Description and Brand Names

Drug information provided by: Merative, Micromedex®

US Brand Name

1. Tykerb

Descriptions

Lapatinib is used in combination with capecitabine to treat advanced or metastatic (cancer that has already spread) HER2-receptor positive breast cancer in patients who have received other cancer treatments (eg, anthracycline, taxane, trastuzumab) that did not work well.

Lapatinib is also used together with letrozole to treat postmenopausal women with hormone-receptor positive and HER2-receptor positive metastatic breast cancer.

Lapatinib belongs to the group of medicines called antineoplastics (cancer medicines). It interferes with the growth of cancer cells, which are eventually destroyed. Since the growth of normal cells may also be affected by the medicine, other unwanted effects will also occur. Some of these may be serious and must be reported to your doctor.

This medicine is available only with your doctor's prescription.

This product is available in the following dosage forms:

• Tablet

Before Using

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

Appropriate studies have not been performed on the relationship of age to the effects of lapatinib in the pediatric population. Safety and efficacy have not been established.

Geriatric

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of lapatinib in the elderly. However, elderly patients are more sensitive to the effects of this medicine than younger adults.

Breastfeeding

There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Drug Interactions

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

• Bepridil
• Cisapride
• Colchicine
• Dronedarone
• Fluconazole
• Levoketoconazole
• Mesoridazine
• Nelfinavir
• Pimozide
• Piperaquine
• Posaconazole
• Saquinavir
• Sparfloxacin
• Terfenadine
• Thioridazine
• Ziprasidone

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Abametapir
• Adagrasib
• Afatinib
• Alfuzosin
• Amiodarone
• Amisulpride
• Amitriptyline
• Amoxapine
• Anagrelide
• Apomorphine
• Aripiprazole
• Aripiprazole Lauroxil
• Arsenic Trioxide
• Asenapine
• Astemizole
• Atazanavir
• Azithromycin
• Bedaquiline
• Berotralstat
• Betrixaban
• Boceprevir
• Buprenorphine
• Buserelin
• Capmatinib
• Carbamazepine
• Ceritinib
• Chloroquine
• Chlorpromazine
• Ciprofloxacin
• Citalopram
• Clarithromycin
• Clofazimine
• Clomipramine
• Clothiapine
• Clozapine
• Cobicistat
• Conivaptan
• Crizotinib
• Cyclobenzaprine
• Cyclosporine
• Dabigatran Etexilate
• Dabrafenib
• Dasabuvir
• Dasatinib
• Degarelix
• Delamanid
• Desipramine
• Deslorelin
• Deutetrabenazine
• Dexamethasone
• Dexmedetomidine
• Digoxin
• Disopyramide
• Dofetilide
• Dolasetron
• Domperidone
• Donepezil
• Droperidol
• Efavirenz
• Encorafenib
• Entrectinib
• Erythromycin
• Escitalopram
• Etrasimod
• Fedratinib
• Fexinidazole
• Fingolimod
• Flecainide
• Fluoxetine
• Formoterol
• Foscarnet
• Fosnetupitant
• Fosphenytoin
• Fostemsavir
• Gatifloxacin
• Gemifloxacin
• Gepirone
• Glasdegib
• Gonadorelin
• Goserelin
• Granisetron
• Halofantrine
• Haloperidol
• Histrelin
• Hydroxychloroquine
• Hydroxyzine
• Ibutilide
• Idelalisib
• Iloperidone
• Imipramine
• Indinavir
• Inotuzumab Ozogamicin
• Itraconazole
• Ivabradine
• Ivosidenib
• Ketoconazole
• Lefamulin
• Lenvatinib
• Leuprolide
• Levofloxacin
• Lofexidine
• Lopinavir
• Lumefantrine
• Macimorelin
• Mavacamten
• Mefloquine
• Methadone
• Methotrexate
• Metronidazole
• Mifepristone
• Mirtazapine
• Mobocertinib
• Moxifloxacin
• Nafarelin
• Nefazodone
• Netupitant
• Nilotinib
• Norfloxacin
• Nortriptyline
• Octreotide
• Ofloxacin
• Omaveloxolone
• Ondansetron
• Osilodrostat
• Osimertinib
• Oxaliplatin
• Ozanimod
• Pacritinib
• Paliperidone
• Panobinostat
• Paroxetine
• Pasireotide
• Pazopanib
• Pexidartinib
• Phenobarbital
• Phenytoin
• Pimavanserin
• Pitolisant
• Ponesimod
• Pralsetinib
• Primidone
• Procainamide
• Prochlorperazine
• Promethazine
• Propafenone
• Protriptyline
• Quetiapine
• Quinidine
• Quinine
• Quizartinib
• Ranolazine
• Relugolix
• Repotrectinib
• Ribociclib
• Rifabutin
• Rifampin
• Rifapentine
• Rimegepant
• Ritonavir
• Selpercatinib
• Sertraline
• Sevoflurane
• Simeprevir
• Siponimod
• Sirolimus Protein-Bound
• Sodium Phosphate
• Sodium Phosphate, Dibasic
• Sodium Phosphate, Monobasic
• Solifenacin
• Sorafenib
• Sotalol
• St John's Wort
• Sulpiride
• Sunitinib
• Tacrolimus
• Telaprevir
• Telavancin
• Telithromycin
• Tenofovir Alafenamide
• Tetrabenazine
• Topotecan
• Toremifene
• Trazodone
• Triclabendazole
• Trifluoperazine
• Trimipramine
• Triptorelin
• Ubrogepant
• Vandetanib
• Vardenafil
• Vemurafenib
• Venetoclax
• Venlafaxine
• Vilanterol
• Vincristine
• Vincristine Sulfate Liposome
• Vinflunine
• Voclosporin
• Voriconazole
• Zuclopenthixol

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Paclitaxel

Other Interactions

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following is usually not recommended, but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use this medicine, or give you special instructions about the use of food, alcohol, or tobacco.

• Grapefruit Juice

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

• Diarrhea or
• Liver disease, or history of or
• Lung disease (eg, interstitial lung disease, pneumonitis), history of—Use with caution. May make these conditions worse.

• Heart disease, history of or
• Heart rhythm problems (eg, congenital long QT syndrome) or
• Hypokalemia (low potassium in the blood), uncorrected or
• Hypomagnesemia (low magnesium in the blood), uncorrected—Use with caution. May cause side effects to become worse.

Proper Use

Medicines used to treat cancer are very strong and can have many side effects. Before receiving this medicine, make sure you understand all the risks and benefits. It is important for you to work closely with your doctor during your treatment.

Take this medicine exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered.

This medicine comes with a patient information leaflet. Read and follow the instructions carefully. Ask your doctor if you have any questions.

Take the tablet at least 1 hour before or 1 hour after a meal. All of the tablets are taken together as one dose.

Lapatinib is given together with capecitabine or letrozole. It is important that you take each medicine at the right time. Follow your doctor's instructions on when to take these medicines.

Do not eat grapefruit or drink grapefruit juice while you are using this medicine.

Dosing

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

• For oral dosage form (tablets):
  • For advanced or metastatic breast cancer with capecitabine:
    • Adults—1250 milligrams (mg) or 5 tablets taken together as a single dose once a day for 21 days. Your doctor may tell you to repeat the 21-day cycle.
    • Children—Use and dose must be determined by your doctor.
  • For metastatic breast cancer with letrozole:
    • Adults—1500 milligrams (mg) or 6 tablets taken together as a single dose once a day.
    • Children—Use and dose must be determined by your doctor.

Missed Dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Precautions

It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

Using this medicine while you are pregnant can harm your unborn baby. It may also cause birth defects if the father is using it when his sexual partner becomes pregnant. Female patients should use effective birth control during treatment with this medicine and for 1 week after the last dose. Male patients who have female partners should use effective birth control during treatment with this medicine and for 1 week after the last dose. If you think you have become pregnant while using the medicine, tell your doctor right away.

Serious heart problems can occur with this medicine. Check with your doctor right away if you are having a fast, pounding, or irregular heartbeat, troubled breathing, or unusual tiredness or weakness.

Check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, a loss of appetite, nausea, unusual tiredness or weakness, or yellow eyes or skin. These could be symptoms of a serious liver problem.

Check with your doctor right away if diarrhea occurs while you are using this medicine. You may need medicines to help manage or prevent the diarrhea.

This medicine may cause swelling of the lungs (pneumonitis) or interstitial lung disease. These are life-threatening conditions and require immediate medical attention. The symptoms may be similar to the symptoms from lung cancer. Check with your doctor right away if you have new or worsening cough, fever, or trouble breathing.

Contact your doctor right away if you have any changes to your heart rhythm. You might feel dizzy or faint, or you might have a fast, pounding, or uneven heartbeat. Make sure your doctor knows if you or anyone in your family has ever had a heart rhythm problem such as QT prolongation.

Serious skin reactions can occur with this medicine. Check with your doctor right away if you have blistering, peeling, or loosening of the skin, red skin lesions, severe acne or skin rash, sores or ulcers on the skin, or fever or chills while you are using this medicine.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal (eg, St. John's wort) or vitamin supplements.

Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common

1. Cough
2. diarrhea
3. difficult or labored breathing
4. itching, skin rash
5. loosening of the fingernails
6. nosebleed
7. redness or soreness around the fingernails
8. redness, swelling, or pain of the skin
9. scaling of the skin on the hands and feet
10. tightness in the chest
11. tingling of the hands and feet ulceration of the skin
12. unusual tiredness or weakness

Rare

1. Chest pain
2. decreased urine output
3. dilated neck veins
4. extreme tiredness or weakness
5. irregular breathing
6. irregular heartbeat
7. swelling of the face, fingers, feet, or lower legs
8. weight gain

Incidence not known

1. Blistering, peeling, or loosening of the skin
2. chest discomfort
3. chills
4. clay-colored stools
5. dark urine
6. decreased appetite
7. difficulty with swallowing
8. dizziness
9. fainting
10. fast heartbeat
11. fever
12. headache
13. hives
14. irregular or slow heart rate
15. loss of appetite
16. nausea
17. puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
18. red skin lesions, often with a purple center
19. red, irritated eyes
20. sore throat
21. sores, ulcers, or white spots in the mouth or on the lips
22. stomach pain or tenderness
23. swelling of the feet or lower legs
24. vomiting
25. yellow eyes or skin

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

1. Back pain
2. belching
3. cracked lips
4. diarrhea (mild)
5. difficulty in moving
6. discoloration of the fingernails or toenails
7. dry skin
8. heartburn
9. indigestion
10. lack or loss of strength
11. muscle pain or stiffness
12. pain in the arms or legs
13. stomach discomfort or upset
14. swelling or inflammation of the mouth
15. thinning of hair or hair loss
16. trouble sleeping

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Portions of this document last updated: April 01, 2024

Original article: https://www.mayoclinic.org/drugs-supplements/lapatinib-oral-route/side-effects/DRG-20070910