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Generic name: lapatinib
Brand name: Tykerb
Oral tablet (250 mg)
Drug classes: EGFR inhibitors, HER2 inhibitors

What is Lapatinib?

Lapatinib can be used to treat advanced oestrogen-related breast cancer that has spread or progressed after treatment with other cancer medications.Lapatinib can only be used to treat this condition if you have a tumour that tests positive for the human epidermal growth factor receptor 2 protein (HER2). The HER2 protein is known to accelerate the growth of cancerous cells.Lapatinib can be given to postmenopausal women in conjunction with a hormone medicine called Letrozole or Femara. Lapatinib may be given in combination with capecitabine or Xeloda.Lapatinib can be used in other ways not mentioned in this guide.

Side effects of Lapatinib

If you experience symptoms of an allergic reaction, such as hives, difficulty breathing, swelling on your face or in your throat, or a severe reaction to the skin (fever or sore throat with burning eyes, burning skin, or a red or purple rash that blisters and peels), seek emergency medical attention.Lapatinib may cause serious or fatal liver issues. Contact your doctor immediately if you experience upper abdominal pain, itchiness, dark urine, clay-coloured stools, or jaundice.

Call your doctor immediately if you:

  • You may experience rapid or pounding pulses, fluttering of the chest, shortness of breath, and sudden dizziness.
  • Severe or persistent diarrhoea
  • Chest pain, wheezing, or a new or worsening cough

Lapatinib can cause the following side effects:

  • Indigestion, loss of appetite
  • Nausea, vomiting, diarrhoea;
  • Itchy skin, rash, itch, acne
  • Pain or redness in the palms or soles of the feet
  • Problems with your nails or fingernails
  • Feeling tired or weak
  • Nosebleeds and mouth sore
  • Hair loss;
  • Headache.

There may be other side effects. For medical advice on side effects, call your doctor. Contact the FDA by dialing 1-800-FDA-1088 in order to report side effects.


Lapatinib can harm an unborn child.Lapatinib may cause serious or fatal liver issues. If you experience upper stomach pain, itchiness, dark urine or clay-coloured stool, or jaundice, call your doctor immediately.

Before you take this drug

If you have an allergy to lapatinib, it is best not to use it.

Notify your doctor of any of the following issues:

  • Heart disease
  • Liver disease
  • An electrolyte imbalance can be caused by a low potassium or magnesium level in the blood.
  • Long-qt syndrome

Before starting the treatment, you may need to take a pregnancy test.Lapatinib may harm the unborn child or cause birth defects when either the mother or father are taking this medication. Continue to use birth control at least one week after the last dose.Do not wait to tell your doctor if you become pregnant while using lapatinib.Breastfeed for one week after taking this medicine.

How to take Lapatinib?

Read all instructions or guides that come with your medication and follow all directions. Follow the directions on the label.Lapatinib should be taken with letrozole at a dose of 6 tablets per day. Letrozole must also be taken daily.Lapatinib is taken at the usual dose of 5 tablets per day for 21 consecutive days. Capecitabine must be taken twice daily for the first 14 days. The 21-day cycle then repeats itself.Do not forget to follow your doctor's instructions.Take lapatinib with an empty stomach at least one hour before or after eating.Take the lapatinib tablets one by one, but the full dose (5 or 6 tablets per day) should be taken at the same time every day.Capecitabine should be taken within 30 minutes after eating or with food.Every 4 to 6 months, you will be required to have blood tests to monitor your liver. You may need to have your heart function checked with an ECG or electrocardiograph (also called an EKG).Lapatinib should be stored at room temperature, away from heat and moisture. When not in use, keep the bottle tightly shut.Your doctor will decide how long you should be treated with lapatinib, capecitabine, or letrozole. Do not stop taking your medication until the prescribed time has passed. The combination chemotherapy is generally continued until your condition worsens or you experience serious side effects.

Details on dosage

Adult dose for breast cancer:

Metastatic breast cancer HER2-positive (in combination with capecitabine)
On Days 1–14 of a 21-day repeating cycle, 1250 mg is administered orally twice a day.
Letrozole in combination with hormone receptor-positive, HER2-positive metastatic breast cancer:
Combining letrozole, 2.5 mg once daily, with 1500 mg once daily continuously
Do not divide this daily dose.
This is not recommended. (See Clinical Pharmacology (12.3). Capecitabine must be taken within 30 minutes of eating or with food. The patient should not take a double dose the following day if he or she misses a dose. The treatment should continue until the disease progresses or unacceptable toxicities occur.
Before starting capecitabine in combination with trastuzumab, patients with metastatic breast cancer who are HER2-positive should show progression of their disease on transtuzumab.

Combination with capecitabine in patients with metastatic or advanced breast cancer, whose tumours express HER2, and who have previously received anthracyclines, taxanes, and trastuzumab
In combination, letrozole is indicated for the treatment of postmenopausal women with metastatic hormone receptor-positive breast cancer who overexpress the HER2 receptor.

What happens if I miss the dose?

If you are almost due for your next dose, skip the missed one. Never take two doses of the same medicine at once.

What happens if I overdose?

Call 1-800-222-1222 immediately if you suspect poison exposure and seek immediate medical care.

What should be avoided?

Grapefruit can interact with lapatinib, causing unwanted side effects. Avoid grapefruit products.

Interaction with other drug

Certain medications should never be taken together. Taking certain drugs together can cause side effects and/or make other medications less effective.Lapatinib can be affected by many drugs. These include prescription and over-the-counter medicines, vitamins, and herbal products.This list does not include all possible interactions. Inform your doctor of all medications you are currently taking and those that you will stop or start using.