HP, a 55-year-old male (80 kg, CrCl: 75 mL/min) is admitted to the hospital with a diagnosis of acute pulmonary embolism (PE). His past medical history includes hypertension, type 2 diabetes, and hyperlipidemia. The team wants to initiate anticoagulation therapy.

Past medical history:

Hypertension: Zestoretic 20-12.5mg daily

Type 2 Diabetes: Metformin 1000mg BID

Hyperlipidemia: Atorvastatin 80mg daily

Which of the following regimens would be appropriate for HP’s anticoagulation? Select all that apply.

A. Lovenox 40mg SQ daily

B. Enoxaparin 30mg SQ Q12H

C. Lovenox 80mg SQ Q12H

D. Heparin 5000 units SQ Q8H

E. Heparin 6400 units IV bolus, then 1500 units/hr continuous IV infusion

Answer with rationale:

Deep vein thrombosis (DVT) and pulmonary embolism (PE) are serious conditions that fall under the category of venous thromboembolism (VTE). DVT’s occur when blood clots form in the deep veins (most commonly in the legs), and they can become PE’s if they break off and travel to the lungs, causing life-threatening complications.

Anticoagulation is the cornerstone of treatment, with Lovenox (enoxaparin) and unfractionated heparin (UFH) commonly used in both prevention and initial treatment. Lovenox is a low molecular weight heparin that is often preferred for its predictable pharmacokinetics, subcutaneous administration, and reduced need for therapeutic drug monitoring. In contrast, UFH is typically administered subcutaneously for prophylaxis and intravenously for treatment in hospital settings and requires the monitoring of aPTT when using for treatment to ensure therapeutic levels. UFH can be favored in patients at high risk of bleeding or with renal impairment, as its effects can be quickly reversed (antidote is protamine), has a short half-life, and is not as affected by kidney dysfunction. Both agents play critical roles in managing DVT/PE and reducing the risk of recurrence or progression.

The dosing regimens for these drugs are generally adjusted for several factors, the most common being renal function, weight, or age, but it is important to understand that individual institutions will have their own specific dosing protocols. Unfractionated heparin dosing when given intravenously for management is adjusted via hospital-based nomogram based on either anti-Xa levels or aPTT. 

Answer A is incorrect: Lovenox can be used either for prophylaxis or treatment of DVT’s and PE’s, but they have different recommended dosing regimens. For prophylaxis, enoxaparin 40mg SQ daily or 30mg SQ Q12H are accepted dosages for a patient without any significant renal impairment. The treatment dose is either 1mg/kg SQ Q12H or 1.5mg/kg SQ daily.

Answer B is incorrect: As in answer choice A, this is a prophylactic dose. If the CrCl is less than 30mL/min, it is recommended to reduce the prophylactic dose to 30mg SQ daily, and the treatment dose to 1mg/kg SQ daily. 

Answer C is correct: Because the patient has a CrCl greater than 30mL/min, it would be appropriate to use the treatment dose of 1mg/kg Q12H or 1.5mg/kg daily. The patient weighs 80kg, so a regimen of 80mg SQ Q12H is appropriate.

Answer D is incorrect: 5000 units SQ Q8-12H is a generally accepted prophylactic regimen for UFH, however treatment doses of UFH are normally IV, not SQ, and are dosed via weight-based approach. UFH levels are not heavily affected by impaired renal function, so most institutions will use this initial dosing, then adjust based on aPTT and protocols with nomograms. 

Answer E is correct: The treatment regimens for UFH can be a little more complicated, and it is important to be aware of specific institutional protocol. In general, there is an initial loading dose of roughly 80 units/kg IV, followed by 18 units/kg/hr of continuous IV infusion, adjusted based on protocol with nomogram. For other indications, UFH may be dosed with a lower bolus dose of approximately 60 units/kg IV followed by an infusion of 12-15 units/kg/hr. 

 Brand/generics Covered:

Lisinopril-HCTZ (Zestoretic), Metformin, Atorvastatin (Lipitor), Enoxaparin (Lovenox), Unfractionated Heparin (UFH)

Naplex Content Domains Covered

1.C.1,2,3 : Calculations of quantities dispensed and rates of administration using patient parameters

2.A.2: Indications, usage, and dosing regimens

3.C.2 : Appropriateness of drug therapy