Mequitazine (trade name Primalan) is an H1 antagonist and anticholinergic of the phenothiazine chemical class. It is used to treat allergies and rhinitis. Mequitazine (trade name Primalan) is an H1 antagonist and anticholinergic of the phenothiazine chemical class. It is used to treat allergies and rhinitis. It was patented in 1969 and came into medical use in 1976.