Used primarily in the treatment of carcinoid syndrome, particularly to manage diarrhea that does not respond adequately to somatostatin analog therapy. It works by inhibiting tryptophan hydroxylase, an enzyme involved in the production of serotonin, which is often overproduced in carcinoid syndrome and contributes to symptoms like diarrhea. By reducing serotonin levels, it helps alleviate diarrhea and improves the quality of life for patients. It is typically administered orally and is often used as part of a broader treatment plan that may include other medications.