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Ibrance: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Oct 4, 2021.

1. How it works

  • Ibrance is a brand (trade) name for the generic drug palbociclib which may be used to treat certain types of breast cancer.
  • Palbociclib targets two particular enzymes, called CDK4 and CDK6. CDK stands for cyclin-dependent kinase, and it is an enzyme that is important for cell division. CDK4/6 inhibitors interrupt signals that stimulate the proliferation of malignant (cancerous) cells. Certain cancers, for example, hormone-receptor-positive breast cancer, are more likely to have disturbances in CDK4/6, and CDK 4/6 inhibitors may form part of the treatment protocol. Most often, CDK4/6 inhibitors are given synergistically with hormonal therapy (such as an aromatase inhibitor or fulvestrant), although some may be used alone to treat hormone receptor-positive, HER2-negative metastatic breast cancer in pre-treated patients.
  • Ibrance belongs to the class of medicines called CDK4/6 inhibitors.

2. Upsides

  • Ibrance is used in women and men to treat advanced or metastatic hormone-receptor-positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) breast cancer.
  • Ibrance is used in combination with a hormonal therapy called an aromatase inhibitor for postmenopausal women or men who have not been treated with hormonal therapy before. It is also approved for use in combination with fulvestrant for those whose disease worsens after using an aromatase inhibitor. Women who have not reached menopause are treated with Ibrance plus fulvestrant therapy and a luteinizing hormone-releasing hormone (LHRH) agonist to suppress ovarian function.
  • Ibrance is taken orally and is available as a capsule or tablet.
  • Ibrance tablets and capsules are both available in a 125 mg, 100 mg, and 75 mg strength.
  • In general, the side effects associated with Ibrance are less severe than those experienced with chemotherapy.
  • No dosage adjustment is required for patients with mild or moderate hepatic impairment (Child-Pugh classes A and B).
  • No dosage adjustment is required for mild, moderate, or severe renal impairment (CrCl >15 mL/min).

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Common side effects include fatigue and gastrointestinal disturbances, such as nausea, diarrhea, and vomiting. Low white blood cell counts resulting in neutropenia and leukopenia may occur, although anemia and thrombocytopenia are less common.
  • Ibrance may lower the ability of your body to fight off infections due to low white blood cell counts or cause lung problems such as inflammation (pneumonitis).
  • Ibrance is more likely to cause hair thinning rather than total hair loss.
  • The monitoring of blood counts is required during Ibrance treatment. Monitor complete blood counts before the start of Ibrance therapy and at the beginning of each cycle, as well as on Day 15 of the first 2 cycles, and as clinically indicated. Further blood cell count monitoring is required for patients who experience a maximum of Grade 1 or 2 neutropenia in the first 6 cycles. For Grade 3 and greater neutropenia, withhold Ibrance until the neutropenia recovers to Grade 2 or less.
  • Ibrance should be permanently discontinued in those with severe interstitial lung disease (ILD)/pneumonitis.
  • Ibrance interacts with several other medications, including strong CYP3A inhibitors such as clarithromycin, nefazodone, itraconazole, ketoconazole, atazanavir, and ritonavir. If there is no alternative medication reduce the Ibrance dose to 75 mg once daily. If the strong inhibitor is discontinued, then the dose of Ibrance will need to be increased after 3 to 5 half-lives of the inhibitor.
  • For severe hepatic impairment (Child-Pugh class C), the recommended dose of Ibrance is 75 mg once daily for 21 consecutive days out of a 28-day cycle.
  • Ibrance may cause fetal harm if administered during pregnancy and should not be given to pregnant women. Breastfeeding is also not recommended.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

Ibrance is a CDK4/6 inhibitor that may be used to treat advanced or metastatic hormone-receptor-positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) breast cancer in combination with other medications. It is usually taken for 21 days out of a 28-day cycle and common side effects include fatigue, low white blood cell counts, and gastrointestinal disturbances, such as nausea, diarrhea, and vomiting.

5. Tips

  • The recommended starting dose of Ibrance is 125 mg. Always follow your doctor’s specific direction for Ibrance dosing.
  • Ibrance is available as a tablet, which can be taken with or without food. Ibrance capsules should be taken with food.
  • Swallow the Ibrance tablet whole. Do not chew, crush, or split the tablets before swallowing them. Capsules should not be ingested if they are broken, cracked, or otherwise not intact.
  • Ibrance is usually taken once a day for 21 days out of a 28-day cycle. This means you will have a 7-day break from taking Ibrance.
  • Take your dose of Ibrance at approximately the same time each day.
  • If you should vomit or miss a dose for any reason, do not take an additional dose of Ibrance. Take your next dose at the normal time.
  • If you experience intolerable side effects from Ibrance, talk to your doctor as your dose may need to be reduced. If you are still experiencing intolerable side effects while taking Ibrance 75 mg/day then you should consider discontinuing Ibrance.
  • Avoid consuming grapefruit juice and grapefruit products during your treatment with Ibrance. Grapefruit may cause your blood levels of Ibrance to rise and lead to worsened side effects.
  • Tell your doctor if you experience any intolerable side effects, such as shortness of breath, cough, vomiting, or any type of infection.
  • Ibrance may harm a developing fetus and should not be given to pregnant women. Males and women of reproductive potential should use effective contraception during treatment with Ibrance and for at least 3 weeks after the last dose.

6. Response and effectiveness

  • Research suggests CDK4/6 inhibitors may increase the time people have before cancer spreads. More evidence is needed to determine their impact on overall survival.
  • In clinical studies of Ibrance plus letrozole, patients with HR+, HER2- advanced or metastatic breast cancer saw a significant delay of disease progression of a median of 24.8 months versus 14.5 months for those that received letrozole and placebo. In clinical studies of Ibrance plus fulvestrant, a delay of disease progression was demonstrated for a median of 9.5 months compared to 4.6 months for the group that took fulvestrant plus placebo. A reduction in tumor size was also seen in each group.
  • Ibrance should be continued along with other medications, such as an aromatase inhibitor or fulvestrant, as long as you are having a benefit and tolerate the side effects of the medicine.
  • In studies in patients taking Ibrance plus letrozole, 36% of patients (36 out of every 100) needed to have a dose reduction due to a side effect. About 9.7% (43 of 444) of patients permanently stopped therapy due to a side effect, such as low white blood cell count (neutropenia, 1.1%) and elevation of liver enzymes (alanine aminotransferase, 0.7%).
  • In studies looking at patients taking Ibrance plus fulvestrant, 36% of patients (36 out of every 100) needed to have a dose reduction due to a side effect. About 6% (19 of 345) of patients permanently stopped therapy due to a side effect such as fatigue (0.6%), infections (0.6%), and thrombocytopenia (0.6%).

7. Interactions

Medicines that interact with Ibrance may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with Ibrance. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with Ibrance include:

  • alfentanil
  • anticonvulsants such as carbamazepine, phenytoin or phenobarbital
  • antipsychotics, such as clozapine
  • biologics, such as adalimumab or baricitinib
  • chloramphenicol
  • cimetidine
  • ciprofloxacin or gatifloxacin
  • cyclosporine
  • dihydroergotamine or ergotamine
  • echinacea
  • everolimus
  • fentanyl
  • grapefruit or grapefruit juice
  • HIV medications, such as amprenavir, atazanavir, fosamprenavir, and ritonavir
  • live vaccines, such as the BCG vaccine, live influenza vaccine, or the measles vaccine
  • midazolam
  • pimozide
  • quinidine
  • sirolimus or tacrolimus
  • red yeast rice
  • rifampin
  • St. John's Wort
  • statins, such as atorvastatin or simvastatin
  • strong CYP3A inducers (eg, phenytoin, rifampin, carbamazepine, enzalutamide, and St John's Wort)
  • strong CYP3A inhibitors (eg, clarithromycin, indinavir, itraconazole, ketoconazole, lopinavir/ritonavir, nefazodone, nelfinavir, posaconazole, ritonavir, saquinavir, telaprevir, telithromycin, and voriconazole)
  • other medications that affect blood sugar levels or are used for diabetes, such as glimepiride, or metformin.

Note that this list is not all-inclusive and includes only common medications that may interact with Ibrance. You should refer to the prescribing information for Ibrance for a complete list of interactions.


Ibrance (palbociclib) 08/2021. Pfizer Laboratories Div Pfizer Inc.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Ibrance only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Copyright 1996-2023 Revision date: April 18, 2022.