Lapatinib (Tykerb): What to Expect, Side Effects, and More

If you’ve been diagnosed with HER2-positive breast cancer, your doctor may recommend lapatinib (brand name: Tykerb). 

Lapatinib is a targeted therapy approved for use in combination with certain chemotherapy and hormonal therapy:

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  to treat advanced-stage, HER2-positive breast cancer that has stopped responding to anthracycline and taxane chemotherapy and Herceptin

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  to treat postmenopausal women diagnosed with hormone receptor-positive, HER2-positive metastatic breast cancer

See Lapatinib prescribing information.

In about 10% to 20% of breast cancers, the HER2 gene doesn't work correctly and makes too many copies of itself, and these extra HER2 genes tell breast cells to make too many HER2 receptors. This makes breast cells grow and divide in an uncontrolled way.

Lapatinib (Tykerb) is a kinase inhibitor that works by interfering with HER2-related kinases inside the cell, limiting the ability of breast cancer cells to grow and multiply. By limiting the amount of energy, Tykerb can slow or stop the growth of breast cancer.

Tykerb is a chemical compound, not an antibody.

Tykerb blocks the action of the HER2 protein inside the cell, whereas Herceptin and Perjeta block the HER2 protein on the surface of breast cancer cells. It's because of this different mechanism that Tykerb may be effective against HER2-positive cancers that have stopped responding to Herceptin. 

Lapatinib is a pill that you’ll take once a day. It’s commonly prescribed with the chemotherapy medication Xeloda (chemical name: capecitabine) or with the hormonal therapy medicine Femara (chemical name: letrozole). 

You can take Tykerb indefinitely to keep the cancer under control. Your doctor would only stop you from taking Tykerb if the cancer stopped responding to it or if you experience any severe side effects.

There are certain medicines and supplements you should avoid if you are taking Lapatinib:

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  The effects of CYP3A inducers may be increased by lapatinib. This class of medicines includes Rifamate (chemical name: rifampin), an antibiotic used to treat tuberculosis, and Carbatrol (chemical name: carbamazepine), which is used to control certain types of seizures in people with epilepsy.

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  The effects of CYP3A4 inhibitors may be increased by lapatinib. This class of medicines includes antifungal medicines such as Onmel (chemical name: itraconazole) and Biaxin (chemical name: clarithromycin), as well as antiretroviral drugs used to treat HIV such as Kaletra (chemical names: lopinavir and ritonavir).

Tykerb can cause some side effects, including:

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  diarrhea

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  vomiting

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  fatigue

Very rarely, Tykerb has been found to cause heart damage. If heart damage occurs, Tykerb is discontinued, and heart-strengthening medication can bring heart function back to normal. Anyone who is considering taking Tykerb and has a preexisting heart condition should be monitored carefully before and during treatment.

Tykerb does not seem to cause the more severe heart and lung problems associated with Herceptin.

If you’re pregnant or planning to get pregnant, you should not be given lapatinib. Lapatinib can cause embryo death and birth defects. You also shouldn’t take lapatinib while breastfeeding.

Members of our community discuss their experiences with lapatinib in the community forum. Here are some of their comments. Remember, it's essential to talk to your doctor about any side effects you're having and ask about ways to manage them.

“In my book, Xeloda and Tykerb are awesome drugs!   The side effects they caused for me were lots of diarrhea, hand and foot syndrome -- major skin splits and bleeding hands and feet while on Xeloda and lots of toenail infections, swelling, painful ingrown nails from the Tykerb, which I am still struggling with.  But, no hair loss.  I was only on Xeloda for 6 months but have been on the Tykerb for almost 3 years now.” — Faith316

“I was off the lapatinib for 10 days and resumed on a lower dose with an antibiotic, and it has been much better. I still have a rash on my hands.  Just on the back of my hands, odd but one of the known side effects.” — thrmine

“I started Xeloda and Tykerb last Tuesday. Today is day 5! My only complaint is 7 trips to the bathroom on day 2, then everything went back to normal. No side effects.” — Yanyan

Read more in our Lapatinib discussion forum.

The cost of Lapatinib may vary. The price you’ll pay depends on the drug manufacturer, your health insurance provider and plan, where you live, and the pharmacy you use. 

Note: Your insurance company may require you to get prior authorization before covering Lapatinib.

You may be eligible to enroll in the Patient Assistance Foundation, sponsored by Novartis (the maker of Tykerb). For more information, you can also call 1-800-277-2254.

Learn more about financial assistance and medicine cost-lowering tips.