Generic name: telotristat ethyl [ tel-OH-tri-stat-ETH-il ]
Dosage form: tablet 250 mg
Drug class: Miscellaneous GI agents

Medically reviewed by Melisa Puckey, BPharm. Last updated on Apr 29, 2025.

What is Xermelo?

Xermelo (telotristat ethyl) tablets are a prescription medicine used to treat carcinoid syndrome diarrhea in adults.  Xermelo targets the underlying cause of carcinoid syndrome diarrhea, which is high serotonin levels. 

Xermelo works by blocking tryptophan hydroxylase, a key enzyme that helps make serotonin. By blocking tryptophan hydroxylase, serotonin levels decrease and diarrhea symptoms improve. Xermelo mechanism of action is as a tryptophan hydroxylase inhibitor, it is not chemotherapy.

Xermelo tablets are taken three times a day.

Xermelo is used with medications such as octreotide (Sandostatin), a somatostatin analog (SSA) when the SSA has not effectively controlled diarrhea on its own.  Xermelo reduces how much serotonin is made and octreotide blocks the amount of serotonin released, so together they improve carcinoid syndrome diarrhea symptoms.

Xermelo FDA approval was granted for the indication of carcinoid syndrome diarrhea when used in combination with a somatostatin analog (SSA) therapy, such as octreotide. It can be used in adults whose carcinoid syndrome diarrhea has not been controlled by somatostatin analog therapy.

What is carcinoid syndrome diarrhea?

Carcinoid syndrome diarrhea is caused by carcinoid tumors releasing too much serotonin into the bloodstream. Excess serotonin stimulates the gut, speeding up movement through the intestines and preventing water and electrolyte absorption which leads to frequent watery diarrhea. Carcinoid syndrome is a rare condition that affects people with metastatic neuroendocrine tumors (mNETs).

Clinical trials: How effective is Xermelo?

Phase III Study Results

A placebo-controlled phase III study (TELESTAR) evaluated Xermelo in 135 carcinoid syndrome patients who experienced 4 or more bowel movements (BM) per day despite taking somatostatin analog therapy. Xermelo dose was three times daily.

Key Findings (12-Week Double-Blind Study):

• BM Frequency Reduction:
• Telotristat ethyl 250 mg: 1.7 fewer bowel movements per day 
• Telotristat ethyl 500 mg: 2.1 fewer bowel movements per day 
• Placebo group: 0.9 fewer bowel movements per day 
• Urinary 5-HIAA Reduction: Both telotristat ethyl dosages significantly lowered 5-hydroxyindole acetic acid (5-HIAA) levels (a marker of serotonin production), confirming the drug's effectiveness.

Conclusion: The study demonstrated that telotristat ethyl effectively reduces diarrhea symptoms in patients with carcinoid syndrome, when SSAs alone are insufficient.

Xermelo side effects

Common Xermelo side effects

Common Xermelo side effects may include:

• Nausea 13%
• Headache 11%
• Depression 9%
• Swelling in your hands or feet 7%
• Decreased appetite 7%, 
• Gas 7%
• Fever 7%
• Abnormal liver function tests 9%.

These common side effects occurred in 5% or more of patients taking Xermelo 250 mg three times a day in the double-blind, placebo-controlled clinical trial of 90 patients with metastatic neuroendocrine tumors and carcinoid syndrome diarrhea.

Serious Xermelo side effects

Get emergency medical help if you have signs of an allergic reaction such as hives, difficulty breathing, swelling of your face, lips, tongue, or throat.

Xermelo may cause other serious side effects. Stop using Xermelo and call your doctor at once if you have:

• severe constipation; or
• severe or worsening stomach pain.

This is not a complete list of side effects, and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Related/similar drugs

Warnings

Use only as directed. Tell your doctor if you use other medicines or have other medical conditions or allergies.

Discontinue this medicine if severe constipation or severe persistent or worsening abdominal pain develops.

Before taking this medicine

Tell your doctor if you have ever had liver disease.

Tell your doctor if you are pregnant or breastfeeding.

Not approved for use by anyone younger than 18 years old.

Xermelo Dosing Information

Usual Xermelo Adult Dose: 250 mg tablet orally 3 times a day with food.

Xermelo comes in a monthly case that contains 4 weekly boxes; 1 box of 7 daily doses for use each week. Keep each tablet in the package until you are ready to take a dose.

Short-acting Octreotide is usually given at least 30 minutes after taking this medicine.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

This medicine is only part of a complete treatment program that may also include other medications. Do not change your doses or medication schedule without your doctor's advice.

Available as Xermelo 250mg tablets,

What happens if I miss a dose?

Skip the missed dose and use your next dose at the regular time. Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking Xermelo?

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

What other drugs will affect Xermelo?

Sometimes it is not safe to use certain medications at the same time. Some drugs can affect your blood levels of other drugs you take, which may increase side effects or make the medications less effective.  Using Xermelo with medicines that are CYP3A4 substrates (e.g., midazolam) may decrease their effectiveness. Tell your doctor about all other medicines you use.

Other drugs may affect Xermelo, including prescription and over-the-counter medicines, vitamins, and herbal products.

Click on the link below to check for interactions with Xermelo.

Xermelo Package Insert

Review the Xermelo Package Insert for more detailed information about this medication. Discuss any medical questions you have with your doctor or other healthcare provider. This is not all the information you need to know about this medication.

Storage

Store at 25°C (77°F) with excursions permitted to 15°C to 30°C (59°F to 86°F) 

Ingredients

Active ingredients: 250 mg of telotristat ethyl (free base) which is equivalent to 328 mg telotristat etiprate. 

Inactive ingredients: colloidal silicon dioxide, croscarmellose sodium, hydroxypropyl cellulose, lactose anhydrous, macrogol/PEG, magnesium stearate, polyvinyl alcohol [part hydrolyzed], talc, and titanium dioxide.

Company

Xermelo Lexicon Pharmaceuticals, Inc. The Woodlands, TX 77381.

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Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer

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