HEPARIN SODIUM 12,500 UNITS IN DEXTROSE 5%
Clinical safety rating: safe
Other drugs that affect hemostasis increase bleeding risk Can cause heparin-induced thrombocytopenia (HIT) and bleeding.
Heparin binds to antithrombin III, inducing a conformational change that accelerates the inhibition of thrombin (factor IIa) and activated factor X (Xa), thereby preventing fibrin clot formation and extension.
| Metabolism | Heparin undergoes partial hepatic metabolism (desulfation) but is primarily cleared by the reticuloendothelial system and excreted in urine as unchanged drug or low molecular weight metabolites. |
| Excretion | Heparin is eliminated primarily via the reticuloendothelial system and liver, with renal excretion of metabolites accounting for approximately 50-60% of the dose. A small fraction (up to 5%) is excreted unchanged in urine. No significant biliary or fecal elimination. |
| Half-life | The terminal elimination half-life of heparin is dose- and concentration-dependent, averaging 1-2 hours after intravenous administration. At therapeutic doses, the half-life is approximately 1.5 hours; with higher doses, it can extend to 2.5-3 hours. The half-life is prolonged in patients with hepatic or renal impairment. |
| Protein binding | Heparin is extensively bound to plasma proteins, including antithrombin III (primary), heparin cofactor II, albumin, and lipoproteins. Protein binding is approximately 95-98%, but this is saturable and variable. |
| Volume of Distribution | The apparent volume of distribution (Vd) for heparin is approximately 0.06-0.1 L/kg (limited to plasma volume, ~5-10 L in adults). This reflects its large molecular weight and high protein binding, restricting it to the intravascular space. |
| Bioavailability | Subcutaneous: bioavailability is approximately 20-30% due to reduced absorption and first-pass metabolism in the vascular endothelium. Intravenous: 100% bioavailability. No oral bioavailability due to degradation in the gastrointestinal tract. |
| Onset of Action | Intravenous: immediate (within 1-2 minutes). Subcutaneous: delayed, with onset within 20-30 minutes (peak effect at 2-4 hours). |
| Duration of Action | Intravenous: 2-6 hours (effects diminish as heparin is cleared; continuous infusion required for sustained anticoagulation). Subcutaneous: 8-12 hours (due to slower absorption, provides more prolonged effect). |
Loading dose: 5000 units IV bolus, then continuous IV infusion at 12,000-18,000 units/24h (10-15 units/kg/h). Adjust to target aPTT 60-80 seconds.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment for GFR; however, monitoring aPTT is recommended due to potential accumulation in severe renal impairment (CrCl <30 mL/min). |
| Liver impairment | No specific Child-Pugh based dose adjustments; increased risk of bleeding in hepatic impairment, monitor aPTT closely. |
| Pediatric use | Loading dose: 75-100 units/kg IV bolus over 10 minutes; maintenance: 25-30 units/kg/h continuous IV infusion, titrated to aPTT 60-85 seconds. |
| Geriatric use | Elderly patients may have reduced clearance; consider lower initial infusion rates (10-12 units/kg/h) and monitor aPTT more frequently. |
| 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 | Heparin is not excreted into breast milk due to its high molecular weight and negative charge; therefore, it is considered compatible with breastfeeding. M/P ratio: Not applicable (no detectable levels in milk). |
| Teratogenic Risk | Heparin does not cross the placenta and is not associated with teratogenicity. First trimester: No increased risk of congenital anomalies. Second and third trimesters: No fetal harm reported; however, increased risk of maternal hemorrhage and osteoporosis with prolonged use. |
■ FDA Black Box Warning
Heparin is not intended for intramuscular (IM) use. Fatal hemorrhages have occurred due to idiosyncratic thrombocytopenia (heparin-induced thrombocytopenia, HIT). For patients with documented HIT or history of HIT, use alternative anticoagulants. Spinal or epidural hematomas can occur with concomitant neuraxial anesthesia, leading to prolonged or permanent paralysis. Monitor for signs and symptoms of neurological impairment.
| Common Effects | bleeding |
| Serious Effects |
["Absolute: History of heparin-induced thrombocytopenia (HIT) or heparin-induced thrombocytopenia and thrombosis (HITT); active major bleeding or hemophilia; severe uncontrolled hypertension; neuraxial anesthesia with concomitant use (relative contraindication).","Relative: Recent major surgery (especially brain, spinal cord, or eye), thrombocytopenia, renal impairment, advanced age, hemorrhagic stroke, ulcerative lesions (e.g., GI), or hypersensitivity to heparin or pork products."]
| Precautions | ["Risk of hemorrhage: monitor for signs of bleeding, decrease dose in elderly or renal impairment.","Heparin-induced thrombocytopenia (HIT): monitor platelet counts frequently, discontinue if HIT suspected.","Hyperkalemia: due to suppression of aldosterone, monitor potassium levels in long-term use.","Hypersensitivity reactions: including urticaria, angioedema, and anaphylaxis.","Use caution in patients with hepatic disease, hypertension, or recent surgery.","Do not use in the presence of active major bleeding or bleeding disorders."] |
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| Fetal Monitoring | Monitor maternal platelet counts (risk of heparin-induced thrombocytopenia), signs of bleeding (e.g., hematuria, ecchymosis), and anti-Xa levels if therapeutic anticoagulation is intended. Fetal monitoring as indicated for maternal condition; no specific fetal monitoring required for heparin alone. |
| Fertility Effects | No known adverse effects on fertility in males or females. Heparin use does not impair spermatogenesis or ovulation. |