Objective: The aim of the study was to evaluate the efficacy, tolerability, and safety of once-a day trazodone tablets (Trittico Prolong (R) 300 mg) in patients with moderate to severe depression in routine clinical practice. Methods: Men and women >= 18 years old with Montgomery-Asberg Depression Rating Scale (MADRS) scores >21 and Clinical Global Impression - Severity (CGI/S) >= 4 were included in this post-authorization, non-interventional, observational prospective safety study, conducted in 8 psychiatric centers in the Czech Republic. The acute treatment phase lasted 5 weeks: 1 week of titration and 4 weeks of full-dose treatment. Patients had follow-up visits 9 and 21 weeks after commencing treatment. Results: Overall, 85 patients were enrolled in the study, of which 80 completed the acute treatment of 5 weeks. There were significant decreases in the overall MADRS score from the baseline mean value of 27.4-21.2 at week 1 (p < 0.001), and a further decrease to 7.9 at week 5 (p < 0.001). The severity of depression according to CGI/S gradually declined. Most patients reported improvement after 6 days of trazodone treatment. The most frequent adverse drug reactions (ADRs) reported were somnolence and fatigue. Conclusions: Trazodone, in the new extended-release formulation, had very good effects in clinical practice, both in previously untreated depressive episodes and in episodes not responsive to previous antidepressive therapy. (C) 2018 S. Karger AG, Basel