Ibrance (palbociclib) is a targeted cancer medicine used to treat hormone receptor-positive, HER2-negative (HR+/HER2-) advanced or metastatic breast cancer in adults. It is used together with hormone therapy (such as an aromatase inhibitor or fulvestrant), not on its own.

Palbociclib belongs to a class of medicines called CDK4/6 inhibitors. It works by blocking proteins (CDK4 and CDK6) that drive cancer cell division, slowing the growth of cancer cells and helping hormone therapy work more effectively.

Take Ibrance by mouth with food, once daily for 21 days, followed by 7 days off (a 28-day cycle). The 7-day break allows your bone marrow to recover.

Swallow capsules whole. Do not crush, chew, or open them.

Take at the same time each day. If you vomit after taking Ibrance, do not take an extra dose. Wait until your next scheduled dose.

If you miss a dose and it has been less than 12 hours since you were supposed to take it, take the missed dose with food. If more than 12 hours have passed, skip it and take your next dose as scheduled. Never take two doses to make up for a missed one.

Contact your oncologist or a poison control centre immediately. Bring your medication packaging.

• Store below 25°C
• Keep in the original container with the lid tightly closed
• Keep out of reach of children

• Low white blood cells (neutropenia): the most common and important side effect. This increases your risk of infection. Blood tests are taken regularly to monitor this
• Fatigue
• Nausea
• Infections (due to low white cells)
• Low red blood cells (anaemia): tiredness, pallor, shortness of breath
• Low platelets: increased bruising or bleeding
• Mouth sores
• Hair thinning

Serious side effects:

• Severe infection: if you develop fever (above 38°C), chills, or feel very unwell, seek urgent medical attention
• Interstitial lung disease: new or worsening cough or breathlessness should be reported promptly

Blood counts are checked before each cycle and may result in dose delays or reductions.

• Strong CYP3A inhibitors (ketoconazole, clarithromycin, grapefruit juice): increase palbociclib levels and side effects
• Strong CYP3A inducers (rifampicin, carbamazepine, phenytoin, St John's Wort): reduce palbociclib levels, making treatment less effective

Tell your oncologist and pharmacist about all medicines and supplements before starting Ibrance.

Why is Ibrance taken for 21 days then stopped for 7 days?

The 21-days-on, 7-days-off cycle is designed to give your bone marrow a recovery window. Palbociclib lowers white blood cell counts, and the break allows levels to recover before the next cycle begins. This schedule balances effectiveness with manageable side effects.

Do I need to avoid grapefruit?

Yes. Grapefruit and grapefruit juice contain compounds that inhibit the enzyme that breaks down palbociclib. This can increase palbociclib levels in the blood, raising the risk of side effects. Avoid grapefruit and grapefruit juice while taking Ibrance.

Ace provides accurate and independent information medically reviewed on prescription medications. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment.