HRH1 and optic neuritis: ■Ethanolamine-derivative;■Approved for symptomatic relief of allergic rhinitis, and mild, uncomplicated allergic skin manifestations of urticaria and angioedema; investigational for chronic progressive and relapsing multiple sclerosis (phase 1), urticaria and optic neuritis (phase 2), dermatitis (phase 3), and allergic diseases (phase 4);■Histamine receptor H1 (HRH1) antagonist.