Triclabendazole, sold under the brand name Egaten among others, is a medication used to treat fascioliasis and paragonimiasis. It is very effective for both conditions. Treatment in hospital may be required. It is taken by mouth with typically one or two doses being required.Side effects are generally few, but can include abdominal pain and headaches. Biliary colic may occur due to dying worms. While no harm has been found with use during pregnancy, triclabendazole has not been studied well in this population. It is a member of the benzimidazole family of medications for worms.Triclabendazole was approved for medical use in the United States in 2019. It is on the World Health Organizations List of Essential Medicines. For human use, it can be obtained from the World Health Organization. It is also used in animals. Chemistry
It is a member of the benzimidazole family of anthelmintics. The benzimidazole drugs share a common molecular structure, triclabendazole being the exception in having a chlorinated benzene ring but no carbamate group. Benzimidazoles such as triclabendazole are generally accepted to bind to beta-tubulin therefore preventing the polymerization of microtubules. History
Since late 1990s, triclabendazole became available as a generic drug, as patents expired in many countries. Many products were developed then. Among them, Trivantel 15,  a 15% triclabendazole suspension, was launched by Agrovet Market Animal Health in the early 2000s. In 2009, the first triclabendazole injectable solution (combined with ivermectin) was developed and launched, also by Agrovet Market Animal Health.
The flushing also results from secretion of kallikrein, the enzyme that catalyzes the conversion of kininogen to lysyl-bradykinin. The latter is further converted to bradykinin, one of the most powerful vasodilators known. Other components of the carcinoid syndrome are diarrhea (probably caused by the increased serotonin, which greatly increases peristalsis, leaving less time for fluid absorption), a pellagra-like syndrome (probably caused by diversion of large amounts of tryptophan from synthesis of the vitamin B3 niacin, which is needed for NAD production, to the synthesis of serotonin and other 5-hydroxyindoles), fibrotic lesions of the endocardium, particularly on the right side of the heart resulting in insufficiency of the tricuspid valve and, less frequently, the pulmonary valve and, uncommonly, bronchoconstriction.The pathogenesis of the cardiac lesions and the bronchoconstriction is unknown, but the former probably involves activation of serotonin 5-HT2B receptors by serotonin. When the primary tumor is in the gastrointestinal tract, as it is in the great majority of cases, the serotonin and kallikrein are inactivated in the liver; manifestations of carcinoid syndrome do not occur until there are metastases to the liver or when the cancer is accompanied by liver failure (cirrhosis). Carcinoid tumors arising in the bronchi may be associated with manifestations of carcinoid syndrome without liver metastases because their biologically active products reach the systemic circulation before passing through the liver and being metabolized.In most patients, there is an increased urinary excretion of 5-HIAA (5-hydroxyindoleacetic acid), a degradation product of serotonin.The biology of these tumors differs from many other tumor types.