Lapatinib (By mouth)


Lapatinib (la-PA-ti-nib)

Treats cancer, including breast cancer. Often used with capecitabine or letrozole.

Brand Name(s)


When This Medicine Should Not Be Used

How to Use This Medicine


  • Medicines used to treat cancer are very strong and can have many side effects. Before receiving this medicine, make sure you understand all the risks and benefits. It is important for you to work closely with your doctor during your treatment.
  • Take your medicine as directed.
  • Take the tablets at least 1 hour before or 1 hour after a meal. You might be told to take several tablets for each dose, and you should take them at the same time.
  • This medicine is given together with capecitabine or letrozole. Follow your doctor's instructions on when to take these medicines.
  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

If a dose is missed:

  • Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

How to Store and Dispose of This Medicine

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any leftover medicine after you have finished your treatment. You will also need to throw away old medicine after the expiration date has passed.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows if you are using medicine to treat an infection (such as clarithromycin, erythromycin, itraconazole, ketoconazole, levofloxacin, rifabutin, rifampin, rifapentine, telithromycin, voriconazole, Avelox®, Levaquin®, Nizoral®, Rifadin®, Rimactane®) or medicine to treat HIV or AIDS (such as atazanavir, indinavir, nelfinavir, ritonavir, saquinavir, Crixivan®, Norvir®, Reyataz®).
  • Tell your doctor if you are using a calcium channel blocker (blood pressure medicine, such as diltiazem, nifedipine, verapamil, Norvasc®), medicine for seizures (such as carbamazepine, phenobarbital), nefazodone (Serzone®), or dexamethasone (Decadron®).
  • Make sure your doctor knows if you are using digoxin (Lanoxin®), midazolam (Versed®), paclitaxel (Taxol®), or St John's wort.
  • Do not eat grapefruit or drink grapefruit juice while you are using this medicine.

Warnings While Using This Medicine

  • It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant.
  • Make sure your doctor knows if you are breastfeeding, or if you have liver disease, lung disease, or low magnesium or potassium in your blood.
  • This medicine might cause heart problems. Make sure your doctor knows if you already have heart disease or heart rhythm problems (such as QT prolongation).
  • Call your doctor right away if you have diarrhea, especially if you also have fever, weakness, or bleeding. The diarrhea caused by this medicine can be severe and lead to other serious health problems such as dehydration. You may need medical treatment, including medicine to manage or prevent diarrhea.
  • Your doctor will check your progress and the effects of this medicine at regular visits. Keep all appointments.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Dark-colored urine or pale stools, nausea, vomiting, loss of appetite, pain in your upper stomach, yellow skin or eyes
  • Diarrhea with cramps, nausea, vomiting, fever, thirst, bleeding
  • Dizziness or lightheadedness
  • Fast, slow, pounding, or uneven heartbeat
  • Severe diarrhea
  • Trouble breathing, cough, chest pain
  • Unusual tiredness or weakness

If you notice these less serious side effects, talk with your doctor:

  • Mild nausea, vomiting
  • Mild skin rash
  • Red, painful hands and feet
  • Sores or white patches on your lips, mouth, or throat

If you notice other side effects that you think are caused by this medicine, tell your doctor

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

Version Info

  • Last reviewed on 8/4/2014

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