9-Methyl-3-((2-methyl-1H-imidazol-1-yl)methyl)-2,3-dihydro-1H-carbazol-4(9H)-one

Ondansetron, marketed under the brand name Zofran, is a medication used to prevent nausea and vomiting caused by cancer chemotherapy, radiation therapy, or surgery. It is also useful in gastroenteritis. It has little effect on vomiting caused by motion sickness. It can be given by mouth, by injection into a muscle or into a vein.
Common side effects include diarrhea, headache, sleepiness, and itchiness. Serious side effects include QT prolongation and severe allergic reaction. It appears to be safe during pregnancy but has not been well studied in this group. It is a serotonin 5-HT3 receptor antagonist. It does not have any effect on dopamine receptors or muscarinic receptors.
Ondansetron was first used medically in 1990. It is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system. It is available as a generic medication. The wholesale cost of the injectable form in the developing world is about 0.10 to 0.76 USD per dose. In the United States it costs about 1.37 USD per tablet.