SODIUM HEPARIN
Clinical safety rating: safe
Other drugs that affect hemostasis increase bleeding risk Can cause heparin-induced thrombocytopenia (HIT) and bleeding.
Binds to antithrombin III, accelerating its inhibition of factor Xa and thrombin (factor IIa), thereby preventing fibrin formation and extension of thrombi.
| Metabolism | Heparin is primarily metabolized in the liver by desulfation and depolymerization via heparinase and other enzymes; partially metabolized in the reticuloendothelial system. |
| Excretion | Renal: negligible; primarily cleared by hepatic and reticuloendothelial system (desulfation and depolymerization). Unchanged drug not excreted in urine. |
| Half-life | Terminal elimination half-life is dose-dependent: 0.5-1.5 hours at low doses, 1.5-2.5 hours at high doses. Clinically, anticoagulant effect half-life is approximately 1-5 hours, with shorter half-life at lower doses. |
| Protein binding | High: 95-98% bound to antithrombin III; also binds to heparin cofactor II, albumin, and other plasma proteins. |
| Volume of Distribution | 0.06-0.07 L/kg (confined to plasma volume). Low Vd indicates limited extravascular distribution. |
| Bioavailability | Subcutaneous: 15-30% (low and variable due to poor absorption and first-pass metabolism). Intravenous: 100%. |
| Onset of Action | Intravenous: immediate (seconds to minutes). Subcutaneous: 1-4 hours (peak effect at 2-4 hours). |
| Duration of Action | Intravenous: 2-6 hours (dose-dependent). Subcutaneous: 8-12 hours (twice-daily dosing regimen). Effect duration is shorter than protamine reversal. |
Initial IV bolus 80 units/kg followed by continuous IV infusion at 18 units/kg/hour; adjusted based on aPTT. Alternatively, subcutaneous: 333 units/kg loading dose then 250 units/kg every 12 hours.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment recommended per GFR; however, clearance may be reduced in severe renal impairment (CrCl <30 mL/min); monitor aPTT frequently. |
| Liver impairment | No standard Child-Pugh based adjustment; hepatic impairment may alter coagulation parameters; monitor aPTT and adjust accordingly. |
| Pediatric use | Neonates and infants: Initial IV bolus 75-100 units/kg, then maintenance 20-30 units/kg/hour continuous infusion. Children: Initial IV bolus 75-100 units/kg, then maintenance 15-25 units/kg/hour; titrate to aPTT 60-85 seconds. |
| Geriatric use | Elderly patients may have reduced heparin clearance; use lower initial bolus (50-75 units/kg) and infusion rates (15-17 units/kg/hour); monitor aPTT closely due to increased bleeding risk. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other drugs that affect hemostasis increase bleeding risk Can cause heparin-induced thrombocytopenia (HIT) and bleeding.
| FDA category | Human |
| Breastfeeding | Compatible with breastfeeding. Heparin is not excreted into breast milk due to its high molecular weight and negative charge, resulting in no detectable levels in breast milk; M/P ratio is not applicable. |
| Teratogenic Risk | No known teratogenic effects. Heparin does not cross the placenta, thus fetal exposure is negligible. No increased risk of congenital anomalies reported. |
■ FDA Black Box Warning
Spinal/epidural hematomas have been reported with the use of enoxaparin or other low molecular weight heparins or heparinoids and neuraxial anesthesia or spinal puncture, resulting in long-term or permanent paralysis. Risk is increased by use of indwelling epidural catheters, concomitant use of drugs that affect hemostasis, traumatic or repeated epidural or spinal puncture, and history of spinal deformity or surgery.
| Common Effects | bleeding |
| Serious Effects |
["History of heparin-induced thrombocytopenia (HIT)","Active major bleeding or bleeding disorders (e.g., hemophilia, thrombocytopenia)","Allergy to heparin or porcine products","Severe uncontrolled hypertension","Recent surgery involving brain, spinal cord, or eye"]
| Precautions | ["Risk of bleeding: Monitor for signs of bleeding, adjust dose accordingly.","Heparin-induced thrombocytopenia (HIT): Monitor platelet counts; discontinue if HIT suspected.","Hyperkalemia: May suppress aldosterone; monitor potassium in renal impairment.","Osteoporosis: Risk with long-term use (>1 month).","Use caution in patients with hepatic disease, renal impairment, or history of GI ulcers."] |
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| Fetal Monitoring | Monitor maternal platelet counts for heparin-induced thrombocytopenia (HIT). Monitor activated partial thromboplastin time (aPTT) to maintain therapeutic range. Assess for signs of bleeding or thrombosis. Fetal monitoring as per routine obstetric care. |
| Fertility Effects | No known adverse effects on fertility. Heparin does not affect reproductive hormones or gamete function. |