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Lapatinib may cause liver damage which can be severe or life-threatening. Liver damage can occur as soon as several days or as late as several months after the start of treatment with lapatinib. Tell your doctor if you have or have ever had liver disease. If you experience any of the following symptoms, call your doctor immediately: itching, yellowing of the skin or eyes, dark urine, pain in the upper right part of the stomach, unusual bleeding or bruising, or pale or dark stools.
Keep all appointments with your doctor and the laboratory. Your doctor will order certain laboratory tests before and during your treatment to see whether your liver is likely to be damaged or has been damaged by lapatinib.
Talk to your doctor about the risks of taking lapatinib.
WHY is this medicine prescribed?
Lapatinib is used with capecitabine (Xeloda) to treat a certain type of advanced breast cancer in people who have already been treated with other chemotherapy medications. Lapatinib is also used with letrozole (Femara) to treat a certain type of breast cancer in postmenopausal women (women who have experienced a change of life; end of menstrual periods) that has spread to other parts of the body. Lapatinib is in a class of medications called kinase inhibitors. It works by blocking the action of the abnormal protein that signals cancer cells to multiply. This helps stop or slow the spread of cancer cells.
HOW should this medicine be used?
Lapatinib comes as a tablet to take by mouth. It is usually taken once a day, at least 1 hour before or 1 hour after a meal. When lapatinib is used to treat advanced or metastatic breast cancer, it is usually given once daily on days 1 to 21 (along with capecitabine on days 1 to 14) of a 21-day cycle. The cycle may be repeated as recommended by your doctor. When lapatinib is used to treat breast cancer in postmenopausal women, it is usually given once daily along with letrozole. Take all of the lapatinib tablets for your daily dose at one time each day; do not divide the tablets to take as separate doses. Take lapatinib at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take lapatinib exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Swallow the tablets whole; do not split, chew, or crush them.
Your doctor may gradually increase or decrease your dose of lapatinib during your treatment. This depends on how well the medication works for you and any side effects you may experience. Continue to take lapatinib even if you feel well. Do not stop taking lapatinib without talking to your doctor.
Ask your pharmacist or doctor for a copy of the manufacturer's information for the patient.
Are there OTHER USES for this medication?
This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.
What SPECIAL PRECAUTIONS should I follow?
Before taking lapatinib,
What SPECIAL DIETARY instructions should I follow?
Do not eat grapefruit or drink grapefruit juice while taking this medication.
What should I do IF I FORGET to take a dose?
Take the missed dose as soon as you remember it that day. However, if you do not remember until the next day, if you cannot remember whether you took the medication, or if you vomit your medication, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
What SIDE EFFECTS can this medicine cause?
Lapatinib may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
Some side effects can be serious. If you experience any of these symptoms or those listed in the IMPORTANT WARNING section or the SPECIAL PRECAUTIONS section, call your doctor immediately:
Lapatinib may change the way your heart beats and pumps blood through your body. Your doctor will monitor you carefully to see whether lapatinib has affected your heart. Talk to your doctor about the risks of taking lapatinib.
Lapatinib may cause other side effects. Call your doctor if you have any unusual problems while you are taking this medication.
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).
What should I do in case of OVERDOSE?
In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at http://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.
Symptoms of overdose may include the following:
What should I know about STORAGE and DISPOSAL of this medication?
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).
Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. Do not flush this medication down the toilet. Use a medicine take-back program. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website http://goo.gl/c4Rm4p for more information.
Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location - one that is up and away and out of their sight and reach. http://www.upandaway.org
What OTHER INFORMATION should I know?
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.
This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.
The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.
AHFS® Patient Medication Information™ Copyright, 2025. The American Society of Health-System Pharmacists®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Selected Revisions: June 15, 2019.