Anticoagulant

Enoxaparin (Lovenox)

Also called Lovenox, LMWH

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

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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

Daily ICU prophylaxisICU Bundles: VTE and stress ulcer prophylaxis, head of bed, glucose

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

Safety

Boxed warning: spinal or epidural hematoma with neuraxial procedures; place or remove catheters at least 12 h after low doses or 24 h after high doses, and wait at least 4 h before the next dose
Bleeding, highest with CrCl under 30, low weight and old age; check anti-Xa 4 h after a dose (twice-daily target about 0.5–1.0 IU/mL) in kidney failure, obesity or pregnancy
HIT is rarer, but most HIT antibodies cross-react: contraindicated within 100 days of HIT or with circulating antibodies
Partial reversal: protamine 1 mg per mg within 8 h (0.5 mg per mg after 8 h) neutralizes all anti-IIa but at most about 60% of anti-Xa
ACS: do not switch between enoxaparin and heparin (SYNERGY: more bleeding)
Mechanical valves in pregnancy: valve thrombosis reported; use preservative-free syringes in pregnancy

In the one-pagers

Practice Bleeding, Reversal, HIT and DIC questions free34 exam-style questions with rationales on the topic where Enoxaparin comes up most. No account or download needed.

In the algorithms

Massive Pulmonary Embolism

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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 the order, the label and your institution's protocols.