Lapatinib (Generic Name)

Other names: Tykerb

About This Drug

Lapatinib is used to treat cancer. It is given orally (by mouth).

Possible Side Effects (Most Common)

  • Bone marrow depression. This is a decrease in the number of white blood cells, red blood cells, and platelets. Bone marrow depression usually occurs seven to 14 days after the drug is given and may increase your risk of infection, fatigue, and bleeding.
  • Diarrhea. You may experience severe diarrhea.
  • Nausea and vomiting
  • Soreness of the mouth and throat. You may have red areas, white patches, or sores that are painful
  • Rash
  • Indigestion
  • Fatigue
  • Weakness
  • Loss of appetite
  • Headache
  • Dry skin
  • Finger nail and toenail changes
  • Hair loss (mild)
  • Back pain
  • Trouble sleeping

 Possible Side Effects (Least Common)

  • Changes in the tissue of the heart. Some changes may occur that can cause your heart to have less ability to pump blood. Your heart function will be checked as needed.
  • Abnormal heart beat
  • Changes in your liver function.  Your doctor will monitor your liver function as needed.
  • Inflammation of the lungs. You may have a dry cough or shortness of breath.

Treating Side Effects

  • If you have vomiting or have diarrhea, drink plenty of fluids, unless your doctor has told you to restrict your fluid intake because of another medical condition. It is important that you do not become dehydrated.
  • Ask your doctor or nurse about medication that is available to help prevent or lessen nausea, vomiting, indigestion, and/or diarrhea.
  • Do not put anything on your rash unless your doctor or nurse says you may. Keep the area clean and dry.
  • Mouth care is very important. Your mouth care should consist of gently brushing with a very soft tooth brush. Also rinse your mouth with a mixture of 1/2 teaspoon of salt in 8 ounces of water, or with a mixture of 1/2 teaspoon of baking soda (sodium bicarbonate) in 8 ounces of water. This should be done at least after every meal and at bed time. Avoid mouthwash that contains alcohol. Avoid alcohol and smoking because they can irritate your mouth and throat.

Important Instructions

  • Take these tablets on an empty stomach at least 1 hour before or 1 hour after eating food
  • Take this drug  at the same time each day.
  • Do not crush, split, or dissolve the tablets.

Food and Drug Interactions

  • Do not eat grapefruit or drink grapefruit juice while taking this drug.
  • Do not take St. John’s Wort.
  • This drug may interact with other medications. Tell your doctor and pharmacist about all the medications and dietary supplements (vitamins, minerals, herbs, and others) that you are currently taking. The safety and effectiveness of dietary supplements and alternative diets are often unknown. Using them might unexpectedly affect your cancer or interfere with your treatment. Until more is known, you should not use dietary supplements or alternative diets without your cancer doctor’s advice.

When to Call the Doctor

Notify your doctor or nurse immediately if you have any of the following symptoms:

  • Shortness of breath
  • Dry cough
  • Feeling your heart beat rapidly (palpitations)
  • Diarrhea
  • Uncontrolled nausea that prevents you from eating or drinking
  • Vomiting more than 3 times in one day
  • Rash
  • Signs of liver problems: dark urine, pale stools, severe stomach pain, severe tiredness or weakness, unusual itching, or yellowing of the eyes

Notify your doctor or nurse as soon as possible if you have any of the following symptoms:

  • Nausea, vomiting, indigestion, and/or diarrhea not relieved by prescribed medications
  • Painful mouth or throat, or inability to eat or drink
  • Indigestion not relieved by prescribed medications
  • Fatigue
  • Loss of appetite that persists
  • Rapid loss of weight, such as 5 pounds in 1 week
  • Trouble sleeping

Reproductive Concerns

  • Pregnancy warning: This drug may have harmful effects on the unborn child, so effective methods of birth control should be used during your cancer treatment. Discuss effective methods of birth control with your doctor.
  • Genetic counseling is available to you to discuss the effects of this drug therapy on future pregnancies. In addition, a genetic counselor can review the potential risks of problems in the fetus due to this medication if an exposure during pregnancy has occurred.
  • Breast feeding warning: It is not known if this drug passes into breast milk.  For this reason, women are advised to discuss with their doctor the risks and benefits of breast feeding during treatment with this drug because this drug may enter the breast milk and seriously harm a breast feeding infant.

Revised June 2013

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