Therapeutic Classification: anticoagulants
Pharmacologic Classification: antithrombotics
Absorption: Erratically absorbed following SUBQ or IM administration. IV administration results in complete bioavailability.
Distribution: Widely distributed to tissues.
Metabolism/Excretion: Probably removed by the reticuloendothelial system (lymph nodes, spleen).
Half-Life: 1–2 hr (↑ with increasing dose); affected by obesity, renal and hepatic function, malignancy, presence of PE, and infections.
Contraindicated in:
- Hypersensitivity;
- Uncontrolled bleeding;
- History of heparin-induced thrombocytopenia (HIT);
- Severe thrombocytopenia;
- Pedi: Avoid use of products containing benzyl alcohol in premature infants.
Use Cautiously in:
- Severe renal impairment;
- Severe hepatic impairment;
- Retinopathy (hypertensive or diabetic);
- Ulcer disease;
- Spinal cord or brain injury;
- History of congenital or acquired bleeding disorder;
- Malignancy;
- Diabetes mellitus, chronic renal failure, metabolic acidosis, increased serum potassium, or concurrent use of potassium-sparing drugs (↑ risk of hyperkalemia);
- OB: Use during pregnancy only if potential maternal benefit justifies potential fetal risk; avoid use of products containing benzyl alcohol;
- Lactation: Use while breastfeeding only if potential maternal benefit justifies potential risk to infant; avoid use of products containing benzyl alcohol;
- Geri: Women >60 yr have ↑ risk of bleeding.
Exercise Extreme Caution in:
- Severe uncontrolled hypertension;
- Bacterial endocarditis, bleeding disorders;
- GI bleeding/ulceration/pathology;
- Hemorrhagic stroke;
- History of thrombocytopenia related to heparin;
- Recent CNS or ophthalmologic surgery;
- Active GI bleeding/ulceration.
Heparin is frequently used concurrently or sequentially with other agents affecting coagulation. The risk of potentially serious interactions is greatest with full anticoagulation.
Drug-drug:
- Risk of bleeding may be ↑ by concurrent use of drugs that affect platelet function, including aspirin, NSAIDs, clopidogrel, dipyridamole, some penicillins, eptifibatide, tirofiban, and dextran.
- Risk of bleeding may be ↑ by concurrent use of drugs that cause hypoprothrombinemia, including quinidine, cefotetan, and valproic acid.
- Concurrent use of thrombolytics↑ risk of bleeding.
- Heparins affect the prothrombin time used in assessing the response to warfarin.
- Digoxin, tetracyclines, nicotine, and antihistamines may ↓ anticoagulant effect of heparin.
Drug-Natural Products:
Therapeutic Anticoagulation
- IV (Adults ): Intermittent bolus: 10,000 units, followed by 5000–10,000 units every 4–6 hr. Continuous infusion: 5000 units (35–70 units/kg), followed by 20,000–40,000 units infused over 24 hr (approx. 1000 units/hr or 15–18 units/kg/hr).
- IV (Children >1 yr): Intermittent bolus: 50–100 units/kg, followed by 50–100 units/kg every 4 hr. Continuous infusion: Loading dose 75 units/kg, followed by 20 units/kg/hr, adjust to maintain activated partial thromboplastin time (aPTT) of 60–85 sec.
- IV (Neonates and Infants <1 yr): Continuous infusion: Loading dose 75 units/kg, followed by 28 units/kg/hr, adjust to maintain aPTT of 60–85 sec.
- SC (Adults ): 5000 units IV, followed by initial SUBQ dose of 10,000–20,000 units, then 8000–10,000 units every 8 hr or 15,000–20,000 units every 12 hr.
Prophylaxis of Thromboembolism
- SC (Adults ): 5000 units every 8–12 hr (may be started 2 hr prior to surgery).
Cardiovascular Surgery
- IV (Adults ): At least 150 units/kg (300 units/kg if procedure <60 min; 400 units/kg if >60 min).
- IA (Neonates , Infants, and Children): 100–150 units/kg via an artery prior to cardiac catheterization.
Line Flushing
- IV (Adults and Children ): 10–100 units/mL (10 units/mL for infants <10 kg, 100 units/mL for all others) solution to fill heparin lock set to needle hub; replace after each use.
Total Parenteral Nutrition
- IV (Adults and Children ): 0.5–1 units/mL (final solution concentration) to maintain line patency.
Arterial Line Patency
- IA (Neonates ): 0.5–2 units/mL.
