Anticholinergic agents refer to medication drugs that block the action of acetylcholine, a neurotransmitter with an effect opposite to that of dopamine. By blocking the action of acetylcholine, these drugs increase the ability of dopamine to control movement. Examples of anticholinergic drugs used in the treatment of Parkinson disease include trihexyphenidyl (Artane®), benztropine (Cogentin®), and ethopropazine (Parsidol®).