etybenzatropine

Etybenzatropine (INN), also known as ethybenztropine (USAN, BAN) and tropethydrylin, is a synthetic anticholinergic and antihistamine drug previously marketed under the trade names Panolid, Ponalid, and Ponalide for the treatment of Parkinson's disease and parkinsonism. Structurally related to benzatropine, etybenzatropine combines a tropane backbone with antihistaminic properties, acting primarily as a muscarinic acetylcholine receptor antagonist. It was used to alleviate motor symptoms such as tremor and rigidity but has been discontinued due to limited efficacy, significant side effects, and the availability of more effective antiparkinsonian therapies. Etybenzatropine may exhibit weak dopamine reuptake inhibitor activity, though this is not well-established.

== Pharmacological properties == Etybenzatropine is a centrally acting anticholinergic that blocks muscarinic acetylcholine receptors, particularly M1 receptors, in the basal ganglia, reducing the cholinergic-dopaminergic imbalance in parkinsonism. Its tropane structure, featuring a diphenylmethoxy group, enhances anticholinergic potency while conferring antihistaminic effects similar to pyrilamine. The antihistaminic activity contributes to sedation, a common side effect. Claims of dopamine reuptake inhibition, potentially increasing striatal dopamine, lack robust evidence and are considered speculative. Etybenzatropine’s oral bioavailability is low due to hepatic first-pass metabolism, with metabolites excreted in urine and bile.