How Do Antidiarrheal Tryptophan Hydroxylase Inhibitors Work?

Antidiarrheals, tryptophan hydroxylase inhibitors are a class of medications used to treat carcinoid syndrome diarrhea. Carcinoid syndrome is a rare type of neuroendocrine tumor that occurs most often in the gastrointestinal tract (stomach, appendix, small intestine, colon, and rectum) or the lungs. It can produce and release hormones into your body causing signs and symptoms of chronic diarrhea or skin flushing, etc.

Carcinoid tumors in the digestive tract are characterized by signs and symptoms such as:

• Abdominal pain
• Diarrhea
• Nausea, vomiting, and inability to pass stool due to intestinal blockage (bowel obstruction)
• Rectal bleeding
• Rectal pain
• Redness or a feeling of warmth in your face and neck (skin flushing)

On February 28, 2017, the US Food and Drug Administration approved tryptophan hydroxylase inhibitors in combination with somatostatin analog (SSA) therapy for the treatment of adults with diarrhea associated with carcinoid syndrome which is inadequately controlled by SSA therapy alone.

Antidiarrheals, tryptophan hydroxylase inhibitors are administered via oral route three times daily with food.

Antidiarrheals, tryptophan hydroxylase inhibitors work in the following ways:

• Carcinoid tumors are well-differentiated neuroendocrine tumors with secretory properties, releasing serotonin, along with several other active peptides.
• Serotonin, a neurotransmitter, plays a key role in several gastrointestinal processes, including secretion, inflammation, motility, and sensation.
• Excess levels of serotonin produced in patients with carcinoid syndrome cause uncontrolled and chronic diarrhea which can cause a serious loss of body water (dehydration) and minerals (electrolytes).
• Tryptophan hydroxylase inhibitors work by inhibiting tryptophan hydroxylase, an enzyme that mediates the rate-limiting stage of serotonin biosynthesis, thereby reducing peripheral serotonin levels and the frequency of carcinoid syndrome diarrhea.

Antidiarrheals, tryptophan hydroxylase inhibitors may be administered simultaneously with SSA therapy to treat carcinoid syndrome-associated diarrhea.

Common side effects include:

• Nausea
• Headache
• Flatulence
• Decreased appetite
• Abdominal pain
• Constipation

Other rare side effects include:

• Depression
• Swelling of the extremities
• Increased gamma-glutamyl transferase (GGT) levels (high levels of GGT in the blood may be a sign of liver disease)
• Fever

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Drug names include:                              

• Telotristat ethyl
• Xermelo