Epinastine- 13 C,d 3 (hydrobromide) is the 13 C- and deuterium labeled Epinastine. Epinastine (WAL801) is an antihistamine and mast cell stabilizer. Epinastine is a potent, selective and orally-active histamine H1 receptor antagonist. Epinastine also inhibits IL-8 release and has an antiallergic action.