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Trade/other name(s): Herceptin, rhuMAb HER2

Why would this drug be used?

This drug is used to treat certain types of breast cancer and stomach cancer, and is being studied for other conditions as well.

How does this drug work?

Trastuzumab is a type of immunotherapy known as a monoclonal antibody. A monoclonal antibody is a man-made version of an immune system protein that fits like a lock and key with one certain protein.

Trastuzumab is designed to seek out and lock onto a protein called human epidermal growth factor receptor 2 (HER2), which is located on certain cells in the body. About 1 out of 4 breast and stomach cancers have higher than normal numbers of these receptors on their cells' surfaces. Once trastuzumab attaches to these cells, it brings in other immune cells to help kill them.

Before taking this medicine

Tell your doctor…

  • If you are allergic to anything, including medicines, dyes, additives, foods.
  • If you have any medical conditions such as kidney disease, liver disease (including hepatitis), heart disease, congestive heart failure, diabetes, gout, or infections. These conditions may require that your medicine dose, regimen, or timing be changed.
  • If you have ever had congestive heart failure, radiation to the chest, or if you have ever had medicines that damaged your heart. This drug may raise your risk of heart failure (see "Precautions" below).
  • If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. This drug can cause harm to the fetus if it is given to a woman during pregnancy (it is not known if this drug might cause problems if the male is taking it at the time of conception). Check with your doctor about what kinds of birth control can be used with this medicine.
  • If you are breast-feeding. While no studies have been done, this drug may pass into breast milk and affect the baby. Women should avoid breast-feeding during treatment and for 6 months after receiving the last dose of trastuzumab.
  • If you think you might want to have children in the future. It is not known whether or not this drug can affect fertility. Talk with your doctor about the possible risk with this drug and the options that may preserve your ability to have children.
  • About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs. In fact, keeping a written list of each of these medicines (including the doses of each and when you take them) with you in case of emergency may help prevent complications if you get sick.

Interactions with other drugs

While in some cases this drug may have damaging effects on the heart (see "Precautions"), this may be more likely if it is used along with certain chemotherapy drugs called anthracyclines, such as doxorubicin (Adriamycin), daunorubicin (Cerubidine, Daunomycin), epirubicin (Ellence), or mitoxantrone (Novantrone).

No other serious interactions are known at this time, but this does not necessarily mean that none exist. Check with your doctor, nurse, or pharmacist about your other medicines, herbs, and supplements, and whether alcohol can cause problems with this medicine.

Interactions with foods

No serious interactions with food are known at this time. Check with your doctor, nurse, or pharmacist about whether some foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Trastuzumab is given by infusion in a vein. The first dose is usually given over 90 minutes. If you don't have any problems, the next dose is given over 30 minutes. The dose depends on your weight. This medicine is often given along with other cancer treatment drugs.

Your doctor or nurse will likely give you medicine before your treatment to try to prevent an infusion reaction.


This drug can cause allergic reactions in some people when the drug is given, especially with the first treatment. Mild reactions usually consist of fever and chills. More serious reactions happen rarely, but can be dangerous. Symptoms can include feeling lightheaded or dizzy (due to low blood pressure), fever or chills, hives, nausea, itching, headache, coughing, tightness in the throat, shortness of breath, or swelling of the face, tongue, or eyes. Tell your doctor or nurse right away if you notice any of these symptoms during or after being given the drug.

This drug may cause damage to the heart, especially if used with chemotherapy drugs called anthracyclines, such as doxorubicin (Adriamycin) or epirubicin (Ellence). Your doctor will probably get tests of your heart before treatment. Possible symptoms of heart damage might include chest pain, increased coughing, trouble breathing (especially at night), rapid weight gain (5 pounds or more in 24 hours), dizziness, fainting, or swelling in the ankles or legs. Tell your doctor right away if you start to notice any of these symptoms once treatment starts.

In rare cases, patients have developed severe lung disease during treatment. Tell your doctor right away if you notice any changes in your breathing or any lung problems such as coughing, wheezing, or shortness of breath.

Your doctor will probably test your blood throughout your treatment, looking for possible effects of the drug on blood counts (described below) or on other body organs. Based on the test results, you may be given medicines to help treat any effects. Your doctor may also need to reduce or delay your next dose of this drug, or even stop it altogether. Keep all your appointments for lab tests and doctor visits.

When used with chemotherapy, this drug can lower your white blood cell count. This can increase your chance of getting an infection. Be sure to let your doctor or nurse know right away if you have any signs of infection, such as fever (100.5° or higher), chills, pain when passing urine, new onset of cough, or bringing up sputum.

When used with chemotherapy, this drug may lower your red blood cell count. If this occurs, it will usually happen a few months after starting treatment. A low red blood cell count (known as anemia) can cause shortness of breath, or make you to feel weak or tired all the time. Your doctor may give you medicines to help prevent or treat this condition, or you may need to get blood transfusions.

Do not get any immunizations (vaccines), either during or after treatment with this drug, without your doctor's OK. Trastuzumab may affect your immune system. This could make vaccinations ineffective, or even lead to serious infections if you get live vaccines during treatment or for some time afterward. Try to avoid contact with people who have recently received a live virus vaccine, such as the oral polio vaccine or smallpox vaccine. Check with your doctor about this.

Both men and women should avoid conceiving a child during and for at least 6 months after treatment in order to prevent harm to the fetus. Talk with your doctor about what kind of birth control you can use with this medicine.

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.


  • mild allergic reaction with first infusion (may include fever, headache, chills, nausea, vomiting, shortness of breath)*

Less common

  • allergic reaction with second and later infusions (same symptoms as above)
  • lowered white blood cell count with increased risk of infection*
  • infection*
  • cough
  • nausea
  • vomiting
  • diarrhea
  • abdominal pain
  • loss of appetite
  • feeling tired (fatigue)
  • muscle aches and pains
  • trouble sleeping


  • serious allergic reaction, which may include trouble breathing, dizziness, shock, tightness in the throat, swelling of the face, mouth, tongue, or eyes*
  • damage to the heart (may cause chest pain, coughing, trouble breathing, or swelling in legs or ankles)*
  • damage to the lungs*
  • lowered red blood cell count*
  • death due to allergic reaction, heart damage, or other cause

*See the "Precautions" section for more detailed information.

There are other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved in 1998.

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.

Last Medical Review: 01/04/2010
Last Revised: 11/03/2010