Indications: Palbociclib (Ibrance) is a kinase inhibitor indicated as intial endocrine-based therapy in combination with letrozole for the treatment of estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer in post-menopausal women.

Dosing: The recommended starting dose is 125 mg once daily taken with food for 21 days, followed by 7 days off treatment.

Pharmacokinetics: Following oral administration, peak concentration occurs between 6 and 12 hours, and a steady state is reached after 8 days of continuous dosing. In some patients, food intake improves absorption and exposure of palbociclib. It is metabolized in the liver and excreted mainly through feces.

Drug Interactions: Palbociclib is primarily metabolized by CYP3A and is a time-dependent inhibitor of CYP3A. Avoid concurrent use with strong CYP3A inhibitors and strong and moderate CYP3A inducers. CYP3A substrate dosing may need to be reduced.

Side Effects/Risks: Most common adverse reactions are neutropenia, leukopenia, fatigue, anemia, upper respiratory infections, nausea, stomatitis, alopecia, diarrhea thrombocytopenia, decreased appetite vomiting, asthenia, peripheral neuropathy, and epistaxis.

Source: Highlights of prescribing information: Ibrance (palbociclib). U.S. Food & Drug Administration website. http://www.accessdata.fda.gov/drugsatfda_docs/label/2015/207103s000lbl.pdf. Revised February 2015. Accessed March 3, 2015.