Promethazine is a first-generation antihistamine belonging to the phenothiazine class, primarily used to treat allergic conditions, motion sickness, nausea, and vomiting, and as a sedative or sleep aid. It works by blocking H1 histamine receptors in the body, thereby reducing allergic reactions and centrally acting on the vomiting center in the brain. Developed in the 1940s, promethazine was initially introduced to provide relief from allergic symptoms and post-operative nausea, representing a major advance in symptomatic treatment of histamine-mediated conditions. Over time, its applications expanded to include pre-anesthetic sedation, management of motion sickness, and adjunct therapy for colds or upper respiratory symptoms, highlighting its versatility. Its widespread use over decades is attributed to its effectiveness, affordability, and relatively safe profile, although care must be taken due to potential sedation and respiratory depression at higher doses.
