The goal of this clinical trial is to explore the potential of metformin in managing olanzapine-induced metabolic disturbance and hyperprolactinemia in patients with schizophrenia. The main questions it aims to answer are:

1. The effect of metformin on olanzapine-induced metabolic disturbance
2. The effect of metformin on olanzapine-induced hyperprolactinemia

Participants will receive metformin 1500 mg/day for 8 weeks and assessments every 2 weeks.

The study was conducted in an inpatient setting, with the dosage of olanzapine remaining consistent throughout the study duration. All participants were administered 1500 mg/day of metformin for eight weeks. Vital signs were measured daily. Physical and neurological examinations were carried out on a weekly basis. Every two weeks, all participants underwent an assessment for general psychopathology. Blood samples were collected in the morning after an overnight fast at the beginning of the study and then every two weeks following the commencement of metformin treatment. Serum prolactin levels were determined through electrochemiluminescence immunoassays. Fasting serum levels of glucose, total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides were measured using enzymatic colorimetric assays. Serum insulin and leptin levels were measured using electrochemiluminescence immunoassay kits.

Inclusion Criteria:

• aged between 18 and 60 years
• diagnosed with schizophrenia under the Diagnostic and Statistical Manual of Mental Disorders-fourth edition criteria
• had been consistently treated with a stable dose of olanzapine for a minimum of three months

Exclusion Criteria:

• Exclusion criteria encompassed any mental disorder other than schizophrenia, ongoing substance abuse, and medical conditions that could interfere with glucoregulatory and endocrine assessment such as diabetes mellitus and other endocrine disorders. Additionally, severe cardiovascular, hepatic, or renal diseases, malignancy, epilepsy, and pregnancy were also reasons for exclusion.