Promethazine

Promethazine's 2D structure. (This image is simply here until the substancebox is made)

Promethazine (commonly sold as Phenergan and also known as an active ingredient in "lean") is a strong muscle relaxant and sedative as well as a weak antipsychotic of the phenothiazine class of medications. It is used primarily for muscle relaxation, preoperative sedation, and nausea. It is also used as an antihistamine, but medications such as diphenhydramine can serve this purpose just as well with the bonus of being over-the-counter and not a strong sedative.

History and culture

Promethazine became especially popular among the Houston rap and hip-hop scene in around 1990, and the trend resurfaced in around 2015 to 16. Often, it was combined with codeine in a preparation called "lean." Lean usually consisted of ice, Sprite or a citrus soda, the promethazine/codeine cough syrup, and sometimes, jolly ranchers added for flavor.

Pharmacology

Promethazine is a direct antagonist of histamine H1 receptors, whereas diphenhydramine is an inverse agonist.