What are the possible Serious Side Effects of Herceptin?

Heart Problems

  • Herceptin treatment can result in heart problems, including those without symptoms (such as reduced heart function) and those with symptoms (such as congestive heart failure). The risk and seriousness of these heart problems were highest in people who received both Herceptin and a certain type of chemotherapy (anthracycline). One patient died in an adjuvant (early) breast cancer trial of significantly weakened heart muscle
  • Herceptin can cause serious heart problems, including:
    • A decline in heart function
    • Irregular heartbeats
    • High blood pressure
    • Serious heart attack
    • Death
  • Your doctor will stop Herceptin therapy if you have weakening of the heart muscle or changes in the heart muscle structure

Monitoring the Heart

  • Your doctor will evaluate your heart function before and during treatment. For adjuvant breast cancer therapy, your doctor will also evaluate heart function after the end of treatment
  • Your doctor may run tests, such as an echocardiogram or a MUGA scan, and will review your health history to see how well the heart muscle is working
  • If you are taking Herceptin and have stopped treatment temporarily because of significant heart problems, your doctor should monitor your heart health more frequently

Infusion Reactions

  • Some patients have had serious infusion reactions and lung problems; infusion reactions leading to death have been reported
  • Symptoms usually happen during or within 24 hours of taking Herceptin
  • Your infusion should be temporarily stopped if you experience shortness of breath or very low blood pressure
  • Your doctor should monitor you until these symptoms completely go away
  • Your doctor may have you completely stop Herceptin treatment if you have:
    • A severe allergic reaction
    • Swelling
    • Lung problems
    • Swelling of the lungs
    • Severe shortness of breath
  • Infusion reaction symptoms consist of:
  • Fever and chills
  • Nausea
  • Vomiting
  • Pain (in some cases at tumor sites)
  • Headache
  • Dizziness
  • Shortness of breath
  • Very low blood pressure
  • Rash
  • Lack of energy and strength


  • Herceptin can cause harm to the fetus (unborn baby), in some cases death to the fetus, when taken by a pregnant woman
  • You should use effective birth control methods while receiving Herceptin and for at least 6 months after you finish taking Herceptin
  • Nursing mothers taking Herceptin may want to stop nursing or stop Herceptin, depending on the importance of the drug to the mother
  • Women exposed to Herceptin during pregnancy may wish to enroll in MotHER—the Herceptin Pregnancy Registry by calling 1-800-690-6720

Taking Herceptin Can Result in Serious and Potentially Deadly Lung Problems, Including:

  • A severe shortness of breath
  • Fluid in or around the lungs
  • Weakening of the valve between the heart and the lungs
  • Too little oxygen in the body
  • Swelling of the lungs
  • Scarring of the lungs

Problems like these may occur after an infusion reaction. If you have trouble breathing at rest due to existing lung disease, or large lung tumors appear, you may have more serious lung problems. Your doctor should stop Herceptin if you experience lung problems.

What is the Additional Important Safety Information associated with Herceptin?

Worsening of Low White Blood Cell Counts Due to Chemotherapy

  • Worsening of low white blood cell counts to serious and life-threatening levels and associated fever were higher in patients taking Herceptin in combination with chemotherapy when compared with those who received chemotherapy alone. The likelihood that a patient will die from infection was similar among patients who received Herceptin and those who did not

HER2 Testing

  • You must have a HER2 test to determine if your cancer is HER2-positive before taking Herceptin, as benefit has only been shown in patients whose tumors are HER2-positive

What Are the Most Common Side Effects Associated with Herceptin?

The most common side effects associated with Herceptin in patients with metastatic stomach cancer are: The most common side effects associated
with Herceptin in patients with breast cancer are:
  • Low white blood cell counts
  • Diarrhea
  • Fatigue
  • Low red blood cell counts
  • Swelling of the mouth lining
  • Weight loss
  • Upper respiratory tract infections
  • Fever
  • Low platelet counts
  • Swelling of the mucous membranes
  • Swelling of the nose and throat
  • Change in taste
  • Fever
  • Nausea
  • Vomiting
  • Infusion reactions
  • Diarrhea
  • Infections
  • Increased cough
  • Headache
  • Fatigue
  • Shortness of breath
  • Rash
  • Low white and red blood cell counts
  • Muscle pain

What should I look for when I'm on Herceptin therapy, and what symptoms should I immediately report to my doctor?

Patient Counseling Information

  • You should contact your doctor immediately for any of the following:
    • New onset or worsening shortness of breath
    • Cough
    • Swelling of the ankles/legs
    • Swelling of the face
    • Palpitations
    • Weight gain of more than 5 pounds in 24 hours
    • Dizziness or loss of consciousness
  • If you are pregnant or of childbearing potential, you should know that Herceptin exposure can result in harm to the fetus (unborn baby)
  • You should use effective birth control methods during treatment and for a minimum of six months following Herceptin
  • If you are nursing your baby, you should stop taking Herceptin or stop nursing
  • If you are exposed to Herceptin during pregnancy, you should enroll in MotHER—the Herceptin Pregnancy Registry by calling 1-800-690-6720

Because everyone is different, it is not possible to predict what side effects any one person will have. If you have questions or concerns about side effects, you should talk to your doctor.

Please see full Prescribing Information for Serious Side Effects and additional important safety information.



Patient Support App

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