Neratinib

Say it: neh-RA-tih-nib · Brand names: Nerlynx

Neratinib is a targeted therapy pill that blocks HER2, a protein that helps some breast cancers grow.

What it is

Some breast cancer cells have too much of a protein called HER2. Neratinib blocks HER2 and related proteins from inside the cell. This can lower the chance of the cancer coming back or slow its growth.

Often used for

• early stage HER2 positive breast cancer, after finishing trastuzumab, to lower the chance it comes back
• HER2 positive breast cancer that has spread, given with capecitabine

How you get it

Neratinib is a pill you take by mouth at home, once a day with food. For early breast cancer it is usually taken for 1 year. Your schedule may be different.

Common side effects and what helps

• Diarrhea, which is very common, especially in the first month. Your team will give you a plan to prevent it. Drink plenty of fluids.
• Feeling sick to your stomach or throwing up. Eat small meals and ask your team about anti-nausea medicine.
• Belly pain. Tell your team if it is new or gets worse.
• Feeling tired or weak. Rest when you need to, and try short walks.
• Rash. Use gentle soap and fragrance free lotion.
• Mouth sores. Brush gently with a soft toothbrush and rinse with a mild salt water rinse. Avoid spicy foods.
• Not feeling hungry or losing weight. Try small, frequent meals and snacks.
• Muscle cramps. Gentle stretching and fluids may help.

Call your care team right away if you have

• Diarrhea that does not get better with the medicine your team gave you, or more than 4 to 6 loose stools in a day
• Feeling dizzy or faint, or not able to keep fluids down
• Diarrhea with fever
• Yellow skin or eyes, dark tea colored urine, or pain on the right side of your belly
• A fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, or chills

Before you start, tell your team

• If you are pregnant, may become pregnant, or are breastfeeding
• If you have liver problems
• If you take medicines for heartburn or stomach acid, since they can change how this medicine works
• All the medicines, vitamins, and herbal products you take, since some can change how this medicine works

Good to know

• Diarrhea can be severe. Most people take a medicine to prevent it during the first 2 months, or start neratinib at a lower dose and slowly increase. Follow your team's plan.
• It can harm the liver. You will have blood tests to check your liver.
• This medicine can harm an unborn baby. Use birth control during treatment and for some time after. Ask your team how long.

At home

• Take the pills at the same time each day with food.
• Swallow the pills whole. Do not chew, crush, or split them.
• Do not eat grapefruit or drink grapefruit juice while taking this medicine.
• Ask your team how to time any heartburn or antacid medicines around your neratinib.
• If you miss a dose or throw up after taking it, ask your team what to do. Do not take extra pills to make up for it.
• Store the pills at room temperature in the original bottle, away from children and pets.

Questions to ask

• How long will I take this medicine?
• What is my plan to prevent diarrhea?
• Which heartburn medicines are safe with this?
• Which side effects should I call about right away, and which can wait until my next visit?

Side effect guides

• Fatigue (tiredness)
• Nausea and vomiting
• Diarrhea
• Mouth sores
• Skin rash (including EGFR-inhibitor rash)
• Pain

Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.