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Precautions and Warnings With Lapatinib

To help minimize risks, make sure you review the precautions and warnings with lapatinib before starting treatment. It is important to know that the drug may lower your ventricular ejection fraction (a measure of how well your heart pumps blood) or cause QT prolongation. Precautions and warnings with lapatinib also include people who are allergic to any components of the drug and women who are pregnant or breastfeeding.

What Should I Tell My Healthcare Provider Before Taking Lapatinib?

You should talk with your healthcare provider prior to taking lapatinib (Tykerb®) if you have:
  • An irregular heart rhythm (arrhythmia), especially long QT syndrome
  • Low blood potassium (hypokalemia) or magnesium (hypomagnesemia)
  • Congestive heart failure
  • Liver disease, including liver failure or cirrhosis
  • Any allergies, including allergies to food, dyes, or preservatives.
Also, let your healthcare provider know if you are:
  • Pregnant or thinking of becoming pregnant
  • Breastfeeding.
Make sure to tell your healthcare provider about all other medicines you may be taking, including prescription and non-prescription medicines, vitamins, and herbal supplements.

Specific Precautions and Warnings With Lapatinib

Warnings and precautions to be aware of prior to taking lapatinib include the following:
  • Liver problems have occurred in people taking lapatinib. Sometimes these liver problems were fatal. It is recommended that you have liver function tests (a simple blood test) before starting lapatinib and every four to six weeks while taking lapatinib.


  • Lapatinib can lower your left ventricular ejection fraction (LVEF), which is a measure of how well your heart pumps blood. This means that the drug can probably increase your risk of congestive heart failure (CHF). Your healthcare provider should perform tests to measure your LVEF before you start lapatinib and periodically thereafter. Often, LVEF is measured using an ultrasound of the heart (an echocardiogram). If lapatinib starts to lower your LVEF, you may need to lower your lapatinib dosage or stop taking the medication altogether.
  • The liver helps clear lapatinib from the body. Therefore, if you have liver or kidney disease, talk with your healthcare provider before taking the medicine. Depending on the severity of your condition, your healthcare provider may recommend adjusting your lapatinib dosage or not taking it at all.
  • Lapatinib can increase your risk of a life-threatening irregular heart rhythm called QT prolongation. This can be especially dangerous for people with long QT syndrome or who are taking other QT-prolonging medications.
  • Let your healthcare provider know if you have severe diarrhea, nausea, vomiting, or mouth sores. Also let your healthcare provider know if you have a fever (or other signs of an infection) or redness and tenderness of the palms of your hands or the soles of your feet.
  • Lapatinib can interact with other medications (see Drug Interactions With Lapatinib).
  • Lapatinib is considered a pregnancy Category D medication. This means that it is likely to cause harm to a fetus during pregnancy. Talk to your healthcare provider about the risks and benefits of taking the drug while pregnant (see Tykerb and Pregnancy).
  • It is not known if lapatinib passes through breast milk. Therefore, if you are breastfeeding or plan to start, discuss this with your healthcare provider prior to taking the drug (see Tykerb and Breastfeeding).
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