n. an alkaloid derived from several tropical American plants but mainly from Pilocarpus jaborandi. Pilocarpine is a powerful parasympathomimetic agent, affecting postganglionic cholinergic receptors (see cholinergic drug). It is used in the treatment of glaucoma and to contract the pupil of the eye. U.S. trade names (among others): Isopto Carpine; Pilocar; Pilostat.