Xermelo (telotristat ethyl) is a prescription oral tablet used in adults to treat diarrhea related to carcinoid syndrome. This drug can interact with other medications. For example, Xermelo can interact with simvastatin and sildenafil.

An interaction can occur because one substance causes another substance to have a different effect than expected. Interactions can also occur if you have certain health conditions.

Keep reading to learn about Xermelo’s possible interactions. And for more information about Xermelo, including details about its uses, see this article.

Before you start taking Xermelo, tell your doctor and pharmacist about any prescription, over-the-counter, or other drugs you take. Sharing this information with them may help prevent possible interactions. (To learn whether Xermelo interacts with supplements, herbs, and vitamins, see the “Are there other interactions with Xermelo?” section below.)

If you have questions about drug interactions that may affect you, talk with your doctor or pharmacist.

The table below lists drugs that may interact with Xermelo. Keep in mind that this table does not include all drugs that may interact with Xermelo. For more information about some of these interactions, see the “Drug interactions explained” section below.

Drug type or drug nameDrug examplesWhat can happen
CYP3A4 substrates*• darunavir (Prezista)
• felodipine
• midazolam (Seizalam, Nayzilam)
quetiapine (Seroquel)
sildenafil (Viagra)
simvastatin (Zocor)
• tacrolimus (Prograf, Astagraf XL, Envarsus XR)
can make CYP3A4 substrates less effective
CYP2B6 substrates*bupropion (Aplenzin, Wellbutrin, others)
• efavirenz
can make CYP2B6 substrates less effective
opioids fentanyl (Fentora, Actiq, others)
morphine (MS Contin)
oxycodone (OxyContin)
can make opioids less effective and increase the risk of side effects
short-acting octreotide (Sandostatin) can make Xermelo less effective

* CYP3A4 substrates and CYP2B6 substrates are drugs that are broken down by liver enzymes (types of protein) called CYP3A4 and CYP2B6.

Certain health conditions or other factors could raise your risk of harm if you take Xermelo. In such cases, your doctor may not prescribe Xermelo for you. These are known as contraindications. Xermelo has one contraindication, which is described below.

If you’ve had an allergic reaction. If you’ve had an allergic reaction to Xermelo or any of its ingredients, your doctor likely won’t prescribe Xermelo. This is because taking the drug could cause another allergic reaction. You can ask your doctor about other treatments that may be better options for you.

Xermelo is not known to interact with alcohol. But Xermelo and alcohol can cause some similar side effects, such as headache and nausea. So you may be more likely to experience these side effects if you drink alcohol during your Xermelo treatment.

Xermelo treats diarrhea that’s related to carcinoid syndrome. Your doctor may recommend avoiding alcohol if you have this condition. Drinking alcohol can worsen some symptoms of carcinoid syndrome, such as diarrhea and flushing (temporary warmth, redness, or deepening of skin color).

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

Learn more about certain drug interactions that can occur with Xermelo.

Interaction with CYP3A4 substrates

Xermelo can interact with drugs that are CYP3A4 substrates. These are drugs broken down by a liver enzyme (a type of protein) called CYP3A4.

Examples of CYP3A4 substrates include:

What could happen

Xermelo can speed up the action of the CYP3A4 enzyme. Taking Xermelo with a CYP3A4 substrate can cause your body to break down the CYP34A substrate too quickly, which may make it less effective.

What you can do

If you take Xermelo with a CYP3A4 substrate, your doctor may prescribe a higher dosage of the CYP3A4 substrate for you. This can help the drug be more effective.

If you have questions about taking Xermelo with one of these drugs, talk with your doctor or pharmacist.

Interaction with opioids

Xermelo can interact with opioids, which are prescribed to relieve pain.

Examples of opioid medications include:

What could happen

Some opioids are CYP3A4 substrates. (See the “Interaction with CYP3A4 substrates” section above to learn more). Taking Xermelo with certain opioids could cause your body to break down the opioid too quickly. This could make the opioid less effective at relieving pain.

If you’re physically dependent on the opioid, taking Xermelo with it could also cause opioid withdrawal symptoms. (With dependence, your body needs the drug to function as usual. And withdrawal symptoms are side effects that can occur when you stop taking a drug your body has become on.)

In addition, both Xermelo and opioids can cause constipation. So taking Xermelo with an opioid could raise your risk of this side effect.

What you can do

If you take Xermelo with an opioid drug, tell your doctor if your pain is not well-managed. Your doctor may increase your dosage of the opioid. Then, if you end your Xermelo treatment while taking an opioid, your doctor may reduce your opioid dosage.

Tell your doctor if you develop constipation while taking Xermelo with an opioid.

If you take Xermelo with an opioid and then stop taking Xermelo, the amount of the opioid in your body could increase. This could raise your risk of serious side effects from the opioid, such as respiratory depression.

Due to this risk, you should not stop taking Xermelo without first talking with your doctor. They may want to lower your opioid dosage first before you end your Xermelo treatment. This decreases your risk of serious side effects from the opioid, such as respiratory depression.

If you have questions about taking Xermelo with an opioid drug, talk with your doctor or pharmacist.

Interaction with short-acting octreotide

Xermelo can interact with short-acting octreotide (Sandostatin). Like Xermelo, it’s prescribed to treat diarrhea related to carcinoid syndrome. These medications are often taken together.

What could happen

Taking Xermelo at the same time as short-acting octreotide can decrease the amount of Xermelo in your body. This can make Xermelo less effective.

What you can do

If you take Xermelo with short-acting octreotide, you should wait at least 30 minutes after taking Xermelo to take your dose of octreotide.

If you have questions about taking Xermelo with short-acting octreotide, talk with your doctor or pharmacist.

Xermelo may have other interactions. They could occur with supplements, foods, vaccines, or even lab tests. See below for details. Note that the information below does not include all other possible interactions with Xermelo.

Does Xermelo interact with supplements?

Before you start taking Xermelo, talk with your doctor and pharmacist about any supplements, herbs, and vitamins you take. Sharing this information with them may help you avoid possible interactions.

If you have questions about interactions that may affect you, talk with your doctor or pharmacist.

Xermelo and herbs

There are currently no reports of Xermelo interacting with herbs. But this doesn’t mean that interactions with herbs won’t be recognized in the future.

For this reason, it’s still important to check with your doctor or pharmacist before taking any of these products while taking Xermelo.

Xermelo and vitamins

There are currently no reports of Xermelo interacting with vitamins. But this doesn’t mean that vitamin interactions won’t be recognized in the future.

For this reason, it’s still important to check with your doctor or pharmacist before taking any of these products while taking Xermelo.

Does Xermelo interact with food?

There are currently no reports of Xermelo interacting with food. If you have questions about eating certain foods during your treatment with Xermelo, talk with your doctor.

Does Xermelo interact with vaccines?

There are currently no reports of Xermelo interacting with vaccines. If you have questions about getting certain vaccines during your Xermelo treatment, talk with your doctor.

Does Xermelo interact with lab tests?

There are currently no reports of Xermelo interacting with lab tests. If you have questions about having certain lab tests during your treatment with Xermelo, talk with the healthcare professional ordering the test.

Does Xermelo interact with cannabis or CBD?

There are currently no reports of Xermelo interacting with cannabis (commonly called marijuana) or cannabis products such as cannabidiol (CBD). But as with any drug or supplement, talk with your doctor before using cannabis with Xermelo.

Note: Cannabis is illegal at a federal level but is legal in many states to varying degrees.

Certain medical conditions or other health factors may raise the risk of interactions with Xermelo. Before taking Xermelo, talk with your doctor about your health history. They’ll determine whether Xermelo is right for you.

Health conditions or other factors that might interact with Xermelo include:

Liver problems. Your liver helps clear Xermelo from your system. If you have liver problems, the amount of Xermelo could build up in your body. This could raise your risk of side effects such as constipation. If you have a liver problem, talk with your doctor about whether Xermelo is right for you. If your liver problem is moderate or severe, your doctor may not prescribe Xermelo for you. They can talk with you about other treatment options.

Dialysis. It’s not known whether Xermelo is safe or effective for people having dialysis for end-stage kidney disease. The drug has not been studied in this group of people. If you’re having dialysis, talk with your doctor about your treatment options.

Pregnancy. It’s not known whether Xermelo is safe to take during pregnancy. If you’re pregnant or planning a pregnancy, talk with your doctor before taking Xermelo.

Breastfeeding. It’s not known whether it’s safe to take Xermelo while breastfeeding. If you’re breastfeeding or planning to breastfeed, talk with your doctor about your options. If you take Xermelo while breastfeeding, tell your doctor if your child experiences constipation.

Allergic reaction. If you’ve had an allergic reaction to Xermelo or any of its ingredients, your doctor will likely not prescribe Xermelo. This is because taking the drug could cause another allergic reaction. You can ask your doctor about other treatments that may be better choices for you.

Taking certain steps can help you avoid interactions with Xermelo. Before starting treatment, talk with your doctor and pharmacist. Things to discuss with them include:

  • Whether you drink alcohol or use cannabis.
  • Other medications you take, as well as any vitamins, supplements, and herbs. Your doctor or pharmacist can help you fill out a medication list.
  • What to do if you start taking a new drug during your Xermelo treatment.

It’s also important to understand Xermelo’s label and other paperwork that may come with the drug. Colored stickers that describe interactions may be on the label. And the paperwork (sometimes called the patient package insert or medication guide) may have other details about interactions. (If you did not get paperwork with Xermelo, ask your pharmacist to print a copy for you.)

If you have difficulty reading or understanding this information, your doctor or pharmacist can help.

Taking Xermelo exactly as prescribed can also help prevent interactions.

If you still have questions about Xermelo and its possible interactions, talk with your doctor.

Questions you may want to ask your doctor include:

  • Should I check with you before taking over-the-counter medications with Xermelo?
  • Will I need any extra monitoring if I take Xermelo with other medications?
  • Do other medications that can treat my condition have similar interactions to Xermelo?

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.