HEPANIR

Indications

• Prevention and treatment of venous thromboembolism
• Unstable angina
• Myocardial infarction
• Prophylaxis for patients undergoing surgery
• Management of atrial fibrillation with embolization risk

Dosage

Children: Paediatric dosing should be guided by the BNF for Children, as it varies based on indication and patient factors. It is critical to refer to the BNF for Children for specific dosing guidelines.

Adults: The dosage of heparin varies by indication and must be determined based on clinical guidelines and protocols, frequently requiring adjustment based on activated partial thromboplastin time (aPTT) monitoring.

Mechanism of action

Heparin works primarily by enhancing the activity of antithrombin III, which inhibits thrombin (factor IIa) and factor Xa, leading to a decrease in the formation of fibrin clots. This action occurs through the binding of heparin to antithrombin, causing a conformational change that increases its inhibitory activity on coagulation factors.

Pharmacodynamics

The anticoagulant effect of heparin is rapid and dose-dependent. It exerts its effect mainly through the inactivation of thrombin and factor Xa, which are crucial for the conversion of fibrinogen to fibrin. The pharmacodynamic response can be influenced by factors such as the patient's weight, underlying conditions, and concurrent medications.

Pharmacokinetics

Heparin has a rapid onset of action when administered intravenously, typically within minutes. Its half-life ranges from 1 to 2.5 hours, depending on the dose and route of administration. Heparin is primarily eliminated by the reticuloendothelial system, and its effects can be reversed with protamine sulfate if necessary.

Contra-indications

• active bleeding
• severe thrombocytopenia
• hypersensitivity to heparin or any component of the formulation
• history of heparin-induced thrombocytopenia
• severe liver disease

Adverse effects

• bleeding complications
• thrombocytopenia
• hypersensitivity reactions
• osteoporosis (with long-term use)
• heparin-induced thrombocytopenia

Interactions

• heparin+vasopressin: Unknown (decreases antidiuretic effect)

Precautions

• monitoring of coagulation parameters (aPTT or anti-Xa levels)
• use with caution in patients with renal impairment
• use with caution in patients with a history of gastrointestinal ulcerations

Pregnancy

Heparin is generally considered safe for use during pregnancy, particularly in women with a history of venous thromboembolism.

Breast-feeding

Heparin is not excreted in significant amounts in breast milk and is considered safe during breastfeeding.

Storage

Store at room temperature (15 to 30 degrees Celsius). Protect from light and keep out of reach of children.

Formulations

• Heparin sodium injection (subcutaneous or intravenous)
• Low molecular weight heparins (e.g., enoxaparin, dalteparin)