any pharmacological agent that stimulates activity in the parasympathetic nervous system because it potentiates the activity of acetylcholine or has effects similar to this neurotransmitter. Cholinergic drugs include such alkaloids as physostigmine and pilocarpine; bethanechol; and anticholinesterases (cholinesterase inhibitors; e.g., edrophonium, neostigmine, and pyridostigmine). They are used for such purposes as treating myasthenia gravis, glaucoma, and urinary retention. Also called parasympathetic drug; parasympathomimetic drug.