Key takeaways
Palbociclib (Ibrance) and abemaciclib (Verzenio) are both medications used to treat hormone receptor-positive, human epidermal growth factor 2-negative (HR+, HER2-) breast cancer. They belong to the same class of medications called cyclin-dependent kinase (CDK) 4/6 inhibitors, which work by blocking proteins that help cancer cells grow. However, there are some differences between them. Palbociclib is typically taken once a day for 21 days followed by a 7-day break, while abemaciclib is taken twice a day without breaks. Palbociclib is used with other medications like an aromatase inhibitor or fulvestrant, whereas abemaciclib can be used alone or with hormone therapy. Common side effects of palbociclib include low white blood cell counts and nausea, while abemaciclib often causes diarrhea and low white blood cell counts. Both medications require regular blood tests to monitor side effects, and you should avoid grapefruit and grapefruit juice while taking them.
