Herceptin is the brand name of the targeted cancer drug trastuzumab.

It’s used to treat cancers that have large amounts of the protein HER2 (epidermal growth factor receptor 2). These HER2-positive cancers include:

More than 1 in 10 people taking Herceptin may have flu-like symptoms that can include:

If you experience side effects, they commonly become less severe after your initial treatment.

Potential heart damage

The risk of heart damage is higher for people using Herceptin. This risk is greater when Herceptin is given with other chemotherapy drugs known to cause heart damage, such as Adriamycin.

Talk to your doctor about a MUGA scan or echocardiogram before starting Herceptin therapy.

If you’re using Herceptin, get emergency medical help if you develop any symptoms of heart failure. They include:

  • shortness of breath
  • trouble breathing
  • an irregular or rapid heartbeat
  • increased cough
  • swelling of lower legs or feet

Potential lung damage

On rare occasions, a person could have a serious reaction to Herceptin that interferes with breathing.

During or shortly after Herceptin is being administered, there’s a chance of sudden swelling and narrowing of the airways. This can result in trouble breathing and wheezing. Hives might also appear.

There’s also a chance of lung tissue swelling known as pulmonary toxicity as well as low blood pressure. Pleural effusions (fluid buildup around the lungs) is also possible.

However, these are all rare side effects.

If one of these reactions should occur, it’s most likely to happen during infusion or within the first 24 hours of the first dose of Herceptin.

If you’re currently receiving treatment with Herceptin and have been tolerating it well, it’s unlikely you’ll experience these serious reactions.

Talk to your doctor about a full examination to identify any possible lung problems before starting Herceptin therapy.

If Herceptin is being administered along with chemotherapy, you may also experience some side effects of chemotherapy, such as:

  • nausea
  • vomiting
  • fatigue
  • mouth and throat sores
  • diarrhea
  • hair changes
  • taste and smell changes
  • weight changes
  • infection
  • nail changes
  • anemia or low red blood cell counts
  • neuropathy

The HER2 protein in some breast and stomach cancers makes the cancer cells grow and divide. Herceptin attaches to the HER2 receptors on the surface of the cancer cells. This blocks the cells from receiving growth signals, thus slowing or stopping growth.

For early breast cancer

Your treatment may be Herceptin alone or Herceptin combined with chemotherapy.

Herceptin is typically administered before or after surgery and chemotherapy every week or every three weeks. Treatment often lasts a year.

For advanced breast cancer

Your first treatment might be combined with the chemotherapy drugs docetaxel (Taxotere) or paclitaxel (Taxol). Sometimes it’s combined with hormone therapies known as aromatase inhibitors.

If you’ve had at least two types of chemotherapy and hormone therapy hasn’t worked, Herceptin may be used on its own weekly or every three weeks.

For advanced stomach cancer

For gastroesophageal cancer, such as adenocarcinoma, Herceptin is typically given if you haven’t received any prior treatments with the chemotherapy drug capecitabine (Xeloda) or with cisplatin and fluorouracil.

For advanced stomach or gastroesophageal cancer, Herceptin will typically be administered every three weeks.

Herceptin can be administered for breast cancer as an injection under the skin (subcutaneous) or intravenously (through a vein into the bloodstream).

For stomach cancer, Herceptin is given intravenously.


The injection is typically given on the outer part of your thigh and takes two to five minutes.


Often, intravenous treatment lasts 30 to 90 minutes.

When your doctor talks to you about Herceptin, ask them about your risk for heart and lung complications. Although these side effects are relatively rare, being prepared is always a wise decision.

Your doctor might recommend an echocardiogram or MUGA scan before you begin Herceptin therapy. Expect to be monitored for serious side effects during treatment as well.

Serious side effects are rare. It’s more likely that you’ll experience flu-like symptoms. These symptoms usually lessen after your first treatment.