OBJECTIVES: To assess the efficacy and safety of agomelatine using pharmacovigilance during 12-week follow-up. METHODS: Agomelatine 25-50 mg was prescribed open label to patients with depressive disorders diagnosed by psychiatrists based on DSM-IV/ICD-10 criteria. Treatment options were intent-to-treat. All 480 patients, including 97 elderly patients were followed up at week 2 if dose titration was necessary. Efficacy was assessed using Montgomery-Äsberg Depression Rating Scale(MÄDRS) and clinical global impression of improvement (CGI-I) and of severity (CGI-S) scales, at weeks 2, 6, and 12. Data on adverse effects and for reports were gathered through patient interviews. RESULTS: Of 480 patients, 20-86 years (mean[SD] 49.6[14.5]), 247(51.5%) were men and 97(20.2%) were elderly (65 to 86; mean[SD] 71.1[5.0]). Among all patients, 225(46.9%) and 255(53.1%) were depressed with a single episode and recurrent episodes. Patients with recurrent episodes were taking various classes of antidepressants, including selective serotonin reuptake inhibitors in 328(50.9%) patients. Generalized anxiety disorder was a concurrent diagnosis in 95(24.3%) of patients. The respective mean(SD) baseline CGI-S, CGI-I, and MADRS scores of 3.90(0.68), 4.15(0.76), and 22.59(3.77) were reduced to 2.1(0.31), 1.11(0.37), and 9.19(2.03), with respective reductions in mean(SD; 95% CI) scores of 1.78(0.75;1.72-1.85), 2.98(0.78;2.91-3.05), and 13.39(4.36; 13.00-13.78). Similar efficacy was evidenced for elderly depressed patients (N=97), in whom mean(SD) MADRS score at baseline 22.37(4.79) was consistently significantly reduced to 14.61(3.04), 10.76(3.04), and 8.72(1.91) at weeks 2, 6, and 12, respectively. After 12 weeks, overall remission (MADRS score <10) was seen in 68.4% of patients with moderate to severe (MADRS >25) depression and in 73.4% of elderly depressed patients. The mild adverse events reported were dizziness(9.5%), headache(7.4%), difficulty sleeping(6.3%), and nausea(3.1%). There were no cases reported of alanine transaminase levels three times above upper limit of normal. CONCLUSIONS: Agomelatine has proven to be a safe and effective new antidepressant in intent-to-treat analysis of depressed, including elderly, patients in daily clinical practice in Thailand.