Lapatinib in combination with capecitabine is indicated for the treatment of patients with advanced or metastatic breast cancer whose tumors overexpress human epidermal growth factor receptor 2 (HER2) and who have received prior therapies including anthracyclines, taxanes, and trastuzumab. (Usage restriction: Before initiating treatment with lapatinib combined with capecitabine, patients must have experienced disease progression during trastuzumab treatment.)

Lapatinib in combination with letrozole is indicated for the treatment of postmenopausal women with hormone receptor-positive, metastatic breast cancer that overexpresses the HER2 receptor. The combination of lapatinib with an aromatase inhibitor (letrozole in this case) has not been compared with trastuzumab-containing chemotherapy regimens for the treatment of metastatic breast cancer.

With capecitabine: 1,250 mg (5 tablets) orally once daily on days 1–21 of a repeating 21-day cycle.

With letrozole: 1,500 mg (6 tablets) orally once daily continuously.

Administer at least one hour before or after a meal. Do not divide daily dose.

Dose adjustments are required for hepatic impairment, severe diarrhea, and concomitant use with strong CYP3A4 inhibitors or inducers.