Objective: The aim of this study was to compare the effectiveness of lithium versus quetiapine immediate release (IR) monotherapy in patients with bipolar I, II, or subthreshold bipolar disorder at any phase.
Methods: Eligible patients were randomized to lithium or quetiapine IR for 16 weeks. The difference in the time to discontinuation from study due to "all causes" between lithium and quetiapine IR groups and changes from baseline to 8 and 16 weeks in depression, mania, anxiety, quality of life (QOL), metabolic profiles, and proinflammatory markers were compared.
Results: Of the 42 patients randomized to lithium (n = 18) and quetiapine IR (n = 24), the median time to discontinuation due to "all causes" was 6 weeks (95% confidence interval, 2-12 weeks) in the lithium group and 8 weeks (95% confidence interval, 6 weeks to not calculable) in the quetiapine IR group. The mean time to discontinuation due to "all causes" was 7.7 ± 1.1 weeks for lithium versus 8.4 ± 0.8 weeks for quetiapine IR (P = 0.54). There was no significant difference between lithium and quetiapine IR in changes in the severity of depression, mania/hypomania, anxiety, and QOL as a whole or only in patients with depressive index episode. The decrease in total cholesterol was significantly larger with lithium than with quetiapine IR (P = 0.05) as a whole, but not only in patients with depression index episode. There was no other significant difference in changes in metabolic panels and inflammatory markers between the 2 groups.
Conclusions: The difference in effectiveness between lithium and quetiapine IR monotherapy in a real-world bipolar population was minimal. Large-sample studies are needed to support or refute this finding.