antihistamine (trade name Phenergan) used to treat allergies; also an antiemetic used to treat motion sickness

Promethazine is a first-generation H1 receptor antagonist antihistamine and antiemetic medication. It is a prescription drug in the United States, but is available over the counter in the United Kingdom, Switzerland, and many other countries (brand names Phenergan®, Promethegan®, Romergan).