Ibrance (palbociclib): What to Expect, Side Effects, and More
If you were diagnosed with advanced-stage or metastatic, hormone receptor-positive, HER2-negative breast cancer, you may be prescribed Ibrance (chemical name: palbociclib) in combination with hormonal therapy.
Ibrance is a CDK4/6 inhibitor, a targeted therapy that disrupts the ability of cancer cells to divide and grow.
If this is the first time you’re receiving hormonal therapy for breast cancer, you’ll likely take Ibrance with an aromatase inhibitor — a medicine that reduces estrogen in the body. Arimidex (chemical name: anastrozole), Aromasin (chemical name: exemestane), and Femara (chemical name: letrozole) are aromatase inhibitors.
If you’ve already taken hormonal therapy for breast cancer and the cancer grew, you’ll likely take Ibrance in combination with Faslodex (chemical name: fulvestrant). Faslodex blocks the effects of estrogen on hormone receptor-positive breast cancer cells.
If you’ve been prescribed Ibrance and haven’t yet gone through menopause, you’ll likely be treated with a medicine that shuts down your ovaries.
Research presented at the 2024 San Antonio Breast Cancer Symposium showed that adding Ibrance to standard treatments for hormone receptor-positive, HER2-positive metastatic disease improves progression-free survival (how long the person lives without the cancer growing). Ibrance is not yet approved by the Food and Drug Administration for this use, however.
See Ibrance prescribing information.
How Ibrance works
Ibrance targets a protein in cells called cyclin-dependent kinase (CDK) 4/6. In breast cancer, these proteins become overactive, leading the cells to divide and grow rapidly. CDK4/6 inhibitors work by interfering with the kinase and stopping cancer cells from dividing and growing.
Kisqali (chemical name: ribociclib) and Verzenio (chemical name: abemaciclib) are alsocyclin-dependent kinase (CDK) 4/6 inhibitors.
What to expect during Ibrance treatment
Ibrance is a pill taken by mouth. The recommended starting dose of Ibrance is 125 mg. When taking Ibrance with an aromatase inhibitor, you take the pills on a 28-day cycle:
for 21 days, you take the Ibrance and aromatase inhibitor pills at the same time each day, with food
then for seven days, you take the aromatase inhibitor only
When taking Ibrance with Faslodex, it’s also taken on a 28-day cycle:
you take Ibrance for 21 days at the same time each day, with food, and then you stop taking the Ibrance pills for seven days
you receive an injection of Faslodex every two weeks for the first three injections and then one injection every four weeks
You keep taking Ibrance with an aromatase inhibitor or Faslodex as long as you are getting benefits from the medicines and aren’t having troubling side effects.
Ibrance side effects
Like almost all breast cancer medicines, Ibrance can cause side effects, some of them severe.
The most common side effects of Ibrance are:
Less commonly, Ibrance may cause serious side effects, including:
Severe neutropenia (very low white blood cell count): Low white blood cell counts are a common side effect of Ibrance. Still, some people’s white blood cell counts may drop so low that they have to decrease the dose of Ibrance or stop treatment. Your doctor will check your white blood cell count before and during treatment with Ibrance.
Severe lung inflammation: In some people, Ibrance may lead to severe pneumonitis or interstitial lung disease. Pneumonitis and interstitial lung disease describe a large group of conditions that cause inflammation or scarring of the lungs. The scarring makes the lungs stiff, which makes it difficult to breathe. Tell your doctor right away if you have difficulty breathing, discomfort when you breathe, or shortness of breath when you’re resting or doing an activity that requires little exertion.
Infection: Ibrance may increase your risk of infections such as pneumonia or other upper respiratory infections. Tell your doctor right away if you have a temperature higher than 100.5 degrees F, chills, or don’t feel well.
Blood clots: Ibrance may cause serious or life-threatening blood clots in your arteries or lungs. Tell your doctor right away if you have shortness of breath, rapid heart rate, rapid breathing, or sudden chest pain.
Because Ibrance is given with an aromatase inhibitor or Faslodex (chemical name: fulvestrant), you also may have side effects from those medicines. Common side effects of aromatase inhibitors are bone thinning and bone and joint pain. Common side effects of Faslodex are hot flashes and nausea.
You shouldn’t take Ibrance if you’re pregnant or breastfeeding.
Ibrance drug interactions
There are certain medicines, supplements, and foods you should avoid when taking Ibrance:.
CYP3A inhibitors: This class of medicines includes antifungal medicines such as Onmel (chemical name: itraconazole) and Biaxin (chemical name: clarithromycin), as well as antiretroviral drugs used to treat HIV such as Kaletra (chemical name: lopinavir and ritonavir). These medicines can increase the effects of Ibrance.
CYP3A inducers: This class of medicines includes Rifamate (chemical name: rifampin), an antibiotic used to treat tuberculosis, and Carbatrol (chemical name: carbamazepine), which is used to control certain types of seizures in people with epilepsy. These medicines can decrease the effects of Ibrance.
St. John’s wort: Taking this herb, which is sometimes used to control depression and anxiety, can decrease the effects of Ibrance.
Grapefruit or pomegranate: Eating or drinking these fruits and their juices can increase the effects of Ibrance.
Real patient reviews
Members of our community discuss their experiences with Ibrance in the community forum. Here are some of their comments. Remember, it's essential to talk to your doctor about any side effects you're having and ask about ways to manage them.
“In my experience, the initial dosage (125mg) was too much for me. I was able to work, but I was very fatigued, and my white blood cell count tanked. I also had some sores and some itchiness, and my skin was very dry. It wasn't unbearable, but I was glad to switch to the 100 mg dosage. Most of the side-effects went away at that point.” — ninetwelve
“I started a couple weeks ago and have had zero side effects. I take both pills in the evening with food.” — nancyh
“The first two weeks I had absolutely no side effects. This week, however, each day I have felt increasing fatigue, almost like mono.” — lenn13ka
Read more in our Ibrance discussion forum.
Paying for Ibrance
The cost of Ibrance may vary. The price you’ll pay depends on the drug manufacturer, your health insurance provider and plan, where you live, and the pharmacy you use.
Note: Your insurance company may require you to get prior authorization before covering Ibrance.
Pfizer has a program called Oncology Together that may be able to help you pay for Ibrance.
Learn more about financial assistance and medicine cost-lowering tips.
— Last updated on February 28, 2025 at 9:22 PM
