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Overview: Lapatinib is commonly used to treat certain breast cancers. Common side effects include diarrhea, hand-foot syndrome, and nausea and vomiting. Call your health care provider right away if you get a fever, skin rashes or sores, shortness of breath, or chest pain. Lapatinib is a tablet that you will swallow.

Uses

What is lapatinib used for?

Lapatinib is commonly used to treat certain HER2-positive breast cancers.

Lapatinib may also be used for other conditions as determined by your health care provider.

How does lapatinib work (mechanism of action)?

Lapatinib is a type of medicine known as a tyrosine kinase inhibitor (TKI). It works by targeting specific receptors on cancer cells. By blocking the action of these receptors, lapatinib can cause cancer cells to die and can prevent cancer cells from growing or spreading.

How is lapatinib supplied (dosage forms)?

Brands and other names

  • Tykerb

Dosage forms and strengths

  • 250 mg oral tablets

How should I store lapatinib?

Lapatinib should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Side Effects

What are the most common side effects of lapatinib?

The most common side effects of lapatinib are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Diarrhea (see below)
  • Hand-foot syndrome
  • Nausea and vomiting
  • Rash
  • Mouth sores
  • Headache
  • Hair loss or thinning
  • Shortness of breath
  • Dry skin
  • Itching
  • Tiredness
  • Back, arm, and leg pain
  • Loss of appetite
  • Upset stomach
  • Nosebleeds
  • Nail problems
  • Trouble sleeping

There may be other side effects of lapatinib that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of lapatinib?

While less common, the most serious side effects of lapatinib are described below, along with what to do if they happen.

Severe Allergic Reactions. Lapatinib may cause allergic reactions, which can be serious. Stop taking lapatinib and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Heart Failure. Lapatinib may increase your risk of heart failure. Tell your health care provider right away if you have any of the following symptoms of heart failure.

  • Shortness of breath or trouble breathing, especially while lying down
  • Swelling in your feet, ankles, or legs
  • Unusually fast weight gain
  • Unusual tiredness

Liver Damage. Liver damage, also called hepatotoxicity, can happen when taking lapatinib. Call your health care provider right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Diarrhea. Diarrhea is common with lapatinib. Call your health care provider right away if you develop diarrhea or if you have more than two bowel movements in one day. If you are given medicine to prevent or treat diarrhea, take it exactly as your health care provider tells you. Call your health care provider right away if you have any of the following.

  • Severe diarrhea
  • Diarrhea that does not go away
  • Diarrhea with weakness, dizziness, or fever

Lung Inflammation. Lapatinib can cause inflammation in your lungs, also called interstitial lung disease orpneumonitis. This can be serious or even life-threatening. Get emergency help if you have trouble breathing. You may also have a cough, fever, or chest pain.

Heart Rhythm Changes. Lapatinib may cause a rare, dangerous heart rhythm problem called QT prolongation and torsade de pointes. Some people have a higher risk of this, including people who are older, have other people in their family who have had these conditions, have low potassium or magnesium levels, or who take medicines that can prolong the QT interval. Tell your health care provider right away if you faint or have changes in your heart rate or rhythm, such as a fast or skipping heartbeat.

Severe Skin Reactions. Lapatinib can cause severe skin reactions, called Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), as well as blistering and peeling of your skin that can lead to death if not treated. If you develop a rash, stop taking lapatinib and call your health care provider right away. Get emergency help if you have any of the following symptoms of SJS or TEN.

  • Painful red or purple skin that looks burned and peels off
  • Flat red rash or blisters on your skin, mouth, nose, and genitals
  • Red, painful, watery eyes
  • Flu-like symptoms including fever, chills, and muscle aches

Warnings & Precautions

Who should not use lapatinib?

Allergies to Ingredients. People who are allergic to any of the following should not take lapatinib.

  • Lapatinib
  • Tykerb
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific lapatinib products they stock.

What should I know about lapatinib before using it?

Do not take lapatinib unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share lapatinib with other people, even if they have the same condition as you. It may harm them.

Keep lapatinib out of the reach of children.

Take lapatinib without food at least one hour before or one hour after a meal.

Your health care provider will have you do regular blood tests before taking and while taking lapatinib. Make sure to attend all appointments so they can make sure that lapatinib is safe for you.

What should I tell my health care provider before using lapatinib?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if lapatinib is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Heart problems, including cardiomyopathy, heart failure, and QT prolongation
  • Any family members who have heart problems like QT prolongation
  • Liver problems

Other Medicines and Supplements. Lapatinib may interact with other medicines and supplements. Before taking lapatinib, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Lapatinib may cause harm to an unborn baby. Your health care provider will give you a test to make sure you are not pregnant before you start taking lapatinib. If you can get pregnant, you should use birth control while taking lapatinib and for one week after your last dose. If you are able to get a partner pregnant, you should use condoms while taking lapatinib and for one week after your last dose. Tell your health care provider if you are or plan to become pregnant.

Breastfeeding. It is not known if lapatinib passes into breast milk. You should not breastfeed while taking lapatinib and for one week after your last dose. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does lapatinib interact with foods or drinks?

Lapatinib should be taken without food at least one hour before or one hour after a meal.

Grapefruit interacts with Lapatinib. It is important to avoid eating grapefruit or drinking grapefruit juice while taking lapatinib. This is because grapefruit can interfere with your body’s ability to break down lapatinib, which can lead to high levels of the medicine and an increased risk of side effects.

It is unknown if drinking alcohol will affect lapatinib, but heavy drinking can slow your immune response and make it harder for your body to fight cancer.

Does lapatinib interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. 

In particular, make sure that you discuss if you are using any of the following before taking lapatinib.

  • St. John’s wort, which is a supplement that may be used for depression
  • Midazolam, a medicine used to relieve anxiety before surgery
  • Digoxin (Lanoxin), which is a medicine used to treat irregular heartbeat and some types of heart failure
  • Paclitaxel, a chemotherapy medicine used to treat some cancers
  • Ketoconazole, which is a medicine used for fungal infections
  • Any medicine that can cause QT prolongation, which is a potentially dangerous heart rhythm problem
  • Any medicine for seizures

Many other medicines may alter the blood levels of lapatinib and vice versa. Tell your health care provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with lapatinib. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much lapatinib?

If you or someone else has used too much lapatinib, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of lapatinib?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.