How Does Lovenox (Enoxaparin) Work? All About Its Mechanism of Action

Lovenox (enoxaparin) is an injectable medicine that helps prevent blood clots from forming. But how does it work, and why is it different from other blood thinners like warfarin? Let’s take a closer look at Lovenox’s mechanism of action to better understand how it works in the body.

How do blood clots form?

To understand how Lovenox works, we need to know a little bit about how blood clots form. Blood clotting is a natural process that happens when our body tries to heal an injury, like a cut or a scrape. When we bleed, blood cells called platelets come together to form a clot. This clot stops the bleeding and helps the wound to heal. This is a good thing because it helps prevent blood loss when we’re injured.

Blood clots are formed by a complex process that involves several different proteins called clotting factors. Each clotting factor activates the next one in a waterfall effect that eventually leads to a stable blood clot. One of the most important clotting factors is called thrombin. Thrombin is responsible for converting a protein called fibrinogen into fibrin, which is the final building block of a blood clot. Factor Xa is another clotting factor that helps to activate thrombin.

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Sometimes, these clotting factors can become overactive and form clots when they shouldn't, like in the veins of your legs or lungs. Clots in your legs are called a deep vein thrombosis (DVT). Clots in your lungs are called a pulmonary embolism (PE). These clots can cause serious health problems, like a stroke or heart attack. And this is where Lovenox comes in.

How does Lovenox prevent blood clots?

Lovenox is a type of medication called a low molecular weight heparin (LMWH). Heparin is a naturally occurring substance in our body that helps to prevent blood clots. LMWHs like Lovenox are made by chemically changing heparin to make it more effective and easier to use.

Lovenox binds to a protein called antithrombin III. This protein prevents factor Xa from working properly. Lovenox makes antithrombin III more effective at blocking factor Xa. This in turn makes factor Xa unable to activate thrombin. Without thrombin, blood clots aren’t able to form or get bigger, which reduces the risk of DVT or PE.

How is Lovenox administered?

Lovenox is given as an injection under the skin, in the stomach or thigh. It’s typically given in a hospital setting to prevent blood clots in people who are undergoing surgery or have a medical condition that increases their risk of clotting. It’s also used while waiting for oral blood thinners to start working.

In most cases, Lovenox is only prescribed for a short period of time. But sometimes it’s also prescribed for longer at-home use. A common example of this is if you need a blood thinner during pregnancy. Lovenox doesn’t cross the placenta, so it won’t affect a growing fetus. It’s the preferred option to prevent blood clots while you’re pregnant.

Good to know: Lovenox prevents clots from forming or getting larger. But it doesn’t break up clots that are already there. So you may need another medication along with Lovenox to break up any existing clots you have.

How is Lovenox different from warfarin?

You don't need regular blood tests with Lovenox like you do with warfarin (Coumadin, Jantoven). Warfarin works by blocking the production of certain clotting factors in the liver. Because of this, it takes longer for warfarin to start working, and it can also take longer to wear off. It also means that everyone responds to warfarin differently, so your dose is based on regular blood tests.

A blood test called the international normalized ratio (INR) measures how well your blood clots. If your INR is too low, you might not be protected against blood clots. If your INR is too high, you might be at risk of bleeding. Your warfarin dosage may change based on your INR levels.

But with Lovenox, there's no need to monitor your INR. This is because it works quickly and is broken down by the body within a few hours. Your dose is based on your body weight, not your INR level. This means that the risk of bleeding is generally lower with Lovenox compared to warfarin. And you don’t need regular blood tests to make sure it’s working properly.

You also don’t have to watch what you eat with Lovenox the way you do with warfarin. Vitamin K in your diet can affect how well warfarin works. So you need to be consistent with how much vitamin K you’re consuming while you’re taking it. But Lovenox isn’t affected by vitamin K, so no dietary changes are needed.

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Written by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

Reviewed by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

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