If you have advanced or metastatic breast cancer, your doctor might suggest Tykerb as a treatment option. It’s a prescription drug used to treat certain kinds of HER2-positive (HER2+) breast cancer in adults. You’ll likely continue to take Tykerb unless you get bothersome side effects or your cancer grows during treatment.

Depending on the type of HER2+ metastatic breast cancer you have, a doctor will usually prescribe Tykerb together with either Xeloda (capecitabine) or Femara (letrozole).

The active ingredient in Tykerb is lapatinib. (An active ingredient is what makes a drug work.)

Tykerb comes as a tablet that you swallow. It’s available in one strength of 250 milligrams (mg).

For more information about Tykerb, including details about its uses, see this in-depth article.

Like other drugs, Tykerb can cause mild to serious side effects. Keep reading to learn more.

Some people may experience mild to serious side effects during Tykerb treatment. Some side effects are more common than others.

Examples of Tykerb’s commonly reported side effects include:

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

While these side effects were common in studies, they won’t affect everyone who takes Tykerb. And these aren’t the only side effects this drug may cause. More mild side effects, plus some serious ones, are described below.

Like most medications, Tykerb can cause mild side effects. Mild side effects that have been reported with this drug 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 don’t stop taking Tykerb unless your doctor recommends it.

Tykerb 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 Tykerb, visit MedWatch.

Treatment with Tykerb can cause serious side effects. People with certain medical conditions, such as heart or lung problems, may be at an increased risk.

Serious side effects that have been reported with Tykerb include:

If you develop serious side effects while taking Tykerb, 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.

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

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

Are my risks of side effects higher if I take Xeloda with Tykerb?

You will take Tykerb with Xeloda (capecitabine) or Femara (letrozole), depending on the type of HER2-positive (HER2+) metastatic breast cancer you have.

There wasn’t a significant difference in side effects when people took Tykerb with Xeloda versus Femara. (You can check out the drug’s full prescribing information for details of the studies.)

While your risk of mild side effects may vary slightly, your risk of serious side effects isn’t expected to differ.

Talk with your doctor or pharmacist to learn more.

How do the side effects of Tykerb compare with those of Herceptin?

Both Tykerb and Herceptin treat certain types of HER2-positive (HER2+) metastatic breast cancer. A doctor may also prescribe Herceptin to treat certain digestive tract cancers.

These medications can cause some similar side effects, including:

But they also have some different side effects.

For example, Herceptin can cause tumor lysis syndrome, a rare but serious side effect that occurs when a large number of cancer cells die in a short time and release their contents into your bloodstream. There have been no reports of this side effect with Tykerb.

But Tykerb can cause long QT syndrome (a condition that affects your heart’s electrical activity), but there were no reports of this in Herceptin’s studies. Tykerb can also cause liver problems, but there were no reports of this side effect with Herceptin.

Talk with your doctor or pharmacist if you’re interested in learning more about how these drugs compare.

Will Tykerb cause any long-term side effects?

It’s possible. Many of Tykerb’s side effects are mild, temporary, and may go away without treatment.

But Tykerb can cause long-term side effects. These are side effects that either:

  • start during treatment and continue for a long time, possibly after you stop taking the drug, or
  • start after you’ve taken Tykerb for a long time

Some of the long-term side effects reported in Tykerb’s studies include:

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

Talk with your doctor or pharmacist if you have other questions about long-term side effects from Tykerb.

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

Risk of liver damage

Tykerb has a boxed warning about the risk of liver damage. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).

Liver damage was reported in Tykerb’s studies. Liver problems can be severe, and deaths have been reported. This side effect can occur within days of starting Tykerb but has also occurred months after treatment began.

Liver damage may not cause symptoms right away. It may go unnoticed except for changes to certain blood tests. (See “What might help” just below.) But it’s possible to have symptoms such as:

What might help

Before you begin treatment, your doctor will order blood tests to check your liver function. They’ll also order these tests every 4 to 6 weeks while you’re taking Tykerb.

You should contact your doctor right away if you notice symptoms of liver damage. If you have symptoms or your doctor notices changes in your blood test results, they may have you:

  • take a lower dose of the drug
  • stop taking Tykerb temporarily, then take another blood test to see if your results have returned to previous levels
  • stop taking Tykerb permanently

Cardiac side effects

It’s possible to have cardiac (heart-related) side effects from Tykerb. Your risk of heart-related side effects increases if you have an existing heart condition, such as heart failure or a heart rhythm problem.

Specific heart-related side effects reported in Tykerb’s studies include:

  • Long QT syndrome. The QT interval is part of your heart rhythm. Long QT syndrome is a condition in which this interval becomes too long. This is a type of heart arrhythmia (irregular heartbeat).
  • Worsened left ventricular function. The left ventricle is the part of your heart responsible for pumping blood to the rest of your body. Issues with left ventricle function can lead to problems with blood supply to your body. It can even lead to heart failure. This side effect is most common in the first 12 weeks of treatment but may occur at any time.

Symptoms of heart-related side effects caused by Tykerb can include:

What might help

Before you start Tykerb treatment, your doctor will check your heart health. They’ll also check your electrolyte levels, such as your blood potassium and magnesium levels. They may prescribe treatment to correct any issues they find before prescribing Tykerb for you.

Your doctor will also monitor your heart health while you’re taking Tykerb. But if you notice symptoms of heart-related side effects, call your doctor right away. Depending on the severity of your symptoms, they may have you:

  • lower your dose of the drug
  • temporarily stop taking Tykerb to see if this helps your symptoms
  • permanently stop taking Tykerb

Severe skin reactions

Since Tykerb was approved for use, there have been rare reports of severe skin infections. These reactions can be life threatening and include:

Symptoms of these reactions can include:

What might help

Call your doctor immediately or seek emergency medical care if you notice symptoms of a severe skin reaction while taking Tykerb. These reactions are life threatening and often require treatment in a hospital.

Your doctor will likely have you stop taking Tykerb if you develop a severe skin reaction. They can discuss alternative treatments for your cancer if this occurs.

Hand-foot syndrome

Hand-foot syndrome is a possible side effect of Tykerb. In studies, this was more common among people who took Tykerb together with Xeloda (capecitabine). But it can also happen when you take Tykerb with Femara (letrozole).

Hand-foot syndrome is a condition that causes burning, numbness, tingling, and swelling in your feet or hands. This burning can be intense, and, in severe cases, your skin can blister or develop ulcers.

What might help

Call your doctor if you develop symptoms of hand-foot syndrome while taking Tykerb. Depending on how severe your symptoms are, they may recommend treatment. Examples include:

But if your symptoms are severe, your doctor may have you stop taking Tykerb.

Allergic reaction

Like most drugs, Tykerb can cause an allergic reaction in some people. While allergic reactions weren’t reported in the drug’s studies, they have been reported since the drug was approved for use.

Symptoms can be mild to serious and 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 over-the-counter oral antihistamine, such as Benadryl (diphenhydramine)
  • a topical product, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Tykerb, they’ll decide if you should continue taking 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 Tykerb, they may have you switch to a different treatment.

Keeping track of side effects

During your Tykerb 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 taking 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 Tykerb affects you. They can then use this information to adjust your treatment plan if needed.

There are certain factors to consider before starting Tykerb treatment.

Boxed warning: Risk of liver damage

Tykerb has a boxed warning for the risk of liver damage. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). Liver damage may be severe, and deaths have been reported in studies.

To learn more, see the “Side effects explained” section above.

Other warnings

Tykerb may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before starting this drug. The list below includes factors to consider.

Heart problems. Tykerb can cause heart-related side effects, including abnormal heart rhythm or problems with heart function. Your risk may be higher if you have an existing heart problem, such as heart failure. Your doctor can determine whether it’s safe for you to take Tykerb. If they decide to prescribe it for you, they may monitor your heart health closely during treatment.

Low magnesium or potassium level. Tykerb can cause problems with your heart rhythm as a side effect. Your risk of this is higher if you have low magnesium or potassium levels. Your doctor will likely want to treat your low levels of these electrolytes (essential minerals) before prescribing Tykerb for you.

Allergic reaction. If you’ve had an allergic reaction to Tykerb 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 Tykerb

There are no known interactions between drinking alcohol and taking Tykerb. But alcohol could worsen certain side effects this drug may cause, such as diarrhea, nausea, and liver problems.

If you consume alcohol, talk with your doctor about how much is safe for you, if any, while taking Tykerb.

Pregnancy and breastfeeding while taking Tykerb

Taking Tykerb during pregnancy or while breastfeeding is not recommended.

  • If you can become pregnant, your doctor will order a pregnancy test and confirm it’s negative before prescribing Tykerb for you. They’ll also recommend using birth control during treatment and for at least 1 week after taking your last dose of Tykerb.
  • You should avoid breastfeeding during treatment with Tykerb and for at least 1 week after your last dose of the drug.

Talk with your doctor to learn more about pregnancy, breastfeeding, and treatments for metastatic breast cancer.

Treatment with Tykerb can cause mild to serious side effects. Mild side effects are common, especially diarrhea and nausea. Serious side effects can also happen.

Talk with your doctor before starting Tykerb treatment. Ask questions that help you feel comfortable about the drug’s side effects. Some examples to get you started are:

  • Can any of my medications interact with Tykerb and increase my risk of side effects?
  • Does my medical history increase my risk of side effects from this drug?
  • If I have side effects from taking Tykerb, is there a lower dose I can try?

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Q:

Is Tykerb safe for older people to take? Are there unique side effects the drug may cause in older adults?

Anonymous

A:

In general, yes. Tykerb is safe for older adults to use.

Tykerb’s studies included adults ages 65 years and above. Researchers did not notice significant differences in side effects between older and younger adults.

But older adults are more likely to take multiple medications. And it’s possible for these drugs to interact with Tykerb, which can increase the risk of side effects. It’s important to talk with your doctor or pharmacist about all medications you take before starting Tykerb so they can check for potential interactions.

Older adults are also more likely to have problems affecting their heart or liver. Heart or liver conditions can increase the risk of side effects, particularly heart-related side effects and liver damage. (To learn more about these, see “Side effects explained” above.) Your doctor can tell you more about whether any of your medical conditions increase your risk of side effects from Tykerb.

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