider when administering LMWH include:
- The anticoagulant effect works by enhancing antithrombin activity, which inhibits factors Xa and IIa, preventing thrombus extension and recurrent ischemic events following the initial MI.
- LMWH is preferred over unfractionated heparin in many cases because it provides more predictable anticoagulation, requires less monitoring, and carries a lower risk of heparin-induced thrombocytopenia.
- The dose of enoxaparin should be adjusted based on the patient's renal function, with a reduced dose recommended for patients with impaired renal function.
- The treatment duration and dose of LMWH may vary depending on the specific clinical scenario, such as primary percutaneous coronary intervention (PCI) for ST-elevation MI (STEMI).
From the FDA Drug Label
DOSAGE AND ADMINISTRATION Indication Dosing Regimen Unstable angina and non-Q-wave MI 120 units/kg subcutaneous every 12 hours (with aspirin) (2. 1)
The recommended method of administration for low molecular weight heparin (LMWH) in acute myocardial infarction (MI) is subcutaneous injection. The dosing regimen for unstable angina and non-Q-wave MI is 120 units/kg every 12 hours, and it should be administered with aspirin 2.
From the Research
Method of Administration for Low Molecular Weight Heparin (LMWH) in Acute Myocardial Infarction (MI)
The recommended method of administration for LMWH in acute MI is subcutaneous injection.
- Enoxaparin is administered as an initial 30 mg intravenous bolus, followed by 1 mg/kg subcutaneously within 15 minutes and then every 12 hours for up to 8 days 3.
- For patients ≥75 years of age, the initial bolus of enoxaparin is not given, and the 12-hourly dosages are reduced to 0.75 mg/kg 3.
- The dose is also reduced to 1 mg/kg every 24 hours in patients of any age who have an estimated creatinine clearance (CL(CR)) of <30 mL/min 3.
- Alternatively, enoxaparin can be administered as a twice-daily subcutaneous injection 4.
- Other LMWHs, such as dalteparin and reviparin, can also be administered subcutaneously, but the specific dosing regimens may vary 5, 6.
Advantages of Subcutaneous Administration
Subcutaneous administration of LMWH has several advantages, including: