Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes Nerlynx (Neratinib). If you are concerned about side effects, discuss the risks and benefits of Nerlynx (Neratinib) with your doctor.

The following side effects have been reported by at least 1% of people taking Nerlynx (Neratinib). Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• Acne
• dry, inflamed mouth
• dry skin
• fatigue
• gas
• heartburn
• hemorrhoids
• loss of appetite
• mild Diarrhea
• mouth sores
• muscle spasms
• nail problems or breaking
• nosebleeds
• rash
• runny nose
• upset stomach
• weight loss
• weakness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• abdominal pain or swelling
• dehydration (e.g., thirst, headache, loss of appetite, not sweating, decreased urine production, Low Blood Pressure)
• Fever or chills
• gallstones (e.g., pain in the upper abdomen, pain in the right shoulder, nausea, vomiting)
• hand-foot syndrome (e.g., pain, tingling, swelling, or redness; calluses and blisters on palms of hands or soles of feet)
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
• skin inflammation or infection (e.g., pain; tenderness; swelling; painful red, raised patches; fever; chills; feeling unwell)
• symptoms of kidney problems (e.g., nausea, vomiting, fatigue, changes in urination)
• symptoms of a urinary tract infection (e.g., pain when urinating, urinating more often than usual, low back or flank pain)
• uncontrolled diarrhea

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking Nerlynx (Neratinib).

Each red, oval-shaped, film-coated tablet, debossed with "W104" on one side and plain on the other side, contains 40 mg of Nerlynx (Neratinib) (as 48.3 mg Nerlynx (Neratinib) maleate). Nonmedicinal ingredients: colloidal silicon dioxide, crospovidone, magnesium stearate, mannitol, microcrystalline cellulose, povidone, and purified water; film coating: iron oxide red, polyethylene glycol, polyvinyl alcohol, talc, and titanium dioxide.

Do not take Nerlynx (Neratinib) if you are allergic to Nerlynx (Neratinib) or any ingredients of the medication.

There may be an interaction between Nerlynx (Neratinib) and any of the following:

• Aliskiren
• Amiodarone
• antacids (e.g., aluminum hydroxide, calcium carbonate, magnesium hydroxide)
• anticancer medications (e.g., azacitidine, Busulfan, Capecitabine, Carboplatin, Cytarabine, Doxorubicin, Etoposide, Ifosfamide, Vincristine)
• Apalutamide
• Aprepitant
• "azole" antifungals (e.g., itraconazole, ketoconazole, Voriconazole)
• Bicalutamide
• bilastine
• Bosentan
• calcium channel blockers (e.g., Amlodipine, Diltiazem, Nifedipine, Verapamil)
• Carvedilol
• cetirizine
• ciprofloxacin
• Colchicine
• conivaptan
• Cyclosporine
• dabigatran
• Deferasirox
• Dexamethasone
• Digoxin
• Dronedarone
• duvelisib
• Edoxaban
• Enzalutamide
• estrogens (e.g., conjugated estrogen, Estradiol, ethinyl estradiol)
• Everolimus
• Fluvoxamine
• "gliptin" Diabetes medications (e.g., Linagliptin, Saxagliptin, Sitagliptin)
• grapefruit juice
• H2 antagonists (e.g., Famotidine, Ranitidine)
• Haloperidol
• Hepatitis C antivirals (e.g., dasabuvir, ombitasvir, paritaprevir)
• HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., efavirenz, etravirine, nevirapine)
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
• Hydrocortisone
• ivermectin
• Lomitapide
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• mifepristone
• Modafinil
• Nadolol
• Naloxegol
• Paliperidone
• proton pump inhibitors (e.g., Lansoprazole, Omeprazole)
• protein kinase inhibitors (e.g., Bosutinib, Crizotinib, Dabrafenib, imatinib, Pazopanib)
• Prucalopride
• quinidine
• quinine
• Ribociclib
• rifabutin
• rifampin
• Risperidone
• Rivaroxaban
• Romidepsin
• St. John's wort
• Sarilumab
• seizure medications (e.g., Carbamazepine, Eslicarbazepine, Phenobarbital, Phenytoin, primidone)
• Sertraline
• Silodosin
• Sirolimus
• "statin" anti-cholesterol medications (e.g., Atorvastatin, Lovastatin, Simvastatin)
• Stiripentol
• Tacrolimus
• Tocilizumab
• Tolvaptan

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with Nerlynx (Neratinib). Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the Nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or Allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health.

Birth control: Women taking Nerlynx (Neratinib) should use effective birth control (e.g., condoms, birth control pill) during treatment and for at least 1 month after treatment is finished. Men who have female partners of childbearing age should use effective birth control for at least 3 months after the final dose of Nerlynx (Neratinib).

If you or your partner become pregnant during treatment with Nerlynx (Neratinib), contact your doctor immediately.

Diarrhea: Nerlynx (Neratinib) can cause diarrhea that can lead to dehydration. Dehydration can cause many symptoms, including decreased urine production, dry and sticky mouth, sleepiness, dizziness, headache, thirst, and confusion. In some cases, dehydration can become a medical emergency. Your doctor will prescribe another medication to help prevent diarrhea. If you have any questions about how to take Nerlynx (Neratinib), talk to your doctor or pharmacist.

Heart problems: Nerlynx (Neratinib) may contribute to heart problems, particularly if you have a history of a heart condition, such as Congestive Heart Failure or a past Heart Attack. If you are at risk of developing heart problems, discuss with your doctor how Nerlynx (Neratinib) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Nerlynx (Neratinib), and whether any special monitoring is needed. If you experience symptoms of heart failure, such as increased difficulty breathing, swelling in the feet and ankles, unusual tiredness or a persistent cough, contact your doctor as soon as possible.

Liver problems:  Liver disease or reduced liver function may cause Nerlynx (Neratinib) to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how Nerlynx (Neratinib) may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Nerlynx (Neratinib), and whether any special monitoring is needed.

Nerlynx (Neratinib) can cause reduced liver function and can cause liver failure, which may be life-threatening. If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Pregnancy: Nerlynx (Neratinib) should not be used during pregnancy. If you become pregnant while taking Nerlynx (Neratinib), contact your doctor immediately.

Breast-feeding: It is not known if Nerlynx (Neratinib) passes into breast milk. If you are a breast-feeding mother and are taking Nerlynx (Neratinib), it may affect your baby. Women should not breast feed while taking Nerlynx (Neratinib) and for at least 1 month after taking the last dose.

Children: The safety and effectiveness of using Nerlynx (Neratinib) have not been established for children.

Seniors: People over the age of 65 are more likely to experience side effects from taking Nerlynx (Neratinib). Depending on how well the medication is tolerated, your doctor may reduce the dose you are taking.