Comparison of risperidone and mosapramine addition to neuroleptic treatment in chronic schizophrenia

There is little information regarding the effects of risperidone addition to neuroleptic treatment in chronic schizophrenia. As a preliminary study, 10 neuroleptic-treated schizophrenic inpatients received risperidone (high 5HT2A/D2 ratio, i.e. the ratio between 5HT2A and D2 receptor occupancy) and mosapramine (low 5HT2A/D2 ratio) in a randomized, single-blind, crossover, add-on study consisting of 8 weeks of treatment each with risperidone and mosapramine. Although both additions resulted in significant, albeit modest, improvement, there was no significant difference in the scores on the Positive and Negative Syndrome Scale for Schizophrenia between risperidone and mosapramine addition. These results suggest that risperidone and mosapramine bring about comparable effects in add-on design. Thus, risperidone with a high 5HT2A/D2 ratio does not seem to be better than mosapramine with a low 5HT2A/D2 ratio when combined with conventional neuroleptics. Further studies including a large number of patients and a double-blind design are needed.