HEPARIN SODIUM 25,000 UNITS IN SODIUM CHLORIDE 0.9%
Clinical safety rating: safe
No significant drug interactions Can cause hypernatremia and fluid overload.
Heparin binds to antithrombin III (ATIII) via a unique pentasaccharide sequence, inducing a conformational change that accelerates ATIII-mediated inactivation of coagulation factors IIa (thrombin), Xa, IXa, XIa, and XIIa. The heparin-ATIII complex primarily inhibits thrombin and factor Xa, with higher molecular weight heparin more effectively inactivating thrombin.
| Metabolism | Heparin is metabolized by the liver (heparinase) and to a lesser extent by the reticuloendothelial system. It is also partially depolymerized and desulfated. The clearance is dose-dependent and involves both saturable (cellular uptake and metabolism) and non-saturable (renal excretion) mechanisms. Heparin is partially excreted unchanged in urine. |
| Excretion | Renal: 40-60% unchanged via urine (dose-dependent saturable mechanism); hepatic: minimal; fecal: negligible. |
| Half-life | Terminal half-life: 1-2 hours (dose-dependent: 30-60 min after IV bolus 100 U/kg, up to 2-3 hours with higher doses or continuous infusion). Clearance is biphasic; prolonged in hepatic/renal impairment. |
| Protein binding | Highly bound to antithrombin III (ATIII) and other plasma proteins (e.g., albumin, lipoproteins); non-specific binding ~95% at therapeutic concentrations (saturable). |
| Volume of Distribution | Vd: 0.05-0.07 L/kg (confined to plasma volume; ~5-7 L in adults). Clinical meaning: low Vd indicates minimal extravascular distribution; primarily intravascular binding to ATIII and endothelial cells. |
| Bioavailability | SC: 20-30% (dose-dependent, lower with higher doses due to saturable absorption); IV: 100%; not administered orally (negligible absorption). |
| Onset of Action | IV: immediate (within seconds); SC: 20-30 minutes (therapeutic effect within 1 hour). |
| Duration of Action | IV: 2-4 hours (bolus dose); SC: 8-12 hours (dose-dependent, sustained anticoagulation with repeated dosing). Clinical notes: aPTT monitoring required; effects reversible with protamine. |
For therapeutic anticoagulation, administer 18 units/kg/hour intravenous infusion after a bolus of 80 units/kg. For prophylactic dosing, 5000 units subcutaneously every 8 to 12 hours.
| Dosage form | INJECTABLE |
| Renal impairment | No specific GFR-based dose reduction required; heparin is not renally cleared. Monitor aPTT and adjust per protocol. |
| Liver impairment | No Child-Pugh based dosing recommendations; use with caution in severe hepatic impairment due to increased bleeding risk. Monitor aPTT closely. |
| Pediatric use | Loading dose: 75-100 units/kg intravenously over 10 minutes. Maintenance infusion: initial 28 units/kg/hour for infants <1 year, 20 units/kg/hour for children >1 year; adjust to target aPTT. |
| Geriatric use | Elderly patients may have reduced heparin clearance; lower initial infusion rates (e.g., 15 units/kg/hour) and more frequent aPTT monitoring recommended to avoid over-anticoagulation. |
| 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; compatible with breastfeeding. M/P ratio: negligible. |
| Teratogenic Risk | Heparin does not cross the placenta; no evidence of teratogenicity in any trimester. FDA pregnancy category C (due to risk of maternal hemorrhage). |
■ FDA Black Box Warning
Heparin is not recommended for use as an anticoagulant in patients with a history of heparin-induced thrombocytopenia (HIT) or HIT with thrombosis (HITT). Monitor platelet counts closely. Risk of bleeding, especially in patients with risk factors. Use preservative-free heparin for neonatal patients to avoid benzyl alcohol toxicity.
| Common Effects | fluid replacement |
| Serious Effects |
["Absolute: History of heparin-induced thrombocytopenia (HIT) or HIT with thrombosis (HITT) (heparin), known hypersensitivity to heparin or pork products (if porcine-derived), active major bleeding (except when due to disseminated intravascular coagulation), severe uncontrolled bleeding disorders (e.g., hemophilia), suspected intracranial hemorrhage, epidural or spinal puncture within 24 hours (for full-dose anticoagulation)","Relative: Severe thrombocytopenia (platelet count <50,000/μL), uncontrolled severe hypertension, recent surgery (especially brain, spinal, or eye), active gastrointestinal ulcer or bleeding, hemorrhagic stroke (acute), pericarditis with effusion, bacterial endocarditis, threatened abortion, severe renal or hepatic impairment, advanced age (>60-70 years)"]
| Precautions |
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| Fetal Monitoring | Monitor aPTT (maintain 1.5-2.5 times control), platelet count for heparin-induced thrombocytopenia (HIT), signs of hemorrhage, and fetal surveillance (ultrasound, non-stress test) if anticoagulation is prolonged. |
| Fertility Effects | No direct impact on fertility. However, underlying conditions requiring heparin (e.g., thrombophilia) may affect fertility and pregnancy outcomes. |
| ["Risk of heparin-induced thrombocytopenia (HIT) type II, immune-mediated; monitor platelet counts every 2-3 days from day 4 to 14 or until heparin stopped","Risk of bleeding: elderly, renal impairment, concomitant antiplatelet agents","Heparin resistance (antithrombin III deficiency, elevated factor VIII)","Hyperkalemia due to aldosterone suppression (risk increased with renal impairment, diabetes, potassium-sparing diuretics)","Spinal/epidural hematoma risk with neuraxial anesthesia; monitor for neurological compromise","Do not administer intramuscularly due to risk of hematoma","Use with caution in patients with severe hypertension, recent surgery, gastrointestinal ulcers, or hemorrhagic stroke"] |