Verzenio (abemaciclib) is a prescription drug that’s used to treat certain breast cancers. Verzenio can cause side effects that range from mild to serious. Examples include weight loss, diarrhea, hair loss, and nausea.

Verzenio is used in adults to treat:

Specifically, Verzenio treats breast cancer that’s hormone receptor-positive (HR-positive) and human epidermal growth factor receptor 2-negative (HER2-negative). Unlike chemotherapy, Verzenio is a targeted therapy, meaning it targets cancer cells without harming healthy cells.

Keep reading to learn about the common, mild, and serious side effects that Verzenio can cause.

Some people may experience mild or serious side effects during their Verzenio treatment. Some of these side effects are more common than others. Examples of side effects that were reported more commonly in studies of people who took Verzenio include:

Learn more about diarrhea, nausea, and vomiting in the “Side effects explained” section.

Some people who take Verzenio may have mild side effects. Examples of mild side effects that have been reported with Verzenio include:

  • weight loss
  • abdominal pain
  • decreased appetite
  • infection, such as the common cold
  • headache
  • fatigue
  • hair loss
  • diarrhea
  • nausea and vomiting

In most cases, these side effects should be temporary, and some may be easily managed. But if you have any symptoms that are ongoing or that bother you, talk with your doctor or pharmacist. And do not stop taking Verzenio unless your doctor recommends it.

Verzenio may cause mild side effects other than the ones listed above. See the Verzenio prescribing information for details.

Learn more about hair loss, diarrhea, nausea, and vomiting in the “Side effects explained” section.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. Sharing your experience helps make medication safer for everyone by giving doctors and researchers more information about how the drug works in real life. If you develop a side effect while taking Verzenio and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

Some people who take Verzenio may have serious side effects. Examples of serious side effects that have been reported with Verzenio include:

If you develop serious side effects while taking Verzenio, call your doctor right away. If the side effects seem life threatening or if you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Learn more about blood clots in the “Side effects explained” section.

Allergic reaction

For some people, Verzenio can cause an allergic reaction. But this side effect wasn’t reported in the drug’s studies.

In general, symptoms of allergic reaction can be mild or serious.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should keep taking Verzenio.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Verzenio, they may have you switch to a different treatment.

Verzenio can cause long-term side effects. Some of these side effects may last for as long as you’re taking the drug. Others may continue even after you stop treatment with Verzenio.

Long-term side effects that were reported in Verzenio’s studies include elevated liver enzymes. This side effect usually doesn’t cause symptoms, but it could be a sign of a liver problem. Because of this risk, your doctor will monitor your liver health throughout treatment with Verzenio.

It’s important to note that this article may not include all possible long-term side effects from Verzenio. For more information about long-term side effects and whether they’ll go away, talk with your doctor or pharmacist.

Below you’ll find more detail about some of the side effects Verzenio may cause.

Hair loss

Some people who take Verzenio may experience hair loss or hair thinning.

Hair loss is also possible with other drugs that are sometimes used with Verzenio. These include fulvestrant (Faslodex), letrozole (Femara), and anastrozole (Arimidex). You may be more likely to have hair loss or thinning if you take Verzenio with one of these drugs.

What might help

You can help minimize hair loss by being gentle when washing, brushing, and styling your hair. You may want to avoid braiding, blow-drying, curling, or straightening your hair.

If you are troubled by hair loss or thinning while taking Verzenio, talk with your doctor. They can suggest ways to help you manage this side effect. For example, they may be able to give you advice about wigs or other scalp coverings, such as scarves.

If your hair gets very thin or you lose it completely, it’s important to protect your scalp from sunlight and cold. You can do this by wearing a hat or headscarf.

Diarrhea

You may have diarrhea while taking Verzenio. It’s one of the drug’s most common side effects.

Diarrhea is usually mild and typically goes away in a few days or weeks. However, diarrhea can sometimes become more severe, possibly leading to dehydration. With dehydration, your body loses too much fluid.

Diarrhea is most likely to occur in the first month after you start taking Verzenio.

What might help

Your doctor will monitor you closely for this side effect during Verzenio treatment. It’s important that this side effect is managed early to keep it from becoming severe. If you start having loose stools, you may want to consider:

  • telling your doctor right away
  • taking medication to treat diarrhea, such as loperamide (Imodium), as directed by your doctor
  • drinking plenty of fluids

If the diarrhea doesn’t ease within 24 hours of taking antidiarrheal medication, tell your doctor. They may ask you to stop taking Verzenio temporarily until the condition gets better. Your doctor will monitor you to make sure the diarrhea doesn’t get worse.

If your doctor recommends you start taking Verzenio again, they may prescribe a lower dose.

If you have particularly troublesome diarrhea with Verzenio, your doctor may recommend switching to a different medication for treating breast cancer.

Nausea

Nausea is another common side effect of Verzenio. Some people also have vomiting while taking this medication.

Nausea is usually mild and goes away in a few days or weeks. But some people have nausea that lasts longer than this or leads to vomiting.

If you have vomiting, this can be more serious because it could lead to dehydration.

What might help

If you have nausea or vomiting with Verzenio, talk with your doctor about ways to manage these side effects. They may recommend taking antinausea medication.

Other things you can try to reduce nausea include:

  • sipping fluids regularly over the day
  • eating little and often rather than having three main meals
  • avoiding greasy, spicy, or very sweet foods
  • trying complementary remedies, such as acupuncture or breathing techniques

If you have nausea after taking Verzenio without food, you could also try taking it with food. Likewise, if you have nausea after taking the drug with food, try taking it without food.

If you vomit after taking a dose of Verzenio, do not take another dose. Just continue with your usual dosing schedule. But if this happens often, be sure to tell your doctor. They may prescribe antinausea medication. Or they may recommend switching to a different medication for breast cancer.

Blood clots

Blood clots are a rare side effect of Verzenio. The blood clots that have been reported include:

These blood clots can be life threatening. In rare cases in studies, the blood clots were fatal.

Symptoms of blood clots may include:

What might help

Talk with your doctor about your risk of blood clots while taking Verzenio.

If you have symptoms of a blood clot while taking Verzenio, see your doctor right away. But if your symptoms feel life threatening, call 911 or your local emergency number.

If you receive a diagnosis of a blood clot, your doctor will prescribe medication to treat it. It’s possible that you might need to stop taking Verzenio. Your doctor may recommend switching to a different medication for breast cancer.

Here are the answers to some frequently asked questions about Verzenio’s side effects.

What happens when you stop taking Verzenio?

There are no specific side effects reported with stopping Verzenio treatment. In fact, if you experience certain side effects while taking Verzenio, stopping the drug may help the side effects go away.

But Verzenio is a treatment for breast cancer. If you stop treatment with Verzenio, it’s possible that this condition may worsen.

Because of this risk, it’s important that you do not stop taking Verzenio unless your doctor advises you to. If your doctor agrees that you should stop taking the drug, they can prescribe another treatment for breast cancer.

How long does it take for your body to adjust to Verzenio?

It depends. The amount of time it takes for your body to adjust to Verzenio can vary based on individual factors. But in the drug’s studies, it took about 5 days for people to have a steady level of Verzenio in their system.

Some reported side effects, such as diarrhea, occurred within a few days of starting treatment with Verzenio. Other side effects, such as low white blood cell levels, may occur a few weeks into treatment.

How long it takes your body to adjust to the drug may also depend on:

  • your dosage of Verzenio
  • the severity of the condition you’re taking Verzenio to treat
  • whether you’re taking Verzenio with any other medications

For more details, talk with your doctor or pharmacist.

Can taking Verzenio lead to eye-related side effects?

No, Verzenio isn’t known to cause any eye-related side effects. There weren’t any vision or eye-related side effects reported in studies of the drug.

Verzenio is sometimes used with other medications to treat breast cancer. These include letrozole (Femara) and anastrazole (Arimidex). Eye-related side effects, such as cataracts, have been reported with these medications.

Talk with your doctor if you notice any changes in your vision while taking Verzenio, either on its own or with other medications.

Will I need any lab tests while taking Verzenio?

Yes, it’s likely. Verzenio can sometimes cause problems with your liver or blood cells. So your doctor may order frequent blood tests to check for these side effects. These include complete blood count tests and liver function tests.

Your doctor will likely order lab tests if you experience the following symptoms:

If you have any of the symptoms above, be sure to tell your doctor. They’ll order the right lab test for you. Depending on the results, you and your doctor will decide how to continue treatment. You can also talk with them to learn more about these tests.

Can Verzenio give you a cough?

Yes, Verzenio may cause a cough. In studies, cough was commonly reported by people taking Verzenio. Cough is usually mild and typically gets better in a few days or weeks.

In rare cases, a cough may be a symptom of a lung problem, which can be a serious side effect of Verzenio.

Serious lung problems reported with Verzenio include pneumonitis (lung inflammation) and interstitial lung disease (inflammation, scarring, and stiffening of the lungs). Other symptoms of these lung problems can include shortness of breath, trouble breathing, chest pain, a fast heartbeat, and confusion.

If you have a cough or any other symptoms of lung problems while taking Verzenio, see your doctor. If you have a serious lung problem, your doctor may reduce your dose of Verzenio. Or they may ask you to stop treatment temporarily.

If the problem doesn’t improve, your doctor may recommend switching to a different medication for breast cancer.

Before taking Verzenio, discuss your health history with your doctor. Verzenio may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:

  • liver or kidney problems
  • allergic reaction
  • low white blood cell count
  • increased risk of blood clots
  • infection
  • alcohol consumption
  • pregnancy
  • breastfeeding

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.