The Effect of N-Acetyl Cysteine on Cortical Erosion in Early Stage Schizophrenia

Overview

The primary objective of this study is to determine if NAC, added to existing antipsychotic treatment, is superior to placebo for cortical erosion in patients with early stage psychosis. The primary hypothesis is that there will be significantly less cortical erosion as measured by cortical thickness, cortical volume and cortical white matter density (assessed by DTI) in patients treated for 12 months with NAC as compared to those treated with placebo. The secondary objectives of this study are to determine if 12 months of NAC add-on treatment is superior to placebo for fMRI determined working memory and semantic memory tasks, cortical MR spectroscopy measures (glutathione, N-acetylaspartate, and glutamine/glutamate levels), electrophysiologically determined attention measures (e.g., mismatch negativity, P300), symptoms, functional measures and cognitive functioning.

Schizophrenia is a severe, debilitating illness that typically begins during the teen-age years and early twenties, and worsens over time as it evolves into a chronic, life-long disorder. Existing treatments suppress psychotic symptoms but do not prevent the evolution of underlying disease processes that results in poor, long term outcomes. Recent studies have shown that progressive erosion of cortical mass occurs during the early stages of schizophrenia (1-3). The investigators hypothesize that arresting cortical erosion during the early phases of schizophrenia will prevent subsequent clinical deterioration and the descending course of illness associated with this disorder. The investigators propose to establish a research program that will assess the ability of agents with neuroprotective properties to halt cortical loss and thereby prevent subsequent clinical deterioration. N-acetyl cysteine (NAC) is an attractive molecule for the proposed study because of two of its mechanistic properties. First, it is an established neuroprotective agent. NAC is a precursor to glutathione which is a primary detoxifier of reactive oxygen and other radical molecules which damage neuronal tissue (4-6). Glutathione deficiencies have been well documented in schizophrenia (7, 8). Second, NAC modulates glutamate release. NMDA hypofunction and altered glutamate release have been hypothesized to contribute to the cortical atrophy observed in early stage schizophrenia (9, 10). NAC has been shown to antagonize both the phencyclidine (PCP) effects of increased frontal glutamate levels and induction of social isolation in rodents (11). PCP is a pharmacological model of schizophrenia. In a controlled clinical trial of patients with chronic schizophrenia, NAC improved mismatch negativity, a pre-attentive measure of cortical information processing that has been consistently implicated in the pathophysiology of schizophrenia and has been shown to correlate with cortical erosion in early stage patients (12, 13). In a double-blind, placebo controlled clinical trial of chronic schizophrenic patients, NAC significantly improved general psychopathology scores, negative symptoms and extrapyramidal symptoms (14). NAC was well tolerated with no significant effects on any safety parameter or adverse events. The favorable tolerability of NAC has been further demonstrated in a recent study conducted at IUSM Riley Hospital in children (ages 4 to 12 years) with autism at relatively high doses (dose range of 900 to 4200 mg/day) in which there were no serious adverse events reported and NAC was well tolerated (15). The investigators propose to determine if NAC has disease modifying potential in early stage schizophrenia. The investigators hypothesize that NAC will improve measures of cortical integrity in early stage schizophrenia and these brain effects will be related to improvements in negative symptoms and cognitive functioning. Primary outcome measures in the trials will be serial assessments of cortical integrity using magnetic resonance structural (cortical thickness, cortical volume, diffuses tensor imaging, DTI). In addition the investigators will assess the possible effects of NAC treatment on other parameters linked to cortical erosion including fMRI coupled with working memory and semantic memory tasks, MR spectroscopy (cortical glutathione, N-acetylaspartate, and glutamine/glutamate levels) and electrophysiological measures (e.g., mismatch negativity, P300). The investigators will also determine the relationship between effects of NAC on negative symptoms, positive symptoms, functional status, cognition (BACS), and safety parameters; and brain indices.