Inclusion Criteria:

1. Diagnostic and Statistical Manual-IV (DSM-IV) diagnosis of schizophrenia,
schizoaffective disorder, psychosis not otherwise specified or schizophreniform
disorder

2. competent and willing to give informed consent

3. stable on medication 4 weeks prior to baseline

4. able to take oral medication and likely to complete the required evaluations

5. female participants of child bearing age must be willing to use adequate
contraceptives for the duration of the study, and, willing to have a pregnancy test
pre treatment and at ten weekly intervals while on study medication.

Exclusion Criteria:

1. Relevant medical illness [renal and hepatic] in the opinion of the investigators

2. history of high alcohol intake

3. any change of psychotropic medications within the previous six weeks

4. diagnosis of substance abuse (except nicotine or caffeine) or dependence within the
last three months according to DSM-IV criteria

5. pregnant or breast-feeding.