Which antiemetic is commonly used to treat hyperemesis gravidarum?

Ondansetron is often used to treat hyperemesis gravidarum, which is a severe form of nausea and vomiting during pregnancy. It acts as a selective 5-HT3 serotonin receptor antagonist. By blocking serotonin receptors in the gastrointestinal tract and the central nervous system, ondansetron effectively reduces the activity that triggers nausea and vomiting. Its effectiveness and relatively favorable safety profile during pregnancy make it a common choice for managing this condition.

Other agents listed, such as aprepitant, meclizine, and diphenhydramine, have their own specific uses in nausea and vomiting control, but they are not the first-line treatments for hyperemesis gravidarum. Aprepitant is primarily used for preventing nausea and vomiting caused by chemotherapy, meclizine is generally utilized for motion sickness, and diphenhydramine is an antihistamine that can help with nausea but is less effective compared to ondansetron in the context of hyperemesis gravidarum.