PROMETHAZINE HYDROCHLORIDE is a phenothiazine group drug that acts as an antihistamine. It is used to treat allergic symptoms including itching, sneezing, itchy skin rashes, watery eyes, hives and runny nose. It works by blocking the activities of histamine and is used in the prevention of motion sickness, nausea, vomiting and after surgery pain. It is also effective as a sleep aid.