A randomized, double-blind, placebo-controlled study of the safety and tolerability of high-dose quetiapine in patients with persistent symptoms of schizophrenia or schizoaffective disorder.

OBJECTIVE: Quetiapine is often prescribed at higher than approved doses. We investigated the safety, tolerability, and efficacy of quetiapine > 800 mg/d.

METHOD: A trial was carried out from October 2003-September 2005 in 19 referral centers. Patients with DSM-IV schizophrenia or schizoaffective disorder were randomized on the basis of persistent symptoms of moderate severity (< 30% improvement in total Positive and Negative Syndrome Scale score after ≥ 4 weeks of quetiapine). The 8 week, double-blind study compared continuation of quetiapine 800 mg/d (n = 43) versus 1,200 mg/d (n = 88). The primary outcome measure was emergent or worsening parkinsonism (Simpson-Angus Scale). Secondary outcomes were adverse events, metabolic side effects, and symptom severity.

RESULTS: Mean doses obtained were 799 mg/d and 1,144 mg/d in the 800-mg/d and > 800-mg/d groups, respectively. Emergent or deteriorating parkinsonism in the high-dose group was 3.1% greater (95% CI, -7.8% to 14.0%; P = .76) than in the 800-mg/d group, a value that was within the a priori limit of 16% defined as noninferiority. Both doses of quetiapine were safe and well tolerated. Weight gain was greater in the high-dose group (1.7 kg over 12 weeks; ≥ 7% body weight, n = 11 [12.5%]) versus the 800-mg/d group (1.1 kg over 12 weeks; ≥ 7% body weight, n = 4 [9.3%]). The mean adjusted difference in weight gain (1.3 kg) was greater in the high-dose group (95% CI, 0.0-2.5; P = .044). Symptom severity declined, with no significant difference between groups.

CONCLUSIONS: The results did not demonstrate any advantage for use of quetiapine outside the approved dose range.

TRIAL REGISTRATION: www.clinicaltrials.gov Identifier: NCT00328978.