HEPARIN SODIUM 25,000 UNITS IN SODIUM CHLORIDE 0.45%
Clinical safety rating: safe
No significant drug interactions Can cause hypernatremia and fluid overload.
Heparin binds to antithrombin III, causing a conformational change that accelerates the inactivation of thrombin (factor IIa) and factor Xa, and to a lesser extent factors IXa, XIa, and XIIa, thereby inhibiting coagulation.
| Metabolism | Heparin is primarily metabolized in the liver by the reticuloendothelial system and to a lesser extent in the kidneys. It undergoes desulfation and depolymerization. Clearance is dose-dependent and involves both saturable (cellular) and non-saturable (renal) mechanisms. |
| Excretion | Primarily hepatic metabolism (partial, via desulfation and depolymerization) and reticuloendothelial system uptake; renal excretion of metabolites; <1% unchanged in urine. |
| Half-life | Terminal elimination half-life: 1-2 hours (dose-dependent, prolonged at high doses); clinical context: half-life increases with dose (nonlinear pharmacokinetics), up to 2.5-3 hours with 25,000 units. |
| Protein binding | ~95%; primarily to antithrombin III, also to low-affinity binding to albumin, fibrinogen, and lipoproteins. |
| Volume of Distribution | 0.05-0.1 L/kg; clinical meaning: low Vd, primarily confined to plasma and extracellular fluid due to high protein binding and limited tissue penetration. |
| Bioavailability | Subcutaneous: 15-35% (highly variable, dose-dependent, often <50% due to tissue binding and degradation); intravenous: 100%. |
| Onset of Action | Intravenous: immediate (within minutes); subcutaneous: 20-60 minutes (peak 2-4 hours). |
| Duration of Action | Intravenous: 2-6 hours (dose-dependent); subcutaneous: 8-12 hours (prolonged effect at higher doses); clinical note: anticoagulant effect persists longer than half-life due to tissue binding. |
5000 units IV bolus followed by continuous IV infusion at 1300 units/hour, adjusted based on aPTT.
| Dosage form | INJECTABLE |
| Renal impairment | No specific GFR-based adjustment recommended; monitor aPTT and adjust dose accordingly. |
| Liver impairment | No specific Child-Pugh based adjustment; increased sensitivity may occur; monitor aPTT. |
| Pediatric use | Loading dose 75-100 units/kg IV over 10 minutes, maintenance 20-25 units/kg/hour continuous infusion, adjusted to aPTT. |
| Geriatric use | Reduce initial maintenance infusion by 20-30% due to higher bleeding risk; monitor aPTT 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 its high molecular weight and polarity. M/P ratio is not measured. Considered safe during breastfeeding. |
| Teratogenic Risk | Heparin does not cross the placenta and is not associated with teratogenicity in the first trimester; however, risk of maternal hemorrhage may increase in the third trimester. |
■ FDA Black Box Warning
Heparin is not intended for intramuscular injection. Epidural or spinal hematomas may occur in patients anticoagulated with heparin who receive neuraxial anesthesia or undergo spinal puncture, resulting in long-term or permanent paralysis. Risk is increased by use of indwelling epidural catheters, concomitant use of drugs affecting hemostasis (e.g., NSAIDs, antiplatelet agents, other anticoagulants), history of spinal deformity or spinal surgery. Monitor patients for signs and symptoms of neurological impairment.
| Common Effects | fluid replacement |
| Serious Effects |
["Absolute: Known hypersensitivity to heparin or pork products","Absolute: History of heparin-induced thrombocytopenia (HIT) or heparin-induced thrombocytopenia with thrombosis (HITT)","Relative: Active major bleeding (except when used in disseminated intravascular coagulation)","Relative: Severe thrombocytopenia (platelet count <100,000/μL) unless due to HIT","Relative: Inability to perform adequate coagulation monitoring (e.g., aPTT)","Relative: Recent central nervous system or eye surgery","Relative: Lumbar puncture or neuraxial anesthesia (increased risk of spinal hematoma; see black box warning)","Relative: Severe uncontrolled hypertension","Relative: Hemophilia or other bleeding disorders (e.g., von Willebrand disease)"]
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| Fetal Monitoring | Monitor maternal platelet count for heparin-induced thrombocytopenia (HIT), activated partial thromboplastin time (aPTT) for anticoagulation effect, signs of bleeding, fetal growth via ultrasound, and fetal heart rate monitoring in high-risk pregnancies. |
| Fertility Effects | Heparin has no direct known effects on fertility. However, anticoagulation may reduce risk of pregnancy loss in women with thrombophilia. |
| Precautions | ["Hemorrhage: Major bleeding risk, especially at high doses or in patients with risk factors (e.g., recent surgery, trauma, bleeding diathesis). Monitor coagulation parameters (aPTT, anti-factor Xa).","Heparin-induced thrombocytopenia (HIT): Type I (non-immune, transient) and Type II (immune-mediated, severe thrombocytopenia with thrombosis). Monitor platelet counts. Discontinue heparin if HIT suspected.","Heparin resistance: Reduced anticoagulant response, often due to antithrombin III deficiency.","Hypersensitivity reactions: Urticaria, rash, anaphylaxis (rare).","Hyperkalemia: Can suppress aldosterone secretion, leading to hyperkalemia, especially in patients with renal impairment or diabetes.","Osteoporosis: Long-term use (e.g., >6 months) can cause osteopenia or fractures.","Elevated liver enzymes: Transient increases in aminotransferases.","Use in renal impairment: Dose adjustment may be needed due to altered clearance."] |
| Food/Dietary | No specific food interactions. Avoid excessive vitamin K-rich foods (e.g., kale, spinach) as they may theoretically alter anticoagulation, but heparin acts by a different mechanism than warfarin; consistent intake is advised. Do not consume alcohol in large amounts as it may increase bleeding risk. |
| Clinical Pearls | Verify patient weight for dosing; use calibrated infusion pump; monitor aPTT 6h after bolus and dose changes; target aPTT 1.5-2.5x control; halve dose if renal impairment; have protamine sulfate available; avoid IM injections during therapy; check platelet counts for HIT; use preservative-free heparin in neonates; do not co-administer with other drugs in same IV line without compatibility check. |
| Patient Advice | Report any unusual bleeding or bruising immediately. · Avoid aspirin, NSAIDs, and other blood thinners unless prescribed. · Use soft toothbrush and electric razor to minimize bleeding risk. · Inform all healthcare providers that you are on heparin. · Do not stop or change dose without consulting your doctor. · Watch for signs of HIT: new rash, fever, or pain at injection site. · Keep all appointments for blood tests (aPTT). · If you miss a dose, contact your healthcare provider promptly. |