Promethazine is a first-generation antihistamine used to treat allergies, difficulty sleeping, and nausea. It may also help with some symptoms associated with the common cold and may also be used for sedating people who are agitated or anxious. Promethazine is available by mouth in syrup or tablet dosage forms, as a rectal suppository, or by injection into a muscle.
The recreational drug purple drank, or lean, often contains a combination of promethazine with codeine containing cold medication.