On the Vietnamese market, Phenergan is available in two forms: Phenergan syrup 0.1%, 90ml and Phenergan 2% cream. The active ingredient of the drug is promethazine, a first-generation antihistamine, which works through competition for the site of action with histamine, a chemical mediator that causes allergic reactions. Depending on the form of use, the drug is used in different indications.