Enoxaparin Duration in Myocardial Infarction
For patients with STEMI receiving fibrinolytic therapy, enoxaparin should be continued until hospital discharge or for a maximum of 8 days, whichever comes first. 1
STEMI with Fibrinolytic Therapy (Non-Invasive Strategy)
The 2025 ACC/AHA guidelines establish enoxaparin as the preferred anticoagulant over unfractionated heparin in STEMI patients treated with fibrinolytics who are not planned for an invasive approach. 1 The evidence supporting this recommendation comes from the ExTRACT-TIMI 25 study, which demonstrated superior outcomes with enoxaparin:
- Primary endpoint (death or nonfatal MI at 30 days): 9.9% with enoxaparin versus 12.0% with UFH 1
- Net clinical benefit (death, MI complication, or major bleeding): 10% with enoxaparin versus 15% with UFH 1
- Duration: Until hospital discharge or maximum 8 days, whichever comes first 1
Dosing Considerations
Age-adjusted dosing is mandatory to minimize bleeding risk, particularly intracranial hemorrhage in elderly patients: 2
- Patients <75 years: 30 mg IV bolus, then 1 mg/kg subcutaneously every 12 hours (maximum 100 mg for first two doses) 1, 3
- Patients ≥75 years: No IV bolus; 0.75 mg/kg subcutaneously every 12 hours (maximum 75 mg for first two doses) 2, 3
- Renal impairment (CrCl <30 mL/min): 1 mg/kg every 24 hours 3
NSTE-ACS (Unstable Angina/NSTEMI)
Conservative Strategy (No Angiography)
For NSTE-ACS patients managed conservatively without angiography, enoxaparin should be continued for the duration of hospitalization, up to 8 days, then discontinued. 1
Medical Management After Angiography
For patients who undergo angiography but are managed medically (no revascularization), enoxaparin should be continued for the duration of hospitalization, up to 8 days, if it was started before diagnostic angiography. 1
Before CABG
Enoxaparin must be discontinued 12 to 24 hours before CABG surgery, with transition to UFH per institutional practice. 1
STEMI with Primary PCI
For STEMI patients undergoing primary PCI, the 2025 guidelines support intravenous enoxaparin as an alternative to UFH, though specific duration recommendations focus on the periprocedural period rather than extended therapy. 1 The ATOLL trial demonstrated that enoxaparin reduced 30-day death, recurrent ACS, or urgent revascularization (7% versus 11% with UFH). 1
Critical Pitfalls to Avoid
Do not continue enoxaparin beyond 8 days in the acute setting, as this was the maximum duration studied in pivotal trials and is associated with increased bleeding risk without additional benefit. 1, 3
Do not use standard dosing in elderly patients (≥75 years) without eliminating the IV bolus and reducing subcutaneous doses, as this significantly increases intracranial hemorrhage risk. 2, 3
Do not continue enoxaparin if the patient transitions to an invasive strategy requiring CABG without appropriate discontinuation timing (12-24 hours pre-procedure). 1
Bleeding Risk Trade-off
Major bleeding increases with enoxaparin compared to UFH (2.1% versus 1.4%), but the net clinical benefit favors enoxaparin due to superior reduction in death and MI. 1, 2 The number needed to treat for net clinical benefit is 20, while the number needed to harm for major bleeding is 143. 2