Lapatinib

Lapatinib is a prescription medication used to treat breast cancer. It is used in combination with other medications to treat a certain type of breast cancer that has spread to other parts of the body and that has not responded to other cancer treatments.

Lapatinib belongs to a group of drugs called kinase inhibitors which work by blocking the action of a certain protein that signals cancer cells to multiply.

This medication comes in tablet form and is taken once daily on an empty stomach.

Common side effects of lapatinib include red, painful hands and feet, diarrhea, rash, and nausea.

Breast cancer is a cancer that forms in the cells of the breasts. Some women have (HER2+) breast cancer. (HER2+) stands for Human Epidermal growth factor receptor 2 positive. (HER2) is a special protein found on breast cancer cells that controls cancer growth and spread.

Lapatinib is approved for treatment of HER2 positive breast cancer, because it is specifically designed to target the HER2 protein. By binding to the HER2 protein, lapatinib prevents the growth of cancer cells.

HER2 testing is done to see whether treatment with lapatinib will likely be effective in treating breast cancer. If testing is not done, treatment with this medication may not be an effective treatment.

Lapatinib is a prescription medication used with another medicine (capcitabine) to treat people with breast cancer that has spread to other areas of the body that is HER2 positive (tumors that produce large amounts of a protein called human epidermal growth factor receptor-2), and who have already had certain other breast cancer treatments.

Lapatinib is also used with a type of medicine called letrozole for the treatment of postmenopausal women with hormone receptor positive, HER2 positive metastatic breast cancer for whom hormonal therapy is indicated. 

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Lapatinib may be found in some form under the following brand names:

• Tykerb

Serious side effects have been reported. See "Lapatinib Precautions" section.

Common side effects of lapatinib in combination with capecitabine or letrozole include:

• diarrhea
• red, painful hands and feet
• nausea
• rash
• vomiting
• tiredness or weakness
• mouth sores
• loss of appetite
• indigestion
• unusual hair loss or thinning
• nose bleeds
• headache
• dry skin
• itching
• nail disorders such as nail bed changes, nail pain, infection and swelling of the cuticles.

Tell your doctor about any side effect that gets serious or that does not go away.

These are not all the side effects with lapatinib. Ask your doctor or pharmacist for more information.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

You may also get side effects from the other drugs taken with lapatinib. Talk to your doctor about possible side effects you may get during treatment.

Tell your doctor about all the medicines you take, including prescription and nonprescription medicines, vitamins, and herbal and dietary supplements. Lapatinib and many other medicines may interact with each other. Your doctor needs to know what medicines you take so he or she can choose the right dose of lapatinib for you.

Especially tell your doctor if you take:

• antibiotics and anti-fungals (drugs used to treat infections)
• HIV (AIDS) treatments
• anticonvulsant drugs (drugs used to treat seizures)
• calcium channel blockers (drugs used to treat certain heart disorders or high blood pressure)
• antidepressants
• drugs that decrease stomach acidity
• St. John’s Wort or other herbal supplements

Know the medicines you take. Keep a list of your medicines with you to show your doctor. Do not take other medicines during treatment with lapatinib without first checking with your doctor.

Because lapatinib is given with other drugs called capecitabine or letrozole, you should also discuss with your doctor or pharmacist any medicines that should be avoided during treatment.

Serious side effects have been reported:

• heart problems including, decreased pumping of blood from the heart and an abnormal heartbeat. Signs and symptoms of an abnormal heartbeat include:
  • feeling like your heart is pounding or racing
  • dizziness
  • tiredness
  • feeling lightheaded
  • shortness of breath
    • Your doctor should check your heart function before you start taking lapatinib and during treatment.
• liver problems. Signs and symptoms of liver problems include:
  • itching
  • yellow eyes or skin
  • dark urine
  • pain or discomfort in the right upper stomach area
  • death
    • Your doctor should do blood tests to check your liver before you start taking lapatinib and during treatment.
• diarrhea, which may cause you to become dehydrated. Follow your doctors instructions for what to do to help prevent diarrhea. Call your doctor immediately at the first sign of diarrhea, as it is important that this is treated right away.
• lung problems. Symptoms of a lung problem with lapatinib include a cough that will not go away or shortness of breath.

Call your doctor right away if you have any of the signs or symptoms of the serious side effects listed above.

Do not take lapatinib if you are allergic to any of its ingredients.

Grapefruit and grapefruit juice may interact with lapatinib and lead to potentially dangerous effects. Discuss the use of grapefruit products with your doctor.

Before you start taking lapatinib, tell your doctor about all of your medical conditions, including if you:

• ever had a severe allergic (hypersensitivity) reaction to lapatinib. Check with your doctor if you think this applies to you. Don’t take lapatinib.
• have heart problems.
• have liver problems. You may need a lower dose of lapatinib.
• are pregnant or may become pregnant. Lapatinib may harm an unborn baby. If you become pregnant during treatment with lapatinib, tell your doctor as soon as possible.
• are breastfeeding. It is not known if lapatinib passes into your breast milk or if it can harm your baby. If you are a woman who has or will have a baby, talk with your doctor about the best way to feed your baby.

Tell your doctor about all the medicines you take, including prescription and nonprescription medicines, vitamins, and herbal and dietary supplements.

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Lapatinib falls into category D. In animal studies, pregnant animals were given this medication and had some babies born with problems. No well-controlled studies have been done in humans.

It is not known if lapatinib crosses into human milk. Because many medications can cross into human milk and because of the possibility for serious adverse reactions in nursing infants with use of this medication, a choice should be made whether to stop nursing or stop the use of this medication. Your doctor and you will decide if the benefits outweigh the risk of using lapatinib.

Take lapatinib exactly as your doctor tells you to take it. Your doctor may change your dose of lapatinib if needed.

• For patients with advanced or metastatic breast cancer, lapatinib and capecitabine are taken in 21 day cycles. The usual dose of lapatinib is 1,250 mg (5 tablets) taken by mouth all at once, one time a day on days 1 to 21. Your doctor will tell you the dose of capecitabine you should take and when you should take it.
• For patients with hormone receptor positive, HER2 positive breast cancer, lapatinib and letrozole are taken daily. The usual dose of lapatinib is 1,500 mg (6 tablets) taken by mouth all at once, one time a day. Your doctor will tell you the dose of letrozole you should take and when you should take it.

Lapatinib should be taken at least one hour before, or at least one hour after food.

Do not eat or drink grapefruit products while taking lapatinib.

If you forget to take your dose of lapatinib, do not take two doses at one time. Take your next dose at your scheduled time.

Take this medication exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.

The dose your doctor recommends may be based on the following:

• the condition being treated
• other medical conditions you have
• other medications you are taking
• how you respond to this medication
• your weight
• your height
• your age
• your gender

The recommended dosage of lapatinib for advanced or metastatic breast cancer is 1,250 mg (5 tablets) given by mouth once daily on Days 1-21.

The recommended dose of lapatinib for hormone receptor-positive (HER2-positive) metastatic breast cancer is 1,500 mg (6 tablets) given orally once daily continuously in combination with letrozole.

If you take too much lapatinib, call your doctor or poison control center, or go to the nearest hospital emergency room right away. Take lapatinib tablets with you when possible.

• Store lapatinib tablets at room temperature at 59° to 86°F (15° to 30°C). Keep the container closed tightly.
• Do not keep medicine that is out of date or that you no longer need. Be sure that if you throw any medicine away, it is out of the reach of children.
• Keep lapatinib and all medicines out of the reach of children.

WARNING: HEPATOTOXICITY

Hepatotoxicity has been observed in clinical trials and postmarketing experience. The hepatotoxicity may be severe and deaths have been reported. Causality of the deaths is uncertain.