Background and aims: Quetiapine (QTP) has been shown to be effective as an acute treatment in patients with bipolar depression. Nonetheless, the time at onset of QTP antidepressant action has not been clarified. We aimed to evaluate the onset of the antidepressant effect of QTP extended release (XR) in bipolar depression. We also compared the different efficacy and adverse effect profile of 300- and 600-mg/d dosages.
Methods: Twenty-one acutely bipolar depressed patients were recruited; 13 were treated with QTP XR 300 and 8 with 600 mg/d. Assessment was performed with Hamilton Depression Rating Scale (also considering clusters "core," "somatic anxiety," "psychic anxiety," "activity," and "delusion"), Hamilton Anxiety Rating Scale, Dosage Record and Treatment Emergent Symptom Scale.
Results: Quetiapine XR was effective since the first 3 days of treatment in reducing all the efficacy measures except for somatic anxiety. The comparison of 300- and 600-mg dosages was limited by the small sample size. However, the analysis did not show any significant difference in terms of efficacy, although with a trend in favor of 600 mg. The incidence of hypotension was significantly higher in patients taking QTP 600 mg (P = 0.004).
Discussion and conclusion: Quetiapine seems to be effective in bipolar depression within the first days of treatment. There may be not a significant advantage for the 600-mg dose in comparison with the 300-mg one. The clinical effect seems to be not associated with sedation, suggesting that it may be due to the molecular drug effect. Further studies focusing on the first days of treatment are needed to confirm our findings.