Palbociclib is approved for use with the aromatase inhibitor letrozole (Femara) as initial or first-line treatment for postmenopausal women with metastatic, hormone receptor-positive, HER2-negative breast cancer.

The most common side effects of palbociclib are:

• neutropenia, a low white blood cell count that makes infection more likely
• low red blood cell count, which can lead to fatigue
• low blood platelet count, which can cause abnormal bleeding
• nausea and vomiting
• small sores or ulcers in the mouth or on the lips
• hair loss
• diarrhea
• low appetite
• weakness
• nerve damage
• nosebleeds

Call your doctor immediately if you have any signs of infection, shortness of breath, chest pain, irregular heartbeat, weakness or unusual bleeding.

Before starting palbociclib, be sure to tell your doctor about any medicines you are taking, including vitamins, herbal supplements and over the counter medicines. Also tell your doctor if you have ever had liver or kidney disease. You should avoid grapefruit and grapefruit juice while you are taking this medicine.

You should avoid becoming pregnant while you are receiving palbociclib and for at least 2 weeks after taking the last dose. Tell your doctor right away if you become pregnant or may be pregnant while you are undergoing treatment.

Your doctor, pharmacist or nurse can help you manage your side effects. You can also go to our section on Side Effects for more information.