ENOXAPARIN SODIUM
Clinical safety rating
safeOther drugs that affect hemostasis increase bleeding risk Can cause spinal or epidural hematoma leading to paralysis with neuraxial anesthesia.
Enoxaparin binds to antithrombin III (ATIII) via its pentasaccharide sequence, enhancing ATIII-mediated inhibition of factor Xa and, to a lesser extent, factor IIa (thrombin). It preferentially inhibits factor Xa over thrombin (anti-Xa:anti-IIa ratio ~3.6:1).
| Metabolism | Enoxaparin is partially metabolized in the liver via desulfation and depolymerization by heparanase and other enzymes. It has a complex pharmacokinetic profile with dose-dependent clearance; renal excretion accounts for elimination of active fragments and the unchanged drug. |
| Excretion | Renal (40-60% as unchanged drug via glomerular filtration and saturable tubular reabsorption). Biliary/fecal: negligible (<10%). |
| Half-life | 4.5-7 hours after single subcutaneous dose; prolonged to 8-12 hours in renal impairment (CrCl <30 mL/min). Clinical context: maintains anti-Xa activity for 12 hours with once-daily dosing. |
| Protein binding | 80% bound to antithrombin III (low affinity to other plasma proteins). |
| Volume of Distribution | 0.04-0.06 L/kg (plasma volume distribution; low Vd indicates limited extravascular distribution). |
| Bioavailability | Subcutaneous: 90-92% (complete absorption). |
| Onset of Action | Subcutaneous: 30-60 minutes (anti-Xa activity detected). Intravenous: immediate (bolus). |
| Duration of Action | Subcutaneous: anti-Xa activity persists for 12 hours after a 40 mg dose; dose-dependent up to 24 hours with higher doses. Clinical notes: used for thromboprophylaxis with once-daily dosing due to sustained effect. |
| Molecular Weight | 4500 |
1 mg/kg subcutaneous every 12 hours or 1.5 mg/kg subcutaneous once daily
| Dosage form | INJECTABLE |
| Renal impairment | CrCl < 30 mL/min: reduce dose to 1 mg/kg subcutaneous once daily |
| Liver impairment | No specific Child-Pugh based adjustment; use with caution in severe hepatic impairment due to increased bleeding risk |
| Pediatric use | Neonates and infants: 1.5 mg/kg subcutaneous every 12 hours; Children < 2 months: 1.5 mg/kg every 12 hours; Children ≥ 2 months: 1 mg/kg every 12 hours |
| Geriatric use | Increased risk of bleeding; consider lower doses (e.g., 0.5 mg/kg every 12 hours or 1 mg/kg once daily) and monitor renal function |
| 1st trimester | Enoxaparin does not cross the placenta in significant amounts (based on animal studies and limited human data) and is not associated with teratogenicity; however, use only if clearly needed due to risk of bleeding and heparin-induced thrombocytopenia (HIT). |
| 2nd trimester | No evidence of fetal harm; used for prophylaxis and treatment of thromboembolism during pregnancy. Monitor for bleeding and HIT. |
| 3rd trimester | Increased risk of bleeding during labor and delivery; use caution. May be used for prophylaxis (e.g., in cesarean section or thrombophilia). Discontinue at least 24 hours prior to induction or elective cesarean if neuraxial anesthesia is planned. |
Clinical note
Other drugs that affect hemostasis increase bleeding risk Can cause spinal or epidural hematoma leading to paralysis with neuraxial anesthesia.
| FDA category | Human |
| Placental transfer | Minimal; enoxaparin does not cross the placenta significantly due to its high molecular weight and polarity, as shown in both animal and human studies. |
| Breastfeeding | Enoxaparin is considered compatible with breastfeeding as it has very low oral bioavailability (due to high molecular weight and polarity) and is not detected in milk in clinically significant amounts. However, use with caution in mothers with bleeding disorders or if the infant has thrombocytopenia; monitor infant for bruising or bleeding. |
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | Enoxaparin sodium does not cross the placenta and is not associated with teratogenicity in humans. However, there is a risk of hemorrhage during delivery. Use during pregnancy requires careful monitoring for bleeding. |
| Fetal Monitoring | Monitor maternal platelet counts (risk of heparin-induced thrombocytopenia), anti-Xa levels to guide dosing, and signs of bleeding. Fetal surveillance includes growth scans and non-stress tests if indicated. |
| Fertility Effects | No known direct effects on fertility. Use in women attempting conception is not contraindicated, but underlying conditions requiring anticoagulation may affect fertility. |
■ FDA Black Box Warning
Enoxaparin carries a black box warning for the risk of spinal or epidural hematomas in patients receiving neuraxial anesthesia or spinal puncture, which can result in long-term or permanent paralysis. Patients should be monitored for signs of neurological impairment, and concomitant use of drugs affecting hemostasis (e.g., NSAIDs, antiplatelet agents, other anticoagulants) increases the risk.
| Common Effects | bleeding |
| Serious Effects |
Active major bleedingHistory of heparin-induced thrombocytopenia (HIT) or heparin-induced thrombocytopenia and thrombosis (HITT)Severe uncontrolled hypertension (e.g., malignant hypertension)Known hypersensitivity to enoxaparin, heparin, or pork productsAcute bacterial endocarditisHemophilia or other severe bleeding disorders (e.g., von Willebrand disease)Recent or planned spinal/epidural puncture (relative contraindication; absolute for certain dosing regimens; see guidelines)Severe renal impairment (CrCl < 30 mL/min) (requires dose adjustment, not absolute contraindication but caution)
| Precautions | Spinal/epidural hematoma risk with neuraxial anesthesia, Increased bleeding risk, especially in patients with renal impairment, thrombocytopenia, or age >65, Heparin-induced thrombocytopenia (HIT) risk; monitor platelet counts regularly, Use with caution in patients with severe renal impairment (CrCl <30 mL/min), as enoxaparin accumulates and increases bleeding risk; dose adjustment required, Not recommended in patients with mechanical heart valves, especially pregnant women, due to risk of valve thrombosis, Do not mix with other injections or infusions |
| Food/Dietary | No specific food interactions. However, foods high in vitamin K (e.g., leafy greens) may theoretically affect coagulation but are not clinically significant with enoxaparin. Avoid excessive alcohol intake due to potential bleeding risk. Maintain consistent diet if also taking warfarin. |
| Clinical Pearls | Enoxaparin is a low molecular weight heparin (LMWH) that preferentially inhibits factor Xa over thrombin. Monitor anti-Xa levels in patients with renal impairment (CrCl <30 mL/min), obesity, or pregnancy. Avoid intramuscular injections and use with caution in patients receiving neuraxial anesthesia due to risk of spinal hematoma. Protamine sulfate partially reverses enoxaparin (up to 60% of anti-Xa activity). Does not routinely require monitoring of aPTT. |
| Patient Advice | Inject subcutaneously as directed, rotating injection sites (e.g., left/right abdomen, alternating). · Do not massage the injection site after administration. · Report any signs of bleeding: unusual bruising, prolonged bleeding from cuts, blood in urine or stool, coughing up blood. · Seek immediate medical attention for symptoms of spinal hematoma after neuraxial procedure: back pain, numbness or weakness in legs, bowel/bladder dysfunction. · Inform all healthcare providers (including dentists) that you are taking enoxaparin. · Avoid NSAIDs, aspirin, or other blood thinners unless prescribed by your doctor. |
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