What is the half-life of Clexane (enoxaparin)?

Half-Life of Clexane (Enoxaparin)

The elimination half-life of Clexane (enoxaparin) is approximately 4-5 hours after subcutaneous administration, which is significantly longer than unfractionated heparin's 1.5-hour half-life. 1

Pharmacokinetic Profile

• Enoxaparin has an elimination half-life of 3-6 hours after subcutaneous injection, with most studies reporting values around 4-5 hours 1, 2, 3
• Peak anti-Xa levels occur 3-5 hours after subcutaneous administration 1
• The bioavailability of enoxaparin is approximately 90-98% when given subcutaneously, which is substantially higher than unfractionated heparin 1, 3

Clinical Implications of the Half-Life

• The longer half-life enables once or twice daily dosing regimens without the need for continuous infusion 1
• This extended half-life provides more predictable anticoagulation with less need for laboratory monitoring compared to unfractionated heparin 1
• The standard prophylactic dose is 40 mg subcutaneously once daily, taking advantage of this prolonged duration of action 4, 5

Important Considerations in Special Populations

Renal Impairment

• The elimination half-life increases significantly with worsening renal function, as enoxaparin is predominantly cleared by the kidneys 1, 6
• In patients with severe renal impairment (creatinine clearance <30 mL/min), the elimination half-life is prolonged and anti-Xa clearance is reduced by approximately 39% compared to healthy volunteers 6
• Dose adjustment is necessary in severe renal impairment to prevent drug accumulation and bleeding risk 6, 7
• No dose adjustment is needed when creatinine clearance is >30 mL/min 5

Pregnancy and Postpartum

• Enoxaparin maintains its favorable pharmacokinetic profile in pregnancy, with a longer half-life (60-90 minutes for UFH versus several hours for enoxaparin) making it the preferred agent 4
• The drug is not secreted in breast milk, making it safe for breastfeeding mothers 5

Comparison with Other Anticoagulants

• Enoxaparin's half-life of 4.1 hours is longer than dalteparin (2.8 hours) and nadroparin (3.7 hours) 2
• This represents a 2.5-3 fold longer half-life compared to unfractionated heparin (1.5 hours) 1
• The longer half-life contributes to enoxaparin's superior pharmacokinetic profile, which is considered its most clinically important advantage 1

Common Pitfalls to Avoid

• Do not assume the half-life remains constant in renal dysfunction—it can be significantly prolonged, leading to drug accumulation 6, 7
• Do not use the same monitoring approach as unfractionated heparin—routine aPTT monitoring is not appropriate for enoxaparin 1
• Do not interchange different LMWHs based on anti-Xa units alone, as they have different pharmacokinetic properties and half-lives 1, 2
• Do not forget that anti-Xa monitoring, when needed, should be performed 4 hours post-dose when peak levels are achieved 1