What is the recommended dosing for Deep Vein Thrombosis (DVT) prophylaxis in an adult inpatient?

DVT Prophylaxis Dosing for Adult Inpatients

For acutely ill hospitalized medical patients, use enoxaparin 40 mg subcutaneously once daily, unfractionated heparin (UFH) 5000 units subcutaneously every 8 hours, or fondaparinux 2.5 mg subcutaneously once daily, continued throughout hospitalization. 1, 2, 3

Standard Prophylactic Regimens

First-Line Options

• Enoxaparin 40 mg subcutaneously once daily is the most commonly used regimen for general medical and surgical patients 1, 2, 3
• UFH 5000 units subcutaneously every 8 hours provides more consistent anticoagulant effect than twice-daily dosing and is preferred in cancer patients 1, 2, 3
• Fondaparinux 2.5 mg subcutaneously once daily is equally effective and may be preferred when heparins must be avoided 1, 2, 3
• Dalteparin 5000 IU subcutaneously once daily serves as an alternative LMWH option 1, 2

Critical Dosing Distinction

UFH dosed three times daily (every 8 hours) is significantly more effective than twice-daily dosing for DVT prevention 1, 2. The 5000 units every 8 hours regimen is specifically recommended over 5000 units every 12 hours. 2

Special Population Adjustments

Renal Impairment (CrCl <30 mL/min)

• Reduce enoxaparin to 30 mg subcutaneously once daily 2, 3, 4
• UFH 5000 units every 8 hours is preferred as it's primarily hepatically metabolized and doesn't accumulate 2, 3, 4
• Fondaparinux is contraindicated in severe renal insufficiency (CrCl <30 mL/min) per FDA labeling 5
• For critically ill patients with severe renal dysfunction, fondaparinux 2.5 mg every 48 hours may be considered based on emerging evidence showing appropriate anti-Xa levels 6

Obesity (BMI >30 kg/m²)

• Increase enoxaparin to 40 mg subcutaneously every 12 hours (intermediate dosing) 2, 3, 4
• Alternatively, use weight-based dosing at 0.5 mg/kg subcutaneously every 12 hours 2, 3
• Standard once-daily dosing may be inadequate in obese patients 1

Cancer Patients

• UFH 5000 units subcutaneously every 8 hours is the preferred regimen 1, 2, 3
• LMWH is generally preferred over UFH for long-term prophylaxis in cancer patients 2
• Three times daily UFH dosing provides superior VTE prevention in this high-risk population 2

Duration of Prophylaxis

• Continue until fully ambulatory or hospital discharge for medical patients 2, 3
• Minimum 7-10 days for surgical patients 1, 2, 3
• Extended prophylaxis (up to 35 days) should be considered for orthopedic surgery patients 1
• For acutely ill medical patients at continued risk, rivaroxaban 10 mg once daily can be used for 31-39 days total duration (in-hospital plus post-discharge) 5

High Bleeding Risk Patients

When pharmacologic prophylaxis is contraindicated due to active bleeding or high bleeding risk:

• Use mechanical prophylaxis with graduated compression stockings and/or intermittent pneumatic compression (IPC) 1, 3
• Transition to pharmacologic prophylaxis once bleeding risk decreases 1, 3
• Do not withhold prophylaxis entirely—mechanical methods provide meaningful protection 1

Critical Timing Considerations

Surgical Patients

• Start enoxaparin 2-4 hours preoperatively OR 10-12 hours preoperatively 2, 3
• For UFH, the last preoperative dose should be given 12 hours before surgery 1
• Never administer anticoagulants within 12 hours of neuraxial anesthesia due to spinal hematoma risk 3, 5
• Resume prophylactic LMWH 12 hours after surgery; therapeutic LMWH requires 48 hours post-surgery 1

Monitoring Requirements

• Routine anti-Xa monitoring is NOT required for prophylactic doses in most patients 2, 3
• Monitor platelet counts every 2-3 days from day 4 to day 14 for heparin-induced thrombocytopenia (HIT) surveillance in patients receiving UFH or LMWH 3, 4
• The risk of HIT with UFH may reach 5%, particularly after orthopedic surgery 4
• Consider anti-Xa monitoring only in extreme body weights or renal impairment 2

Common Pitfalls to Avoid

Dosing errors: Enoxaparin 30 mg twice daily (the treatment dose for renal impairment) results in significantly higher DVT rates compared to 40 mg once daily for prophylaxis—this is a critical error to avoid 7. The 30 mg twice daily regimen is NOT appropriate for standard prophylaxis. 7

Inadequate prophylaxis in obesity: Standard prophylactic doses achieve subtherapeutic anti-Xa levels in obese patients, requiring dose adjustment 1, 2

Premature discontinuation: Stopping anticoagulation without bridging to another agent increases thrombotic risk 5

Rivaroxaban misuse: While rivaroxaban 10 mg daily is FDA-approved for VTE prophylaxis in acutely ill medical patients, it was noninferior but not superior to enoxaparin in trials and carried higher bleeding risk with extended use 1, 5. It is not recommended as first-line by current guidelines for general medical patients. 1