Enoxaparin

• DVT Prevention and Treatment
• Pulmonary Embolism
• Acute Coronary Syndromes
• Anticoagulation Therapy

Enoxaparin is a low molecular weight heparin (LMWH) anticoagulant used for the prevention and treatment of venous thromboembolism and in acute coronary syndromes. This injectable anticoagulant offers predictable pharmacokinetics, subcutaneous dosing, and reduced monitoring requirements compared to unfractionated heparin.

Mechanism of Action

Enoxaparin is produced by controlled depolymerization of unfractionated heparin, resulting in fragments with a mean molecular weight of about 4,500 daltons. Like heparin, enoxaparin enhances the activity of antithrombin III (AT), but with a more selective mechanism. Enoxaparin has a higher ratio of anti-factor Xa to anti-factor IIa (thrombin) activity (approximately 4:1) compared to unfractionated heparin (1:1). This preferential inhibition of factor Xa prevents thrombin generation while causing less effect on thrombin directly, potentially reducing bleeding risk while maintaining efficacy. The predictable dose-response and longer half-life allow weight-based dosing without routine laboratory monitoring.

Available Formulations

Enoxaparin sodium is available as a solution for subcutaneous or intravenous injection in prefilled syringes and multi-dose vials. Concentrations include 30 mg/0.3 mL, 40 mg/0.4 mL, 60 mg/0.6 mL, 80 mg/0.8 mL, 100 mg/1 mL, 120 mg/0.8 mL, and 150 mg/1 mL. Multi-dose vials (300 mg/3 mL) contain benzyl alcohol as a preservative and should not be used in neonates or pregnant women.

Medical Uses

Enoxaparin is FDA-approved for prophylaxis of DVT in hip replacement, knee replacement, and abdominal surgery; prophylaxis of DVT in medical patients with severely restricted mobility; inpatient treatment of acute DVT with or without PE; outpatient treatment of acute DVT without PE; prophylaxis of ischemic complications of unstable angina and non-Q-wave MI; and treatment of acute STEMI. It is one of the most widely used anticoagulants in hospital and outpatient settings.

Dosing Guidelines

For DVT prophylaxis, doses range from 30 mg SC every 12 hours to 40 mg SC once daily depending on surgical procedure and patient risk. For DVT/PE treatment, the dose is 1 mg/kg SC every 12 hours or 1.5 mg/kg SC once daily. For acute coronary syndromes, 1 mg/kg SC every 12 hours with concurrent aspirin is used. For STEMI, an initial IV bolus is followed by SC dosing. Dose adjustment is required for CrCl less than 30 mL/min (typically once daily dosing instead of twice daily). Anti-Xa monitoring may be helpful in certain populations.

Important Safety Information

Enoxaparin carries a boxed warning for spinal/epidural hematomas in patients receiving neuraxial anesthesia or spinal puncture, which may result in long-term or permanent paralysis. Risk factors include indwelling epidural catheters, concurrent use of other drugs affecting hemostasis, traumatic or repeated spinal puncture, and spinal deformity or surgery. Hemorrhage is the primary adverse effect. The medication should be used with caution in patients with renal impairment, low body weight, or conditions predisposing to bleeding.

Drug Interactions

Drugs affecting hemostasis (anticoagulants, antiplatelet agents, NSAIDs, thrombolytics) increase bleeding risk. Concurrent use with other LMWHs, heparin, or heparinoids should be avoided. Probenecid may increase enoxaparin levels. No significant interactions with digoxin, warfarin (at steady state), or common medications when used appropriately.

Special Populations

Enoxaparin has been used during pregnancy; the multi-dose vials should not be used due to benzyl alcohol content. It is the preferred anticoagulant in many pregnancy situations but requires careful monitoring. Small amounts may be present in breast milk; caution is advised. The multi-dose vial should not be used in neonates due to benzyl alcohol toxicity risk. Elderly patients may have reduced enoxaparin clearance. Dose adjustment is required for severe renal impairment (CrCl less than 30 mL/min). Use with caution in hepatic impairment; patients with hepatic dysfunction may have reduced AT levels.