What is Verzenio (Abemaciclib)?

Verzenio is a prescription medication that contains the active ingredient abemaciclib. It is classified as a cyclin-dependent kinase (CDK) inhibitor and is primarily used in the treatment of certain types of advanced or metastatic breast cancer. Verzenio works by inhibiting specific proteins called CDK4 and CDK6, which play a role in cell division and growth. By targeting these proteins, it helps slow down the progression of cancer cells. It is usually taken orally, and the dosage may vary based on individual factors and specific treatment plans. It is important to follow the prescribed regimen and consult with a healthcare professional for personalized guidance, potential side effects, and drug interactions.

Verzenio (Abemaciclib) | Metastatic Breast Cancer Treatment
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What is Verzenio?

Verzenio (Abemaciclib) is used to treat adults in all stages of with hormone-receptor-postive (HR+), HER2-, node-positive, early breast cancer that has a high risk of returning.

It is also used in some cases of Metastatic breast cancer (MBC), given with an aromatase inhibitor as initial endocrine-based therapy of males or postmenopausal women.

How does Verzenio work?

Verzenio is used as a combination treatment along with endocrine therapy. Cancer cells grow in uncontrolled fashion. Verzenio stops cancer cells from metastasizing (dividing and growing) by inhibiting cyclin-dependent kinases. By interfering with kinase, a type of protein in the body that controls cell division, Verzenio can prevent growth of cancer cells.

It can be used alone or in combination with Faslodex to treat hormone-receptor-positive, HER2-negative, metastatic, or advanced-stage breast cancer. It may also be used in combination with an aromatase inhibitor to treat advanced-staged breast cancer in post-menopausal women who have not previously received hormone therapies.

It may also be used in tandem with tamoxifen to reduce recurrence of risk for early-stage, hormone-receptor-positive, HER2-negative, node-positive breast cancer that is highly likely to come back.


Verzenio is a pill that is taken orally. The starting doses of Verzenio are

  • 150 mg twice daily, taken in combination with another endocrine treatment such as Faslodex, tamoxifen, or an aromatase inhibitor
  • 200 mg taken twice daily, used alone

To get the most benefit from the drug, take it regularly. Do not increase your dose or use this drug for longer than prescribed. Your condition will not improve faster, and the risk of serious side effects is guaranteed to increase.


If someone experiences symptoms, namely fainting or trouble breathing, call emergency services (911) or a poison control center immediately. US resident can call 1-800-222-1222 to reach their local poison control center.

Missed Doses

If you vomit your dose of Verzenio, do not take another. Plan to take your next dose at your regularly scheduled time. Refrain from taking two doses at once.

Side Effects

Like most other breast cancer medicines, Verzenio can cause intense side effects.

One of the most common side effects of Verzenio is diarrhea. For most, this symptom begins during the first week (give or take) of treatment. Your doctor will likely prescribe an anti-diarrheal as a preventative measure.

Additional side effects include:

  • lowered white blood cell count
  • fatigue
  • nausea
  • abdominal pain
  • increased risk of infection
  • anemia
  • vomiting
  • headache
  • hair loss
  • low platelet counts

In rarer but more serious cases, Verzenio can cause severe side effects, including:

  • Liver issues – yellowing of skin or eyes, dark urine, extreme fatigue, loss of appetite, bleeding or bruising more than usual
  • Severe Neutropenia (low white blood cell count) – low white blood cell counts are a typical side effect, but in cases of severe neutropenia, one may have to decrease or halt their dosage of Verzenio. Before and during treatment with Verzenio, your doctor will monitor your white blood cell count.
  • Blood clots – Verzenio may cause serious or life-threatening clots in your lungs and arteries. If you experience shortness of breath, rapid heart rate, rapid breathing, or a sudden sharp chest pain, tell your doctor immediately.

Since you may take Verzenio in combination with other drugs such as Faslodex, tamoxifen, or an aromatase inhibitor, you may also experience side effects from those medications. Common Faslodex side effects feature hot flashes, nausea, and vomiting. Tamoxifen may also cause hot flashes, nausea, and fatigue. Aromatase inhibitors are also known to cause joint stiffness and pain.

Overall, this medicine has been prescribed because your provider has determined that projected benefits outweigh the negative effects. If any symptoms become bothersome or your health worsens on Verzenio, be sure to notify your provider to see about alternatives or techniques for reducing severity of side effects.

Tell your doctor immediately if you experience serious side effects, namely: unusual tiredness, bruising or bleeding easily, liver damage (frequent nausea and vomiting, loss of appetite), stomach or abdominal pain, yellowing of the skin or eyes, and dark urine.

Serious allergic reactions to this drug are rare. However, if you noticed symptoms of an allergic reaction, such as: itchiness, rash, swelling/inflammation, dizziness, or trouble breathing, seek emergency help immediately.

Serious side effects can be reported to the FDA at 1-800-FDA-1088 or fda.gov/medwatch.

Warnings & Precautions

With diarrhea as a side effect, it is important to try and mitigate dehydration. Tell your doctor if you have loose stools so they can prescribe an anti-diarrheal. Be sure to drink plenty of fluids to reduce your risk of dehydration.

Temporary hair loss might occur. Your hair should grow back as normal upon finishing treatment with Verzenio.

Before taking this medication, tell your doctor or pharmacist your full medical history, especially if you have a history of liver disease or bleeding/clotting issues.

This drug may lower your ability to fight off pathogens. Your risk of developing a serious or fatal infection is more likely on this medication. If you experience signs of infection such as sore throat, fever, chills, or cough, notify your doctor promptly.

This drug can be absorbed through skin and lungs and may harm an unborn baby. As such, women who are pregnant should not handle the medication, breath dust from the tablets, or or ingest this medication.

Storage & Safety

For safety and best results, store your prescription at its recommended temperature. Keep it away from light and high moisture (e.g. away from your bathroom). Keep all medications out of reach from children and pets.

Do not flush or pour medications down the toilet or drain (unless you are told to do so). If this product is no longer needed or expired, consult your pharmacist or local waste disposal company on how to properly discard your medication.

Drug Interactions

There are specific medicines, supplements, and foods you should avoid if you are taking Verzenio.

  • Consuming grapefruit or grapefruit juice can increase the effects of Verzenio.
  • Taking a strong CYP3A inhibitor is not recommended while on Verzenio. This class of medicines includes antifungal medicines such a Nizoral.
  • Taking a strong CYP3A inducer may decrease the effects of Verzenio. This class of medicine includes Rifamate, an antibiotic often used for tuberculosis treatment.

Before taking a new medication, be sure to consult with your provider on all other medications you are currently on. This includes supplements and over-the-counter medications, as they might have active ingredients that interact with the drug.

Women who are pregnant or planning to become pregnant should not take Verzenio, as it can be harmful to a developing fetus. Using effective birth control while taking Verzenio is highly recommended for preventing unwanted pregnancy and birth defects.

Women who are breast-feeding or plan to breast-feed should not take Verzenio, as it can cause harm to unborn fetuses.

Consulting with a medical professional can help limit unwanted side effects or drug interactions that may be very risky or even fatal. Be sure to keep a list of all the products you use and share it with your doctor or pharmacist so they can determine the right dosage for you.

Alternative Medications

Ibrance is another form of kinase inhibitor that is used for treatment of breast cancer. While Verzenio can be used as a monotherapy (on its own), Ibrance is always taken in combination with another drug, usually an aromatase inhibitor or fulvestrant (an estrogen receptor antagonist).

Ibrance is taken every day for course of 21 days, followed by a 7 day break, where Verzenio is taken twice daily, every day.

Comparative trials between Verzenio and Ibrance are underway as of 2023 and the advantages of treatment with either or both of them are not yet fully understood. Lab trials thus far have shown that there may be benefits of stopping Ibrance temporarily and switching to Verzenio after a treatment break. Scientists are awaiting further results before providing sweeping advice for treatment.

Verzenio is a small molecule drug that is a kinase inhibitor. It is used for treatment of early breast cancer and metastatic breast cancer in men and women.

Verzenio will start inhibiting CDK4/6 enzymes shortly after taking ingestion, but it may take two to four months to observe any major changes in outcomes. Side effects, such as diarrhea, often occur within one week of beginning treatment.

Within five days of taking Verzenio twice daily, you should reach consistent blood levels.

You will typically stay on Verzenio until you experience unacceptable side effects or your disease progresses. It is not recommended to stop taking your medicine or to change your dose unless advised by your medical provider. Take Verzenio exactly as described.

Despite being used to treat various kinds of breast cancer, Verzenio is considered a targeted treatment rather than chemo. It belongs to the class of medicines known as CDK4/6 inhibitors, which are made to reduce and prevent growth of cancer cells in the body.

No. Taking Verzenio while pregnant, breast-feeding, or planning to become pregnant is not recommended. Verzenio can cause fetal birth defects and other harm in utero.