BACKGROUND The efficacy of low doses of certain neuroleptics in improving negative symptoms is still controversial. This study assessed the efficacy of amisulpride, a benzamide which increases dopaminergic transmission at low doses via presynaptic dopamine receptor blockade, on negative symptoms of schizophrenia.

METHOD The study was designed as a parallel-group, double-blind, placebo-controlled trial. Patients had to fulfil DSM-III criteria for schizophrenia, Andreasen's criteria for negative schizophrenia, and to have a total score of at least 75 on the SANS; those treated with neuroleptics or antidepressants underwent a six-week placebo wash-out. One hundred and four in-patients were randomly assigned to amisulpride 100 mg/d, amisulpride 300 mg/d, or placebo for six weeks; 85 patients completed the study.

RESULTS Both amisulpride doses were significantly more effective than placebo on the primary evaluation criterion (SANS total score, MANOVA P < 0.02). No significant changes were found in positive symptoms or in extrapyramidal symptoms.

CONCLUSIONS Negative symptoms can be improved by low doses of amisulpride, favouring the hypothesis of dopaminergic hypofunction as one of the causes of negative symptoms.