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Drug Reference

enoxaparin

low molecular weight heparin· Brands: Lovenox, ClexaneIVSC

Mechanism of action
Enoxaparin is a low molecular weight heparin that binds to antithrombin III, enhancing its ability to inactivate clotting factors. It primarily potentiates the inhibition of factor Xa and, to a lesser extent, thrombin (factor IIa). This action prevents thrombus formation and extension, with a higher anti-Xa to anti-IIa ratio than unfractionated heparin.
Pharmacokinetics
Following subcutaneous administration, enoxaparin is well absorbed with near-complete bioavailability. Peak anti-factor Xa activity occurs 3 to 5 hours after injection. It is metabolised in the liver and eliminated renally. The elimination half-life is approximately 4.5 hours. Dose adjustments are necessary in severe renal impairment to prevent accumulation.
Indications & dosing

Prophylaxis of VTE in surgical patients (moderate risk)

For general or moderate-risk surgical procedures. Extended prophylaxis may be required in some patients.

  • adult · SC: 20 mg q24h · For general or moderate-risk surgical procedures. Extended prophylaxis may be required in some patients.

Prophylaxis of VTE in surgical patients (high risk)

For hip or knee replacement, or major abdominal/pelvic surgery. Alternative regimen: 30 mg q12h.

  • adult · SC: 40 mg q24h · For hip or knee replacement, or major abdominal/pelvic surgery. Alternative regimen: 30 mg q12h.

Prophylaxis of VTE in acutely ill medical patients

Limited to patients at risk of thromboembolism with restricted mobility.

  • adult · SC: 40 mg q24h · Limited to patients at risk of thromboembolism with restricted mobility.

Treatment of DVT and PE

Alternative: 1.5 mg/kg once daily. Adjust dose in severe renal impairment (CrCl <30 mL/min).

  • adult · SC: 1 mg/kg q12h · Alternative: 1.5 mg/kg once daily. Adjust dose in severe renal impairment (CrCl <30 mL/min).

Unstable angina and NSTEMI

Use in combination with aspirin. Adjust in renal impairment.

  • adult · SC: 1 mg/kg q12h · Use in combination with aspirin. Adjust in renal impairment.

STEMI (patients <75 years)

Give 30 mg IV bolus immediately before first SC dose. Continue for the duration of hospital stay.

  • adult · SC: 1 mg/kg q12h · Give 30 mg IV bolus immediately before first SC dose. Continue for the duration of hospital stay.

STEMI (patients ≥75 years)

No initial IV bolus is given. Adjust in renal impairment.

  • elderly · SC: 0.75 mg/kg q12h · No initial IV bolus is given. Adjust in renal impairment.
Contraindications & precautions
  • Active major haemorrhage · Enoxaparin must be stopped and appropriate treatment initiated.
  • Hypersensitivity to enoxaparin or other low molecular weight heparins · Includes history of hypersensitivity reactions, such as urticaria or anaphylaxis.
  • History of heparin-induced thrombocytopenia (HIT) · Within the last 100 days, or a history of type II HIT.
  • Severe renal impairment (creatinine clearance < 30 mL/min) · Dose reduction or alternative anticoagulant may be required; risk of accumulation.
  • Active peptic ulceration or other high bleeding risk conditions · Weigh benefits against risk of bleeding.
  • Recent intracranial haemorrhage, CNS surgery, or trauma · Increases risk of bleeding.
  • Concomitant use of other anticoagulants or thrombolytics · Increases bleeding risk; monitor closely.
  • Severe uncontrolled hypertension · May increase bleeding risk.
  • Monitor platelet count before and during treatment, especially if the patient has thrombocytopenia or a history of HIT.
  • Adjust dose in renal impairment (creatinine clearance < 30 mL/min); consider using unfractionated heparin if renal function worsens.
  • Use with caution in patients receiving concurrent antiplatelet or NSAID therapy, as bleeding risk is increased.
  • For epidural or spinal anaesthesia, observe strict timing recommendations to minimise risk of spinal haematoma.
  • Assess bleeding risk before starting treatment, including recent surgery, trauma, or bleeding disorders.
  • Do not switch directly with other low molecular weight heparins without careful monitoring.
Adverse effects
  • Haemorrhageserious
  • Injection site bruising or pain
  • Thrombocytopenia (including heparin-induced thrombocytopenia)serious
  • Hyperkalaemia
  • Elevation of hepatic transaminases
  • Allergic reactions (including rash, urticaria, anaphylaxis)serious
  • Osteoporosis with long-term useserious
Interactions
  • aspirinmajorUse with caution and only if clearly indicated. Consider alternatives such as clopidogrel or other antiplatelets if antiplatelet therapy is necessary, or consider non-steroidal anti-inflammatory drugs with lower gastrointestinal bleeding potential, but note that all NSAIDs can increase bleeding risk. When co-prescribed, monitor for signs of bleeding, including occult blood loss, and check haemoglobin, haematocrit, and platelet counts periodically. Consider gastroprotective agents such as proton pump inhibitors to reduce gastrointestinal bleeding risk. Adjust doses and durations of both agents to the minimum necessary. If possible, separate administration times, though this does not eliminate the interaction. Do not use in patients with active bleeding, recent major surgery, or high bleeding risk unless benefit outweighs risk.
Renal & hepatic adjustment
  • eGFR 0–29: For VTE treatment: reduce to 1 mg/kg sc once daily (usual: 1 mg/kg twice daily or 1.5 mg/kg once daily). For VTE prophylaxis: reduce to 20 mg sc once daily (usual: 40 mg once daily). Monitor anti-Xa levels if possible.
  • Hepatic impairment (severe): No specific dose adjustment, but use with caution. Monitor coagulation status and bleeding risk.
Monitoring, pregnancy & toxicity
  • Anti-Xa activity · In renal impairment, obesity, pregnancy, or when efficacy is uncertain
  • Platelet count · Baseline and every 2 to 3 days during treatment to monitor for HIT
  • Serum creatinine · Before treatment and periodically during therapy, especially in patients at risk of renal impairment
  • Signs of bleeding · Regularly assess for bleeding, bruising, or melaena
  • Haemoglobin and haematocrit · Baseline and if bleeding is suspected
  • Pregnancy: Enoxaparin is the preferred anticoagulant for prevention and treatment of VTE in pregnancy and for antiphospholipid syndrome. It does not cross the placenta, so is considered safe. Dose may need adjustment in renal impairment.
  • Toxicity: Bleeding, which may present as haemorrhage, bruising, or melaena · Stop enoxaparin; supportive care; in severe bleeding, give protamine sulfate 1 mg IV per 1 mg enoxaparin given within the last 8 h, or 0.5 mg per 1 mg if longer than 8 h. Protamine only partially reverses anti-Xa activity. Repeat if needed.
Antidotes & reversal
  • Protamine sulfate · Partial reversal only (about 60-75% of anti-Xa activity); 1 mg per 1 mg enoxaparin within 8 h.
Clinical notes
Enoxaparin is used for prophylaxis and treatment of venous thromboembolism, and in the management of acute coronary syndromes. It is given by subcutaneous injection, usually once or twice daily, with dose based on body weight and clinical indication. In renal impairment, dose reduction is often required. Anti-Xa activity may be monitored in special populations. Protamine sulfate provides partial reversal of its anticoagulant effect. For teaching purposes, prescribing and dosing should follow current local guidelines and formularies.

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BNF; local formulary