This research outcomes can be summarized as follows:

1. Pharmacogenomic analysis of Substance Use Disorder (SUD) and medications used for the treatment of SUD.
2. Identification of novel genetic variations related to SUD specifically in the Egyptian population.
3. Validation of currently known genetic variations associated with SUD. When the functional interpretation of common or rare variants in studied genes becomes available, such pharmacogenomic information can be used to improve pharmacotherapy individualization.

This is a correlational cross-sectional study to investigate the correlation of some genetic variants to the predisposition to SUD in addicted patients as well as to the clinical response of the medications they receive as a part of their treatment plan.

Subjects participating in this study are those receiving outpatient or inpatient programs for the management of SUD with or without psychiatric disorders, supported by the specialized mental health care facility; "Al-Maa'moura Hospital for Psychiatry" in Alexandria.

An informed consent is obtained from each participant prior their contribution to the study. Approval from the General Secretariat of Mental Health and Addiction Treatment (GSMHAT), Ministry of Health and Population (MoHP), has been obtained before conducting the study as well as from the Ethics Committee, Faculty of Medicine, Alexandria University.

A minimal total sample size of 100 participants with SUD, male or female, and another 40 controls will be included in the study. This sample size was calculated with the assistance of instructors in the Department of Medical Statistics, Medical Research Institute, Alexandria University. The targeted sample is selected regarding the inclusion and exclusion criteria.

Patients' medical records will be checked to select the medications of interest. The medications selected include those most prescribed by the psychiatrists assigned at the hospital. They include quetiapine, carbamazepine, amitriptyline, olanzapine, sertraline, chlorpromazine, risperidone, and mirtazapine.

A structured questionnaire will be designed for proper patient data collection. It will be validated for its content using the jury method. The reliability, internal consistency of the questionnaire, will be estimated through the calculated value of Cronbach's alpha. Face to face interviewing with the eligibly selected patients will be done after they sign the patient consent. The questionnaire will be divided into sectors regarding the patients' sociodemographic data, their general health condition, their SUD, and the medications they receive for treatment.

Blood samples will be collected from controls and patients receiving their treatment. These samples will be used for preparation of plasma in which the drug levels will be estimated. They will also be used for isolation of DNA to screen selected mutations, sequence selected genes or perform whole genome sequencing.

Inclusion Criteria:

• Addicted patients receiving outpatient or inpatient treatment for SUD with or without psychiatric disorders at a mental health care facility.

Exclusion Criteria:

• Patients with renal or hepatic impairment.
• Patients receiving chemotherapy or radiotherapy.

Subjects participating in this study are those receiving outpatient or inpatient programs for the management of SUD with or without psychiatric disorders, supported by the specialized mental health care facility; "Al-Maa'moura Hospital for Psychiatry" in Alexandria, Egypt.