Verzenio
Verzenio (abemaciclib) is an oral medication used to treat certain types of breast cancer. It's FDA approved for hormone receptor-positive, human epidermal growth factor 2-negative (HR+, HER2‑) breast cancer, including early and advanced or metastatic stages. This medication belongs to a group called CDK4/6 inhibitors, which slow down the growth of cancer cells. It comes as a pill that’s taken by mouth twice a day, without breaks. You might take Verzenio (abemaciclib) on its own or with hormone therapy. Common side effects include diarrhea, low white blood cell counts, and tiredness.
What is Verzenio (abemaciclib)?
What is Verzenio (abemaciclib) used for?
Early breast cancer (HR+, HER2-), used with tamoxifen or an aromatase inhibitor in adults at high risk of the cancer coming back
Advanced or metastatic breast cancer (HR+, HER2-), used with
An aromatase inhibitor as the first hormone-based treatment OR
Fulvestrant either as the first treatment or after the cancer has stopped responding to hormone-based treatment
Advanced or metastatic breast cancer (HR+, HER2-), used alone if the cancer has worsened after both hormone-based treatment and chemotherapy
How Verzenio (abemaciclib) works
Verzenio (abemaciclib) is a cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitor. CDK 4/6 are proteins that help control how cells grow. In cancer, these proteins can become too active, causing cells to grow and divide too quickly. Verzenio (abemaciclib)] blocks these proteins to help slow down the growth of cancer cells.
Drug Facts
More on Verzenio (abemaciclib) essentials
What are the side effects of Verzenio (abemaciclib)?
Common Side Effects
- Rise in creatinine (99%)
- Lower white blood cell count (up to 91%)
- Diarrhea (90%)
- Anemia (69%)
- Tiredness (65%)
- Nausea (64%)
- Reduced appetite (45%)
- Lower platelet count (41%)
- Stomach pain (39%)
- Vomiting (35%)
- Infections (31%)
- Rise in liver enzymes (up to 31%)
- Headache (20%)
Other Side Effects
- Cough
- Changes in taste
- Constipation
- Mouth sores
- Joint pain
- Dizziness
- Dry mouth
- Dehydration
- Weight loss
- Fever
- Hair loss
Serious Side Effects
- Severe diarrhea: frequent loose stools, stomach pain, weakness
- Serious infections: fever, chills, dizziness, trouble breathing, weakness, easy bruising or bleeding
- Lung problems: cough, trouble breathing, shortness of breath, chest pain
- Liver problems: tiredness, pain on the upper right side of your stomach area, loss of appetite, bleeding or bruising more easily
- Blood clots: pain or swelling in your arms or legs, shortness of breath, chest pain, rapid breathing, rapid heart rate
Source: DailyMed
More on Verzenio (abemaciclib) side effects
The following side effects have also been reported
Side effects that you should report to your care team as soon as possible:
- Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
- Blood clot—pain, swelling, or warmth in the leg, shortness of breath, chest pain
- Dry cough, shortness of breath or trouble breathing
- Infection—fever, chills, cough, sore throat, wounds that don't heal, pain or trouble when passing urine, general feeling of discomfort or being unwell
- Liver injury—right upper belly pain, loss of appetite, nausea, light-colored stool, dark yellow or brown urine, yellowing skin or eyes, unusual weakness or fatigue
- Low red blood cell level—unusual weakness or fatigue, dizziness, headache, trouble breathing
- Severe or prolonged diarrhea
- Unusual bruising or bleeding
Side effects that usually do not require medical attention (report these to your care team if they continue or are bothersome):
Pros and cons of Verzenio (abemaciclib)
Pros
Taken by mouth twice a day, every day without breaks
First-choice treatment option for metastatic and certain early breast cancers
Can be taken with or without food
Cons
Can cause severe diarrhea and low white blood cells
Requires regular blood tests to monitor for side effects
Interacts with many products and medications
Pharmacist tips for Verzenio (abemaciclib)
You can take Verzenio (abemaciclib) with or without food. Take it at the same time each day, and always swallow the tablet whole. Don’t chew, crush, or split it.
If you miss a dose of Verzenio (abemaciclib) or vomit after taking it, don’t take another dose that day. Just take your next dose at the usual scheduled time.
Avoid grapefruit and grapefruit juice while taking Verzenio (abemaciclib). These can raise the levels of the medication in your body and increase side effects.
Some medications can interact with Verzenio (abemaciclib). Tell your care team about all the medications you take, including supplements and over-the-counter (OTC) medications.
Diarrhea is very common with Verzenio (abemaciclib). Your oncologist might prescribe an antidiarrheal medication like loperamide to keep on hand. If you have diarrhea, take the antidiarrheal, drink fluids to stay hydrated, and tell your care team.
Verzenio (abemaciclib) can lower your blood cell counts. This raises your risk for bleeding and infections, so keep up with lab work. If you develop signs of infection, such as chills or a fever of 100.4°F or higher, seek medical attention right away.
Although rare, Verzenio (abemaciclib) can cause blood clots. Call your care team right away if you have chest pain, shortness of breath, a racing heartbeat, or swelling or pain in your arms or legs.
If you’re taking Verzenio (abemaciclib) for early stage breast cancer, treatment usually lasts 2 years unless your cancer comes back or you can't tolerate it. For advanced or metastatic breast cancer, you might take it longer until the cancer worsens or you can't tolerate the medication.
Verzenio (abemaciclib) can harm unborn babies. If you can get pregnant, you'll need a pregnancy test before starting treatment. You’ll also need to use effective birth control while taking the medication and for 3 weeks after your last dose. Talk to your oncologist if you're pregnant or plan to get pregnant.
It's not known if it's safe to breastfeed while taking Verzenio (abemaciclib). To be safe, don’t breastfeed while taking this medication and for at least 3 weeks after your last dose.
More on Verzenio (abemaciclib) tips
Frequently asked questions about Verzenio (abemaciclib)
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What are the risks and warnings for Verzenio (abemaciclib)?
Verzenio (abemaciclib) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Diarrhea
Diarrhea is a very common side effect of Verzenio (abemaciclib), and in some cases it can cause serious dehydration or infection. Most people will have diarrhea within the first few weeks of treatment, and symptoms can last up to 2 weeks. At the first sign of loose stools, contact your care team as you might need to take an antidiarrheal like loperamide. Depending on how severe the diarrhea is, you might need to pause treatment or continue with a lower dose. Be sure to drink plenty of fluids to replace what you lose and help prevent dehydration.
Low white blood cell counts
Verzenio (abemaciclib) can lower your white blood cell count, which makes it easier for you to get infections. In studies, severe cases usually started about 1 month after treatment began and lasted around 2 weeks. Your oncologist will check your blood counts every 2 weeks for the first 2 months, monthly for the next 2 months, then as needed after that. Tell your oncologist right away if you get a fever or start feeling sick. They might need to lower your dose of Verzenio (abemaciclib) or have you stop it for a short time.
Lung problems
It's not common, but Verzenio (abemaciclib) can cause serious lung problems, like lung inflammation or interstitial lung disease. Let your cancer care team know right away if you have new or worsening breathing issues, such as coughing or shortness of breath. Your oncologist might tell you to stop taking the medication while they figure out what’s causing the symptoms. If the symptoms are serious or keep coming back, you might need to stop the medication for good.
Liver problems
Verzenio (abemaciclib) can raise your liver enzyme levels, which might be a sign of liver irritation or problems. In studies, this usually happened about 2 to 3 months after starting treatment and lasted for around 2 weeks. Your care team will check your liver with blood before you start, every 2 weeks for the first 2 months, then monthly for the next 2 months, and later as needed. If your enzyme levels get too high, your oncologist might pause or lower your dose of Verzenio (abemaciclib). Call your care team if you feel very tired, lose your appetite, have pain on the right side of your stomach, or notice easy bruising or bleeding.
Blood clots
Although uncommon, Verzenio (abemaciclib) can cause blood clots, in places like your legs, lungs, pelvis, brain, or other veins. Some blood clots have been fatal. Get medical help right away if you notice pain or swelling in your arms or legs, chest pain, shortness of breath, or a fast heartbeat.
Harm to unborn baby
Verzenio (abemaciclib) might harm an unborn baby. In animal studies, it caused birth defects and low birth weight. If you’re able to become pregnant, your oncologist will have you take a pregnancy test before starting treatment. You’ll also need to use effective birth control while taking Verzenio (abemaciclib) and for at least 3 weeks after your last dose. Tell your oncologist right away if you become pregnant during this time.
Verzenio (abemaciclib) dosage forms
Typical dosing for Verzenio (abemaciclib)
If used with other medications: The typical starting dose is 150 mg taken by mouth twice a day.
If used alone: The typical starting dose is 200 mg taken by mouth twice a day.
Your dose might be different if you experience certain side effects, have liver problems, or you’re taking medications that interact with Verzenio (abemaciclib).
More on Verzenio (abemaciclib) dosage forms
What are alternatives to Verzenio (abemaciclib)?
Early breast cancer (HR+, HER2-), used with tamoxifen or an aromatase inhibitor in adults at high risk of the cancer coming back
Advanced or metastatic breast cancer (HR+, HER2-), used with
An aromatase inhibitor as the first hormone-based treatment OR
Fulvestrant either as the first treatment or after the cancer has stopped responding to hormone-based treatment
Advanced or metastatic breast cancer (HR+, HER2-), used alone if the cancer has worsened after both hormone-based treatment and chemotherapy
Early breast cancer (HR+, HER2-), used with an aromatase inhibitor in adults at high risk of the cancer coming back
Advanced or metastatic breast cancer (HR+, HER2-), used with
Advanced or metastatic breast cancer (HR+, HER2-), used with
Advanced or metastatic breast cancer (HR+, HER2-) with a PIK3CA mutation, used with inavolisib and fulvestrant after the cancer has come back following hormone therapy
What is the latest news about Verzenio (abemaciclib)?
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References
Best studies we foundConner, K., et al. (2023). What are CDK4/6 inhibitors? Breastcancer.org.
Eli Lilly and Company. (2025). Verzenio- abemaciclib tablet [package insert]. DailyMed.
National Cancer Institute. (n.d.). pneumonitis.
National Comprehensive Cancer Network. (2025). Inflammatory breast cancer.
National Comprehensive Cancer Network. (2025). Metastatic breast cancer.
Raschi, E., et al. (2021). Skin Toxicities with Cyclin-Dependent Kinase 4/6 Inhibitors in Breast Cancer: Signals from Disproportionality Analysis of the FDA Adverse Event Reporting System. American Journal of Clinical Dermatology.
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