Xermelo (telotristat ethyl) is a prescription drug that’s used to treat diarrhea related to carcinoid syndrome. Xermelo can cause side effects that range from mild to serious. Examples include nausea and headache.

Specifically, Xermelo is prescribed to adults to treat carcinoid syndrome diarrhea that isn’t managed with somatostatin analog drugs. Xermelo is taken together with these drugs.

The active ingredient in Xermelo is telotristat ethyl. (An active ingredient is what makes a drug work.) The drug comes as an oral tablet.

Keep reading to learn about the common, mild, and serious side effects that Xermelo can cause. For a general overview of the drug, including details about its uses, see this article.

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

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

The following sections include more side effects of Xermelo. Each person’s experience with side effects may differ.

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

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

Xermelo 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 Xermelo, but this side effect wasn’t reported in studies.

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

If you develop serious side effects while taking Xermelo, 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 Xermelo, 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 Xermelo, visit MedWatch.

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

Constipation

Constipation was a common side effect reported in studies of Xermelo. It’s usually mild, but on rare occasions, it can be severe. Severe constipation may cause serious complications such as a blockage or tear in your intestines. This can cause symptoms such as:

  • severe, ongoing, or worsening pain in the abdomen
  • severe, ongoing, or worsening swelling in the abdomen

Some factors can increase the risk of severe constipation when taking this drug. These include having liver problems or taking other medications that can cause constipation. Examples include:

What might help

If you have constipation during Xermelo treatment, talk with your doctor right away. They may recommend pausing Xermelo until your constipation reduces or goes away. In some cases, they may recommend taking medication to treat the constipation.

But if you have symptoms of a blockage or tear in your intestines, call 911 or go to your local emergency department right away. You may need urgent treatment.

Increase in liver enzymes

An increase in liver enzymes was a common side effect reported in studies of Xermelo.

Liver enzymes are proteins that help your liver carry out its usual functions. When liver enzyme levels in your blood are higher than usual, this can indicate your liver isn’t working correctly. It can also be a sign of liver damage. Liver damage can cause symptoms such as:

What might help

Before prescribing Xermelo, your doctor may order liver function tests to be sure Xermelo is safe for you. They’ll also repeat these tests during your treatment to check whether the medication is affecting your liver.

If you have symptoms of liver damage while you’re taking Xermelo, contact your doctor. They’ll likely order a liver function test. If your liver enzyme levels are raised, your doctor may recommend pausing Xermelo treatment until the levels reduce enough.

Allergic reaction

Like most drugs, Xermelo can cause an allergic reaction in some people. This side effect wasn’t reported in studies but has been noted since the drug was approved.

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, contact your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:

  • an oral antihistamine, 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 Xermelo, they’ll decide whether you should continue taking it.

If you have symptoms of a severe allergic reaction, such as swelling or difficulty 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 Xermelo, they may have you switch to a different treatment.

Keeping track of side effects

During your Xermelo treatment, consider making 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 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 Xermelo affects you. They can then use this information to adjust your treatment plan if needed.

Below is important information you should consider before taking Xermelo.

Warnings

Xermelo 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 Xermelo is a good treatment option for you.

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

Alcohol and Xermelo

No interactions between alcohol and Xermelo are known.

But alcohol and Xermelo can cause some similar side effects, such as headache and nausea. So you may be more likely to have these side effects if you drink alcohol during treatment with Xermelo.

Also, drinking alcohol can worsen symptoms of carcinoid syndrome diarrhea, which Xermelo is prescribed to treat.

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

Pregnancy and breastfeeding with Xermelo

Before starting Xermelo treatment, it’s important to talk with your doctor if you’re pregnant, breastfeeding, or planning either.

Pregnancy

It’s not known whether it’s safe to take Xermelo during pregnancy. If you’re pregnant or planning to become pregnant, talk with your doctor before starting treatment with Xermelo.

Breastfeeding

It isn’t known whether Xermelo is safe to take while breastfeeding. If you’re breastfeeding or planning to do so, talk with your doctor before starting this medication.

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

Examples of questions to help get you started include:

  • Do I have a high risk of constipation with Xermelo?
  • If I have constipation with Xermelo, will it help to change my dosage?
  • Is it safe to take Xermelo if I’m taking an antidepressant drug?

To learn more about Xermelo, 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.