From the Guidelines
The half-life of heparin is approximately 30 minutes to 150 minutes when administered intravenously, depending on the dose, with higher doses resulting in a longer half-life. This variability in half-life is due to the complex kinetics of heparin clearance, which involves a combination of rapid saturable and slower first-order mechanisms 1. The half-life can vary based on several factors including dose administered, patient's liver function, and individual metabolic differences. Heparin works by binding to antithrombin III, enhancing its ability to inactivate several coagulation factors including thrombin and factor Xa. Due to this short half-life, unfractionated heparin is typically administered as a continuous IV infusion in clinical settings requiring ongoing anticoagulation. For procedures or situations where rapid reversal of anticoagulation may be necessary, heparin's short half-life is advantageous compared to other anticoagulants. In contrast, low molecular weight heparins (like enoxaparin) have longer half-lives of 3-6 hours, allowing for once or twice daily subcutaneous dosing rather than continuous infusion.
Some key points to consider when administering heparin include:
- The dose and route of administration can affect the half-life and anticoagulant response 1
- Heparin is not absorbed orally and must be administered parenterally 1
- The anticoagulant response to heparin can be nonlinear at therapeutic doses, with both the intensity and duration of effect rising disproportionately with increasing dose 1
- Heparin is contraindicated in patients with heparin-induced thrombocytopenia (HIT) and should only be used with extreme caution in patients with a history of HIT 1.
Overall, the half-life of heparin is an important consideration in clinical practice, and healthcare providers should be aware of the potential for variability in half-life and adjust dosing accordingly to minimize the risk of bleeding or thrombosis.
From the FDA Drug Label
The plasma half-life is dose-dependent and it ranges from 0.5 to 2 h. The half-life of heparin is dose-dependent, ranging from 0.5 to 2 hours 2, 2.
- The half-life is affected by the dose of heparin administered.
- It is also influenced by the patient's age, with geriatric patients potentially having a longer half-life.
From the Research
Half-Life of Heparin
- The half-life of heparin is not explicitly stated in the provided studies, but it can be inferred from the pharmacokinetic properties of unfractionated heparin (UH) and low molecular weight heparin (LMWH) 3, 4.
- Unfractionated heparin is removed from the blood via two mechanisms: saturable and non-saturable, with the saturable mechanism being more prominent at low doses 4.
- The half-life of UH varies depending on the dose, with higher doses resulting in a longer half-life due to the increased contribution of the non-saturable mechanism 4.
- In contrast, LMWHs are mainly removed by non-saturable renal excretion, resulting in a more predictable half-life that is dose-independent 4.
- The biological half-life of LMWH is almost twice as long as that of UH, with a half-life that is prolonged in cases of chronic renal insufficiency 3.
Comparison of Half-Life between UH and LMWH
- The half-life of anti-factor Xa activity is considerably longer for LMWH than for UH after intravenous administration 3.
- The anti-factor IIa half-lives are similar between UH and LMWH 3.
- The bioavailability of LMWH is substantially higher than that of UH, making LMWH a more convenient and effective option for anticoagulation therapy 3, 5, 6, 7.