Difference Between Enoxaparin and Heparin

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  • 0:04 Background Scenario
  • 0:40 The Basics
  • 1:50 Mechanism of Action
  • 3:03 Administration
  • 5:34 Side Effects
  • 7:03 Lesson Summary
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Lesson Transcript
Instructor: Alexandra Unfried

Alexandra earned her master's degree in nursing education and is currently a hospital supervisor/administrator.

Heparin and enoxaparin are both considered blood thinners to reduce blood clots. However, there are different reasons for using each medication. This lesson discusses the differences between heparin and enoxaparin.

Background Scenario

In this lesson, we're going to follow the medical course of two people to differentiate between the common uses of heparin and enoxaparin.

Roger has been admitted to the hospital for a pulmonary embolism, which is a blood clot in the lungs, that may affect his overall health and well-being. Luckily, the blood clot is small, but he is still started on continuous heparin.

Bob just had knee surgery and is being discharged home. He is still recovering, so his lower activity level places him at risk to develop a blood clot. He is sent home with a prescription to give himself an injection of enoxaparin twice a day for two weeks.

The Basics

Heparin and enoxaparin are both anticoagulants that reduce and prevent blood clots. Heparin is known as unfractionated heparin, while enoxaparin, also made from heparin, is known as low molecular weight heparin.

Both medications are used for:

  • Deep vein thrombosis (DVT): blood clot deep in the veins
  • Pulmonary embolism (PE): blood clot in the lungs
  • Myocardial infarction (MI) or acute coronary syndrome (ACS): heart attack
  • Pre-surgical and post-surgical intervention: preventing blood clots
  • Atrial fibrillation (A-fib): heart arrhythmia

Heparin is less costly in the United States than enoxaparin, so it is used often in the hospital setting where it can be monitored more closely. Enoxaparin, however, has been shown to be more predictable and safe when used for a variety of indications. That is why enoxaparin is used outside of the hospital and at home.

Roger and Bob are still trying to figure out how their medications work. Hopefully this helps clear some things up.

Mechanism of Action

Here are some definitions:

  • Antithrombin: small protein (glycoprotein) in the blood that inactivates enzymes during coagulation
  • Factor Xa: enzyme that helps with coagulation process in the blood
  • Prothrombin: protein in the blood that becomes activated thrombin during coagulation
  • Thrombin: enzyme in the blood that converts fibrinogen into fibrin
  • Fibrinogen: glycoprotein that helps form blood clots
  • Fibrin: protein that forms the mesh to slow down blood flow

Heparin works to bind to antithrombin in order to disable factor Xa. This prevents the conversion of prothrombin to thrombin and fibrinogen to fibrin. It also binds to plasma proteins and skin cells when given subcutaneously, making the dose a little unpredictable.

Enoxaparin binds to the antithrombin but has a longer lasting effect on disabling factor Xa. It is less able to prevent thrombin production and binds less to the plasma proteins and skin cells. Therefore, enoxaparin is more predictable and lasts longer than heparin.


Heparin can be given subcutaneously (SQ) or intravenously (IV) depending on the reason for the medication. SQ medication is given as an injection under the skin, and IV medication is given as a continuous or intermittent medication that goes directly into the bloodstream.

Levels of IV heparin in the blood must be carefully monitored to reduce the risk of side effects. When given SQ, the monitoring is less frequent, and risk for side effects decreases. Bob is getting enoxaparin, which can only be give SQ and does not require frequent monitoring.

Because heparin can be given continuously IV, it is frequently used as a first defense against life-threatening DVTs, PEs, and MIs. This ensures that enough anticoagulant medication is being given to reduce any more blood clots from forming. This is what is happening in Roger's situation. As he is stabilized, the IV medication is stopped, and either SQ heparin or enoxaparin is substituted while a pill form of anticoagulant is started.

Dosing of Heparin and Enoxaparin

The half-life of a medication is the amount of time it lasts in the body before half of it is out of your system. This determines dosing for medications and how often it is needed to produce a therapeutic response.

Heparin has a much shorter half-life than enoxaparin. That means that heparin is given in a higher dose amount and more frequently than enoxaparin. Heparin's half-life is 45 minutes, and enoxaparin's half-life is four to five hours.

Because of the half-life and dosing frequency of enoxaparin, it is the usual choice when thinking about home administration. Bob, who had knee surgery, will have limited movement and need an anticoagulant until his activity returns to normal. Heparin SQ has to be given two to three times a day for prevention of blood clots, while enoxaparin can be given one to two times a day to have the same effect. Therefore, enoxaparin is used for home administration.

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