What is the recommended heparin (Low Molecular Weight Heparin (LMWH)) regimen for Deep Vein Thrombosis (DVT) prophylaxis?

Heparin DVT Prophylaxis Regimens

For DVT prophylaxis, unfractionated heparin (UFH) 5,000 units subcutaneously every 8 hours or enoxaparin 40 mg subcutaneously once daily are the standard recommended regimens, with UFH every 8 hours preferred over every 12 hours dosing for superior efficacy. 1

Standard Prophylactic Dosing Options

Unfractionated Heparin (UFH)

• UFH 5,000 units subcutaneously every 8 hours is the preferred regimen for most hospitalized patients requiring DVT prophylaxis 2, 1, 3
• Three-times-daily dosing (every 8 hours) provides more consistent anticoagulant effect and superior DVT prevention compared to twice-daily dosing 1, 4
• UFH is the agent of choice for patients with renal impairment (creatinine clearance <30 mL/min) as it is primarily metabolized by the liver rather than renally cleared 1

Low Molecular Weight Heparin (LMWH) Options

• Enoxaparin 40 mg subcutaneously once daily is equally effective to UFH and offers convenient once-daily dosing 2, 1
• Dalteparin 5,000 units subcutaneously once daily is an alternative LMWH option 2, 1
• Tinzaparin 4,500 units or 75 units/kg subcutaneously once daily can also be used 2, 1
• Fondaparinux 2.5 mg subcutaneously once daily is another option for prophylaxis 2

Timing and Duration

Initiation

• Medical patients: Start prophylaxis upon admission for patients with acute medical illness or reduced mobility 2
• Surgical patients: Administer UFH 5,000 units 2 hours before surgery, or start LMWH 2-4 hours preoperatively or 10-12 hours preoperatively 2, 1, 3

Duration

• Medical patients: Continue until fully ambulatory or hospital discharge 1
• Surgical patients: Minimum 7-10 days postoperatively 2, 1
• High-risk patients (hip/knee replacement, hip fracture): Consider extended prophylaxis for 4 weeks post-discharge 2
• Cancer patients: Extended prophylaxis should be considered, especially with ongoing risk factors 1

Special Population Adjustments

Renal Impairment

• For creatinine clearance <30 mL/min: Use UFH 5,000 units every 8 hours (preferred) or reduce enoxaparin to 30 mg subcutaneously once daily 1
• Avoid standard LMWH dosing in severe renal impairment due to accumulation risk 2

Obesity (BMI >30 kg/m²)

• Consider intermediate-dose enoxaparin 40 mg subcutaneously every 12 hours or weight-based dosing at 0.5 mg/kg every 12 hours 1
• Standard prophylactic doses may be inadequate in morbidly obese patients 1

Cancer Patients

• UFH 5,000 units subcutaneously every 8 hours is specifically recommended for hospitalized cancer patients 2, 1
• LMWH is generally preferred over UFH for cancer patients when renal function is normal 2
• Continue prophylaxis as long as cancer is active or chemotherapy is ongoing 2, 1

Pregnancy

• LMWH is strongly preferred over UFH and warfarin for both prophylaxis and treatment in pregnant patients 2
• Prophylactic doses: enoxaparin 40 mg once daily or dalteparin 5,000 units once daily 2
• Continue for at least 6 weeks postpartum with minimum total duration of 3 months if treating acute VTE 2

Critical Clinical Pitfalls

Timing with Neuraxial Anesthesia

• Administering anticoagulants too close to spinal or epidural anesthesia significantly increases spinal hematoma risk 1
• Ensure appropriate time intervals between anticoagulant administration and neuraxial procedures per anesthesia guidelines 1

Monitoring

• Routine anti-Xa monitoring is not required for prophylactic doses in most patients 1
• Consider monitoring in patients with extreme body weights (very low or very high), renal impairment, or unexpected bleeding 1
• aPTT monitoring is not useful for LMWH 5, 6

Inadequate Dosing

• Every 12-hour UFH dosing is less effective than every 8-hour dosing for DVT prevention 1, 4
• Low-dose UFH (5,000 units every 12 hours) is not recommended as sole therapy for high-risk orthopedic surgery 2

Bleeding Risk Assessment

• Screen all patients for bleeding disorders before initiating prophylaxis 3
• Injection site bruising occurs in approximately 20% of patients receiving subcutaneous heparin but is not a contraindication to continue therapy 4
• Major bleeding rates are lower with LMWH (3.3%) compared to UFH (5.7%) 7

Premature Discontinuation

• Continue prophylaxis for the full recommended duration even if patients appear mobile, as most thromboembolic events occur within the first 7-10 days postoperatively 2, 3
• For hip and knee replacement, extending prophylaxis beyond hospital discharge reduces VTE risk 2