How soon after stopping heparin (Heparin Sodium) infusion can you start Enoxaparin (Low Molecular Weight Heparin) 1 milligram/kilogram twice daily (BID) dosing?

Timing of Enoxaparin Initiation After Stopping Heparin Infusion

You can start enoxaparin 1 mg/kg BID immediately after stopping the heparin infusion without any waiting period. 1

Direct Transition Protocol

• No gap period is required when transitioning from unfractionated heparin (UFH) infusion to enoxaparin therapy 1
• The American College of Cardiology/American Heart Association guidelines describe starting enoxaparin with a 30 mg IV bolus immediately followed by 1 mg/kg subcutaneously every 12 hours, which can be initiated as soon as the heparin infusion is discontinued 1
• For patients with acute coronary syndromes, enoxaparin dosing begins immediately upon stopping UFH, with the first subcutaneous dose given shortly after any initial IV bolus 1

Standard Dosing Regimen

• Therapeutic dosing: Enoxaparin 1 mg/kg subcutaneously every 12 hours (BID) 1
• An optional 30 mg IV bolus may be given immediately before the first subcutaneous dose in selected patients, particularly those with acute coronary syndromes 1
• The first subcutaneous dose should be administered at the same time the heparin infusion is stopped 1

Critical Safety Considerations

• Avoid switching back and forth between enoxaparin and UFH, as this significantly increases bleeding risk 2, 3
• Once you transition to enoxaparin, commit to that anticoagulation strategy unless there is a compelling clinical reason to change 2
• The seamless transition is safe because both agents work through similar mechanisms (anti-factor Xa and anti-factor IIa activity), and there is no risk of a "gap" in anticoagulation 1

Special Population Adjustments

Renal Impairment

• Severe renal failure (CrCl <30 mL/min): Reduce to 1 mg/kg subcutaneously once daily instead of BID 2, 3
• Consider switching to UFH entirely in severe renal impairment, as enoxaparin accumulates and increases bleeding risk 2.25-fold 3
• Monitor anti-Xa levels 4 hours after the third dose in patients with CrCl <30 mL/min 3

Elderly Patients

• Age ≥75 years: Consider reducing to 0.75 mg/kg subcutaneously every 12 hours (no initial IV bolus) 2
• Elderly patients have higher bleeding risk and may require closer monitoring 3

Obesity

• BMI >30 kg/m²: Standard weight-based dosing (1 mg/kg BID) is appropriate; no adjustment needed 2, 4
• BMI >40 kg/m²: Consider 0.5 mg/kg BID for prophylactic dosing, but therapeutic dosing remains 1 mg/kg BID 2

Common Pitfalls to Avoid

• Do not wait 4-6 hours after stopping heparin to start enoxaparin—this creates an unnecessary gap in anticoagulation and increases thrombotic risk 1
• Do not use once-daily dosing (1.5 mg/kg) for therapeutic anticoagulation in critically ill patients, as trough levels fall below therapeutic range in most patients 5
• Do not forget renal dose adjustment—failure to reduce dosing in severe renal impairment increases major bleeding risk nearly 4-fold 3
• Do not continue standard BID dosing in patients on hemodialysis—administer the daily dose 6-8 hours after dialysis completion to minimize bleeding at vascular access sites 3

Monitoring Recommendations

• Check baseline platelet count, hemoglobin, and creatinine clearance before initiating enoxaparin 6
• Monitor platelets every 2-3 days from day 4 to day 14 to detect heparin-induced thrombocytopenia 6
• Hold enoxaparin if platelets fall below 50,000/mcL 6
• In severe renal impairment, monitor anti-Xa levels with target therapeutic range of 0.5-1.0 IU/mL (peak at 4 hours post-dose) 3, 4