Pemazyre (pemigatinib) is a prescription oral tablet used to treat bile duct cancer and a type of blood cancer in certain adults. Pemazyre can cause mild and serious side effects, including mouth sores and eye problems.

Some people may experience mild to serious side effects during their Pemazyre treatment. Examples of the drug’s commonly reported side effects include:

Mild side effects have been reported with Pemazyre. These include:

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop taking Pemazyre unless your doctor recommends it.

Pemazyre may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after taking Pemazyre, but this side effect wasn’t reported in studies.

Serious side effects have been reported with Pemazyre. These include:

If you develop serious side effects while taking Pemazyre, 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.
† An allergic reaction is possible after taking Pemazyre, but this side effect wasn’t reported in studies.

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

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

How do side effects of Pemazyre compare with those of Keytruda?

Many side effects of Pemazyre are similar to those of pembrolizumab (Keytruda). But each drug can cause unique side effects as well.

For example, both Pemazyre and Keytruda may cause hair loss and digestive problems, including diarrhea, nausea, and constipation.

But Pemazyre may also cause a high phosphate level, which isn’t known to occur with Keytruda. And Keytruda may cause severe skin and infusion-related reactions,* while Pemazyre isn’t known to cause these side effects.

For lists of Pemazyre’s side effects, see the sections above. To learn more about Keytruda’s side effects, see this article. You can also talk with your doctor or pharmacist.

* Keytruda is given as an intravenous (IV) infusion, which is an injection given into a vein over time. Infusion-related reactions are side effects that can happen during or shortly after a Keytruda infusion.

Does Pemazyre cause long-term side effects?

Possibly. Most side effects of Pemazyre are expected to be temporary. But certain side effects of the drug may have an impact that lasts after the drug is stopped.

For example, detached retina has been reported in Pemazyre’s studies. And this condition may lead to long-term vision loss. (To learn more about this side effect, see the “Side effects explained” section below.)

Talk with your doctor to learn more about possible side effects of Pemazyre and how long they may last.

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

Mouth sores

Mouth sores were a common side effect reported in studies of Pemazyre. Mouth sores may cause symptoms such as:

  • blisters or discolored patches on your cheeks, gums, tongue, or lips
  • bleeding, pain, or swelling in your mouth
  • difficulty swallowing, drinking, or eating

What might help

If you have mouth sores during your Pemazyre treatment, talk with your doctor. They can recommend ways to help relieve your symptoms. A few examples include:

  • practicing good oral hygiene
  • rinsing your mouth with a mixture of water and salt or baking soda
  • using an over-the-counter pain reliever, such as acetaminophen (Tylenol) or benzocaine (Orajel)

If your symptoms are severe, your doctor may also have you temporarily stop taking Pemazyre until your symptoms ease. They’ll tell you when it’s safe to continue taking the drug.

Eye problems

Eye problems were a common side effect reported in studies of Pemazyre. These can range from mild conditions, such as dry eye, blurred vision, or an ingrown eyelash, to a more serious condition such as a detached retina. (The retina is a thin layer of tissue that lines the back of your eye.)

A detached retina may cause symptoms such as:

What might help

Before starting Pemazyre treatment, your doctor will likely advise you to visit an eye specialist. The eye specialist may continue to check your eyes every 2–3 months during your Pemazyre treatment.

If you have symptoms of an eye problem while taking Pemazyre, contact your eye specialist right away. They’ll monitor your symptoms at least every 3 weeks until your eye condition improves. They may also recommend over-the-counter treatments for your symptoms, such as eye drops for dry eye.

Be sure to tell your doctor who is prescribing Pemazyre about any eye problems you have. If your symptoms are severe, your doctor may need to adjust your dosage or have you stop taking Pemazyre.

Allergic reaction

Like most drugs, Pemazyre can cause an allergic reaction in some people. But this side effect wasn’t reported in studies.

Symptoms can be mild to serious and can 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 to manage your symptoms. Examples include:

  • an oral antihistamine, such as diphenhydramine (Benadryl)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Pemazyre, they’ll decide whether 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 you’ve had a serious allergic reaction to Pemazyre, they may have you switch to a different treatment.

Keeping track of side effects

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

Your side effect notes can include things such as:

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

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

Below is important information you should consider before taking Pemazyre.

Warnings

Pemazyre can sometimes cause harmful effects in people who have certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Pemazyre is a good treatment option for you.

Talk with your doctor about your health history before you take Pemazyre. Be sure to tell them if any of the following factors apply to you:

  • liver problems
  • kidney problems
  • vision or eye problems
  • previous allergic reaction to Pemazyre
  • pregnancy
  • breastfeeding

Alcohol and Pemazyre

There are no known interactions between alcohol and Pemazyre. But drinking alcohol during your Pemazyre treatment may worsen some of the drug’s side effects. Examples include dehydration, dizziness, and fatigue.

If you have questions about consuming alcohol during Pemazyre treatment, talk with your doctor or pharmacist.

Pregnancy and breastfeeding with Pemazyre

See below for details about whether Pemazyre is safe to take while pregnant or breastfeeding.

Pregnancy

Pemazyre is not safe to take during pregnancy. Due to the way the drug works, it may cause problems with fetal development (commonly known as birth defects). It could also cause pregnancy loss. If you can become pregnant, your doctor will have you take a pregnancy test to confirm that you’re not pregnant before starting Pemazyre treatment.

If you or your partner are able to become pregnant, your doctor will recommend that you use birth control during your Pemazyre treatment and for 1 week after your last dose.

Breastfeeding

You should not take Pemazyre while breastfeeding. It’s not known whether Pemazyre may pass into breast milk or what effects the drug may have on a child who is breastfed. But because of the risk of harm to a breastfed child, breastfeeding is not recommended while taking Pemazyre and for at least 1 week after your last dose.

If you’re breastfeeding or planning to do so, talk with your doctor about your options.

Like most drugs, Pemazyre can cause a number of side effects that range from mild to serious. However, most are temporary and go away after a few days to weeks. If you have questions about side effects that Pemazyre can cause, talk with your doctor.

Examples of questions to help get you started include:

  • Will I need to have any lab tests done to monitor for side effects from Pemazyre?
  • Are there any side effects of Pemazyre that I should tell you about right away?
  • Do any of the other medications I take raise my risk of side effects from Pemazyre?

To learn more about Pemazyre, see these articles:

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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.