If you’ve been diagnosed with breast cancer, your doctor may prescribe Nerlynx. It’s a prescription drug that’s used in adults to treat certain forms of HER2-positive breast cancer in specific situations.

HER2-positive cancer cells have certain proteins on their surface.

To learn more about HER2-positive breast cancer and how Nerlynx treats it, see the “What is Nerlynx used for?” section below.

Nerlynx basics

Nerlynx contains the active ingredient neratinib. It comes as tablets you’ll take by mouth.

Nerlynx is available only as a brand-name medication. It’s not yet available in a generic form.

Read on to learn more about Nerlynx’s side effects, cost, uses, and more.

Like most drugs, Nerlynx may cause mild or serious side effects. The lists below describe some of the more common side effects that Nerlynx may cause. These lists don’t include all possible side effects.

Keep in mind that side effects of a drug can depend on:

  • your age
  • other health conditions you have
  • other medications you may be taking

Your doctor or pharmacist can tell you more about the potential side effects of Nerlynx. They can also suggest ways to help reduce side effects.

Mild side effects

Here’s a short list of some of the mild side effects that Nerlynx can cause. To learn about other mild side effects, talk with your doctor or pharmacist, or read Nerlynx’s patient information.

Mild side effects of Nerlynx that have been reported include:

Mild side effects of many drugs may go away within a few days or a couple of weeks. But if they become bothersome, talk with your doctor or pharmacist.

* For more information on this side effect, see the “Side effect focus” section below.

Serious side effects

Serious side effects from Nerlynx can occur, but they aren’t common. If you have serious side effects from Nerlynx, call your doctor right away. However, if you think you’re having a medical emergency, you should call 911 or your local emergency number.

Serious side effects of Nerlynx that have been reported include:

Note: Allergic reaction wasn’t reported in studies of Nerlynx. But it’s still possible with this drug.

* For more information on this side effect, see the “Side effect focus” section below.

Side effect focus

Learn more about some of the side effects Nerlynx may cause.

Diarrhea

The most common side effect of Nerlynx is diarrhea. Your doctor will rate the severity of this side effect depending on the number of bowel movements you have each day.

Your diarrhea may be considered severe if:

  • your number of bowel movements each day increases by seven or more, compared with before you started taking Nerlynx, or
  • your diarrhea is severe enough to require treatment in the hospital, or
  • your diarrhea prevents you from completing your daily activities

You should contact your doctor right away if you have severe diarrhea. You should also call them if you have diarrhea with symptoms such as:

  • dizziness
  • weakness
  • fever

What might help

Your doctor will prescribe medication to help prevent diarrhea while you’re taking Nerlynx. With the first dose of Nerlynx you’ll also start taking loperamide (Imodium). And during the first 56 days of treatment with Nerlynx, you’ll have to continue taking loperamide.

After day 56, you can continue taking loperamide as needed to limit your bowel movements to one or two each day.

You may have severe diarrhea with Nerlynx and find that loperamide doesn’t work for you. In this case, your doctor may need to prescribe additional medications to treat the diarrhea. You may also need to replace lost fluids and electrolytes.

Changing your diet may also help you manage diarrhea. Your doctor may recommend eating foods that are low in fiber, such as:

  • bananas
  • toast
  • oatmeal
  • white rice
  • applesauce
  • soup or broth

If needed, your doctor may lower your dosage of Nerlynx to help manage your diarrhea. Your doctor may also tell you to stop taking Nerlynx for a while if you have severe or long-lasting diarrhea. If your diarrhea is too severe, your doctor may have you stop taking Nerlynx permanently.

Don’t stop taking Nerlynx or change your dosage without talking with your doctor.

Problems with your liver

You may develop problems with your liver while you’re taking Nerlynx. Specifically, your liver might make more liver enzymes (a type of protein) than it should. This can be a common side effect when you’re taking Nerlynx.

If you have any of the following symptoms, tell your doctor right away:

What might help

Before starting Nerlynx, your doctor will check your liver function. They’ll do this by measuring the levels of certain types of liver enzymes in your blood. These enzymes are called liver transaminases.

Then your doctor will regularly check your liver function tests once every month for the first 3 months of treatment. After the first 3 months, your doctor will check your liver function once every 3 months. But if you’re having any signs and symptoms of liver failure, your doctor will check your liver function more often.

Your doctor may have you stop taking Nerlynx if your liver function tests show severe problems or if you have symptoms of liver problems. Don’t stop taking Nerlynx without talking with your doctor.

Rash

You may develop a rash with Nerlynx. Rashes caused by cancer drugs, such as Nerlynx, can appear anywhere on the body. The rashes can cause itching, burning, stinging, or pain. And they may develop at any time during your treatment.

You may develop a rash if Nerlynx is affecting your liver, which is described in the section just above. Rashes may also occur if you’re allergic to Nerlynx. See the section just below for more information about allergic reaction.

What might help

If you develop a rash while you’re taking Nerlynx, talk with your doctor. They may recommend that you use mild soaps without fragrances and that you moisturize your skin. If needed, your doctor may prescribe a medication to help soothe or treat the rash.

When washing your skin, use a gentle soap, a soft cloth, and warm water. After washing, apply a moisturizer to your skin. Also wear protective clothing to help shield your skin from extreme temperatures and wind. Sun exposure might worsen your rash too, so protect yourself from sunlight.

Be sure to call your doctor if:

  • your rash gets worse after you’ve used over-the-counter or prescription creams or ointments
  • your rash itches for 2 or more days
  • you’ve scratched the rash, and it’s bleeding or the skin has opened
  • your rash keeps you up at night
  • you develop blisters, skin discoloration, or crusts on your skin
  • your rash develops pus
  • you develop yellow skin, or your urine is the color of tea
Allergic reaction

Some people may have an allergic reaction to Nerlynx. While allergic reaction wasn’t reported in studies of Nerlynx, it can still happen.

Symptoms of a mild allergic reaction can include:

  • rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)

A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include swelling under your skin, typically in your eyelids, lips, hands, or feet. They can also include swelling of your tongue, mouth, or throat, which can cause trouble breathing.

Call your doctor right away if you have an allergic reaction to Nerlynx. But if you think you’re having a medical emergency, call 911 or your local emergency number.

Costs of prescription drugs can vary depending on many factors. These factors include what your insurance plan covers and which pharmacy you use. To find current prices for Nerlynx in your area, visit WellRx.com.

If you have questions about how to pay for your prescription, talk with your doctor or pharmacist. You can also visit the Nerlynx manufacturer’s website to see if they have support options.

If you’ve been diagnosed with breast cancer, your doctor may prescribe Nerlynx. It’s a prescription drug that’s used in adults to treat certain forms of HER2-positive breast cancer in specific situations.

HER2 is a protein that promotes cell growth. It’s present on the surface of all breast cancer cells. HER2 stands for human epidermal growth factor receptor 2. Some people with breast cancer have high levels of HER2, meaning their cancer is HER2-positive.

HER2-positive breast cancer grows and spreads faster than others. But this type of breast cancer responds to treatments that target the HER2 protein.

Specifically, Nerlynx is used to treat the following conditions:

  • Early stage HER2-positive breast cancer. For this use, Nerlynx is used for cancer that’s been treated in the past with trastuzumab (Herceptin). With early stage breast cancer, the cancer hasn’t spread from your breasts or has only spread to lymph nodes in your underarms.
  • Advanced HER2-positive breast cancer. For this use, Nerlynx is used for cancer that’s been treated in the past with other drugs targeting the HER2 protein. With advanced cancer, the cancer has spread beyond your breast and lymph nodes to other parts of your body. These other parts could include your bones, lungs, brain, or liver. For advanced HER2-positive breast cancer, Nerlynx is taken with the chemotherapy drug capecitabine (Xeloda).

Nerlynx works by entering cancer cells and attaching itself to the HER2 protein. By binding to this protein, Nerlynx blocks its action of promoting cell growth. With HER2 being inactivated, the cancer cells stop growing and spreading in your body.

Your doctor will explain how you should take Nerlynx. They will also explain how much to take and how often. Be sure to follow your doctor’s instructions. Below are commonly used dosages, but always take the dosage your doctor prescribes.

Taking Nerlynx

Nerlynx comes as tablets you’ll take by mouth. Each tablet contains 40 milligrams (mg) of neratinib.

Dosage

You’ll take Nerlynx once daily at the same time every day. Depending on whether you have early stage or advanced breast cancer, your doctor will prescribe a specific dosage schedule.

For example, if you have early stage breast cancer, your doctor may have you take Nerlynx for up to 1 year. This is because Nerlynx is used as an adjuvant to treat early stage breast cancer. (Adjuvant means the treatment is used after you’ve received another treatment, to help prevent your cancer from returning. Nerlynx is prescribed to people who’ve used the drug trastuzumab for treatment in the past.)

But if you’re taking Nerlynx for advanced breast cancer, you’ll take it with capecitabine (Xeloda), which is a chemotherapy drug. You’ll take Nerlynx on days 1 to 21 and capecitabine on days 1 to 14. You’ll continue to take Nerlynx with capecitabine. You’ll continue this dosing schedule until you either have side effects that are intolerable or your cancer becomes worse.

To learn about early stage and advanced breast cancer, see the “What is Nerlynx used for?” section above.

Taking Nerlynx with other drugs

If you have early stage breast cancer and you’ve already received treatment with trastuzumab (Herceptin), your doctor may prescribe Nerlynx without other cancer drugs.

But because of the risk of diarrhea when taking Nerlynx, your doctor will give you a preventive treatment with loperamide (Imodium). You’ll start taking loperamide with your first dose of Nerlynx.

If you continue to have diarrhea while you’re taking loperamide, your doctor may prescribe additional diarrhea medications.

If you have advanced breast cancer, you’ll need to take Nerlynx with capecitabine (Xeloda). Your doctor will prescribe these cancer drugs in a 21-day cycle. For the first 14 days, you’ll take both Nerlynx and capecitabine. Then, you’ll take only Nerlynx for the remaining 7 days of the cycle.

You’ll repeat this cycle until either you have side effects that are intolerable or your cancer gets worse.

To learn about early stage and advanced breast cancer, see the “What is Nerlynx used for?” section above.

Questions about taking Nerlynx

Below are answers to some questions you may have about taking Nerlynx.

  • What if I miss a dose of Nerlynx? If you miss a dose of Nerlynx, don’t replace the missed dose. Instead, skip the missed dose, then take your next dose at your regularly scheduled time. If you have questions about what to do after a missed dose, talk with your doctor or pharmacist.
  • Will I need to use Nerlynx long term? If you’re taking Nerlynx for early stage breast cancer, your doctor may prescribe it for up to 1 year. For advanced breast cancer, you’ll continue taking the drug until you experience side effects that are intolerable, or your cancer gets worse.
  • Can Nerlynx be chewed, crushed, or split? No, you shouldn’t chew, crush, or split Nerlynx tablets. They must be swallowed whole. If you have trouble swallowing the pills, talk with your doctor or pharmacist. They can suggest ways to make it easier to take Nerlynx.
  • Should I take Nerlynx with food? Yes, you will need to take Nerlynx with food.
  • How long does Nerlynx take to work? It’s unknown how long it takes Nerlynx to work. You may not notice if the drug is working. Your doctor will perform tests to see if your breast cancer is coming back. This is how your doctor will know if the drug is working for you.

To learn about early stage and advanced breast cancer, see the “What is Nerlynx used for?” section above.

Questions for your doctor

You may have questions about Nerlynx and your treatment plan. It’s important to discuss all your concerns with your doctor.

Here are a few tips that might help guide your discussion:

  • Before your appointment, write down questions such as:
    • How will Nerlynx affect my body, mood, or lifestyle?
  • Bring someone with you to your appointment if doing so will help you feel more comfortable.
  • If you don’t understand something related to your condition or treatment, ask your doctor to explain it to you.

Remember, your doctor and other healthcare professionals are available to help you. And they want you to get the best care possible. So don’t be afraid to ask questions or offer feedback on your treatment.

Find answers to some commonly asked questions about Nerlynx.

How does Nerlynx work?

Nerlynx is a targeted therapy that has a unique mechanism of action. (A drug’s mechanism of action is the way it works to cause an effect in the body.)

Nerlynx works by targeting and attacking specific features of breast cancer cells that are not present on healthy cells. It blocks the HER2 protein in breast cancer cells, which is a specific protein in their structure that isn’t found in healthy cells. In HER2-positive cancer, the cancer cells have more of this protein. The HER2 protein is involved in controlling cell growth.

Nerlynx enters the cancer cells and attaches itself to the HER2 protein. By attaching to the HER2 protein, Nerlynx blocks its action of promoting cell growth. Without active HER2 protein, the cancer cells stop growing and spreading.

Is Nerlynx a chemotherapy drug?

No, Nerlynx isn’t a chemotherapy drug. Instead, it’s a targeted therapy. Targeted therapies act on specific elements of cancer cells that differ from healthy cells.

These therapies are made to act on cancer cells, whereas chemotherapy may destroy both cancer cells and healthy cells.

Targeted therapies such as Nerlynx also help prevent cancer cells from spreading in your body. They can stop cancer cells from making new cancer cells. Chemotherapy, on the other hand, doesn’t prevent cancer cells from making new cancer cells. It just kills cancer cells that are already present.

Some important things to discuss with your doctor when considering Nerlynx treatment include your overall health and any medical condition you may have. Tell your doctor if you’re taking any medications. This is important because some drugs may interfere with Nerlynx.

These and other considerations to discuss with your doctor are described below.

Interactions

Taking medications, vaccines, foods, and other things with a certain drug can affect how the drug works. These effects are called interactions.

Before taking Nerlynx, be sure to tell your doctor about all medications you take (including prescription and over-the-counter types). Also describe any vitamins, herbs, or supplements you use. Your doctor or pharmacist can tell you about any interactions these items may cause with Nerlynx.

Interactions with drugs or supplements

Nerlynx can interact with several types of drugs. These drugs include:

This list does not contain all types of drugs that may interact with Nerlynx. Your doctor or pharmacist can tell you more about these interactions and any others that may occur with use of Nerlynx.

Other interactions

Certain foods can affect how your body absorbs Nerlynx. For instance, grapefruit may cause your body to absorb more Nerlynx than usual. This can increase your risk for side effects. You should avoid eating grapefruit, or drinking grapefruit juice, while taking Nerlynx.

Warnings

Nerlynx may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you take Nerlynx. Factors to consider include those in the list below.

  • Allergic reaction. If you’ve had an allergic reaction to Nerlynx or any of its ingredients, you shouldn’t take Nerlynx. Ask your doctor what other medications are better options for you.
  • Problems with your liver. Before starting Nerlynx, your doctor will check your liver function through blood tests. Once you start taking Nerlynx, your doctor will continue checking your liver function every month. After the first 3 months, your doctor may check your liver function every 3 months. If you start showing signs or symptoms of liver problems, your doctor may advise you to stop taking Nerlynx for a while. Or you may need to stop taking it permanently.

Use with alcohol

Some medications may interact with alcohol. Nerlynx isn’t one of them. But before starting Nerlynx, ask your doctor or pharmacist if it’s safe for you to drink alcohol.

Pregnancy and breastfeeding

Doctors are unsure whether it’s harmful to take Nerlynx during pregnancy.

Tell your doctor if you’re pregnant. Your doctor may have you take a pregnancy test before they prescribe Nerlynx.

If you’re a female* taking Nerlynx, your doctor may recommend that you use an effective method of birth control while you’re taking the drug. You’ll need to continue using birth control for 1 month after your last dose.

If you’re a male* taking Nerlynx, your doctor may recommend that you use birth control, such as condoms, while taking the drug. You’ll need to continue using birth control for 3 months after your last dose.

It’s unknown whether Nerlynx passes into breast milk or can cause harm to a child who is breastfed. So you shouldn’t breastfeed your child while taking Nerlynx. You’ll also need to avoid breastfeeding for at least 1 month after your last dose.

* In this article, we use the terms “male” and “female” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Don’t take more Nerlynx than your doctor prescribes. Using more than this can lead to serious side effects. If you take too much Nerlynx, your doctor will closely monitor you for signs and symptoms of overdose.

Symptoms of overdose

Symptoms caused by an overdose can include:

The severity of these symptoms depends on how much Nerlynx you’ve taken.

What to do in case you take too much Nerlynx

Call your doctor if you think you’ve taken too much Nerlynx. You can also call 800-222-1222 to reach the American Association of Poison Control Centers, or use their online resource. However, if you have severe symptoms, immediately call 911 (or your local emergency number) or go to the nearest emergency room.

If you have questions about taking Nerlynx, talk with your doctor or pharmacist. Your doctor can tell you about other treatments you can use for your condition.

Here’s a list of articles that you might find helpful:

Some questions to ask your doctor about Nerlynx may include:

  • What options do I have if I have trouble swallowing Nerlynx tablets whole?
  • When is the best time to take Nerlynx?
  • Are there any foods or beverages I should avoid while taking Nerlynx?
  • Can Nerlynx cure my cancer?
  • How do I know if my breast cancer is HER2-positive?

You can learn more about breast cancer, which Nerlynx is used for, by subscribing to Healthline’s breast cancer newsletter.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.