What Is Tykerb® (lapatinib)?

Reviewed by: HU Medical Review Board | Last reviewed: June 2023

Tykerb® (lapatinib) is a targeted therapy used to treat advanced or metastatic breast cancer in certain people. It is used in combination with:1

  • Capecitabine for advanced or metastatic breast cancer that is positive for human epidermal growth factor receptor 2 (HER2+) in people who have had prior treatment with an anthracycline, a taxane, and trastuzumab
  • Letrozole in postmenopausal women with hormone receptor-positive metastatic breast cancer that is also positive for human epidermal growth factor receptor 2 (HER2+) where hormone therapy is appropriate

What are the ingredients in Tykerb?

The active ingredient in Tykerb is lapatinib.1

How does lapatinib work?

In breast cancers that are HER2+, the surface of the cancer cells has too many HER2 receptors. This can cause the breast cancers to grow and spread quickly.2

Lapatinib helps block HER2 receptors from inside the cell. Lapatinib is a small molecule that can pass through the cell wall and connect to the HER2 receptor to disrupt its activity. When used in combination with capecitabine or letrozole, lapatinib may slow the progression of breast cancer.1,2

What are the possible side effects?

The most common side effects of lapatinib include:1,2

  • Diarrhea
  • Red, painful hands and feet
  • Nausea, vomiting, loss of appetite
  • Rash
  • Fatigue
  • Headache
  • Hair loss
  • Shortness of breath
  • Nose bleeds
  • Difficulty sleeping
  • Mouth inflammation and sores
  • Itching
  • Dry skin
  • Heartburn
  • Nail changes
  • Pain

Lapatinib has a boxed warning, the strictest warning from the US Food and Drug Administration (FDA). This is because it may cause toxic liver disease (hepatotoxicity). Your doctor should monitor your liver function before and during treatment with lapatinib.1,2

These are not all the possible side effects of lapatinib. Talk to your doctor about what to expect when taking lapatinib. You also should call your doctor if you have any changes that concern you when taking lapatinib.

Other things to know

Avoid eating or drinking grapefruit products while taking lapatinib. These products may increase the levels of lapatinib in the body, which can increase the potential for side effects.2

Lapatinib can harm an unborn baby. If you can become pregnant, you should use birth control during treatment and for some time after the last dose of lapatinib. You should also not breastfeed during treatment with lapatinib and for some time after the last dose. Talk to your doctor about your options for birth control and breastfeeding while taking lapatinib.1,2

Before beginning treatment for breast cancer, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

For more information, read the full prescribing information of lapatinib.

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