The importance of serotonin-dopamine interactions in the action of clozapine

Clozapine has an affinity for the dopamine (DA) D2 receptor which is relatively weak but is in line with its average clinical dose when compared with typical neuroleptic drugs. A few atypical antipsychotic drugs may have high absolute affinities for the D2 receptor, but most are weak D2 blockers. The atypical antipsychotic drugs also differ from the typical antipsychotic drugs by a relatively high affinity for the serotonin (5-HT2) receptor. This is evident on both in vitro and in vivo binding to cortical 5-HT2 receptors. The atypical antipsychotics are best distinguished from the typical antipsychotics on the basis of the relationship between strong 5-HT2 and weak D2 affinities. High D1 receptor binding is not characteristic of the group of atypical drugs. A new group of putative atypical antipsychotic drugs with high affinities for 5-HT2 compared to D2 receptors is under study.