Promethazine is a first-generation H1 receptor antagonist used medically as an antihistamine and antiemetic. It can also have strong sedative effects and in some countries is prescribed for insomnia when benzodiazepines are contraindicated. It is a prescription drug in the United States and Australia but is available over the counter in the United Kingdom, Canada, Switzerland, and many other countries (brand names Phenergan, Promethegan, Romergan, Fargan, Farganesse, Prothiazine, Avomine, Atosi… (More on Promethazine)