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. |
| Molecular Weight | 3000-30000 Da (unfractionated heparin is a mixture; average ~15000 Da) |
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 | Heparin does not cross the placenta; no known teratogenic effects. Use if indicated (e.g., thromboembolism, antiphospholipid syndrome). Avoid in severe preeclampsia or eclampsia. |
| 2nd trimester | Safe for use; monitor platelet counts and signs of bleeding. No increased fetal risk. |
| 3rd trimester | Safe; increased risk of maternal hemorrhage at delivery. Consider discontinuing 24-48 hours before planned delivery or manage with protamine reversal if bleeding occurs. |
Clinical note
Other drugs that affect hemostasis increase bleeding risk Can cause heparin-induced thrombocytopenia (HIT) and bleeding.
| FDA category | Human |
| Placental transfer | Does not cross the placenta due to high molecular weight and negative charge. |
| Breastfeeding |
■ 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 |
Active major bleedingHistory of heparin-induced thrombocytopenia (HIT) (unless desensitized)Hypersensitivity to heparin or pork productsSevere thrombocytopenia (platelet count <100,000/mm³)Uncontrolled severe hypertensionSuspected or confirmed intracranial hemorrhageRecent brain, spinal, or eye surgeryHemophilia or other coagulation disorders
| 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. |
Loading safety data…
| Heparin is not excreted into breast milk due to its high molecular weight and polarity. Considered compatible with breastfeeding. Monitor infant for signs of bleeding if high maternal doses used. |
| Lactation Rating | L1 (Compatible) |
| Teratogenic Risk | No known teratogenic effects. Heparin does not cross the placenta, thus fetal exposure is negligible. No increased risk of congenital anomalies reported. |
| 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. |
| Food/Dietary | Avoid high-dose vitamin K rich foods (e.g., kale, spinach, broccoli) as they may antagonize effect; however, consistent intake is key. Grapefruit juice has no significant interaction. Alcohol increases bleeding risk; limit intake. |
| Clinical Pearls | Monitor aPTT 6h after initiation and dose changes; target 1.5-2.5x control. Use weight-based dosing (initial bolus 80 units/kg, infusion 18 units/kg/h). Avoid IM injections due to hematoma risk. Protamine sulfate (1 mg per 100 units heparin) reverses effects. Check platelet count regularly for HIT (type II, 5-10 days after start). Use with caution in renal impairment (dose reduction may be needed). |
| Patient Advice | Report unusual bleeding or bruising immediately. · Avoid aspirin, NSAIDs, and other blood thinners unless prescribed. · Use soft toothbrush and electric razor to minimize bleeding. · Inform all healthcare providers you are on heparin. · Do not stop or change dose without consulting your doctor. |