What it's for (Indications)
- Enoxaparin, a low molecular weight heparin (LMWH), is indicated for a range of thromboembolic conditions.
- It is primarily used for the prophylaxis of deep vein thrombosis (DVT), which can lead to pulmonary embolism (PE), in patients undergoing abdominal surgery, hip replacement surgery, or knee replacement surgery, as well as in acutely ill medical patients with severely restricted mobility.
- Furthermore, enoxaparin is indicated for the treatment of acute DVT, with or without associated PE, typically administered concurrently with warfarin for oral anticoagulation transition.
- It also plays a crucial role in the prophylaxis of ischemic complications associated with unstable angina and non-Q-wave myocardial infarction (NSTEMI) when administered with aspirin.
- Lastly, enoxaparin is indicated for the treatment of acute ST-segment elevation myocardial infarction (STEMI) that is managed medically or followed by percutaneous coronary intervention (PCI), often involving an initial intravenous bolus.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | Enoxaparin dosage is highly individualized based on the specific indication, patient body weight, renal function, and concomitant medical conditions. It is typically administered via subcutaneous (SC) injection, although an intravenous (IV) bolus may be used in certain acute settings like STEMI. For DVT prophylaxis, common regimens include 40 mg SC once daily (e.g., for abdominal surgery or medical patients) or 30 mg SC every 12 hours (e.g., for hip/knee replacement). For the treatment of DVT/PE, dosages are often 1 mg/kg SC every 12 hours or 1.5 mg/kg SC once daily. In unstable angina/NSTEMI, 1 mg/kg SC every 12 hours is typical, combined with aspirin. For STEMI, an initial 30 mg IV bolus is followed by 1 mg/kg SC every 12 hours. Careful dose adjustments are mandatory for patients with severe renal impairment (creatinine clearance < 30 mL/min). Monitoring of anti-Xa levels may be considered in specific patient populations, such as those with renal impairment, obesity, or during pregnancy, to ensure therapeutic efficacy and minimize bleeding risk. |
Safety & Warnings
Common Side Effects
- The most significant and frequently encountered side effect of enoxaparin is bleeding, which can range from minor ecchymosis or injection site hematomas to major, life-threatening hemorrhage.
- Other common adverse reactions include anemia, local irritation, pain, or redness at the injection site.
- Transient elevations in liver transaminases (AST, ALT) are also reported.
- Thrombocytopenia, including a rare but severe immune-mediated form known as heparin-induced thrombocytopenia (HIT) with or without thrombosis, is a serious potential complication requiring diligent platelet count monitoring.
- Less common but serious adverse events include spinal or epidural hematoma, particularly in patients undergoing neuraxial anesthesia or spinal puncture, which can lead to neurological impairment or permanent paralysis.
- Allergic reactions, such as rash, urticaria, and rarely anaphylaxis, may occur.
- Long-term use of enoxaparin, similar to unfractionated heparin, may be associated with osteoporosis, though this is less common with LMWHs.
Serious Warnings
- Black Box Warning: SPINAL/EPIDURAL HEMATOMA: Epidural or spinal hematomas may occur with the concomitant use of enoxaparin and neuraxial anesthesia (spinal/epidural anesthesia) or spinal puncture, resulting in long-term or permanent paralysis. These events are rare but severe. The risk is increased by the use of indwelling epidural catheters for analgesia, concomitant use of other drugs affecting hemostasis such as non-steroidal anti-inflammatory drugs (NSAIDs), platelet inhibitors, or other anticoagulants, a history of traumatic or repeated epidural or spinal punctures, spinal deformity or spinal surgery. Monitor patients frequently for signs and symptoms of neurological impairment. If neurological compromise is noted, urgent treatment is necessary. Consider the potential benefits and risks before neuraxial intervention in patients anticoagulated or to be anticoagulated for thromboprophylaxis. The timing of enoxaparin administration relative to the neuraxial procedure is crucial and specific guidelines must be followed to minimize this risk.
- Enoxaparin carries several critical warnings requiring careful consideration and patient monitoring.
- The primary concern is the inherent risk of hemorrhage; therefore, enoxaparin must be used with extreme caution in patients predisposed to bleeding, including those with active bleeding, a history of hemorrhagic stroke, severe uncontrolled hypertension, recent major surgery (especially ophthalmological, spinal, or brain surgery), or known bleeding diatheses.
- Patients should be closely monitored for signs of bleeding.
- Platelet counts must be routinely monitored due to the risk of heparin-induced thrombocytopenia (HIT), a severe, immune-mediated adverse reaction.
- Renal impairment significantly reduces enoxaparin clearance, necessitating dose adjustment in patients with creatinine clearance less than 30 mL/min to prevent drug accumulation and increased bleeding risk.
- Enoxaparin is not interchangeable (unit-for-unit) with other low molecular weight heparins or unfractionated heparin, as their pharmacokinetic and pharmacodynamic profiles differ.
- Particular caution is advised in patients with prosthetic heart valves, particularly pregnant women, where cases of valve thrombosis have been reported with LMWH use.
- Close attention to body weight is important for appropriate dosing, especially in obese patients where anti-Xa monitoring might be considered.
How it Works (Mechanism of Action)
Enoxaparin is a low molecular weight heparin derived from unfractionated heparin. Its primary anticoagulant effect is mediated through its high affinity for antithrombin III (AT-III). By binding to AT-III, enoxaparin significantly potentiates AT-III's inhibitory action on various activated coagulation factors, most notably Factor Xa and to a lesser extent, Factor IIa (thrombin). Unlike unfractionated heparin, which requires a longer polysaccharide chain to bridge both AT-III and thrombin for effective thrombin inactivation, enoxaparin's shorter chain length results in a more selective inhibition of Factor Xa. This preferential anti-Factor Xa activity means it largely inhibits thrombus formation by preventing the conversion of prothrombin to thrombin, without significantly altering global clotting times like aPTT at therapeutic doses. This specific mechanism provides a more predictable dose-response relationship, a longer half-life, and reduced non-specific binding to plasma proteins and cells compared to unfractionated heparin, allowing for less frequent subcutaneous administration.