Tukysa (tucatinib) is a brand-name prescription medication. It’s approved by the Food and Drug Administration (FDA) to treat advanced forms of HER2-positive breast cancer in adults. It’s used for breast cancer that’s either:

  • locally advanced (has spread into nearby tissues) and unresectable (can’t be removed with surgery), or
  • metastatic (has spread into other parts of the body)

Tukysa is used in people who’ve had past treatment with one or more anti-HER2 drugs for their cancer. It’s used in combination with two other drugs: Herceptin (trastuzumab) and Xeloda (capecitabine).

Tukysa is typically a long-term treatment.

Here are some fast facts about Tukysa:

  • Active ingredient: tucatinib
  • Drug class: tyrosine kinase inhibitor
  • Drug form: oral tablet
  • FDA approval year: 2020

Like other drugs, Tukysa can cause side effects. Read on to learn about potential common, mild, and serious side effects. For a general overview of Tukysa, including details about its uses, see this article.

Tukysa can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took Tukysa in clinical trials:

* For more information about this side effect, see “Side effect specifics” below.

Mild side effects can occur with Tukysa use. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to Tukysa’s prescribing information.

Mild side effects that have been reported with Tukysa include:

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you develop a side effect while taking Tukysa and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Side effect specifics” below.

Tukysa may cause serious side effects. The list below may not include all possible serious side effects of the drug. For more information, you can refer to Tukysa’s prescribing information.

If you develop serious side effects while taking Tukysa, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Serious side effects can include:

* For more information about this side effect, see “Side effect specifics” below.
† An allergic reaction is possible after taking Tukysa. However, this side effect wasn’t reported in clinical trials.

Tukysa may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Does Tukysa cause hair loss?

No, Tukysa is not known to cause hair loss. In clinical trials of Tukysa, hair loss wasn’t reported. However, Tukysa is used in combination with a chemotherapy drug called Xeloda (capecitabine) to treat breast cancer. And hair loss is a possible side effect of capecitabine.

If you’re concerned about hair loss during treatment for your breast cancer, talk with your doctor. They can suggest ways to help manage your hair loss.

Can Tukysa affect fertility?

It might. Based on animal studies, Tukysa may reduce female* and male* fertility. So this drug may affect your ability to have children.

Note that Tukysa is used in combination with Xeloda (capecitabine) to treat breast cancer. Capecitabine may also reduce fertility.

If you plan to have children in the future, talk with your doctor before starting treatment for your breast cancer. It may be possible to store your eggs or sperm for use in future fertility treatment, such as in vitro fertilization.

* Sex and gender exist on spectrums. Use of the terms “male” and “female” in this article refers to sex assigned at birth.

Does Tukysa cause long-term side effects?

It’s possible. However, most of Tukysa’s side effects generally get better within a few days or weeks. Your doctor may prescribe medication to help ease side effects. They may also lower your Tukysa dose or suggest taking a break from treatment.

However, some side effects may last longer despite these measures. For example, if you have liver damage with Tukysa, this can sometimes cause long-term problems.

If you have questions about long-term side effects with Tukysa, talk with your doctor.

Learn more about some of the side effects that Tukysa may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Tukysa.

Hand-foot syndrome

Tukysa commonly causes a side effect called hand-foot syndrome. This side effect is also common with Xeloda (capecitabine), which is used in combination with Tukysa to treat breast cancer.

Hand-foot syndrome is also called palmar-plantar erythrodysesthesia. It’s a condition that affects the palms of your hands and soles of your feet. It can cause the following symptoms:

  • redness
  • tightness
  • pain or tenderness
  • tingling or burning
  • itching
  • rash
  • blistering
  • cracking
  • peeling

Severe hand-foot syndrome may cause trouble walking. It can also cause trouble with daily activities that involve using your hands.

Hand-foot syndrome occurs when a medication leaks out of small blood vessels in your hands and feet. The medication can then damage the tissue it leaks into. Applying heat or pressure to your hands or feet can increase your risk for this side effect.

What you can do

To help prevent hand-foot syndrome with Tukysa, avoid activities that apply heat, pressure, or friction to your hands and feet. Examples of things to avoid include:

  • exposing your hands and feet to heat for long periods of time, such as when washing dishes or taking a bath
  • rubbing or massaging your hands or feet
  • wearing tight shoes
  • playing racquet sports, such as tennis
  • doing sports that involve running or jumping
  • using hand tools such as hammers, screwdrivers, or gardening tools
  • chopping using knives

If you have symptoms of hand-foot syndrome while taking Tukysa, talk with your doctor. They can recommend ways to manage this side effect. For example, they may suggest:

  • gently applying moisturizer to your hands or feet
  • applying ice packs to the affected areas to help ease pain or burning sensations
  • avoiding harsh soaps or cleaning products that could irritate your skin

If you have severe hand-foot syndrome, your doctor may also prescribe a corticosteroid cream to help reduce inflammation in your skin. And if your hands or feet are very painful, they may recommend taking a pain reliever such as Tylenol (acetaminophen). Your doctor may also lower your dose of Tukysa or ask you to stop taking Tukysa temporarily until your symptoms are managed.

Diarrhea

You may have diarrhea while taking Tukysa. In clinical trials, diarrhea was the most common side effect reported with this medication. Diarrhea is also a common side effect of Herceptin (trastuzumab) and Xeloda (capecitabine), which are used in combination with Tukysa to treat breast cancer.

Diarrhea is usually mild with Tukysa, but it can sometimes be severe and can quickly become serious. Severe diarrhea can make your body lose fluids and electrolytes. It can lead to dehydration, low blood pressure, and kidney damage. In rare cases, it can be life threatening.

What you can do

If you have diarrhea while taking Tukysa, talk with your doctor right away. They may prescribe medication such as Imodium (loperamide) to help stop your diarrhea.

It’s also important to drink plenty of fluids to prevent dehydration while you have diarrhea. Your doctor may recommend oral rehydration solutions, such as Pedialyte. These solutions help replace fluids and electrolytes that you can lose with diarrhea.

Depending on how severe your diarrhea is, your doctor may also lower your dose of Tukysa. Or they may ask you to stop taking Tukysa temporarily until your diarrhea is managed. If you have very severe diarrhea, you may need to permanently stop Tukysa.

Liver damage

While you take Tukysa, you may have problems with your liver function. This medication can sometimes cause liver damage. In clinical trials, liver damage was commonly reported with Tukysa.

Symptoms of liver damage can include:

  • pain in your upper right abdomen
  • dark-colored urine
  • jaundice
  • fatigue
  • itching
  • bruising or bleeding easily

Your doctor will order frequent blood tests to check the health of your liver while you’re taking Tukysa. These tests are called liver function tests (LFTs). They measure levels of liver enzymes in your blood.

Liver enzymes are proteins in your liver that help your liver work correctly. If you have liver damage, these proteins can leak into your blood. So if LFTs show you have raised levels of liver enzymes, this suggests you have damage to your liver.

What you can do

While you take Tukysa, be sure to keep all your appointments for LFTs. You’ll typically have these tests every 3 weeks. They help your doctor see if Tukysa is affecting your liver.

If you have any symptoms of liver damage while taking Tukysa, see your doctor right away. They may order extra LFTs.

If your LFTs or symptoms suggest you have liver damage, your doctor may lower your dose of Tukysa. Or they may ask you to stop taking Tukysa temporarily until your liver function improves. However, if you have severe liver damage, you’ll likely need to permanently stop Tukysa.

Stomatitis

Tukysa commonly causes stomatitis, which is inflammation inside your mouth and throat. This side effect is also common with Xeloda (capecitabine), which is used in combination with Tukysa to treat breast cancer.

Stomatitis can cause symptoms such as:

  • sores or ulcers inside your mouth or throat
  • sore or swollen tongue
  • blisters or ulcers on your tongue or lips
  • sore mouth or throat

Stomatitis can make it painful to chew and swallow, so you may have trouble eating and drinking. You may find you lose your appetite because of this problem. The sores can also make it painful to talk.

What you can do

If you have symptoms of stomatitis while taking Tukysa, be sure to tell your doctor right away. They can help you manage this side effect. For example, they may prescribe an antiseptic mouthwash or a numbing gel or spray. If you have ulcers or sores that are very painful, your doctor may also recommend taking a pain reliever such as Tylenol (acetaminophen).

Other things you can try to help ease your symptoms of stomatitis include:

  • sucking ice chips
  • frequently rinsing your mouth with salt water
  • eating cold sour cream or yogurt before meals to coat your mouth and throat
  • avoiding foods and drinks that are hot, spicy, or acidic
  • choosing softer foods over those that are crunchy or need lots of chewing
  • using a toothbrush with soft bristles
  • avoiding smoking and drinking alcohol

If you have severe stomatitis, your doctor may lower your dose of Tukysa. Or they may ask you to stop taking Tukysa temporarily until your symptoms are managed.

Allergic reaction

As with most drugs, Tukysa can cause an allergic reaction in some people. However, this side effect wasn’t reported in clinical trials.

Symptoms can be mild or serious and can include:

  • skin rash
  • itching
  • flushing
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep taking Tukysa. However, if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Be sure to talk with your doctor about your health history before you take Tukysa. This drug may not be the right treatment for you if you have certain medical conditions or other factors that affect your health. The conditions and factors to consider include:

Liver problems. Tukysa is removed from your body by your liver. If your liver doesn’t work well, Tukysa could build up in your body and increase your risk of side effects. Tukysa can also cause liver damage. If you have an existing problem with your liver, Tukysa could make it worse. Your doctor will monitor your liver while you take Tukysa. If you have a severe liver problem, your doctor will likely prescribe a dose of Tukysa that’s lower than usual.

Kidney problems. If you have severe kidney problems, your doctor will likely not prescribe Tukysa. Tukysa is used in combination with Xeloda (capecitabine) to treat breast cancer. However, capecitabine isn’t suitable for people with severe kidney problems. If you have kidney problems, talk with your doctor about other medications that may be better options for you.

Other medications. Taking Tukysa with certain other medications can cause Tukysa to build up in your body. This may increase your risk of side effects with Tukysa. Be sure to tell your doctor about any other medications you take before starting treatment with Tukysa. If you take certain medications, such as Lopid (gemfibrozil), your doctor may prescribe a dose of Tukysa that’s lower than usual.

Allergic reaction. If you’ve had an allergic reaction to Tukysa or any of its ingredients, your doctor will likely not prescribe Tukysa. Ask your doctor what other medications may be better options for you.

Alcohol and Tukysa

Tukysa doesn’t interact with alcohol. However, drinking alcohol may increase your risk of certain side effects with Tukysa. For example, alcohol may worsen diarrhea, nausea, or headaches that you may have with Tukysa. If you have mouth sores, drinking alcohol may also be painful.

Consuming alcohol may also increase your risk of liver damage with Tukysa. Both alcohol and Tukysa can affect your liver.

Talk with your doctor about whether it’s safe for you to drink alcohol while taking Tukysa.

Pregnancy and breastfeeding while taking Tukysa

Tukysa isn’t safe to take during pregnancy. If you can become pregnant, your doctor will order a pregnancy test to make sure you’re not pregnant before you start taking Tukysa.

Females* who can become pregnant should use birth control while taking Tukysa and for at least 1 week after stopping Tukysa. Males* with a female partner who can become pregnant should also use birth control while taking Tukysa and for at least 1 week after stopping Tukysa.

If you’re pregnant or plan to become pregnant, talk with your doctor about other medications that may be better options for you.

It’s not known if Tukysa passes into breast milk. Due to the possible risks for a breastfed child, you should avoid breastfeeding while taking Tukysa and for at least 1 week after your last dose. If you’re breastfeeding, talk with your doctor about healthy ways to feed your child while taking Tukysa.

* Sex and gender exist on spectrums. Use of the terms “male” and “female” in this article refers to sex assigned at birth.

As with many cancer treatments, it’s common to have side effects with Tukysa. Most side effects are mild and easily managed. However, side effects can sometimes be more severe or serious.

If you’d like to learn more about Tukysa, talk with your doctor or pharmacist. They can help answer any questions you have about side effects of taking the drug.

Keep in mind that Tukysa is used in combination with Herceptin (trastuzumab) and Xeloda (capecitabine) to treat breast cancer. So you should talk with your doctor about possible side effects of these treatments as well.

Besides talking with your doctor, you can do some research on your own. These articles might help:

  • More information about Tukysa. For details about other aspects of Tukysa, refer to this article.
  • Drug comparison. Learn how Tukysa compares with Kadcyla and Perjeta.
  • A look at breast cancer. For details about your breast cancer, see our breast cancer hub as well as this list of related articles.

Disclaimer: Medical News Today 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 another 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.