Antihistamines like hydroxyzine (Atarax®, Vistaril®), diphenhydramine (Benadryl®), promethazine (Phenergan®). Antihistamines work by blocking histamine receptors, which play a role in nausea and vomiting. Some, like diphenhydramine, are available over the counter, but be sure to discuss their use with your physician before taking.