Abemaciclib
Pronunciation: pronunciation varies by local usage.
- Generic name
- abemaciclib
- Brand names
- Verzenio, Verzenios
- Drug class
- Cyclin-dependent kinase 4/6 (CDK4/6) inhibitor; antineoplastic protein kinase inhibitor
- Form
- Film-coated tablets
- Route
- Oral
- Legal status
- Prescription-only anticancer medicine
Availability and supply rules vary by country
Trade names by country: United States
Australia: · Full directory
What abemaciclib is and how it works
Abemaciclib is a kinase inhibitor that blocks cyclin-dependent kinases 4 and 6 (CDK4/6), thereby inhibiting cell cycle progression in hormone receptor-positive breast cancer cells. It is used to treat certain types of breast cancer. (1) (2)
Approved uses include adjuvant treatment of early breast cancer and treatment of advanced or metastatic breast cancer, in various combinations or as monotherapy, depending on the precise indication. Eligibility, combination partner, and dosing are determined by a specialist.
What abemaciclib is used for
Adjuvant treatment of early breast cancer
In combination with endocrine therapy (tamoxifen or an aromatase inhibitor) for adult patients with hormone receptor (HR)-positive, HER2-negative, node-positive early breast cancer at high risk of recurrence. (1)
First-line advanced or metastatic breast cancer
In combination with an aromatase inhibitor as initial endocrine-based therapy for adults with HR-positive, HER2-negative advanced or metastatic breast cancer. (1)
Advanced or metastatic breast cancer after endocrine therapy
In combination with fulvestrant for adults with HR-positive, HER2-negative advanced or metastatic breast cancer with disease progression following endocrine therapy. (1)
Monotherapy for advanced or metastatic breast cancer
As monotherapy for adults with HR-positive, HER2-negative advanced or metastatic breast cancer after prior endocrine therapy and prior chemotherapy in the metastatic setting. (1)
Before taking abemaciclib
Do not take / not appropriate for
- UK/EU label: do not take abemaciclib if you have a known hypersensitivity to abemaciclib or to any of the tablet excipients (contraindication per UK EMC SmPC). (UK/EU product (Verzenios)) (2)
- US label: the FDA prescribing information lists no contraindications. (US product (Verzenio)) (1)
Tell your clinician about
- If you are pregnant or plan to become pregnant; abemaciclib may cause fetal harm.
- If you are breastfeeding or plan to breastfeed; it is not known if abemaciclib passes into breast milk, but breastfeeding is not recommended.
- All medical conditions, especially liver problems or a history of blood clots.
- All other medicines, including over-the-counter and herbal products, particularly those affecting liver enzymes (CYP3A).
- If you have signs of infection, fever, or unusual bleeding or bruising (suggestive of low blood cell counts).
- If you develop severe or persistent diarrhea, cough, shortness of breath, or signs of a blood clot.
How to take abemaciclib
- Take abemaciclib exactly as prescribed by your oncologist. The usual dose is 150 mg twice daily when combined with endocrine therapy, or 200 mg twice daily when used alone (US label).
- Tablets can be taken with or without food, but do not take with grapefruit or grapefruit juice (EU SmPC).
- Swallow the tablets whole with water; do not crush, chew, or split them.
- Take abemaciclib exactly as prescribed. Do not decide on your own to change your dose or to interrupt or stop treatment — always contact your oncology team first; they will advise on any changes needed.
- How long you need treatment depends on your specific situation and is decided by your oncologist: for early breast cancer, the UK SmPC describes treatment usually continuing for two years, or until recurrence or unacceptable toxicity; for advanced or metastatic breast cancer, treatment usually continues for as long as it is helping you, or until unacceptable side effects occur.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2)
Missed dose
Missing dose instructions were not explicitly stated in the reviewed official labels. Contact your prescriber or pharmacist for advice if you miss a dose.
Overdose
Specific overdose interventions and antidote information were not captured in the sources reviewed for this page. If an overdose is suspected, seek emergency medical attention immediately. (1) (2)
Side effects
Abemaciclib commonly causes diarrhea, low blood cell counts (neutropenia, anemia, leukopenia, thrombocytopenia), fatigue, nausea, abdominal pain, infections, decreased appetite, vomiting, headache, and hair thinning. More serious effects include interstitial lung disease, liver injury, and blood clots.
Diarrhea
What to notice: Loose or watery stools; may start within the first week of treatment. Incidence 81–90%, with severe (Grade 3) diarrhea in 8–20% of patients.
What to do: Contact your oncology team promptly for individualized advice about diarrhea management, including whether an antidiarrheal medicine (such as loperamide) is appropriate for you and how it should be used. Increase your fluid intake and let your team know if diarrhea is severe or persistent. (1) (2)
Neutropenia
What to notice: Low white blood cell count, increasing infection risk; may cause fever or other signs of infection. Incidence 37-46%, with severe neutropenia in 19-32%.
What to do: Your clinician will monitor your blood counts regularly. Report any signs of infection (fever, chills) promptly. (1) (2)
Fatigue and weakness
What to notice: Tiredness or lack of energy; common across trials.
What to do: Inform your clinician if fatigue becomes debilitating or affects your daily activities. (1) (2)
Interstitial lung disease (ILD) / pneumonitis
What to notice: The specific symptom list for lung inflammation was not detailed in the sources reviewed for this page — ask your care team what to watch for and report any new or worsening breathing problems promptly.
What to do: Seek prompt medical attention for any new or worsening breathing symptoms. Your treating clinician will assess this and decide on permanent discontinuation of abemaciclib if it reaches Grade 3 or 4, as required by product labeling. (1) (2)
Liver injury (hepatotoxicity)
What to notice: The specific symptom list for liver problems was not detailed in the sources reviewed for this page — ask your care team what to watch for.
What to do: Contact your oncologist promptly. They will check your blood tests and decide whether your dose needs to be reduced or treatment stopped — do not make this decision yourself. (1) (2)
Venous thromboembolism (blood clots)
What to notice: The specific symptom list for blood clots was not detailed in the sources reviewed for this page — ask your care team what to watch for.
What to do: Seek emergency care immediately. Blood clots have been reported in 2-5% of patients across trials; your treating team will decide on further management. (1) (2)
Serious warnings
Interstitial lung disease / pneumonitis — emergency
Symptoms: The specific symptom list for lung inflammation was not detailed in the sources reviewed for this page — ask your care team what to watch for and report any new or worsening breathing problems promptly.
Action: Seek prompt medical attention for any new or worsening breathing symptoms. Your treating clinician will assess this and decide on permanent discontinuation of abemaciclib if it reaches Grade 3 or 4, as required by product labeling. (1) (2)
Febrile neutropenia — emergency
Symptoms: Fever or other signs of infection occurring while your white blood cell count may be low. The full symptom list was not detailed in the sources reviewed for this page.
Action: Seek immediate medical evaluation. Febrile neutropenia has been reported in a small proportion of patients (0.3% to 0.9%, UK SmPC); your treating team will assess and decide on further management. (1) (2)
Severe hepatotoxicity — emergency
Symptoms: The specific symptom list for liver problems was not detailed in the sources reviewed for this page — ask your care team what to watch for.
Action: Contact your oncologist urgently. Your treating team will check liver function tests and decide on any changes to treatment. (1) (2)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Strong CYP3A inhibitors (e.g., ketoconazole, itraconazole, clarithromycin, voriconazole, ritonavir) | Can significantly increase abemaciclib blood levels, raising the risk of side effects. | Tell your prescriber about any strong CYP3A inhibitor you are taking, including new prescriptions or over-the-counter products. Your prescriber will decide whether to avoid the combination or, if it cannot be avoided, reduce your abemaciclib dose (product labeling specifies 100 mg twice daily) and monitor you for toxicity. Do not change your own dose or stop any medicine on your own. (1) (2) |
| Moderate CYP3A inhibitors | May increase abemaciclib exposure to a lesser degree. | Tell your prescriber about any moderate CYP3A inhibitor you are taking. They will monitor you for adverse reactions and decide whether to reduce your dose (product labeling describes 50 mg decrements). Do not change your own dose. (1) |
| Strong or moderate CYP3A inducers (e.g., rifampicin, carbamazepine, phenytoin, St. John's wort) | Can dramatically reduce abemaciclib plasma levels, potentially making it less effective. Rifampicin decreased exposure by ~70% (US) to ~95% (EU). | Tell your oncology team about all CYP3A inducers you take or are prescribed. Whether to delay, avoid, or adjust abemaciclib treatment in relation to these medicines is a decision for your oncology team to make, not something to decide on your own. (1) (2) |
| Grapefruit and grapefruit juice | May increase abemaciclib blood levels (CYP3A inhibition). | Avoid consumption during treatment (EU SmPC advises against it). (2) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
Abemaciclib can cause fetal harm based on animal studies. Avoid use during pregnancy. Females of reproductive potential must use effective contraception during treatment and for at least 3 weeks after the last dose. (1) (2)
Breastfeeding
It is unknown whether abemaciclib passes into breast milk. In the US, breastfeeding is not recommended during treatment and for 3 weeks after the last dose (FDA label). The UK SmPC advises against breastfeeding during treatment but the materials reviewed for this page did not establish a specific post-treatment interval for the UK/EU label. (1) (2)
Fertility
Abemaciclib may impair male fertility based on nonclinical findings. Female fertility did not show adverse effects in animal studies. (2)
Pediatric use
Ask your oncologist about use in children if relevant. (1) (2)
Renal impairment
Ask your oncologist whether any dose adjustment is needed if you have kidney problems.
Monitoring
Before starting
- Confirm hormone receptor (HR)-positive, HER2-negative status and eligibility for the specific indication.
- Obtain a complete blood count (CBC) with differential and liver function tests (ALT, AST). Ensure absolute neutrophil count (ANC) ≥1,500/mm³, platelets ≥100,000/mm³, and hemoglobin ≥8 g/dL.
- Your clinician may also assess your history of hypersensitivity reactions, infection risk, and prior blood clots as part of your overall pre-treatment evaluation (a general clinical consideration, not a specific requirement stated in the sources reviewed for this page).
- Review all concomitant medications for potential CYP3A interactions.
During treatment
- CBC and liver function tests: every 2 weeks for the first 2 months, then monthly for the next 2 months, and as clinically indicated thereafter.
- Monitor for diarrhea: patients are advised to contact their oncology care team promptly at the first sign of loose stools for advice on fluid intake and whether, and how, to use antidiarrheal treatment.
- Watch for signs of infection, and report any new or worsening symptoms that could suggest lung, liver, or blood-clot problems promptly to your care team, who will advise on the specific warning signs to watch for.
- Dose adjustments (interruption, reduction, or discontinuation) are based on severity of adverse events per product labeling.
Storage
Follow the instructions on the pharmacy label and package insert, or ask your pharmacist.
Professional information
Clinician-facing context only. Use the current local indication, dosing table, and management guidelines. Abemaciclib requires specialist oncologist oversight.
United States (FDA)
Indication: All approved indications
Dose summary: With endocrine therapy (tamoxifen, aromatase inhibitor, or fulvestrant): 150 mg by mouth twice daily. As monotherapy: 200 mg twice daily. Dose adjustments for adverse reactions and drug interactions are detailed in the label. Specific tablet strengths were not captured in the sources reviewed for this page.
Renal context: No dosage adjustment is required for mild or moderate renal impairment (CLcr 30-89 mL/min, Cockcroft-Gault). Pharmacokinetics in severe renal impairment (CLcr <30 mL/min), end-stage renal disease, or dialysis are unknown. Note: abemaciclib increases serum creatinine (~0.2-0.3 mg/dL within the first cycle) by inhibiting renal tubular secretion transporters without affecting glomerular function; the rise is stable and reversible on discontinuation. (1)
United Kingdom (EMC SmPC)
Indication: All approved indications
Dose summary: In combination with endocrine therapy: 150 mg twice daily. Monotherapy dose was not specified in the SmPC materials reviewed for this page. When coadministered with strong CYP3A4 inhibitors, reduce dose to 100 mg twice daily. Specific tablet strengths were not captured in the sources reviewed for this page.
Renal context: The UK SmPC section on renal impairment was not among the sources reviewed for this page. The FDA label for the same active ingredient states that no dosage adjustment is required for mild or moderate renal impairment (CLcr 30-89 mL/min, Cockcroft-Gault), and that pharmacokinetics in severe renal impairment (CLcr below 30 mL/min), end-stage renal disease or dialysis are unknown. Confirm local guidance with the prescriber. (2)
Hepatic guidance
Abemaciclib is metabolized via CYP3A4. Liver function tests (ALT, AST) should be monitored before treatment, every 2 weeks for the first 2 months, then monthly for the next 2 months, and as clinically indicated. Dose reduction or discontinuation is required based on the grade of transaminase/bilirubin elevation per product labeling.
Overdose note
The sources reviewed for this page did not detail specific overdose interventions or state whether an antidote exists. In case of suspected overdose, seek emergency medical assessment. (1) (2)
Frequently asked questions
Can I take abemaciclib with grapefruit or grapefruit juice?
No. Grapefruit products can increase the level of abemaciclib in your blood and raise the risk of side effects. The EU label specifically advises against taking abemaciclib with grapefruit or grapefruit juice. (2)
What should I do if I have diarrhea while taking abemaciclib?
Contact your oncology team promptly for personalized instructions about diarrhea management, including whether an antidiarrheal medicine (such as loperamide) is appropriate for you and how it should be used. Increase your fluid intake and let your team know if diarrhea is severe or does not improve. (1) (2)
How will my blood counts be monitored?
You will have blood tests before starting abemaciclib and then regularly: every 2 weeks for the first 2 months, then monthly for the next 2 months, and as needed after that. This checks for low white blood cells (neutropenia), low red blood cells (anemia), and low platelets. (1) (2)
References
- VERZENIO — abemaciclib tabletU.S. Food and Drug Administration (DailyMed) · United States · accessed 2026-08-05 · source 1
- Verzenios 100 mg film-coated tablets — Summary of Product Characteristicselectronic Medicines Compendium (UK) · United Kingdom · accessed 2026-08-05 · source 2
- Abemaciclib — patient drug information (MedlinePlus)U.S. National Library of Medicine (MedlinePlus) · US · accessed 2026-08-14 · source 3
- Verzenio — FDA approval record (Drugs@FDA NDA208716)U.S. Food and Drug Administration · US · accessed 2026-08-14 · source 4
- abemaciclib — RxNorm normalized drug concept (RXCUI 1946825)U.S. National Library of Medicine (RxNorm) · US · accessed 2026-08-14 · source 5
Brand names by country
Single-ingredient abemaciclib names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- Verzenio150 mg, 100 mg, 200 mg, 50 mg · eli lilly and company