What condition does ondansetron primarily treat?

Ondansetron is primarily used to treat nausea and vomiting that often occurs as a result of chemotherapy, as well as postoperative nausea and vomiting. It is a selective serotonin 5-HT3 receptor antagonist that effectively blocks the action of serotonin, a natural substance that can cause vomiting. By preventing the signaling in the brain that leads to these symptoms, ondansetron is especially beneficial for patients undergoing cancer treatment, where the risk of nausea and vomiting is significantly elevated. This specific action distinguishes ondansetron from other medications that may treat different conditions, such as motion sickness, insomnia, or restless leg syndrome, which are not its primary indications.