Low Molecular Weight Heparin (LMWH) Pregnancy: Enoxaparin should be used during pregnancy only if the physician has established a clear need. There is no evidence in humans that enoxaparin crosses the placental barrier during the second and third trimester, and no information is available for the first trimester. Pregnant women should be carefully monitored for bleeding or excessive anticoagulation and warned of the haemorrhagic risk. If epidural anaesthesia is planned, it is recommended to withdraw enoxaparin before. Can be used during breastfeeding.

Enoxaparin (Orthopaedic VTE Prophylaxis)

Brand names: Clexane

Enoxaparin is a low-molecular-weight heparin given subcutaneously for venous thromboembolism (VTE) prophylaxis after major orthopaedic surgery such as hip and knee arthroplasty and hip-fracture repair.

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: 4,000 IU (40 mg) — patients at high risk of thromboembolism, the group that includes major orthopaedic surgery

Route: Subcutaneous injection (enoxaparin must not be administered by the intramuscular route)

Frequency: Once daily, preferably started 12 hours before surgery

For patients who undergo major orthopaedic surgery, an extended thromboprophylaxis of up to 5 weeks is recommended. If preoperative initiation earlier than 12 hours is needed (e.g. a high-risk patient waiting for deferred orthopaedic surgery), the last injection should be administered no later than 12 hours prior to surgery and resumed 12 hours after surgery. Individual thromboembolic risk can be estimated using a validated risk stratification model. Patients at MODERATE risk of thromboembolism: 2,000 IU (20 mg) once daily by subcutaneous injection; preoperative initiation 2 hours before surgery was proven effective and safe in moderate risk surgery, and treatment should be maintained for a minimum period of 7-10 days whatever the recovery status and continued until the patient no longer has significantly reduced mobility. Medical patients: 4,000 IU (40 mg) once daily SC for at least 6 to 14 days (benefit not established beyond 14 days). Doses are expressed in anti-Xa IU with the mg equivalent exactly as stated in the SPC (product basis: 10,000 IU (100 mg)/1 mL pre-filled syringe). Treatment (not prophylaxis) regimens on the same SPC, for reference: DVT and PE - 150 IU/kg (1.5 mg/kg) SC once daily or 100 IU/kg (1 mg/kg) SC twice daily. Elderly: for all indications except STEMI no dose reduction is necessary unless kidney function is impaired. Hepatic impairment: limited data, use with caution. Paediatric: the SPC states the safety and efficacy of enoxaparin sodium in the paediatric population have not been established.

Dose adjustments

Renal

Severe renal impairment (creatinine clearance 15-30 mL/min): VTE prophylaxis dose is 2,000 IU (20 mg) SC once daily (treatment doses are also reduced - see SPC table). Not recommended in end stage renal disease (creatinine clearance below 15 mL/min) due to lack of data, other than for the prevention of thrombus formation in extracorporeal circulation during haemodialysis. No dose adjustment is recommended in moderate (30-50 mL/min) or mild (50-80 mL/min) renal impairment, 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 of the excipients
History of immune mediated heparin-induced thrombocytopenia (HIT) within the past 100 days, or in the presence of circulating antibodies
Active clinically significant bleeding and conditions with a high risk of haemorrhage - including 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 or major intraspinal or intracerebral vascular abnormalities
Spinal or epidural anaesthesia or loco-regional anaesthesia when enoxaparin sodium is used for treatment in the previous 24 hours

Side effects

Haemorrhage, haemorrhagic anaemia, thrombocytopenia, thrombocytosis (common)
Allergic reaction (common); headache (common)
Spinal haematoma / neuraxial haematoma (rare)
Immuno-allergic thrombocytopenia with thrombosis, in some cases complicated by organ infarction or limb ischaemia (rare)
Anaphylactic / anaphylactoid reactions including shock (rare); eosinophilia (rare); acute generalised exanthematous pustulosis (AGEP)

Interactions

(US labelling) Whenever possible, agents which may enhance the risk of haemorrhage should be discontinued prior to initiation of enoxaparin - these include anticoagulants, platelet inhibitors including acetylsalicylic acid, salicylates, NSAIDs (including ketorolac), dipyridamole or sulfinpyrazone; if coadministration is essential, conduct close clinical and laboratory monitoring
Note: the UK SPC section 4.5 was not captured in the retrieved bundle - clinician to check the full interaction section

Clinical monograph

How it works

It binds antithrombin to accelerate inhibition of factor Xa (and, to a lesser extent, thrombin), reducing clot formation in the high-risk post-operative period.

Prescribing in practice

Account for bleeding risk and the timing relative to neuraxial (spinal/epidural) anaesthesia, as the SPC specifies intervals to reduce the risk of spinal haematoma.
Dose requires reduction and increased caution in significant renal impairment because of accumulation; avoid in active major bleeding.
Monitor for heparin-induced thrombocytopenia and avoid in those with a history of immune HIT.

Monitoring

Monitor platelet count, renal function and haemoglobin, with anti-Xa levels reserved for selected patients such as those with renal impairment or extremes of weight.

Counselling the patient

Injections are given just under the skin of the abdomen; rotate sites.
Report unusual bruising, bleeding that will not stop, or blood in urine or stool.
Continue for the full prescribed prophylaxis duration after your operation.

Evidence & guidelines

NICE NG89 recommends extended pharmacological VTE prophylaxis after major orthopaedic surgery, with LMWH a standard option.

Reference: NICE NG89 VTE Prevention; Thrombosis UK Orthopaedic Guidelines; 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.

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