Dextromethorphan as an Augmentation Agent in Treatment-resistant Schizophrenia

Inclusion Criteria: * Schizophrenia patients who are diagnosed as treatment-resistant schizophrenia (TRS) defined as having been tried and not responded to any two antipsychotic medication for a duration of 6 weeks with dose equivalent of 600 mg of chlorpromazine and initiated on clozapine for the treatment of the same. * The patients who are on stable dose of clozapine. * Patients of either sex with age \>18 years. * Patients for whom legally authorized representative (LAR) are willing to give informed consent. Exclusion Criteria: * Patients with significant medical comorbidity. * Patients with significant psychiatric comorbidity. * Patients having active substance abuse history during the time of screening. * Female patients who are pregnant or in reproductive age not using contraception. * Female patients who are breast feeding