HEPARIN SODIUM 12,500 UNITS IN SODIUM CHLORIDE 0.45% IN PLASTIC CONTAINER
Clinical safety rating: safe
No significant drug interactions Can cause hypernatremia and fluid overload.
Heparin binds to antithrombin III (ATIII), accelerating its inhibition of thrombin (factor IIa) and factor Xa, thereby preventing fibrin clot formation.
| Metabolism | Heparin undergoes hepatic metabolism (desulfation) and is partially depolymerized; clearance is via reticuloendothelial system and renal excretion. |
| Excretion | Primarily renal (via reticuloendothelial system); 40-50% excreted unchanged in urine; 20-30% metabolized to uroheparin and excreted renally; minor biliary (<5%). |
| Half-life | Terminal elimination half-life: 1-2 hours (dose-dependent, saturable clearance); prolonged to 2-6 hours in renal impairment, obese patients, or with high doses; clinical anticoagulant effect may persist 2-4 hours after a single IV bolus. |
| Protein binding | Heparin binds extensively to antithrombin III (AT-III) and multiple plasma proteins including histidine-rich glycoprotein, platelet factor 4, vitronectin, fibronectin, and lipoproteins; very high overall protein binding (nearly 100% to AT-III when bound, but free fraction varies due to competition). |
| Volume of Distribution | Vd approximately 0.03-0.10 L/kg (largely confined to plasma volume; limited extravascular distribution); increased Vd in pregnancy, obesity, and nephrotic syndrome. |
| Bioavailability | SC: 80-93% relative to IV (due to first-pass hepatic metabolism and local degradation); IV: 100%. |
| Onset of Action | IV: immediate (within seconds); SC: 20-30 minutes. |
| Duration of Action | IV: 2-4 hours (aPTT returns to baseline); SC: 8-12 hours (duration depends on dose and monitoring); continuous infusion: effect persists as long as infusion continues. |
Intravenous: Initial bolus of 5,000 units followed by continuous infusion of 13-21 units/kg/hour (typically 1,000-2,000 units/hour) titrated to aPTT 1.5-2.5 times control. Subcutaneous: 5,000 units every 8-12 hours for prophylaxis; 10,000-20,000 units every 12 hours for treatment.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment for GFR; monitor aPTT closely in renal impairment (CrCl <30 mL/min) due to increased bleeding risk. For continuous infusion, consider lower initial rates (e.g., 13 units/kg/hour) and titrate carefully. |
| Liver impairment | No established guidelines; use with caution in Child-Pugh B or C due to coagulopathy and decreased antithrombin III levels. Monitor aPTT more frequently. |
| Pediatric use | Intravenous: Bolus 50-100 units/kg, then continuous infusion 15-25 units/kg/hour. Subcutaneous: 50-100 units/kg every 6-8 hours for prophylaxis; 100-150 units/kg every 6 hours for treatment. Titrate to age-appropriate aPTT (e.g., 60-85 seconds in neonates). |
| Geriatric use | Lower initial doses (e.g., 50-70% of usual) with careful titration; increased risk of bleeding due to altered clearance. Monitor aPTT and renal function closely. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
No significant drug interactions Can cause hypernatremia and fluid overload.
| FDA category | Animal |
| Breastfeeding | Heparin is not excreted into breast milk due to high molecular weight and protein binding; M/P ratio not applicable. Considered compatible with breastfeeding. |
| Teratogenic Risk | Pregnancy category C. Heparin does not cross the placenta; no risk of fetal teratogenesis. However, increased risk of maternal bleeding, which may indirectly affect fetal well-being. Use only if clearly needed. |
■ FDA Black Box Warning
Spinal/epidural hematomas: Risk hemiparesis or paralysis with neuraxial anesthesia or spinal puncture, especially in patients on anticoagulants or with indwelling catheters.
| Common Effects | fluid replacement |
| Serious Effects |
["Severe thrombocytopenia (including HIT)","Active major bleeding or bleeding diathesis (e.g., hemophilia, severe liver disease)","Hypersensitivity to heparin or pork products","History of HIT or HIT with thrombosis","Use for spinal/epidural anesthesia in patients with indwelling epidural catheter (relative to black box warning)","Severe uncontrolled hypertension or recent brain/spinal cord surgery (relative)"]
| Precautions | ["Hemorrhage risk (monitor for bleeding; adjust dose based on aPTT)","Heparin-induced thrombocytopenia (HIT) Type II (immune-mediated, monitor platelets)","HIT Type I (non-immune thrombocytopenia)","Hyperkalemia due to aldosterone suppression (risk in renal impairment, diabetes, or K+-sparing drugs)","Heparin resistance (low ATIII levels)","Osteoporosis with long-term use (>6 months)"] |
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| Fetal Monitoring | Monitor maternal coagulation parameters (aPTT, anti-Xa), platelet count (risk of HIT), and signs of bleeding. Assess fetal heart rate and uterine activity if used during labor. Monitor for maternal hemorrhage. |
| Fertility Effects | No known direct effects on fertility. Heparin may be used in treatment of recurrent pregnancy loss associated with thrombophilia, potentially improving fertility outcomes. |