Breast Cancer Home > Tykerb Warnings and Precautions

Before starting treatment with Tykerb, warnings and precautions for the drug should be discussed with your healthcare provider. You should know that the drug may lower your left ventricular ejection fraction or cause a life-threatening irregular heart rhythm called QT prolongation. Tykerb warnings and precautions also extend to people who have low blood potassium, congestive heart failure, or liver disease.

What Should I Tell My Healthcare Provider Before Taking Tykerb?

You should talk with your healthcare provider prior to taking Tykerb® (lapatinib) 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 Tykerb Warnings and Precautions

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


  • The medication can lower your left ventricular ejection fraction (LVEF), which is a measure of how well your heart pumps blood. This means that Tykerb can probably increase your risk of congestive heart failure (CHF). Your healthcare provider should perform tests to measure your LVEF before you start Tykerb and periodically thereafter. Often, LVEF is measured using an ultrasound of the heart (an echocardiogram). If Tykerb starts to lower your LVEF, you may need to lower your Tykerb dosage or stop taking the medication altogether.
  • The liver helps clear Tykerb from the body. 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 Tykerb dosage or not taking Tykerb at all.
  • Tykerb 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.
  • Tykerb can interact with other medications (see Tykerb Drug Interactions).
  • Tykerb 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 using the drug while pregnant (see Tykerb and Pregnancy).
  • It is not known if Tykerb 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).
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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