HEPARIN SODIUM 25,000 UNITS IN SODIUM CHLORIDE 0.9%
Clinical safety rating
safeNo 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. |
| Molecular Weight | 12000-15000 Da (average 15000 Da for unfractionated heparin) |
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 | Heparin does not cross the placenta due to its high molecular weight and is not associated with teratogenic risk. Use for thromboembolism prophylaxis or treatment is generally considered safe. |
| 2nd trimester | Safe for use as heparin does not cross the placenta and has no known fetal adverse effects. Monitor for maternal bleeding and osteoporosis with prolonged use. |
| 3rd trimester | Safe for use. Risk of maternal hemorrhage at delivery; consider discontinuation or protamine reversal if needed. No fetal harm expected. |
Clinical note
No significant drug interactions Can cause hypernatremia and fluid overload.
| FDA category | Animal |
| Placental transfer | Does not cross the placenta due to high molecular weight and negative charge. No measurable fetal concentrations. |
| Breastfeeding | Heparin is not excreted into breast milk due to its large molecular size and is considered compatible with breastfeeding. Monitor infant for signs of bleeding if high maternal doses are used, though risk is negligible. |
| Lactation Rating | L1 - Safe |
| 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). |
| 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. |
■ 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 |
Active major bleedingSevere thrombocytopenia (e.g., heparin-induced thrombocytopenia, immune type)Known hypersensitivity to heparin or pork productsInability to perform appropriate coagulation monitoring (e.g., aPTT)
| Precautions | 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 |
| Food/Dietary | No direct food interactions. Avoid excessive consumption of vitamin K-rich foods (e.g., leafy greens) if transitioning to warfarin, as it may affect INR. |
| Clinical Pearls | For heparin infusion, monitor aPTT 6 hours after initiation or dose change; goal typically 1.5-2.5 times control. Use weight-based dosing (e.g., 18 units/kg/hr). Avoid intramuscular injections due to hematoma risk. Check platelet counts for heparin-induced thrombocytopenia (HIT) every 2-3 days. Protamine sulfate reverses heparin at a ratio of 1 mg per 100 units. |
| Patient Advice | Report any unusual bleeding, bruising, or dark stools. · Inform all healthcare providers that you are on heparin. · Use an electric razor and soft toothbrush to avoid injury. · Do not take aspirin or NSAIDs without doctor approval. · Notify your doctor if you experience chest pain, shortness of breath, or leg swelling. |
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