Therapeutics Letter Issue 79 / Sep - Dec 2010

Quetiapine (Seroquel® and generics) has been available in Canada since 1998. It is approved for schizophrenia, bipolar disorder and, as of 2010, for major depressive disorder (MDD) refractory to treatment with antidepressants.¹ It is widely prescribed in low doses for management of sleep disorders, despite lacking approval for this use.²

In 2010 almost $20 million was spent on quetiapine in British Columbia, placing it 21^st in cost, ahead of pantoprazole and amlodipine. At almost 1 million prescriptions, quetiapine was the 9^th most frequently prescribed drug in B.C., leading rabeprazole and citalopram and close behind zopiclone and metformin. Given the wide range of drugs available for psychosis and mood disorders, these indications likely account for a minority of quetiapine’s use in 2010. This is supported by the fact that 58% of B.C. quetiapine prescriptions were for the 25 mg tablet, whereas the recommended dose range for the approved disorders is 150 to 800 mg/day. Similarly in the United States, up to 70% of newer antipsychotic prescribing is for conditions other than psychosis.³

This letter examines efficacy and safety evidence about use of low dose quetiapine for sleep disorders.

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