Dosing of Quetiapine in Schizophrenia: How Clinical Practice Differs From Registration Studies

Background: A substantial number of patients with psychosis receive quetiapine in amounts that are greater than what is recommended in the product labeling approved by drug regulatory agencies. The purpose of this article is to review the past and present dosing patterns of quetiapine for the treatment of schizophrenia.

Method: A PubMed search for the period January 1, 1990, to July 1, 2005, was conducted to identify English-language articles related to quetiapine dose in schizophrenia using the search terms quetiapine, dose, and schizophrenia. Trends in dosing of quetiapine in a large, state-operated psychiatric hospital system and the anecdotal evidence describing the use of quetiapine in excess of 800 mg/day were also reviewed.

Results: The registration studies of quetiapine suggest a target dose range of 300 to 500 mg/day for schizophrenia. In contrast, among inpatients hospitalized in New York State in the period of April 1, 2004, to June 30, 2004, the mean dose of quetiapine prescribed was 620 mg/day, with 33.6% receiving doses in excess of 750 mg/day. Patients with nonwhite ethnicity, length of stay of at least 1 year, or history of prior state hospital admission were more likely to receive doses greater than 750 mg/day. Patients receiving quetiapine as antipsychotic monotherapy or in combination with other antipsychotics were equally likely to receive doses greater than 750 mg/day. Published anecdotal reports describe the use of quetiapine in excess of 800 mg/day and up to 2400 mg/day among patients not responding to lower doses, but currently there are no published reports from double-blind randomized clinical trials establishing the utility of this high-dose treatment strategy.

Conclusions: Dosing of quetiapine in clinical practice is higher than what has been established in the registration program for schizophrenia. Although there is anecdotal evidence describing the use of quetiapine in excess of 800 mg/day, double-blind randomized clinical trials are needed.