Herceptin (generic: trastuzumab) is a prescription medication used to treat breast cancer and stomach cancer.  It may be used alone or in combination with other medications. Herceptin belongs to a group of drugs called monoclonal antibodies, which help stop the growth of cancer cells.

This medication comes in an injectable form and is given into the vein (intravenously) by a healthcare provider once every week or once every 3 weeks.

Common side effects of Herceptin include fever, nausea, and vomiting.