Amisulpride - A selective dopamine antagonist and atypical antipsychotic: Results of a meta-analysis of randomized controlled trials

The pharmacological profiles of the atypical antipsychotics, clozapine, olanzapine, quetiapine and risperidone, all show a combined serotonin (5-HT ₂) and dopamine type-2 (D₂) receptor antagonism. Amisulpride, a highly selective dopamine D₂/D₃ receptor antagonist that binds preferentially to receptors in the mesolimbic system, is also an 'atypical' antipsychotic despite having a different receptor-affinity profile. A meta-analysis of 18 clinical trials was undertaken to compare the efficacy and safety of amisulpride with conventional antipsychotics. The improvement in mental state was assessed using the Brief Psychiatric Rating Scale (BPRS) or the Scale for the Assessment of Negative Symptoms (SANS). In a pooled analysis of 10 studies of acutely ill patients, amisulpride was significantly more effective than conventional neuroleptics with regard to improvement of global symptoms. Amisulpride is, to date, the only atypical antipsychotic for which several studies on patients suffering predominantly from negative symptoms have been published. In four such studies, amisulpride was significantly superior to placebo. Three small studies with conventional neuroleptics as a comparator showed only a trend in favour of amisulpride in this regard. Amisulpride was associated with fewer extrapyramidal side-effects and fewer drop-outs due to adverse events than conventional neuroleptics. These results clearly show that amisulpride is an 'atypical' antipsychotic, and they cast some doubt on the notion that combined 5-HT₂-D₂ antagonism is the only reason for the high efficacy against negative symptoms and fewer extrapyramidal side-effects.