Background: Borderline Personality disorder is a disabling disease affecting 2% of general population. Various drugs have been suggested for treatment of borderline Personality disorder. If a drug could alleviate a wide range of symptoms, it would be more suitable. In these disorders drug addiction is very common. This fact makes the symptoms complicated and the treatment more difficult. This study is designed to evaluate the effect of Olanzapine and Sertraline in patients suffering from personality disorders who are on methadone maintenance therapy.

Materials and Methods: This clinical trial study was carried out on 120 male and female cases chosen for methadone maintenance therapy through interview by a psychiatrist based on DSM-IV-TR diagnostic criteria for BPD. Afterwards they were randomly divided into two groups. These groups separately received Olanzapine (5-10 mg daily) and Sertraline (50-100 mg daily) therapy. The SCL-90 questionnaire was filled out by the participants before treatment and at the 4^th, 8^th and 12^th weeks of the treatment.

Results: According to this clinical trial, Olanzapine and Sertraline were effective in ameliorating symptoms of depression, anxiety and aggression, reducing sensitivity in interpersonal relationship and alleviating obsessive symptoms, pessimistic behaviors and somatization disorders in patients with personality disorders on methadone maintenance therapy.

Conclusion: As results of this study stated that Olanzapine and Sertraline are definitely effective in alleviating symptoms of patients with personality disorder, prescribing theses drugs are highly recommended for these patients.

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