Lapatinib - Oral

Lapatinib is used together with other medicines to treat certain types of breast cancer.

It is used for those whose tumour has spread to other parts of the body.

Take Lapatinib exactly as directed by your doctor or according to the instructions on the label. Do not take more or less than instructed by your doctor.

Take it on an empty stomach, at least 1 hour before or 1 hour after a meal. Try to take it at the same time each day.

Swallow the tablets whole with a glass of water, one after the other.

The dose of this medicine will be decided by your doctor. Your doctor will advise you on the course of treatment depending on the type of your condition and your response to the medication.

Lapatinib must be taken regularly for it to be effective. Continue taking this medicine even when you feel better. Do not stop taking it unless instructed by the doctor.

If you miss a dose, skip the missed dose and return to your normal dosing schedule.

DO NOT double a dose under any circumstances.

If you often forget to take your medicine, let your doctor and pharmacist know.

Inform your doctor if you have the following conditions:

• heart problem or disease e.g. congenital long QT syndrome (an inherited disease causing abnormally fast and erratic heartbeats), left ventricular dysfunction (a condition wherein the left ventricle of the heart does not pump blood as effectively as it should)
• low potassium or magnesium levels in the blood
• severe liver disease

Let your doctor know if you are pregnant or planning to become pregnant.

Both men and women must use proven birth control methods during Lapatinib therapy and for 1 week after stopping the treatment. You may wish to discuss birth control methods with your doctor or pharmacist.

If you are breastfeeding, inform your doctor. You should not breastfeed during treatment and for 1 week after stopping the treatment.

Some genetic traits can cause serious side effects from Lapatinib. Individuals with certain genes called HLA-DRB1*07:01 or HLA-DQA1*02:01 are more likely to develop severe liver injury. If you know you have this gene type, inform your doctor. Monitor for signs and symptoms of liver injury (e.g. yellowing of the skin or eyes, abdominal pain, dark coloured urine) and let your doctor know immediately.

Why is it important to keep my appointments with the doctor?

Keep your appointments with your doctor. Your doctor needs to monitor your condition and check your response to the medication regularly.

• Pregnancy tests must be done before treatment to know if this medicine is suited for you to take.
• Routine tests (e.g. heart and liver function, complete blood count, electrolyte levels) may be done while you are being treated with this medicine. Your doctor will advise you about how often you need to have these tests.
• Regular monitoring of signs and symptoms of lung problems, severe diarrhoea and skin reactions may also be needed.

Lapatinib may cause any of the following side effects: headache, nausea, vomiting, diarrhoea, stomach pain, constipation, indigestion, pain in arms or legs, back or joint pain, difficulty sleeping, weakness, hair loss, and loss of appetite.

Some side effects may need immediate medical help. Alert your doctor quickly if you experience any of the following:

• yellowing of the skin or eyes, abdominal pain, dark coloured urine, tiredness, swelling in the legs and ankles
• signs and symptoms of lung problem e.g. shortness of breath, cough, fever
• severe diarrhoea or diarrhoea accompanied by excessive water loss from the body, vomiting, upset stomach or fever
• signs and symptoms of heart problem e.g. shortness of breath, fast or abnormal heartbeat, dizziness or passing out
• signs and symptoms of allergic reaction e.g. rashes, breathlessness, swelling of the face, eyes or mouth
• rashes with peeling of the skin or blistering of the lips, mouth or eyes accompanied by fever

Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.

Inform your doctor and pharmacist if you are taking any of these medicines:

• other medicines for cancer e.g. paclitaxel, irinotecan
• certain antibiotics e.g. clarithromycin, telithromycin
• medicines for HIV infection e.g. ritonavir, saquinavir
• medicines to treat fungal infection e.g. itraconazole, ketoconazole
• medicines for epilepsy (fits or seizures) e.g. carbamazepine, phenytoin, phenobarbital
• medicines for irregular heartbeat
• digoxin (medicine for heart failure [weakness and inability of the heart to pump blood])
• rifampicin (medicine used to treat TB, lung infection known as tuberculosis)
• St. John's wort (herbal medicine)

This list does not include all medicines that may interact with Lapatinib.

Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics such as traditional Chinese medicines, supplements, and medicines that you buy without a prescription.

Avoid alcohol.

Avoid excessive consumption of grapefruit or grapefruit juice (more than 1 litre a day).

Store in a cool, dry place away from the reach of children.

Medicines must not be used past the expiry date.

As Lapatinib is a cancer medicine, always return any unused or expired tablets to the clinic, hospital, or pharmacy for disposal. Do not throw it away in the household waste.