Lapatinib, Oral

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KEY POINTS

• This medicine is taken by mouth to treat breast cancer. Take it exactly as directed.
• This medicine can cause liver problems. You need to have liver function tests regularly.
• If you develop diarrhea at any time while taking this medicine, or for several weeks after you stop taking this medicine, contact your healthcare provider right away.
• This medicine may cause unwanted side effects. Tell your healthcare provider if you have any side effects that are serious, continue, or get worse.
• Tell all healthcare providers who treat you about all the prescription medicines, nonprescription medicines, supplements, natural remedies, and vitamins that you take.

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What are other names for this medicine?

Type of medicine: antineoplastic (anticancer); kinase inhibitor

Generic and brand names: lapatinib, oral; Tykerb

What is this medicine used for?

This medicine is taken by mouth to treat breast cancer. It is used when other cancer medicines have not worked. It is used along with another medicine.

This medicine may be used to treat other conditions as determined by your healthcare provider.

What should my healthcare provider know before I take this medicine?

Before taking this medicine, tell your healthcare provider if you have ever had:

• An allergic reaction to any medicine
• Chemotherapy or radiation therapy
• Heart failure, long QT syndrome (problems with electrical activity in the heart muscle), or any other heart disease
• Liver or kidney disease
• Low levels of potassium or magnesium in your blood

Females of childbearing age: This medicine is not usually given to pregnant women because it can harm the baby. If you are pregnant, tell your healthcare provider. Do not become pregnant during treatment with this medicine. If you become pregnant, contact your healthcare provider right away. Do not breast-feed while you are taking this medicine.

How do I use it?

Check the label on the medicine for directions about your specific dose. Take this medicine exactly as your healthcare provider prescribes. Do not take more of it or for longer than prescribed. Taking too much increases the risk of serious side effects.

Take this medicine on an empty stomach, at least 1 hour before or 1 hour after food.

What if I miss a dose?

If you miss a daily dose and do not remember until the next day, skip that dose and take the regular daily dose. Do not take double doses. If you are not sure of what to do if you miss a dose, or if you miss more than one dose, contact your healthcare provider.

What if I overdose?

If you or anyone else has intentionally taken too much of this medicine, call 911 or go to the emergency room right away. If you pass out, have seizures, weakness or confusion, or have trouble breathing, call 911. If you think that you or anyone else may have taken too much of this medicine, call the poison control center. Do this even if there are no signs of discomfort or poisoning. The poison control center number is 800-222-1222.

Symptoms of an acute overdose may include: fast heartbeat, severe diarrhea, vomiting.

What should I watch out for?

Contact your healthcare provider right away if you develop unusual tiredness or weakness; severe nausea or vomiting; dark urine; light-colored bowel movements; or yellowing of your eyes or skin. Rarely, this medicine can cause liver problems. You need to have liver function tests regularly.

Diarrhea is common with this medicine and may be severe. If you develop diarrhea at any time while taking this medicine, contact your healthcare provider right away. Do not treat it yourself.

You need to have blood tests regularly to see how this medicine affects you. Keep all appointments for tests.

If you need emergency care, surgery, lab tests, or dental work, tell the healthcare provider or dentist you are taking this medicine.

What are the possible side effects?

Along with its needed effects, your medicine may cause some unwanted side effects. Some side effects may be very serious. Some side effects may go away as your body adjusts to the medicine. Tell your healthcare provider if you have any side effects that continue or get worse.

Life-threatening (Report these to your healthcare provider right away. If you cannot reach your healthcare provider right away, get emergency medical care or call 911 for help.): Allergic reaction (hives; itching; rash; trouble breathing; tightness in your chest; swelling of your lips, tongue, and throat).

Serious (Report these to your healthcare provider right away.): Shortness of breath; cough; pounding or racing heartbeat; dizziness; lightheadedness; unusual tiredness or weakness; severe nausea or vomiting; dark urine; light-colored bowel movements; or yellowing of your eyes or skin; severe diarrhea; unusual bruising or bleeding; skin rash, blistering or peeling.

Other: Mild rash, dry skin, diarrhea, tiredness, headache, trouble sleeping, nausea, vomiting, loss of appetite, mouth sores, red or painful hands or feet.

What products might interact with this medicine?

When you take this medicine with other medicines, it can change the way this or any of the other medicines work. Nonprescription medicines, vitamins, natural remedies, and certain foods may also interact. Using these products together might cause harmful side effects. Talk to your healthcare provider if you are taking:

• Antacids that contain aluminum, calcium, or magnesium, such as Gaviscon, Maalox, Mylanta, Phillips' Chewable Tablets, Rolaids, or TUMS (Take antacids at least 2 hours before or 4 hours after you take this medicine.)
• Antiarrhythmic medicines (to treat irregular heartbeat) such as amiodarone (Cordarone, Pacerone), disopyramide (Norpace), dofetilide (Tikosyn), dronedarone (Multaq), flecainide, propafenone (Rythmol), quinidine, and sotalol (Betapace, Sorine)
• Antibiotics such as ciprofloxacin (Cipro), clarithromycin (Biaxin), erythromycin (E.E.S., Ery-Tab, Erythrocin), isoniazid, rifabutin (Mycobutin), rifampin (Rifadin), and telithromycin (Ketek)
• Antidepressants such as amitriptyline, citalopram (Celexa), desvenlafaxine (Pristiq), escitalopram (Lexapro), fluoxetine (Prozac), fluvoxamine (Luvox), imipramine (Tofranil), nefazodone, nortriptyline (Pamelor), sertraline (Zoloft), trazodone, and venlafaxine (Effexor)
• Antifungal medicines such as itraconazole (Sporanox), ketoconazole (Nizoral), and voriconazole (Vfend)
• Antipsychotic medicines such as aripiprazole (Abilify), chlorpromazine, haloperidol (Haldol), iloperidone (Fanapt), pimozide (Orap), thioridazine, and ziprasidone (Geodon)
• Antiseizure medicines such as carbamazepine (Carbatrol, Epitol, Equetro, Tegretol), phenobarbital, phenytoin (Dilantin, Phenytek), and primidone (Mysoline)
• Antiviral medicines such as ombitasvir/paritaprevir/ritonavir/dasabuvir (Viekira) and simeprevir (Olysio)
• Aprepitant (Emend)
• Artemether/lumefantrine (Coartem)
• Calcium channel blockers such as diltiazem (Cardizem, Cartia, Tiazac), felodipine, isradipine (DynaCirc), nicardipine (Cardene), nifedipine (Adalat CC, Procardia), and verapamil (Calan, Covera, Verelan)
• Cholesterol-lowering medicines such as atorvastatin (Lipitor), lovastatin (Altoprev), rosuvastatin (Crestor), and simvastatin (Zocor)
• Colchicine (Colcrys)
• Conivaptan (Vaprisol)
• Cyclosporine (Gengraf, Neoral, Sandimmune)
• Dexamethasone
• Dextromethorphan/quinidine (Nuedexta)
• Diabetes medicines such as pioglitazone (Actos), repaglinide (Prandin), and rosiglitazone (Avandia)
• Digoxin (Lanoxin)
• Doxepin (Silenor)
• Erectile dysfunction medicines such as avanafil (Stendra), sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra, Staxyn)
• HIV medicines such as delavirdine (Rescriptor), fosamprenavir (Lexiva), indinavir (Crixivan), nelfinavir (Viracept), nevirapine (Viramune), ritonavir (Norvir), saquinavir (Invirase), and stavudine (Zerit)
• Medicines to block or prevent stomach acid such as cimetidine (Tagamet), esomeprazole (Nexium), lansoprazole (Prevacid), omeprazole (Prilosec), pantoprazole (Protonix), and ranitidine (Zantac)
• Medicines to treat or prevent blood clots such as dabigatran (Pradaxa), edoxaban (Savaysa), rivaroxaban (Xarelto), and warfarin (Coumadin)
• Methadone (Dolophine, Methadose)
• Mifepristone (Korlym, Mifeprex)
• Nausea medicines such as dolasetron (Anzemet) and ondansetron (Zofran)
• Other cancer medicines such as arsenic trioxide (Trisenox), crizotinib (Xalkori), daunorubicin (Cerubidine), doxorubicin (Doxil), idarubicin (Idamycin), lapatinib (Tykerb), nilotinib (Tasigna), sorafenib (Nexavar), sunitinib (Sutent), toremifene (Fareston), vandetanib (Caprelsa), and vemurafenib (Zelboraf)
• Paroxetine (Brisdelle, Paxil, Pexeva)
• Quinine
• St. John's wort
• Stimulants such as armodafinil (Nuvigil) and modafinil (Provigil)
• Triazolam (Halcion)

Do NOT eat or drink products that contain grapefruit, Seville oranges, and tangelos at any time while you are taking this medicine. These fruits and juices affect the way this medicine works and increase your risk of serious side effects. Talk with your healthcare provider or pharmacist about this.

If you are not sure if your medicines might interact, ask your pharmacist or healthcare provider. Keep a list of all your medicines with you. List all the prescription medicines, nonprescription medicines, supplements, natural remedies, and vitamins that you take. Be sure that you tell all healthcare providers who treat you about all the products you are taking.

How should I store this medicine?

Store this medicine at room temperature. Keep the container tightly closed. Protect it from heat, high humidity, and bright light.

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This advisory includes selected information only and may not include all side effects of this medicine or interactions with other medicines. Ask your healthcare provider or pharmacist for more information or if you have any questions.

Ask your pharmacist for the best way to dispose of outdated medicine or medicine you have not used. Do not throw medicine in the trash.

Keep all medicines out of the reach of children.

Do not share medicines with other people.