Herceptin (trastuzumab) is a prescription drug that’s used to treat certain types of breast cancer and stomach cancer. Herceptin can cause side effects that range from mild to serious. Examples include nausea, bone pain, and infusion reactions.

Doctors prescribe Herceptin to treat the following kinds of cancer in adults:

The active ingredient in Herceptin is trastuzumab. (The active ingredient is what makes the drug work.) Trastuzumab is a kind of biologic drug. A biologic is made from living cells, while other drugs are made from chemicals.

Keep reading to learn about the common, mild, and serious side effects that Herceptin can cause. For a general overview of the drug, including details about its uses, see this article.

Below are just a few of the more common side effects reported by people using Herceptin in studies. These side effects can vary depending on what condition the drug is being used to treat.

More common side effects in people using Herceptin for HER2-positive breast cancer include:

  • fever
  • diarrhea
  • infection
  • nausea* and vomiting
  • infusion reactions†

More common side effects in people using Herceptin for stomach or gastroesophageal junction cancer include:

* To learn more about this side effect, see the “Side effects explained” section below.
† Herceptin has a boxed warning for this side effect. This is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Side effects explained” section below.

Keep in mind that not everyone who uses Herceptin will have these side effects. And these aren’t the only side effects Herceptin may cause. Additional mild and serious side effects are discussed below.

Like most medications, Herceptin can cause mild side effects. Depending on the condition it’s used to treat, Herceptin may be used alone or together with other cancer drugs. In studies, people who used Herceptin with chemotherapy (traditional drugs used to treat cancer) were more likely to have mild side effects compared with people who used Herceptin alone.

Examples of mild side effects that have been reported with Herceptin include:

* To learn more about this side effect, see the “Side effects explained” section below.

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And do not stop Herceptin treatment unless your doctor recommends it.

Herceptin may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Herceptin, visit MedWatch.

Treatment with Herceptin may cause serious side effects. In studies, serious side effects weren’t as common in people using Herceptin to treat breast cancer as they were in people with stomach cancer or gastroesophageal junction cancer.

Serious side effects that have been reported with Herceptin include:

If you develop serious side effects during Herceptin treatment, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* Herceptin has a boxed warning for this side effect. This is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Side effects explained” section below.
† Herceptin also has a boxed warning for this side effect. To learn more, see “Pregnancy and breastfeeding while using Herceptin” below.
‡ To learn more about this side effect, see the “Side effects explained” section below.

Get answers to some frequently asked questions about Herceptin’s side effects.

Are there any long-term side effects from Herceptin?

It’s possible for Herceptin to cause long-term side effects. These are side effects that start during treatment and continue for a long time, possibly after treatment ends. Or the side effects start after someone has used the medication for a long time or after treatment ends.

Long-term side effects that Herceptin may cause include:

  • heart issues
  • lung issues

Herceptin has a boxed warning for heart and lung issues. This is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Side effects explained” section below.

You can also talk with your doctor or pharmacist if you have more questions about Herceptin and long-term side effects.

Will Herceptin cause hair loss?

Herceptin isn’t expected to affect hair growth. Hair loss wasn’t reported in the drug’s studies.

Other medications used to treat certain kinds of breast cancer, such as Tykerb (lapatinib), may cause hair loss. And many chemotherapy drugs (traditional drugs used to treat cancer), such as paclitaxel and docetaxel, can cause hair loss. Herceptin may be prescribed with chemotherapy drugs, including paclitaxel and docetaxel.

Talk with your doctor if you’re concerned about hair loss and your cancer treatment. This side effect isn’t expected with Herceptin. Your doctor can tell you more about whether other medications you’re prescribed may cause hair loss.

Is there a higher risk of side effects when using Herceptin with Perjeta and chemotherapy?

Maybe. Herceptin wasn’t used with Perjeta (pertuzumab) in Herceptin’s studies. But this combination was examined in Perjeta’s studies, which included people whose conditions were treated with Perjeta, Herceptin, and chemotherapy. In general, side effects were more common in people taking this combination of drugs compared with Herceptin used alone or with drugs other than Perjeta.

To learn more about side effects Perjeta may cause, check out this article. You can also talk with your doctor or pharmacist to learn more.

Learn more about some of the side effects Herceptin may cause.

Risk of heart issues

Herceptin has a boxed warning about the risk of cardiac side effects (heart issues). Boxed warnings are the most serious warnings from the Food and Drug Administration (FDA).

Heart issues Herceptin may cause can include heart damage that isn’t reversible. Herceptin’s heart-related side effects may even be fatal.

While heart issues were not common in Herceptin’s studies, examples that were reported include:

Symptoms can vary depending on the exact heart issue, but some general symptoms include:

These heart issues can require long-term treatment with medication.

What might help

Your doctor will order tests to check your heart health before and during your Herceptin treatment. If the results of these tests show heart issues, they will either prescribe drugs or other treatments for these issues or stop your Herceptin treatment.

If you develop any of the symptoms listed above while using Herceptin, contact your doctor immediately.

Risk of infusion reactions or lung issues

Herceptin is given as an intravenous (IV) infusion (an injection into a vein given over time). Treatment with Herceptin can cause infusion reactions or lung issues. Since Herceptin was approved for use, there have also been reports of infusion reactions causing death in extreme cases. Because of this risk, Herceptin has a boxed warning about these side effects. Boxed warnings are the most serious warnings from the Food and Drug Administration (FDA).

Infusion reactions to Herceptin can include:

These symptoms are most likely to occur within 24 hours of receiving Herceptin, though in rare cases they can happen after this period.

Herceptin can also cause lung issues, such as:

These lung issues can happen as a result of infusion-related reactions. But they can also occur independently. Symptoms of lung issues can include:

What might help

A healthcare professional will monitor you while you receive your Herceptin IV infusion. If you show symptoms of an infusion reaction, they’ll stop the infusion and treat the reaction if needed.

If your infusion reaction is severe, your doctor may suggest that you stop Herceptin treatment. Or they may have you continue treatment, but prescribe medication (such as dexamethasone, a corticosteroid) to take before future infusions. This may help prevent adverse reactions.

If you have symptoms of lung issues during treatment with Herceptin, contact your doctor right away. They can examine your symptoms and determine the best way to treat them. This may include having you permanently stop treatment with Herceptin.

Headache

Headache is a possible side effect Herceptin may cause. In the drug’s studies, headache was common in people using Herceptin to treat breast cancer. But this side effect wasn’t reported among people using the drug for gastroesophageal junction or stomach cancer.

Headache can also be a symptom of an infusion reaction, a serious side effect Herceptin can cause. (To learn more, see “Risk of infusion reactions or lung issues” above.)

What might help

Talk with your doctor if you develop a headache with Herceptin. They may recommend using an over-the-counter (OTC) treatment, such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol). They may also suggest trying other treatments, such as a cold or hot compress, or doing a relaxing activity, such as yoga.

Bone pain

Treatment with Herceptin may cause bone pain as a side effect, but this wasn’t common in the drug’s studies. Bone pain was only reported in people using Herceptin to treat breast cancer. It wasn’t reported in people using the drug for gastroesophageal junction or stomach cancer.

It’s important to note that metastatic (late stage) breast cancer, which Herceptin may be used to treat, can also cause symptoms of bone pain.

What might help

Contact your doctor if you develop bone pain during Herceptin treatment. They may recommend using an OTC treatment, such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol).

Nausea

Nausea is among the more common side effects Herceptin may cause. It can also be a symptom of an infusion reaction, a possible serious side effect of this drug. (To learn more, see “Risk of infusion reactions or lung issues” above.)

What might help

Let your doctor know if you have nausea while you’re being treated with Herceptin. They can suggest ways to manage this side effect, such as avoiding certain foods. They may also prescribe a medication to help relieve nausea, such as ondansetron.

For nausea remedies to try at home, see this article.

Allergic reaction

Like most drugs, Herceptin can cause an allergic reaction in some people. While these reactions were rare in Herceptin’s studies, they can occur.

Symptoms can be mild to serious and may include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, usually in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:

  • an antihistamine you take by mouth, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Herceptin, they’ll decide whether you should continue using it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Herceptin, they may have you switch to a different treatment.

Keeping track of side effects

During Herceptin treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were using when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how it affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Herceptin affects you. They can then use this information to adjust your treatment plan if needed.

Before you start Herceptin treatment, there are certain warnings and precautions to consider, including several boxed warnings.

Boxed warnings

Herceptin has the following boxed warnings. These are the most serious warnings from the Food and Drug Administration (FDA).

Risk of heart issues: Treatment with Herceptin can cause heart issues, including heart failure. You may be at higher risk if you have existing heart conditions.

Risk of infusion reactions or lung issues: Infusion reactions or lung issues are possible side effects Herceptin may cause. You may be at higher risk if you have existing breathing or lung problems.

Risk of fetal harm: Herceptin should not be used during pregnancy due to the risk of fetal harm. People who can become pregnant should use effective contraception during Herceptin treatment.

For details on heart issues, infusion reactions, or lung issues, see the “Side effects explained” section above. For details on fetal harm, see the “Pregnancy and breastfeeding while using Herceptin” section below.

Other warnings

Herceptin may not be right for you if you have certain medical conditions. These are known as drug-condition interactions. Other factors may also affect whether Herceptin is a good treatment option for you. Talk with your doctor about your health history before starting Herceptin. The list below includes factors to consider.

Kidney problems: Herceptin can cause kidney problems as a side effect. If you have existing kidney problems, such as chronic kidney disease, Herceptin could worsen your condition. Your doctor can determine whether this drug is safe for you if you have kidney problems.

Allergic reaction: If you’ve had an allergic reaction to Herceptin or any of its ingredients, your doctor will likely not prescribe it for you. Ask them about other medications that might be better treatment options.

Alcohol and Herceptin

There’s no known interaction between alcohol and Herceptin treatment. But alcohol can cause similar side effects to this drug, such as:

  • diarrhea
  • headache
  • nausea and vomiting
  • fatigue (low energy)

Drinking alcohol could increase your risk of these side effects and may worsen them if they occur. If you drink alcohol, talk with your doctor about how much is safe for you to consume while being treated with Herceptin.

Pregnancy and breastfeeding while using Herceptin

Herceptin should not be used during pregnancy due to the risk of fetal harm. People who can become pregnant should use effective contraception during treatment with this drug.

Risk of fetal harm

Herceptin has a boxed warning about the risk of fetal harm if used during pregnancy. This is the most serious warning from the FDA.

Since the drug was approved for use, there have been reports that it has caused the following pregnancy-related issues:

  • problems with fetal development (commonly known as birth defects)
  • loss of pregnancy

Due to this risk, if you can become pregnant, your doctor will likely order a pregnancy test before prescribing Herceptin. This is to ensure you are not pregnant before receiving the drug. They’ll also recommend you use effective birth control during treatment and for at least 7 months after your last dose of Herceptin.

Herceptin and breastfeeding

It’s not known whether Herceptin passes into human breast milk or whether it causes side effects in a child who is breastfed. Talk with your doctor about safe ways to feed your child while you’re using Herceptin.

Before starting Herceptin, talk with your doctor. Ask questions that help you feel comfortable with the drug and any possible side effects you may have. Some examples to get you started are:

  • Will any of the drugs I take increase my risk of side effects from Herceptin?
  • If I have side effects from this drug, is there a lower dose you can prescribe?
  • Are the side effects of Herceptin the same as a similar drug called Herceptin Hylecta?

To learn more about Herceptin, see these articles:

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Q:

Are older adults at higher risk of side effects from Herceptin?

Anonymous

A:

Older adults (ages 65 years and older) may have an increased risk of cardiac (heart-related) side effects from Herceptin. Examples of heart-related side effects reported in the drug’s studies include:

Before starting Herceptin and during treatment, your doctor should order tests to check your heart health. If you’re an older adult, your doctor may order these tests more frequently.

Apart from heart-related side effects, studies didn’t find older adults to have a higher risk of other side effects from Herceptin. But it’s important to note that some of these studies only included a few older adults. So enough data may not have been collected to know for sure whether older adults using Herceptin are at increased risk of side effects. It’s also not known for certain whether they experienced different side effects compared with younger adults.

The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.