Ciclindole (INN; developmental code name WIN-27,147-2), also known as cyclindole (USAN), is an antipsychotic with a tricyclic and tryptamine-like structure that was never marketed. It displaces spiperone binding in vitro and elevates dopamine levels in the striatum, indicating that it acts as a dopamine D2 receptor antagonist. It also shows apparent affinity for the α1-adrenergic receptor, the serotonin S1 receptor, and the serotonin S2 receptor. However, its affinities for all of the preceding targets are weak, in the low micromolar range. The related drug flucindole is about 5 to 10times more potent than ciclindole both in vitro and in vivo.