What is the recommended dose of heparin (unfractionated heparin) or low molecular weight heparin (LMWH) for subcutaneous Deep Vein Thrombosis (DVT) prophylaxis?

Recommended Dosing for Subcutaneous DVT Prophylaxis

For DVT prophylaxis, unfractionated heparin should be administered at 5,000 units subcutaneously every 8 hours, while LMWH options include enoxaparin 40 mg subcutaneously once daily or dalteparin 5,000 units subcutaneously once daily. 1, 2

Unfractionated Heparin (UFH) Dosing

UFH is an effective option for DVT prophylaxis with specific dosing recommendations:

• Standard prophylactic dose: 5,000 units subcutaneously every 8 hours 2
• Alternative dosing: 5,000 units subcutaneously every 12 hours (though less effective than the 8-hour regimen) 3, 1

The three-times-daily regimen (every 8 hours) has been shown to significantly reduce the risk of DVT from 73% to 22% and pulmonary embolism from 20% to 5% compared to no prophylaxis 1.

Low Molecular Weight Heparin (LMWH) Options

LMWHs offer advantages including once-daily dosing and no need for routine monitoring:

• Enoxaparin: 40 mg subcutaneously once daily 2
• Dalteparin: 5,000 units subcutaneously once daily 2
• Tinzaparin: 4,500 units or 75 units/kg subcutaneously once daily 2
• Fondaparinux: 2.5 mg subcutaneously once daily (synthetic pentasaccharide) 2

Special Populations and Considerations

Cancer Patients

For cancer patients, the higher frequency UFH regimen (5,000 units every 8 hours) is preferred over the twice-daily regimen due to greater efficacy 1.

Renal Impairment

• UFH: Preferred in severe renal impairment (CrCl <30 mL/min) as it doesn't require dose adjustment 2
• LMWH: Use with caution in renal impairment; specific recommendations include:
  • Enoxaparin: 30 mg subcutaneously once daily when CrCl <30 mL/min 2
  • Consider avoiding dalteparin and tinzaparin in severe renal impairment or adjust based on anti-factor Xa levels 2

Obesity

Weight-based dosing may be required for patients with obesity (>120 kg), though optimal dosing is unclear 2.

Contraindications

Absolute contraindications to heparin prophylaxis include:

• Recent central nervous system bleeding
• Active major bleeding
• Severe thrombocytopenia with positive HIT antibodies 1

In patients with contraindications to pharmacological prophylaxis, mechanical prophylaxis with intermittent pneumatic compression devices is recommended 2.

Monitoring

• Routine monitoring of coagulation parameters is not necessary for prophylactic doses in patients with normal baseline coagulation 3
• Monitor platelet counts regularly to detect heparin-induced thrombocytopenia (HIT), particularly between days 4-14 of therapy 2, 1

Duration of Prophylaxis

Continue prophylaxis until the patient is fully ambulatory or until hospital discharge, with a minimum recommended duration of 7 days for high-risk patients 3, 2.

Comparative Efficacy

LMWH has been shown to be more effective than UFH in certain high-risk populations. In a study of patients undergoing hip replacement, enoxaparin 40 mg once daily reduced the incidence of proximal DVT from 18.5% to 7.5% compared to UFH 5,000 units every 8 hours 4.

The choice between UFH and LMWH should be based on patient factors, cost considerations, and institutional protocols, as both are effective for DVT prophylaxis when administered at appropriate doses.