If you have breast cancer, your doctor might suggest Tukysa as a treatment option for you. It’s a prescription medication used to treat certain kinds of HER2-positive breast cancer in adults.

For this use, Tukysa is prescribed with two other cancer drugs:

Tukysa comes as a tablet you swallow. The active ingredient in Tukysa is tucatinib. An active ingredient is what makes a drug work. Tucatinib is a type of biologic (a drug made from parts of living organisms).

Tukysa is usually taken for as long as possible. Treatment may last until you have side effects that you can’t tolerate, or the cancer spreads.

For more information about Tukysa, including details about its uses, see this in-depth article.

Like other drugs, Tukysa can cause mild to serious side effects. Keep reading to learn more.

Some people may experience mild to serious side effects while taking Tukysa. Examples of commonly reported side effects include:

* To learn more about this side effect, see the “Side effects explained” section below.

Some side effects are more likely than others. For example, most people who take Tukysa will have diarrhea as a side effect. On the other hand, many people are able to take Tukysa without vomiting, even though this is one the more common side effects.

It’s important to note that Tukysa is prescribed with two other medications for treating breast cancer:

These drugs can also cause side effects, including some of the same ones that Tukysa may cause.

A number of other mild to serious side effects are possible with Tukysa. See below for more information.

Most people who took Tukysa in studies experienced at least one mild side effect. Examples that have been reported with this drug include:

* To learn more about this side effect, see the “Side effects explained” section below.

In most cases, these side effects should be temporary. And some may be easily managed.

Tukysa may cause mild side effects other than the ones listed above. See the Tukysa prescribing information for details.

It’s important to note that Tukysa is prescribed with two other medications for treating breast cancer:

These drugs can also cause side effects, including some of the same ones that Tukysa may cause.

If you have symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And do not stop taking Tukysa unless your doctor recommends it.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Tukysa, visit MedWatch.

Serious side effects of Tukysa are possible, but they weren’t common in the drug’s studies.

Serious side effects of Tukysa that have been reported include:

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.

* To learn more about this side effect, see the “Side effects explained” section below.

Get answers to some frequently asked questions about Tukysa’s side effects.

Can Tukysa cause long-term side effects?

Yes, long-term side effects of Tukysa are possible. They may start at any time, even after you’ve been taking the drug for a long time. The side effects may not go away, even after you stop taking the drug.

Long-term side effects reported in Tukysa studies include:

* To learn more about this side effect, see the “Side effects explained” section below.

Keep in mind that Tukysa is prescribed with two other medications that treat breast cancer:

These drugs can also cause side effects, including some that are long term. To learn more about side effects that these medications can cause, check out the full prescribing information for Herceptin and Xeloda.

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

Can Tukysa cause hair loss?

It’s unlikely. Hair loss wasn’t reported as a side effect by people taking Tukysa in studies.

But Tukysa is prescribed with other medications for breast cancer. And hair loss has been reported with Xeloda (capecitabine), which is one of these medications.

If you have questions or concerns about hair loss and your breast cancer treatment, talk with your doctor.

If I have side effects of Tukysa, is there a lower dosage I can try?

Possibly. It depends on your side effects and what you and your doctor decide is best for your breast cancer treatment plan.

Depending on the side effects of Tukysa and the symptoms you have, your doctor may reduce your dosage. If the lowest dose still causes intolerable side effects, your doctor will likely recommend that you stop taking Tukysa.

Your doctor or pharmacist can tell you more about different dosages of Tukysa, and how side effects may affect your dosage.

Learn more about some of the side effects that Tukysa may cause.

Diarrhea

Diarrhea is the most common side effect that Tukysa has caused. Most people who took Tukysa in studies reported this side effect.

Less often, Tukysa can cause diarrhea that is severe. In extreme cases, diarrhea caused by Tukysa has led to dehydration, kidney injury, and even death.

On average, diarrhea occurs about 12 days after starting Tukysa. It usually goes away within 8 days and may require treatment. In rare cases, people have had their Tukysa dosage lowered or permanently stopped due to diarrhea.

Tukysa is also prescribed with two other medications that can cause diarrhea as a side effect:

What might help

Contact your doctor right away if you have diarrhea while taking Tukysa. They can recommend a medication to treat this side effect, such as loperamide (Imodium A-D). Depending on how severe your diarrhea is, they may lower your Tukysa dosage. They may also temporarily or permanently have you stop taking the medication.

If you have diarrhea while taking Tukysa, it’s important to drink plenty of fluids. This can help prevent dehydration. Try sipping fluids throughout the day, especially after a bowel movement. Having a sports drink may be helpful because these drinks contain salts such as sodium and potassium, which are sometimes lost through diarrhea.

Hand-foot syndrome

Treatment with Tukysa may cause a side effect known as hand-foot syndrome. This was one of the most common side effects reported in Tukysa’s studies.

With hand-foot syndrome, you develop any of the following on the palms of your hands or the soles of your feet:

Keep in mind that Tukysa is prescribed with other medications for treating breast cancer. One of these medications, capecitabine (Xeloda), can also cause hand-foot syndrome.

What might help

Contact your doctor if you notice symptoms of hand-foot syndrome while taking Tukysa. They can recommend ways to help manage this side effect. Depending on how severe your symptoms are, they may lower your dosage or suggest that you stop taking the drug until this side effect goes away.

Below are some tips that your doctor may recommend to help manage symptoms of hand-foot syndrome:

  • Apply an ice pack to the affected areas to help cool burning sensations.
  • Avoid wearing shoes that are too tight or rub your feet.
  • Pat your skin dry, because rubbing with a towel can irritate your skin.
  • Apply a lotion or cream to your hands and feet, but don’t rub too hard.

Liver damage

Liver damage is a rare side effect that Tukysa may cause. Some people had to take a lower dosage or stop taking Tukysa due to liver damage. But most people who had this side effect in studies were able to keep taking it.

Symptoms of liver damage include:

Keep in mind that Tukysa is prescribed with other medications for treating breast cancer. One of these, capecitabine (Xeloda), can also cause liver problems, but the risk is lower than with Tukysa.

What might help

Before prescribing Tukysa, your doctor will order blood tests to check your liver health. If you already have severe liver problems, they may decide to prescribe you a lower dosage of Tukysa.

They’ll also monitor you for liver damage while you’re taking Tukysa. They’ll do this by ordering blood tests every 3 weeks during your treatment. These check the levels of your liver enzymes, since increased enzyme levels can be a sign of liver damage.

If you have symptoms of liver problems while taking Tukysa, call your doctor right away. They’ll likely have you stop taking it temporarily. Then, depending on how severe your symptoms are, they’ll have you restart the treatment at a lower dosage or stop taking the drug altogether.

Nerve damage in your arms, hands, feet, or legs

Taking Tukysa can cause nerve damage in your arms, hands, feet, or legs. This side effect is known as peripheral neuropathy and was mild in most people who reported it in studies. While there were a few serious cases, it’s not known if anyone stopped taking Tukysa due to this side effect.

What might help

Call your doctor if you notice symptoms of peripheral neuropathy while taking Tukysa. They can help recommend ways to manage this side effect.

You can also learn more about managing peripheral neuropathy by checking out these tips from the American Cancer Society. A couple of examples include:

  • Avoid alcohol, since it can also cause nerve damage and may worsen or increase your risk of this side effect from Tukysa.
  • Avoid triggers that worsen nerve pain, such as:
    • hot or cold temperatures
    • wearing shoes that are too tight or rub your feet

Allergic reaction

Like most drugs, Tukysa can cause an allergic reaction in some people. But this was rare in the drug’s studies, and serious allergic reactions weren’t reported at all.

Symptoms include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, usually in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment for your symptoms, such as:

  • an over-the-counter oral antihistamine, such as Benadryl (diphenhydramine)
  • a topical product, such as hydrocortisone cream

If your doctor confirms that you’ve had a mild allergic reaction to Tukysa, they’ll decide if you should continue taking it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms that you’ve had a serious allergic reaction to Tukysa, they may have you switch to a different treatment.

Keeping track of side effects

During your Tukysa treatment, consider keeping notes about any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dosage of the drug you were taking when you had the side effect
  • how soon you had it after starting that dosage
  • what your symptoms were
  • how they affected your daily activities
  • any other medications you were taking
  • any other information you feel is important

Taking notes and sharing them with your doctor will help them learn more about how Tukysa affects you. They can then use this information to adjust your treatment plan if needed.

Tukysa 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 starting Tukysa treatment. Below are a few factors to consider.

Liver problems. Tukysa can cause liver problems, including liver damage, as a side effect. If you already have a liver problem, such as hepatitis, there may be a risk of your condition getting worse with this medication. Depending on the severity of your liver problem, your doctor may prescribe a lower Tukysa dosage, then monitor your liver health closely.

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

Alcohol and Tukysa

It may be best to minimize or avoid drinking alcohol while taking Tukysa.

There’s no known direct interaction between alcohol and Tukysa. But drinking alcohol can increase your risk of certain side effects that this drug may cause, or it may make them more severe. These side effects include:

If you have questions about drinking alcohol while taking Tukysa, talk with your doctor.

Pregnancy and breastfeeding while taking Tukysa

Tukysa is not safe for use during pregnancy or breastfeeding. If you can become pregnant, your doctor will likely order a pregnancy test. They’ll need to confirm that it’s negative before they’ll prescribe Tukysa for you.

If you’re pregnant, breastfeeding, or planning either, talk with your doctor about breast cancer treatments that may be safer for you.

Like most medications, Tukysa can cause side effects. Most people who take Tukysa have some that are mild. While it’s also possible for the drug to cause serious side effects, these aren’t common.

Before starting Tukysa treatment, talk with your doctor. Ask questions to help you become familiar with the medication and its side effects. Some examples to help get you started are:

  • Are there ways I can reduce my risk of side effects from Tukysa?
  • Does my medical history place me at an increased risk of any particular side effects?
  • How do Tukysa’s side effects compare with those of other treatments for my cancer?

To get news about treatments and advice about managing symptoms of your condition, sign up for Healthline’s breast cancer newsletter. And if you’re looking for a supportive community of others who are also living with breast cancer, consider joining Bezzy BC.

Q:

Are there medications that increase my risk of side effects if I take them with Tukysa?

Anonymous

A:

Yes, certain drugs can increase the level of Tukysa in your body, which increases your risk of side effects. Due to this risk, doctors typically won’t prescribe these drugs with Tukysa.

Examples include:

Before starting Tukysa, tell your doctor and pharmacist about all the medications you take, including any over-the-counter drugs or supplements. They can check these for any interactions with Tukysa.

If you and your doctor decide that you need to take a drug that interacts with Tukysa, they may adjust your dosage of Tukysa. They’ll also monitor you closely for side effects during your treatment.

The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

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 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.