PANHEPRIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PANHEPRIN (PANHEPRIN).
Heparin binds to antithrombin III, causing a conformational change that accelerates the inactivation of thrombin (factor IIa) and activated factor X (factor Xa), thereby inhibiting blood coagulation.
| Metabolism | Heparin is metabolized primarily by the reticuloendothelial system and undergoes desulfation and depolymerization. Renal clearance also contributes; approximately 50% is excreted unchanged in urine at higher doses. |
| Excretion | Primarily renal excretion of metabolites (desulfated heparin) with a minor biliary/fecal component. Unchanged heparin is not excreted renally; clearance occurs via saturable hepatic metabolism and reticuloendothelial system uptake. Renal excretion accounts for approximately 50% of total clearance at therapeutic doses, while biliary/fecal elimination is <10%. |
| Half-life | Terminal elimination half-life is dose-dependent: at standard IV doses (100 U/kg), mean t½ = 60 min (range 40–90 min); at high doses (400 U/kg), t½ increases to 150 min due to saturable clearance mechanisms. Clinical context: Short t½ necessitates continuous infusion or frequent subcutaneous dosing for sustained anticoagulation. |
| Protein binding | Highly protein-bound to antithrombin III (ATIII) and other plasma proteins; non-specific binding: 95–98% at therapeutic concentrations. Binding to heparin cofactor II occurs to a lesser extent. |
| Volume of Distribution | Apparent Vd: 0.05–0.1 L/kg (confined to plasma volume; low distribution due to high protein binding and negative charge). Clinical meaning: Low Vd indicates minimal extravascular distribution; heparin remains largely intravascular. |
| Bioavailability | Subcutaneous: 20–30% (due to poor absorption and first-pass hepatic metabolism? actually, heparin has low bioavailability SC because of binding to endothelial cells and macrophages). Intramuscular: highly variable and not recommended due to risk of hematoma. Note: Heparin is not absorbed orally. |
| Onset of Action | Intravenous: immediate (within 1–2 minutes). Subcutaneous: delayed onset 20–60 minutes due to slow absorption from injection site. |
| Duration of Action | Intravenous: 2–4 hours (dose-dependent). Subcutaneous: 8–12 hours. Clinical note: Duration is prolonged in hepatic or renal impairment; monitoring of aPTT is required to adjust dosing. |
80 units/kg IV bolus followed by 18 units/kg/hour continuous IV infusion; adjust to maintain aPTT 1.5-2.5 times control.
| Dosage form | INJECTABLE |
| Renal impairment | If CrCl <30 mL/min: reduce initial infusion rate by 50% and monitor aPTT closely. No standard dose adjustment for CrCl 30-60 mL/min, but increased monitoring recommended. |
| Liver impairment | No specific Child-Pugh based guidelines. Use with caution in severe hepatic impairment due to increased bleeding risk; monitor aPTT frequently. |
| Pediatric use | Initial: 75 units/kg IV bolus (over 10 minutes), then 20 units/kg/hour continuous IV infusion; adjust to aPTT 60-85 seconds. |
| Geriatric use | No specific dose adjustment, but lower initial doses (e.g., 50 units/kg bolus) may be considered due to increased bleeding risk from altered clearance; monitor aPTT and renal function closely. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PANHEPRIN (PANHEPRIN).
| Breastfeeding | Not excreted into breast milk; compatible with breastfeeding; M/P ratio not applicable as heparin is not secreted into milk. |
| Teratogenic Risk | Heparin does not cross the placenta; no evidence of teratogenicity in first trimester; no known fetal risk in second or third trimester. |
| Fetal Monitoring | Monitor platelet count, signs of bleeding, anti-Xa levels if therapeutic dosing, and uterine bleeding in pregnancy. |
■ FDA Black Box Warning
Heparin-induced thrombocytopenia (HIT) and thrombosis: Monitor platelet counts closely; HIT can progress to thrombotic events. Neuroaxial anesthesia risk: Risk of spinal/epidural hematoma with concurrent use of anticoagulants.
| Serious Effects |
Active major bleeding, history of heparin-induced thrombocytopenia (HIT) or heparin-induced thrombocytopenia and thrombosis (HITTS), severe hypersensitivity to heparin (including pork products), and inability to perform appropriate blood monitoring.
| Precautions | Risk of heparin-induced thrombocytopenia (HIT), hemorrhage (especially in patients with coagulopathies, recent surgery, or concurrent antiplatelet therapy), hyperkalemia (suppresses aldosterone), and osteoporosis with long-term use. Monitor platelet counts and aPTT regularly. |
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| Fertility Effects | No known adverse effects on fertility in animal studies or human reports. |