Which medication can be used to help alleviate severe nausea?

Ondansetron is a medication specifically designed to prevent and treat nausea and vomiting. It is most commonly used in settings where nausea is a significant concern, such as post-operative recovery, chemotherapy, and radiation therapy. By blocking the action of serotonin, a natural substance that can cause nausea and vomiting in the body, ondansetron effectively alleviates severe nausea.

In the context of managing nausea, other options listed do not serve that purpose. Ibuprofen and acetaminophen are analgesics and antipyretics, primarily used for pain relief and reducing fever rather than addressing nausea. Diphenhydramine, while it has sedative properties and can sometimes relieve nausea related to motion sickness, is not as effective as ondansetron for severe cases typically associated with other medical conditions. Thus, ondansetron stands out as the appropriate choice for controlling severe nausea.