Objective: To compare the efficacy and tolerability of lithium versus quetiapine for the treatment of manic or mixed episodes in youths with early course bipolar I disorder. Methods: Six-week, randomized, double-blind clinical trial of lithium versus quetiapine for the treatment of adolescents with acute manic/mixed episode. Target dose of quetiapine dose was adjusted to a target dose of 400–600 mg and target serum level for lithium was 1.0–1.2 mEq/L. Primary outcome measure was baseline-to-endpoint change in the Young Mania Rating Scale (YMRS). Secondary outcomes were treatment response (50% or more decrease from baseline in YMRS score) and remission (YMRS score ≤12, Children's Depression Rating Scale-Revised [CDRS-R] total score ≤28 and Clinical Global Impression Bipolar Severity Scale [CGI-BP-S] overall score of ≤3, respectively). Results: A total of 109 patients were randomized (quetiapine = 58 and lithium = 51). Participants in the quetiapine treatment group showed a significantly greater reduction in YMRS score than those in the lithium group (−11.0 vs. −13.2; p
