About mequitazineh 1 antagonist, sedative, phenothiazine derivativemechanism of action of mequitazinemequitazine binds to the histamine h1 receptor sites on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract. this blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms brought on by histamineindications for mequitazine1.hypersensitivity reactions 2.urticaria 3.rhinitis 4.conjuctivitis 5.pruritus interactions for mequitazinealcohol, barbiturates, hypnotics, opioid analgesics, anxiolytic sedatives and antipsychotics: enhanced effects of cns depressants can mask signs of ototoxicity caused by aminoglycosides qt prolongation reported with spiramycin