Biperiden Hydrochloride (KL 373 Hydrochloride) is an antiparkinsonian agent, which is the selective central M1 cholinoreceptors blocker and it is used for the adjunctive treatment of all forms of Parkinson's disease (postencephalitic, idiopathic, and arteriosclerotic)[1]. Target: M1 receptors Biperiden is an antiparkinsonian agent of the anticholinergic type. Biperiden has an atropine-like blocking effect on all peripheral structures which are parasympathetic-innervate and 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