What is the optimal timing for administering Clexane (enoxaparin) based on a patient's platelet count and International Normalized Ratio (INR) range?

When to Administer Clexane Based on Platelet Count and INR

Clexane (enoxaparin) should be administered when platelet count is ≥50,000/mm³ for prophylactic dosing and ≥100,000/mm³ for therapeutic dosing, with no specific INR threshold required before initiation, though INR should be monitored if transitioning from or to warfarin. 1

Platelet Count Thresholds

For Prophylactic Dosing (VTE Prevention)

• Initiate Clexane when platelet count is ≥50,000/mm³ in hospitalized patients requiring thromboprophylaxis 1
• Hold prophylactic enoxaparin if platelet count drops below 50,000/mm³ due to increased bleeding risk 1
• Monitor platelet count at least every 2-3 days for the first 14 days after initiation, then every 2 weeks thereafter 1

For Therapeutic Dosing (VTE Treatment)

• Initiate therapeutic Clexane when platelet count is ≥100,000/mm³ for treatment of established DVT or PE 1
• Consider holding therapeutic anticoagulation if platelets fall below 50,000/mm³ unless thrombotic risk substantially outweighs bleeding risk 1
• In cancer patients with thrombocytopenia, the decision requires careful assessment of bleeding versus thrombotic risk 1

Monitoring for Thrombocytopenia

• Obtain baseline CBC with platelet count before initiating enoxaparin 1
• Paradoxically, enoxaparin may cause reactive thrombocytosis rather than thrombocytopenia in some patients, with platelet counts occasionally exceeding 600,000/mm³ without causing thrombotic complications 2, 3
• Heparin-induced thrombocytopenia (HIT) is less common with enoxaparin than unfractionated heparin, but monitoring remains essential 4

INR Considerations

When Starting Clexane

• No specific INR threshold is required before initiating enoxaparin - it can be started regardless of baseline INR 1
• Obtain baseline PT/INR before starting therapy for reference 1

When Transitioning Between Anticoagulants

• When bridging from enoxaparin to warfarin: Overlap enoxaparin with warfarin for minimum 5-7 days and continue until INR is therapeutic (2.0-3.0) for 2 consecutive days 1
• When transitioning from warfarin to enoxaparin: Start enoxaparin when INR falls below therapeutic range 1
• Critical warning: Never switch between enoxaparin and unfractionated heparin once treatment is initiated, as this substantially increases bleeding risk 5

Target INR Ranges for Warfarin (When Applicable)

• Standard VTE treatment: INR 2.0-3.0 1
• Mechanical mitral valves: INR 2.5-3.5 1

Contraindications to Clexane Administration

Absolute Contraindications

• Active major bleeding 1
• Severe thrombocytopenia (platelet count <50,000/mm³ for prophylaxis, <100,000/mm³ for therapeutic dosing) 1
• History of heparin-induced thrombocytopenia 1

Relative Contraindications Requiring Dose Adjustment

• Severe renal impairment (CrCl <30 mL/min): Reduce therapeutic dose to 1 mg/kg once daily instead of twice daily 1, 5
• Age ≥75 years (for ACS patients): Reduce dose to 0.75 mg/kg every 12 hours without initial IV bolus 5
• Recent neuraxial anesthesia: Wait minimum 8-12 hours after epidural catheter removal before administering enoxaparin 1, 5

Timing of Administration

Initial Dosing

• Hospitalized medical patients: Start within 24-36 hours of admission 5
• Surgical patients: Administer 2-4 hours preoperatively or 10-12 hours preoperatively depending on protocol 1
• Trauma patients: Initiate within 36 hours of injury 5

Special Populations

• Cancer patients: Duration should be at least 3 months or as long as cancer is active or under treatment 1
• Post-surgical patients: Continue for minimum 7-10 days; consider extended prophylaxis up to 4 weeks for high-risk patients 1

Common Pitfalls to Avoid

• Do not delay thromboprophylaxis beyond 36 hours in eligible ICU or hospitalized patients without clear contraindications 5
• Do not switch between enoxaparin and unfractionated heparin during treatment course - this dramatically increases bleeding risk 5
• Do not use fixed dosing in obese patients (BMI >30) - consider weight-based intermediate dosing 5
• Do not administer enoxaparin within 8-12 hours of epidural catheter manipulation to avoid spinal hematoma 1, 5
• Do not ignore renal function - failure to adjust dose in severe renal impairment (CrCl <30 mL/min) leads to drug accumulation and bleeding 1, 5