Pyridobenzthiazines

Isothipendyl is a 1st generation H1 antagonist (antihistamine) and anticholinergic used as an antipruritic. In the 2020s, at least, it is rarely used in the first line relief of allergies due to the anticholinergic side effect of somnolence but does have some limited use through topical application in the relief of insect bites and related itching (pruritus).

Pipazetate () (brand names Dipect, Lenopect, Selvigon, Theratuss, Toraxan), or pipazethate (), is a 1-azaphenothiazine drug that was briefly marketed as a cough suppressant. It binds to the sigma-1 receptor with an IC50 value of 190 nM. It also has local anesthetic action, and in large doses can produce seizures.