Herceptin (Trastuzumab) Side Effects, Important Information, What to Avoid?

Herceptin is a monoclonal antibody. It attaches itself to the HER2 cancerous cells, stops them from dividing and growing any further. It helps in destroying cancer cells itself as well as signaling the human body to do so.


Trastuzumab is used in the treatment of specific types of breast cancer, along with other medications. It is also used for specific kinds of stomach cancer. The tumors which produce abnormal amounts of HER2 protein are treated using Trastuzumab.

Side Effects

If you are using Herceptin with consultation from your doctor, then you should keep the fact in mind that he has weighed the pros and cons of the medicine before prescribing them to you.



Minor Side Effects

There are minor side effects of using Herceptin. Depending on their severity, they may not even need medical attention. Since it is foreign for the body, it will take some time to adjust to Herceptin, and these side effects will go after some time naturally. Common side effects experienced include:

  • Diarrhea
  • Redness at the injection site
  • Back pain
  • Abdominal pain
  • Trouble sleeping
  • Nausea
  • Vomiting
  • Mouth sores
  • Loss of appetiteIf nausea and vomiting get severe, as is seen in several cases, your doctor may give you medication to prevent that.

    If these side effects don’t go away for a long time, contact your physician.

Serious Side effects

Inform your healthcare provider if any of these serious side effects occur:

  • Weakness on one side of the body
  • Slurred speech
  • Vision changes
  • Confusion


It is rare to develop an allergic reaction to Herceptin. It is rare to get a severe allergic reaction such as difficulty in breathing or swelling of the tongue, throat or face due to this drug.

If you notice any side effects other than the ones listed above, you should contact your physician and discuss it as soon as possible.

How to use

Trastuzumab is given through slow injection by a healthcare professional, over a period of 90 minutes, once every week or once in three weeks, as prescribed by your doctor.

The amount of medication and the time period for which it is to be taken depends on your medical condition and other factors and is determined by your physician. Inform your doctor about all the medications that you are taking at the time. Do not skip any doses and take the dosage at the proper, indicated time. Your doctor may prescribe you some other medications before starting your treatment in order to reduce the side effects during and after the treatment.

If your health deteriorates, inform your healthcare provider.




If you are allergic to it or if you have any other kind of allergies, it is better to inform your healthcare provider before taking Herceptin. There can be some inactive ingredients in Herceptin which may also cause allergic reactions.

Your physician should be familiar with your complete medical history as this is very crucial. If you have suffered from the following in the past or are under treatment for the following, your doctor should know beforehand:

  • Previous cancer treatments such as radiation therapy to the chest
  • Current infection
  • Virus infections such as herpes, shingles, etc.
  • Heart disease
  • High blood pressure
  • Lung problems
  • A previous reaction, if any, to monoclonal antibody treatment




Do not get vaccinated without the consent of your doctor.

This medication may cause drowsiness and will make you dizzy. Do not use this medication if you are going to operate heavy machinery or do anything that requires your complete focus.

Adults who are of older age may be more sensitive to the side effects of the medication especially heart failure.