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.
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.
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.
At this point, Roger needs a high dose of anticoagulants and needs to be continuous while he is being assessed for the best way to treat his blood clot. A PE is considered a medical emergency and must be treated aggressively while being monitored closely to make sure it does not block circulation to the lung or travel to the brain.
Bob is stable after surgery and needs an anticoagulant for preventative care. Therefore, he does not need continuous medication or close monitoring. Twice-a-day injections will be enough to prevent blood clots.
Both heparin and enoxaparin have similar side effects and adverse reactions including:
- Excessive bleeding
- Mild pain, redness, swelling, or bruising at the site of injection
- Nausea and vomiting
- Increased fatigue
Heparin-induced thrombocytopenia (HIT) is a severe reaction to heparin, in which the heparin reacts with antibodies in the blood, causing platelets to decrease. Platelets play an important role in clotting the blood, so a reduction in platelets puts you more at risk for uncontrollable bleeding. Because of the low molecular weight of enoxaparin in relation to heparin, it has a decreased incidence of HIT occurring, although it is still possible.
Because both medications are anticoagulants, there are certain medications that must be avoided or used cautiously. Other anticoagulants, certain antibiotics, some heart medications, and antihistamines should be used carefully with heparin and enoxaparin because they can increase side effects or decrease the effectiveness of the medication. You need to inform your doctor about any medications that you are taking.
Roger is having mild side effects of bleeding. He picked at a scab on his arm, and it took a long time for the bleeding to stop because of the continuous heparin he is getting. Bob is also having mild side effects of some bruising at the site of injection for his enoxaparin. Luckily, there are no signs of HIT, so treatment can continue for both Roger and Bob.
Let's take a few moments to recap what we learned about the differences between enoxaparin and heparin.
Heparin and enoxaparin are different types of anticoagulants, which prevent and reduce blood clots. Heparin is classified as unfractionated heparin, and enoxaparin is classified as low molecular weight heparin. Anticoagulants are administered for treatment of DVTs, MIs, PEs, A-fib, and pre- and post-surgical interventions. Heparin can be given subcutaneously (SQ), which is given as an injection under the skin or intravenously (IV), meaning given directly into the blood stream through an injection. But, enoxaparin can only be given SQ.
The half-life, or the amount of time it takes for half of a substance to leave your system, of both medications helps to determine when to use it. Heparin has a shorter half-life of 45 minutes, while enoxaparin has a half-life of four to five hours. Heparin is usually given in the hospital setting where it can be more closely monitored and is often used IV for emergencies. Enoxaparin is safe to give in the hospital and at home. The most severe side effect of heparin and enoxaparin is heparin-induced thrombocytopenia (HIT), which causes uncontrolled bleeding. An alternative medication must be considered if this occurs. It is more commonly seen with heparin.
Medical Disclaimer: The information on this site is for your information only and is not a substitute for professional medical advice.