Amisulpride, an unusual "atypical" antipsychotic: a meta-analysis of randomized controlled trials

The "atypical" profile of the new antipsychotics clozapine, olanzapine, quetiapine, and risperidone has been linked to combined antagonism of serotonin 2 (5-HT(2)) and dopamine 2 (D(2)) receptors. Although amisulpride is a highly selective D(3)/D(2) receptor antagonist, it is assumed to have atypical properties as well. The purpose of this article was to compare the atypical profile of amisulpride with that of the 5-HT(2)/D(2) antagonists.

Randomized controlled trials that compared amisulpride with conventional antipsychotics or placebo for patients with schizophrenia were identified and included in a meta-analysis. The mean effect sizes found for amisulpride were compared with those of an updated meta-analysis of the 5-HT(2)/D(2) antagonists.

Eighteen randomized controlled trials of amisulpride (N=2,214) were found. In 11 studies of acutely ill patients it proved to be consistently more effective than conventional antipsychotics for global schizophrenic symptoms (measured with the Brief Psychiatric Rating Scale) and negative symptoms. Amisulpride is to date the only atypical antipsychotic for which several studies of patients suffering predominantly from negative symptoms have been published. In four such studies amisulpride was significantly more effective than placebo. Three small studies with conventional antipsychotics as comparators showed only a trend in favor of amisulpride in this regard. Amisulpride was associated with clearly lower use of antiparkinsonian medication and with fewer dropouts due to adverse events than conventional antipsychotics.

These results cast some doubt on the notion that combined 5-HT(2)/D(2) antagonism is the reason that the newer antipsychotic medications are effective for negative symptoms and have fewer extrapyramidal side effects.