NEW YORK (Reuters Health) Jul 29 – Increasing the dose of quetiapine won’t improve symptoms of schizophrenia or schizoaffective disorder, new trial results show.
And while parkinsonian symptoms didn’t increase at the higher dose, patients did gain more weight, said Dr. William G. Honer of the British Columbia Mental Health and Addictions Research Institute in Vancouver and his colleagues.
Higher-than-approved doses of quetiapine are prescribed frequently, without much data to support the practice, Dr. Honer and his team wrote in a June 14th online paper in the Journal of Clinical Psychiatry.
They designed their study to see whether patients who improved less than 30% on the Positive and Negative Syndrome Scale (PANSS) score after four weeks on the maximum approved quetiapine dose (800 mg/day) would do better on 1,200 mg/day for an additional eight weeks.
The primary outcome was emergent or worsening extrapyramidal symptoms, given that “this side effect of antipsychotics has shown the clearest dose-response relationship,” the authors said.
They randomized 43 patients to a placebo group that continued to take 800 mg/day; the other 88 received an average dose of 1,144 mg/ day.
Emerging or worsening parkinsonism was 3.1% more frequent in the higher dose group, which was within the 16% preset limit for non-inferiority.
On average, patients in the higher-dose group gained 1.7 kg, while 12.5% gained 7% or more of their baseline weight, compared to 1.1 kg and 9.3% for the lower-dose group.
Symptom severity declined in both groups over time, but without any significant differences between the two groups.
The researchers conclude, “The results of this study did not demonstrate any advantage for use of quetiapine at doses outside of the approved dose range.”
J Clin Psychiatry 2011.