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.