Low Molecular Weight Heparin Pregnancy: In humans there is no evidence that enoxaparin crosses the placental barrier during the second and third trimesters; no information is available for the first trimester. Animal studies show no foetotoxicity or teratogenicity. Use during pregnancy only if the physician has established a clear need; monitor carefully for bleeding or excessive anticoagulation and warn of the haemorrhagic risk. Withdraw before planned epidural anaesthesia. Can be used during breastfeeding.

Enoxaparin (Vascular)

Brand names: Clexane

This is enoxaparin, a low-molecular-weight heparin given subcutaneously for prophylaxis and treatment of venous thromboembolism and in acute coronary syndromes within the vascular setting.

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 — high thromboembolic risk surgical patients and medical patients: 4,000 IU (40 mg) once daily by subcutaneous injection; moderate risk surgical patients: 2,000 IU (20 mg) once daily SC. Treatment of DVT and PE: 150 IU/kg (1.5 mg/kg) SC once daily, OR 100 IU/kg (1 mg/kg) SC twice daily

Route: Deep subcutaneous injection (must NOT be given by the intramuscular route). IV bolus only for acute STEMI initiation and for the additional PCI bolus; arterial line of the dialysis circuit for haemodialysis

Frequency: Once daily for prophylaxis and for the 150 IU/kg (1.5 mg/kg) treatment regimen; every 12 hours for the 100 IU/kg (1 mg/kg) treatment regimen

Max: Stated for acute STEMI only: maximum 10,000 IU (100 mg) for each of the first two SC doses (maximum 7,500 IU / 75 mg for each of the first two SC doses in patients aged 75 years and over). No maximum is stated for the prophylaxis or DVT/PE treatment regimens.

Regimen choice for DVT/PE is made by the physician on individual assessment: 150 IU/kg (1.5 mg/kg) once daily in uncomplicated patients at low risk of VTE recurrence; 100 IU/kg (1 mg/kg) twice daily in all other patients (obesity, symptomatic PE, cancer, recurrent VTE, proximal/vena iliaca thrombosis). Duration — moderate-risk surgery: minimum 7-10 days and until the patient no longer has significantly reduced mobility; high-risk surgery: preferably started 12 hours before surgery, extended prophylaxis up to 5 weeks after major orthopaedic surgery and up to 4 weeks after abdominal or pelvic cancer surgery; medical patients: at least 6-14 days (benefit not established beyond 14 days); DVT/PE treatment: average 10 days, with oral anticoagulant started when appropriate. Pre-operative initiation 2 hours before surgery applies to the 2,000 IU (20 mg) moderate-risk regimen; if prophylaxis must start earlier than 12 hours pre-op, the last injection should be no later than 12 hours before surgery and resumed 12 hours after. Extended treatment of DVT/PE in active cancer: 100 IU/kg (1 mg/kg) SC twice daily for 5-10 days, then 150 IU/kg (1.5 mg/kg) SC once daily up to 6 months; reassess after 6 months. Haemodialysis (prevention of thrombus formation in the extracorporeal circuit): 100 IU/kg (1 mg/kg) into the arterial line at the start of the session (reduce to 50 IU/kg (0.5 mg/kg) for double vascular access or 75 IU/kg (0.75 mg/kg) for single vascular access if high haemorrhage risk); a further 50-100 IU/kg (0.5-1 mg/kg) may be given if fibrin rings are found. Unstable angina/NSTEMI: 100 IU/kg (1 mg/kg) every 12 hours SC with antiplatelet therapy, minimum 2 days, usually 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 for 8 days or until discharge; in patients 75 years and over no initial IV bolus — start 75 IU/kg (0.75 mg/kg) SC every 12 hours. PCI: if the last SC dose was more than 8 hours before balloon inflation, give an IV bolus of 30 IU/kg (0.3 mg/kg). Neuraxial anaesthesia/lumbar puncture: at prophylactic doses keep a puncture-free interval of at least 12 hours before needle/catheter placement or catheter removal (at least 24 hours if CrCl 15-30 mL/min); at treatment doses at least 24 hours (at least 48 hours if CrCl 15-30 mL/min); the 2-hour pre-operative 2,000 IU (20 mg) initiation is not compatible with neuraxial anaesthesia; do not restart until at least 4 hours after puncture or catheter removal. Enoxaparin cannot be used interchangeably (unit for unit) with other LMWHs. Paediatric: safety and efficacy have not been established. Source is the AROVI 10,000 IU (100 mg/1 mL) SPC (eMC product 9329); §4.4 and §4.8 were truncated at source fetch, so the warnings/adverse coverage below is partial, and eMC §4.5 was not retrieved.

Dose adjustments

Renal

Not recommended in end-stage renal disease (creatinine clearance <15 mL/min) other than for prevention of thrombus formation during haemodialysis. Severe renal impairment (CrCl 15-30 mL/min): VTE prophylaxis 2,000 IU (20 mg) SC once daily; treatment of DVT/PE, extended treatment in active cancer, and unstable angina/NSTEMI all 100 IU/kg (1 mg/kg) SC once daily; acute STEMI under 75 years 3,000 IU (30 mg) IV bolus plus 100 IU/kg (1 mg/kg) SC then 100 IU/kg (1 mg/kg) SC every 24 hours; acute STEMI over 75 years no IV bolus, 100 IU/kg (1 mg/kg) SC then 100 IU/kg (1 mg/kg) SC every 24 hours. These adjustments do not apply to the haemodialysis indication. Moderate (CrCl 30-50 mL/min) and mild (50-80 mL/min) impairment: no dose adjustment recommended, but careful clinical monitoring is advised.

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.

Contraindications

Hypersensitivity to enoxaparin sodium, heparin or its derivatives, including other low molecular weight heparins, or to 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 — recent haemorrhagic stroke, gastrointestinal ulcer, malignant neoplasm at high risk of bleeding, recent brain, spinal or ophthalmic surgery, known or suspected oesophageal varices, arteriovenous malformations, vascular aneurysms, major intraspinal or intracerebral vascular abnormalities
Spinal or epidural anaesthesia or loco-regional anaesthesia when enoxaparin has been used at treatment doses in the previous 24 hours

Side effects

Haemorrhage and haemorrhagic anaemia (common)
Thrombocytopenia and thrombocytosis (common); rare immuno-allergic thrombocytopenia with thrombosis, sometimes complicated by organ infarction or limb ischaemia
Allergic reaction (common); anaphylactic/anaphylactoid reactions including shock (rare)
Headache (common)
Spinal (neuraxial) haematoma (rare); acute generalised exanthematous pustulosis has been reported

Interactions

Agents that may enhance the risk of haemorrhage should where possible be discontinued before starting enoxaparin — anticoagulants, platelet inhibitors including acetylsalicylic acid, salicylates, NSAIDs (including ketorolac), dipyridamole, sulfinpyrazone; if coadministration is essential, conduct close clinical and laboratory monitoring [taken from the US label §7 — the UK SPC §4.5 was not retrieved in this bundle]
Switching to/from vitamin K antagonists — intensify INR monitoring; continue enoxaparin at a constant dose until the INR is in range on two successive tests; when switching from a VKA, give the first enoxaparin dose once the INR has dropped below the therapeutic range (§4.2)
Switching to/from direct oral anticoagulants — start the DOAC 0 to 2 hours before the next scheduled enoxaparin dose would be due; when switching from a DOAC, give the first enoxaparin dose at the time the next DOAC dose would be taken (§4.2)

Clinical monograph

How it works

It binds antithrombin to inhibit factor Xa more than thrombin, producing predictable anticoagulation that reduces venous and arterial thrombus formation.

Prescribing in practice

It accumulates in renal impairment, so dose reduction and consideration of anti-Xa monitoring are needed when renal function is significantly reduced to limit bleeding.
Heparin-induced thrombocytopenia can occur, so platelet counts should be checked during prolonged treatment and enoxaparin stopped if it develops.
Spinal or epidural haematoma is a risk with neuraxial anaesthesia, requiring careful timing around procedures.

Monitoring

Routine coagulation monitoring is unnecessary, but check platelets in extended use and use anti-Xa levels to guide dosing in renal impairment, pregnancy or extremes of body weight.

Counselling the patient

It is injected under the skin; rotate sites and do not expel the small air bubble in pre-filled syringes.
Report unusual bruising or bleeding.
Keep to the prescribed dose and timing, especially around any planned procedure.

Evidence & guidelines

Trials across venous thromboembolism prophylaxis, treatment and acute coronary syndromes established enoxaparin's efficacy and predictable dosing, underpinning wide UK use.

Reference: BCSH guidelines; NICE NG158; 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

Tinzaparin sodium · Low molecular weight heparin

Pathways