The lifetime of substance use disorders in schizophrenia is close to 50%. Substance abuse in schizophrenia is associated with negative consequences. Unfortunately, there no clear guidelines for the pharmacological treatment of this dual diagnosis population. Preliminary results suggest that second-generation antipsychotic drugs (mainly clozapine) may relieve drug cravings in schizophrenia. We performed a 12-week pilot study to evaluate the impact of quetiapine, a second-generation antipsychotic, on substance abuse parameters, psychiatric symptoms and side effects in patients schizophrenia and comorbid substance use disorders. Our expectation was a 20 % decrease in drug cravings from baseline to end-point.

Inclusion Criteria:

• Patients with as schizophrenia spectrum disorder
• Patients with a comorbid substance use disorder

Exclusion Criteria:

• Patients already on quetiapine or clozapine
• Patients hospitalized or acutely ill
• Total score lower than 65 on the PANSS
• Pregnancy
• Female subjects of childbearing potential without adequate contraception
• Abnormal liver function (hepatic enzymes more than 3 times the upper normal limits)
• Any clinically meaningful unstable renal, hepatic, cardiovascular, respiratory, cerebrovascular disease or other serious, progressive physical disease.