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What type of diarrhea does Xermelo treat?

Medically reviewed by Philip Thornton, DipPharm. Last updated on Feb 23, 2023.

Official answer


Xermelo (telotristat ethyl) is a tablet used to treat carcinoid syndrome diarrhea. It is taken in combination with somatostatin analog therapy, when this type of therapy by itself does not adequately control the diarrhea.

What is carcinoid syndrome?

Carcinoid syndrome is a syndrome that can develop in people with carcinoid tumors - a type of cancer - in their gastrointestinal (GI) tract. Some of these tumors release substances into the bloodstream which causes carcinoid syndrome. The symptoms of carcinoid syndrome include:

  • Severe diarrhea
  • Facial flushing
  • Wheezing
  • Rapid heartbeat

Stress, drinking alcohol and heavy exercise can make these symptoms worse.

Carcinoid syndrome diarrhea causes multiple watery, loose stools each day

People with carcinoid syndrome diarrhea may have considerable urgency associated with each loose stool.

Carcinoid syndrome diarrhea is primarily caused by excess serotonin secreted by carcinoid tumors. Serotonin is important for normal gut function, but in people with carcinoid syndrome diarrhea, excessive amounts of serotonin can cause the series of wave-like of contractions in the gut (peristalsis) to significantly increase, which reduces water and electrolyte absorption and leads to diarrhea.

How does Xermelo work to stop carcinoid syndrome diarrhea?

Xermelo is a tryptophan hydroxylase inhibitor. Tryptophan hydroxylase is an enzyme involved in the synthesis of serotonin. By inhibiting this enzyme the overproduction of serotonin is reduced, which helps to prevent the diarrhea.


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