Anticoagulant
Enoxaparin (Lovenox)
Also called Lovenox, LMWH
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Heparin vs Warfarin: aPTT vs INR, HIT, Bridging, Antidotes and DOAC Reversal
Indications
- VTE prophylaxis after abdominal, hip or knee surgery and in immobile medical patients
- Treatment of acute DVT with or without PE
- Unstable angina and NSTEMI; STEMI, managed medically or with PCI
- VTE prophylaxis after major trauma (off-label)
- Bridging while warfarin is interrupted (off-label)
Dosing
| Where | Dose |
|---|---|
| Daily ICU prophylaxis | Enoxaparin: 40 mg SC daily; 30 mg daily if CrCl under 30; trauma often 30 mg every 12 h; BMI 40 or more often 40 mg every 12 h |
| Other ICU drugs | Enoxaparin: CrCl under 30: 1 mg/kg once daily (treatment), 30 mg daily (prophylaxis); heparin preferred in severe AKI or dialysis |
On the quick cards
Mechanism of action
Enoxaparin is heparin cut into shorter chains that still carry the antithrombin-binding pentasaccharide. Binding changes antithrombin's shape so it inhibits factor Xa quickly, but only chains of 18 or more saccharides (25–50% of LMWH chains) can bridge antithrombin to thrombin. Activity is therefore mostly anti-Xa: about 3.6:1 anti-Xa to anti-IIa in vitro (EU SmPC), 14:1 by in vivo activity curves (US label), against 1:1 for heparin.
Pharmacology
- Hematologic: acts mainly by blocking thrombin generation at Xa rather than thrombin itself; the aPTT barely moves, so it cannot guide dosing
- Hematologic: binds plasma proteins, endothelium and PF4 less than heparin, so the weight-based response is predictable and HIT rarer (0.2% vs 2.6% on prophylaxis)
- Other: hyperkalemia in prone patients; osteoporosis with long use, less than with heparin; asymptomatic AST and ALT rises in about 6%
Pharmacokinetics
| Onset and peak | IV bolus acts at once; SC anti-Xa peaks at 3–5 h |
|---|---|
| Half-life | 4.5 h after one dose, about 7 h with repeated doses |
| Bioavailability | About 100% SC |
| Distribution | Vd about 4.3 L (plasma volume); little or no placental transfer in humans |
| Metabolism | Liver desulfation and depolymerization to weaker fragments |
| Elimination | Urine: 40% of a dose as fragments, 10% still active |
| Organ failure | CrCl under 30 raises anti-Xa exposure about 65%, so doses are reduced; heparin is preferred in severe AKI or dialysis |
| Body size | Fixed doses give 52% more exposure in women under 45 kg, 27% more in men under 57 kg |
| Routes | Deep SC in the abdomen (keep the air bubble, do not rub); IV in ACS and PCI |
Chemistry
- Made by alkaline depolymerization (β-elimination) of the benzyl ester of porcine intestinal heparin; contraindicated in pork allergy
- Mean MW about 4,500 Da (about 15 saccharides); at least 68% of chains are 2,000–8,000 Da
- Chains end in an unsaturated uronic acid, and 15–25% carry a 1,6-anhydro ring; short chains carry too little charge for protamine to neutralize fully
- Dosed in mg (1 mg is about 100 anti-Xa IU): preservative-free syringes of 100 or 150 mg/mL and a multidose vial with benzyl alcohol; not interchangeable with other heparins
Adverse effects and cautions
In the one-pagers
- Pulmonary EmbolismAnticoagulation: LMWH over UFH in C1 to E1 (AHA/ACC 2026, Class 1; 2a if a procedure is likely): enoxaparin 1 mg/kg every 12 h
- ACS and STEMIInitial medications: Heparin (UFH): PCI: 70-100 units/kg to ACT; lytic: 60 units/kg (max 4,000): Or bivalirudin, enoxaparin
- Obstetric EmergenciesSepsis and venous thromboembolism: Treat with LMWH (enoxaparin 1 mg/kg every 12 h) or UFH; warfarin and DOACs are avoided (PB 196), and UFH is often substituted near term. Neuraxial block waits 12 h after prophylactic and 24 h after therapeutic LMWH, which restarts 12 or 24 h after the puncture and 4 h after catheter removal (SOAP, ASRA). Thrombolysis for massive PE gave 94% survival, but major bl
- Spinal Motion RestrictionDaily care, VTE and troubleshooting: Series without adequate prophylaxis report thromboembolism in 7–100% of patients, mostly within 3 months. AANS/CNS 2013 recommends prophylaxis for severe motor deficits (Level I) with LMWH, rotating beds or a combination, not low-dose heparin alone, started within 72 hours and continued 3 months (Level II); filters only when anticoagulation fails or is impossib
- Trauma: Primary and Secondary SurveyICU phase: tertiary survey, missed injuries and late complications: Enoxaparin beat heparin after major trauma (DVT 31% vs 44%; Geerts 1996); many centers weight-adjust it toward an anti-Xa of 0.2–0.4 IU/mL (AAST 2021). After operative extremity or any pelvic fracture, aspirin 81 mg twice daily was noninferior for 90-day death (0.78% vs 0.73%) with more DVT (2.51% vs 1.71%; PREVENT CLOT 2023).
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Sources
- FDA label: Lovenox (2025)
- EU SmPC: enoxaparin
- Garcia, ACCP Parenteral Anticoagulants (Chest 2012)
- ASRA antithrombotic guideline (2025)
For education and exam preparation only. Follow your institution’s protocols. Typical adult values for study. Follow your local protocols and medical direction.