Promethazine is a phenothiazine derivative with histamine H1-blocking, antimuscarinic, and sedative properties. Promethazine HCl Oral Solution is useful for: perennial and seasonal allergic rhinitis. Allergic conjunctivitis due to inhalant allergens and foods. Anaphylactic reactions, as adjunctive therapy to epinephrine and other standard measures, after the acute manifestations have been controlled. Preoperative, postoperative, or obstetric sedation. Prevention and control of nausea and vomiting associated with certain types of anesthesia and surgery. Therapy adjunctive to meperidine or other analgesics for control of post-operative pain. Active and prophylactic treatment of motion sickness. Antiemetic therapy in postoperative patients.

Pamoic acid, also called embonic acid, is a naphthoic acid derivative, used as a counter ion of a drug compound to increase the solubility of the drug in water. Pamoic acid has agonist activity for the orphan G protein-coupled receptor GPR35 by which it activates ERK and beta-arrestin2, and causes antinociceptive activity. Although (like other drug salts) it has been considered an inactive compound by the FDA.

Promethazine hydroxyethyl quaternary derivative of promethazine with antihistamine and anticholinergic properties. The drug lacked the sedative properties of promethazine. It was used in the clinic under tradename Aprobit.