Introduction Droxidopa (L-DOPS) is an orally administered, synthetic catecholamine that is converted to the sympathetic neurotransmitter norepinephrine (NE) through a single step of decarboxylation by the endogenous enzyme 3,4-dihydroxyphenylalanine (DOPA) decarboxylase. Droxidopa was originally developed by Sumitomo Pharmaceuticals Co. Ltd., and has been marketed in Japan since 1989 for the indications listed below.