If you have a certain kind of cancer, your doctor might suggest Retevmo as a treatment option for you.

Retevmo is a prescription medication that’s used to treat certain kinds of the following cancers:

The active ingredient in Retevmo is selpercatinib. An active ingredient is what makes a drug work.

Retevmo comes as a capsule that you swallow. If Retevmo is safe and effective for you, your doctor will likely recommend that you take it long term.

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

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

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

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

Examples of mild side effects that have been reported with Retevmo 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, too. But if you have any symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And do not stop taking Retevmo unless your doctor recommends it.

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

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 Retevmo, visit MedWatch.

Though most side effects of Retevmo are mild, it’s possible to experience serious side effects from this medication. Serious side effects that have been reported with Retevmo include:

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after using Retevmo. But it’s not clear whether this side effect occurred in studies.

If you develop serious side effects while taking Retevmo, 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.

Retevmo is used to treat certain types of thyroid cancer and medullary thyroid cancer in some children. Most side effects that children have from Retevmo are similar to those of adults taking the drug.

In addition, it’s possible for Retevmo to cause bone growth problems in children who are still growing. Due to this risk, Retevmo should only be used in children ages 12 years and older.

If your child is taking Retevmo, their doctor will be able to check whether they’re still growing. The doctor may monitor your child’s growth throughout their treatment. In some cases, they may recommend pausing or stopping Retevmo treatment if growth problems occur.

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

Increased liver enzyme levels or liver problems

You may have increased levels of liver enzymes in your blood during your treatment with Retevmo. In studies, this was a common side effect reported by people taking Retevmo.

An increase in liver enzymes in the blood may indicate liver problems. In some cases, these problems can be serious.

It’s important to know the possible symptoms of liver problems so you can tell a doctor right away if you have them. Symptoms may include:

What might help

Before you start treatment with Retevmo, your doctor will check your liver enzyme levels through liver function tests. Then they’ll monitor your liver enzyme levels throughout treatment to be sure they do not increase.

If you have any symptoms of liver problems, tell your doctor. They can order blood tests to see if your liver enzyme levels are high.

If you do develop an increase in liver enzyme levels or liver problems, your doctor may recommend pausing your treatment or decreasing your dosage of Retevmo. In some cases, your doctor may stop your treatment with Retevmo and recommend a different medication to treat your condition.

Diarrhea

Diarrhea was one of the more commonly reported side effects in studies of Retevmo. You may have diarrhea if your bowel movements are happening more often than usual. Feeling urgency to have a bowel movement is another symptom of this side effect.

What might help

If you’re experiencing diarrhea during your treatment with Retevmo, tell your doctor. In some cases, they may be able to recommend medications to treat this side effect. An example is Imodium (loperamide). They will likely also recommend that you stay hydrated, since diarrhea can cause dehydration.

Skin rash

You may develop a rash from taking Retevmo. This was a common side effect in studies of this medication. Symptoms of a rash may include:

  • redness or darkening of your skin
  • bumps or hives
  • itching

What might help

If you notice a rash during your treatment with Retevmo, tell your doctor. In some cases, rash can be a symptom of a more serious side effect, such as an allergic reaction.

Your doctor can determine what may be causing your rash. In addition, they may be able to recommend medications to ease your symptoms.

Increase in cholesterol levels

Retevmo may cause an increase in your cholesterol levels. In studies, this was a common side effect reported by people taking the medication.

What might help

During treatment with Retevmo, your doctor will likely monitor your cholesterol levels through blood tests. If you develop high cholesterol, your doctor may recommend taking a medication to decrease your cholesterol levels.

Allergic reaction

Like most drugs, Retevmo can cause an allergic reaction in some people. But it’s not clear whether this side effect occurred 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 over-the-counter antihistamine you swallow, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

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

Keeping track of side effects

During your Retevmo 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 new drugs 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 it 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 Retevmo affects you. They can then use this information to adjust your treatment plan if needed.

Retevmo may not be right for you if you have certain medical conditions. These are known as drug-condition interactions. Other factors may also affect whether Retevmo is a good treatment option for you.

Talk with your doctor about your health history before starting Retevmo. The list below includes factors to consider.

Liver problems. Retevmo may increase your liver enzyme levels, possibly causing liver problems. If you already have liver problems, Retevmo may make your condition worse.

Tell your doctor about conditions affecting your liver before starting Retevmo. In some cases, your doctor may recommend using a lower dose of Retevmo. They will likely monitor your liver function through blood tests while you’re taking Retevmo. If your liver problems worsen, your doctor may recommend a different treatment option for you.

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

High blood pressure. Retevmo can cause high blood pressure. If you already have high blood pressure, this medication may make your condition worse. Before you start taking Retevmo, tell your doctor if you have high blood pressure. They may monitor your blood pressure throughout treatment as well as recommend that you take blood pressure medication.

Heart problems, especially long QT syndrome. If you have any heart problems, tell your doctor before Retevmo treatment. This medication can cause long QT syndrome. If you already have a heart problem or long QT syndrome, this medication may make your condition worse. Your doctor may recommend treating your heart condition before you start taking Retevmo.

Bleeding problems. Retevmo may increase your risk of bleeding. If you have any bleeding disorders, such as a blood clotting problem, tell your doctor before starting Retevmo treatment. This medication may make your condition worse. Your doctor will be able to determine if it may be safe for you to take Retevmo.

Upcoming surgery. Retevmo can hinder your body’s healing ability. This means it may take longer to heal than usual. If you have any upcoming surgeries planned, tell your doctor before starting Retevmo. They can help you determine how to take Retevmo around the time of your surgery.

For instance, they may recommend stopping treatment with Retevmo 7 days before surgery. For certain major surgeries, they may also pause treatment for 2 weeks afterward so your body can heal.

Alcohol and Retevmo

There are no known interactions between alcohol and Retevmo. However, it’s possible that side effects of Retevmo may become worse from drinking alcohol during treatment.

For example, Retevmo may cause liver problems to occur. Alcohol can also increase your risk of liver problems. So drinking alcohol during Retevmo treatment may further increase this risk.

Talk with your doctor to see how much alcohol may be safe for you to drink while taking Retevmo.

Pregnancy and breastfeeding while taking Retevmo

You should not take Retevmo during pregnancy or while breastfeeding.

At this time, there haven’t been any studies of Retevmo during pregnancy. But due to the way the drug works, it may cause problems with fetal development (commonly known as birth defects). It may also result in loss of pregnancy. If you can become pregnant, your doctor will have you take a pregnancy test to confirm that you are not pregnant before starting Retevmo treatment.

It’s recommended that females* who can become pregnant use birth control during treatment with Retevmo and for at least 1 week after taking the last dose. Males* with partners who can become pregnant should also use contraception during treatment and for at least 1 week after the last dose.

It’s not known if Retevmo may be present in breast milk or what effects the drug may have on a breastfeeding baby. But it’s not recommended to breastfeed while taking Retevmo and for at least 1 week after stopping treatment.

If you’re pregnant or breastfeeding, or planning to become pregnant or breastfeed, talk with your doctor before starting treatment with Retevmo.

* 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.

You may experience side effects during treatment with Retevmo. In most cases, side effects from this medication are mild. But it’s possible to experience serious side effects as well.

Try to discuss your risk of side effects with your doctor before starting treatment with Retevmo. Here are some questions that may help you get started:

  • How can I treat side effects that I experience from Retevmo?
  • What should I do if I become pregnant while I’m taking Retevmo?
  • Do my other medications increase my risk of side effects from Retevmo?

Q:

Will I need to have blood tests to monitor for certain side effects during treatment with Retevmo?

Anonymous

A:

Yes, your doctor will recommend certain blood tests throughout your treatment with Retevmo. This is to watch for possible side effects that may occur from taking Retevmo, including:

Before you start taking Retevmo, your doctor will check your liver function through blood tests. They will have you get these tests every 2 weeks for the first 3 months of treatment. After that, you will go for blood tests every month or if you develop symptoms of liver problems.

In addition, your doctor will monitor for certain side effects through other blood tests during treatment.

If you develop any side effects from taking Retevmo, tell your doctor. In some cases, they may recommend additional blood tests.

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