Low Molecular Weight Heparin (LMWH) Pregnancy: No evidence enoxaparin crosses the placenta in the second and third trimesters (no first-trimester information); use during pregnancy only if a clear need is established, with careful monitoring for bleeding. Can be used during breastfeeding.

Enoxaparin

Brand names: Clexane

Enoxaparin is a low-molecular-weight heparin given by subcutaneous injection for the prevention and treatment of venous thromboembolism and in acute coronary syndromes.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: VTE prophylaxis: 2,000 IU (20 mg) once daily (moderate risk) or 4,000 IU (40 mg) once daily (high risk / medical patients); DVT/PE treatment: 150 IU/kg (1.5 mg/kg) once daily OR 100 IU/kg (1 mg/kg) twice daily

Route: Subcutaneous injection (intravenous bolus component in acute STEMI)

Frequency: Once or twice daily depending on indication

Enoxaparin cannot be used interchangeably (unit for unit) with other LMWHs. Surgical VTE prophylaxis: moderate risk 2,000 IU (20 mg) once daily (first dose 2 hours pre-op), minimum 7-10 days; high risk 4,000 IU (40 mg) once daily started preferably 12 hours pre-op; extended prophylaxis up to 5 weeks after major orthopaedic surgery and up to 4 weeks after abdominal/pelvic cancer surgery. Medical VTE prophylaxis: 4,000 IU (40 mg) once daily for 6-14 days. DVT/PE treatment: 150 IU/kg (1.5 mg/kg) once daily in uncomplicated low-recurrence-risk patients, or 100 IU/kg (1 mg/kg) twice daily in others (obesity, symptomatic PE, cancer, recurrent VTE, proximal thrombosis), average 10 days. Active-cancer extended treatment: 100 IU/kg (1 mg/kg) twice daily for 5-10 days then 150 IU/kg (1.5 mg/kg) once daily up to 6 months. Unstable angina/NSTEMI: 100 IU/kg (1 mg/kg) every 12 hours with antiplatelet therapy, usual duration 2-8 days. Acute STEMI: single IV bolus 3,000 IU (30 mg) plus 100 IU/kg (1 mg/kg) SC, then 100 IU/kg (1 mg/kg) SC every 12 hours (max 10,000 IU / 100 mg for each of the first two SC doses); in patients >=75 years no IV bolus and start 75 IU/kg (0.75 mg/kg) SC every 12 hours (max 7,500 IU for first two doses). Haemodialysis: 100 IU/kg (1 mg/kg) into the arterial line. Safety and efficacy in paediatric population not established.

Dose adjustments

Renal

Source (eMC excerpt) notes dose reduction is required where kidney function is impaired (see elderly guidance for STEMI); specific severe renal impairment table truncated in source — clinician to confirm against full SPC.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

See full prescribing information for dosing and administration information. ( 2 ) 2.1 Pretreatment Evaluation Evaluate all patients for a bleeding disorder before starting enoxaparin sodium treatment, unless treatment is urgently needed. 2.2 Adult Dosage Abdominal Surgery The recommended dose of enoxaparin sodium is 40 mg by subcutaneous injection once a day (with the initial dose given 2 hours prior to surgery) in patients undergoing abdominal surgery who are at risk for thromboembolic complications. The usual duration of administration is 7 to 10 days [see Clinical Studies (14.1) ]. Hip or Knee Replacement Surgery The recommended dose of enoxaparin sodium is 30 mg every 12 hours …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2024-06-21. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Hypersensitivity to enoxaparin sodium, heparin or its derivatives, including other LMWHs, or any excipient
History of immune-mediated heparin-induced thrombocytopenia (HIT) within the past 100 days or presence of circulating antibodies
Active clinically significant bleeding and conditions with a high risk of haemorrhage (e.g. recent haemorrhagic stroke, GI ulcer, recent brain/spinal/ophthalmic surgery, known or suspected oesophageal varices, arteriovenous malformations, vascular aneurysms)
Spinal or epidural anaesthesia or loco-regional anaesthesia when enoxaparin is used for treatment in the previous 24 hours

Side effects

Haemorrhage; haemorrhagic anaemia
Thrombocytopenia; thrombocytosis
Allergic reaction
Headache
Spinal/neuraxial haematoma (rare); immuno-allergic thrombocytopenia with thrombosis (rare)

Interactions

Anticoagulants, platelet inhibitors including acetylsalicylic acid, salicylates, NSAIDs, dipyridamole, sulfinpyrazone: increased risk of haemorrhage; discontinue if possible before starting or conduct close monitoring
Neuraxial anaesthesia/spinal puncture with concomitant drugs affecting haemostasis (e.g. NSAIDs): increased risk of spinal/epidural haematoma

Clinical monograph

How it works

It potentiates antithrombin, mainly inhibiting factor Xa (with relatively less effect on thrombin than unfractionated heparin).

Prescribing in practice

Doses are by indication and body weight; reduce in renal impairment, as it is renally cleared.
Consider anti-Xa monitoring at extremes of body weight, in significant renal impairment, and in pregnancy.
Observe timing windows around neuraxial anaesthesia/procedures, and be alert to heparin-induced thrombocytopenia.

Monitoring

Monitor platelets (for heparin-induced thrombocytopenia) and renal function; check anti-Xa levels in selected patients.

Counselling the patient

It is given as an injection under the skin; rotate injection sites.
Some bruising at the site is common; report unusual or heavy bleeding.

Evidence & guidelines

LMWH is standard for VTE prophylaxis and treatment and in ACS, per NICE guidance, with renal dose adjustment.

Reference: NICE NG158; RCOG GTG 37a; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Pathways

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Featured in these MRCEM clinical pathways

Enoxaparin is a core drug in the following exam-focused workups on our sister siteReviseMRCEM.

MRCEM Primary / Intermediate / OSCE candidates: each pathway includes exam-style questions, RCEM/NICE citations, and FAQ summaries.