A Random-Assignment, Double-Blind, Clinical Trial of Once- vs Twice-Daily Administration of Quetiapine Fumarate in Patients with Schizophrenia or Schizoaffective Disorder: A Pilot Study

Objective: To evaluate the efficacy and safety of administering quetiapine once vs twice daily. Method: Utilizing a double-blind design, 21 hospitalized adult men or women with DSM-IV schizophrenia or schizoaffective disorder, who had received unchanged doses (for 2 weeks) of either 400 or 600 mg daily of quetiapine administered in 2 doses, were randomly assigned to once-or twice-daily administration for 4 weeks and then crossed over to the opposite dosing regimen for an additional 4 weeks. Standard psychopathology and safety measures were used in the study. Results: Nearly 70% (15/21) of the subjects met the a priori efficacy responder criteria with no statistical differences in response between those assigned to once-or twice-daily quetiapine administration. Statistical analyses confirmed that most subjects maintained efficacy during the switch to once-or twice-daily administration with quetiapine. A minority (15%) did experience worsening of symptoms or orthostatic hypotension during the crossover. Quetiapine was generally well tolerated at either twice-or once-daily administration. Conclusions: These pilot data suggest that it is clinically feasible to switch most quetiapine-treated subjects receiving a therapeutic twice-daily dosing schedule to a once-daily regimen. A minority may experience worsening of symptoms or orthostatic hypotension during the switch. This strategy of administering quetiapine entirely at bedtime may promote improved adherence to treatment. (Can J Psychiatry 2003;48:187-194)