NAPLEX Question of the Week: VTE Prophylaxis Dosing

Dosing is an important part of the NAPLEX. VTE prophylaxis can be accomplished with many agents that varying dosing strategies.

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A 68 year old male with a past medical history of hypertension, hyperlipidemia, and COPD is admitted to your hospital for community acquired pneumonia. His labs include a WBC 15, Hgb 11.2, Na+ 135, K+ 4.1, Chloride 108, Glucose 110, SCr 2.4 mg/dL, and estimated of CrCl 26 mL/min (Cockcroft-Gault). CBC demonstrates a platelet count of 195K. Upon working up the patient, you find that the patient does not have chemical prophylaxis for venous thromboembolism (VTE). Which of the following would be appropriate VTE prophylaxis for this patient?

 

A. Heparin 5000 units SQ daily

B. Heparin 7500 units SQ q8h

C. Enoxaparin 30 mg SQ daily

D. Enoxaparin 40 mg SQ daily

 

 

The correct answer is C.

 

As pharmacists, it is important to identify patients who are indicated or contraindicated for VTE prophylaxis. The CHEST Guidelines recommend VTE prophylaxis in all acutely ill hospitalized medical patients at increased risk of thrombosis unless contraindicated (i.e. active bleeding). Additionally, it is crucial to distinguish differences in dose and frequency for prophylaxis vs. treatment.

While heparin can be used for VTE prophylaxis, the dose and frequency make answers A and B incorrect. The appropriate dose of heparin for VTE prophylaxis is 5000 units SQ q8h. There is no renal or hepatic dose adjustment necessary. Although controversial, some clinicians recommend a higher prophylactic dose of 7500 units q8h in obese patients (BMI ≥ 30 kg/m2).

The usual prophylactic dose of enoxaparin is 40 mg SQ daily. However, enoxaparin requires a renal dose adjustment to 30 mg SQ daily for patients with a CrCl < 30 mL/min. Because this patient has an estimated CrCl of 26 mL/min, answer D is incorrect.

Another agent that can be used for VTE prophylaxis is fondaparinux. While it is FDA approved for VTE prophylaxis in certain surgical patients, fondaparinux does not have an on label indication for medical patient prophylaxis. It is also important to note that prophylactic use of fondaparinux is contraindicated in patients < 50 kg.

Certain direct oral anticoagulants, such as rivaroxaban at 10mg daily, have FDA-approval for medical VTE prophylaxis. The advantage to these agents is their oral dosage form however their cost may preclude broad usage for some patients.

For patients who have a contraindication to chemical prophylaxis, mechanical prophylaxis can be initiated with graduated compression stockings or intermittent pneumatic compression (IPC). Intermittent pneumatic compression devices “squeeze” the legs to increase blood flow in the area to prevent clot formation.

Christopher M. Bland

Clinical Associate Professor, University of Georgia College of Pharmacy

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