Biperiden Hydrochloride (KL 373 Hydrochloride) is an antiparkinsonian agent, which is the selective central M1 cholinoreceptors blocker. Target: M1 receptors Biperiden is an antiparkinsonian agent of the anticholinergic type. It is used for the adjunctive treatment of all forms of Parkinson's disease (postencephalitic, idiopathic, and arteriosclerotic)[1]. Biperiden has an atropine-like blocking effect on all peripheral structures which are parasympathetic-innervate. It also has a prominent central blocking effect on M1 receptors [2]. Biperiden (0.11 mg/kg), benactyzine (0.3 mg/kg),caramiphen (10 mg/kg), procyclidine (3 mg/kg), and trihexyphenidyl (0.12 mg/kg) separately and each in combination with physostigmine (0.1 mg/kg) is to make a comparative assessment of potential cognitive effects. The results showed that benactyzine, caramiphen, and trihexyphenidyl reduced rats' innate preference for novelty, whereas biperiden and procyclidine did not [3]. Clinical indications: parkinsonism FDA Approved Date: Toxicity: Drowsiness; vertigo; headache; dizziness