Zuclopenthixol is a potent neuroleptic of the thioxanthene series with a piperazine side-chain. The antipsychotic effect of neuroleptics is related to their dopamine receptor blocking effect. The thioxanthenes have a high affinity for both the adenylate cyclase coupled dopamine D1 receptors and for the dopamine D2 receptors; in the phenothiazine group the affinity for D1 receptors is much lower than that for D2 receptors, whereas butyrophenones, diphenylbutylpiperidines and benzamides only have affinity for D2 receptors.