New pharmacotherapeutic modalities for negative symptoms in psychosis

Negative symptoms in schizophrenia comprise a psychopathologic and pathophysiologic syndrome which is absent from normal mental function. Renewed interest in negative symptoms has led to the development of better measuring instruments, among which is the Positive And Negative Syndrome Scale (PANSS), which provides a way of measuring and reporting positive and negative symptoms in a balanced and convenient form. A number of strategies are being investigated for treating negative symptoms. Dopamine agonists such as levodopa, amphetamines and bromocriptine have been shown to produce improvements in negative symptoms, although good, well-controlled clinical trials are lacking. Partial dopamine agonists, such as MAR 327, are also currently under investigation and results are expected soon. Tricyclic, selective serotonin reuptake inhibitors and monoamine oxidase antidepressants appear to be able to modify negative symptoms in schizophrenia, although, once again, carefully designed trials are needed. Modification of GABAergic transmission has shown little promise, but the use of glycine to augment transmission at N-methyl-D-aspartate (NMDA) synapses suggests that the strategy may be beneficial. These results also imply that altered glutamate receptor function may be partly responsible for negative symptoms. One strategy that has been shown to have a beneficial effect against negative symptoms is combined serotonin/dopamine antagonism. Clozapine was found to have this profile after its introduction, and the recently introduced antipsychotic, risperidone was developed intentionally to be a combined 5-HT2/D2 antagonist. Both risperidone and clozapine have been shown to be effective against negative symptoms. One problem associated with the assessment of drug effects on negative symptoms, however, is that drugs can act on both primary and secondary negative symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)