Patient Handout: Lapatinib

What is Lapatinib?

Lapatinib is a medication used to treat certain types of cancer, specifically breast cancer. It works by blocking the signals that cancer cells need to grow. It is often prescribed for advanced or metastatic breast cancer that has spread to other parts of the body and may be HER2-positive. This means that the cancer cells have higher-than-normal levels of the HER2 protein, which promotes cancer cell growth.

Lapatinib is usually used in combination with other chemotherapy drugs, such as capecitabine, and is often prescribed when the cancer has not responded to other treatments.

How Does Lapatinib Work?

Lapatinib belongs to a class of drugs called tyrosine kinase inhibitors. These drugs work by blocking specific enzymes (called tyrosine kinases) that play a role in the growth of cancer cells. By blocking these enzymes, lapatinib helps slow down or stop the growth of cancer cells.

How to Take Lapatinib

• Form: Lapatinib is usually taken as a tablet by mouth.
• Dosage: The exact dosage will depend on your doctor’s recommendations and the type of cancer being treated. It is important to follow your healthcare provider’s instructions exactly. Do not take more or less than prescribed.
• When to Take: Lapatinib is typically taken once or twice a day, with or without food. Taking it at the same time every day helps you remember.
• Swallowing: Swallow the tablet whole. Do not chew, break, or crush it.
• Missed Dose: If you miss a dose, take it as soon as you remember, unless it is close to the time for your next dose. In that case, skip the missed dose and take your next dose at the usual time. Do not take two doses at once.

Possible Side Effects

Lapatinib can cause side effects, some of which may be serious. It’s important to contact your healthcare provider if you experience any of the following:

Common Side Effects:

• Diarrhea: This is one of the most common side effects. Drink plenty of fluids and inform your doctor if diarrhea becomes severe.
• Nausea and Vomiting: These symptoms may improve over time, but if they persist, talk to your doctor.
• Fatigue: You may feel tired or weak. Rest and stay hydrated, but inform your doctor if the fatigue is severe.
• Skin Rash: Some people develop a rash or dry skin. Let your doctor know if you notice any changes in your skin.
• Appetite Loss: Loss of appetite can occur, but try to maintain a healthy diet. Consult your doctor if this becomes an issue.

Serious Side Effects:

• Heart Problems: Lapatinib can affect your heart, leading to changes in heart function. Your doctor will monitor your heart health with regular tests.
• Liver Problems: Lapatinib can cause liver damage. Watch for symptoms like yellowing of your skin or eyes, dark urine, or upper stomach pain, and report them immediately.
• Infection: If you have signs of infection (fever, chills, sore throat, or unusual weakness), seek medical attention right away.
• Severe Diarrhea: If diarrhea becomes severe or persists, seek immediate medical advice.

Precautions Before Taking Lapatinib

Before starting lapatinib, inform your doctor about:

• Heart conditions: Lapatinib can affect heart function, so it’s important to disclose any history of heart problems.
• Liver issues: If you have liver disease or any liver problems, talk to your doctor before taking lapatinib.
• Pregnancy and Breastfeeding: Lapatinib may harm an unborn baby. Inform your doctor if you are pregnant, planning to become pregnant, or breastfeeding. Birth control is recommended during treatment.
• Other Medications: Tell your doctor about any other medications, including over-the-counter drugs, vitamins, and herbal supplements. Some medications may interact with lapatinib, affecting how it works or increasing side effects.

What to Avoid While Taking Lapatinib

• Grapefruit and Grapefruit Juice: Avoid consuming grapefruit or grapefruit juice as it may increase the risk of side effects by affecting how lapatinib is processed in your body.
• Infections: Try to avoid people who are sick or have infections, as lapatinib can weaken your immune system.

Regular Monitoring

Your healthcare provider will monitor you regularly to check for any potential side effects, including tests to evaluate your liver function, heart health, and blood counts. Be sure to attend all scheduled appointments.

When to Contact Your Doctor

Contact your healthcare provider if you experience:

• New or worsening symptoms
• Signs of infection (fever, chills, sore throat)
• Heart-related symptoms like shortness of breath, swelling in your feet or ankles, or irregular heartbeats
• Any other concerning side effects

Disclaimer:

This handout is for educational purposes only and should not be considered medical advice. Always follow the instructions provided by your healthcare provider regarding treatment and care. For personalized advice, consult your healthcare provider or pharmacist.