Trastuzumab is a cancer medication. It interferes with the growth of cancer cells and slows their growth and spread in your body.

Trastuzumab is used to treat breast cancer that has progressed after treatment with other chemotherapy.

Trastuzumab may also be used for other purposes not listed in this medication guide.

Do not use this medication without telling your doctor if you are pregnant. It could harm the unborn baby. Use effective birth control, and tell your doctor if you become pregnant during treatment.

Before receiving trastuzumab, tell your doctor if you have heart disease, congestive heart failure, a history of heart attack, or any allergies or breathing problems. You may not be able to receive trastuzumab, or you may need a dosage adjustment or special tests during treatment.

Some people receiving a trastuzumab injection have had a reaction to the infusion (when the medicine is injected into the vein). Tell your caregiver right away if you feel dizzy, nauseated, light-headed, weak, itchy, or short of breath during the injection.

Before using trastuzumab, tell your doctor if you are allergic to any drugs, or if you have:

• heart disease;

• congestive heart failure;

• a history of heart attack; or

• any allergies or breathing problems.

If you have any of these conditions, you may not be able to receive trastuzumab, or you may need a dosage adjustment or special tests during treatment.

FDA pregnancy category D. Trastuzumab can cause harm to an unborn baby. Do not use trastuzumab without telling your doctor if you are pregnant. Use effective birth control, and tell your doctor if you become pregnant during treatment.

If you are pregnant, your name may need to be listed on a Cancer and Childbirth registry when you start using this medication.

It is not known whether trastuzumab passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.