The antipsychotic agent quetiapine was introduced in Norway in 2003. We have assessed changes in dispensed prescriptions, including dosing, of quetiapine in Norway from 2004 to 2015.
Data on the sales of antipsychotics and antidepressants were drawn from the Norwegian Prescription Database. A total of 47,474 outpatients filled 195,622 prescriptions of quetiapine. Reimbursement codes, use of antipsychotics or antidepressants 12 months prior to the first prescription of quetiapine and estimated mean volume used measured as defined daily doses (DDDs) per day were used as proxies for diagnoses. We conducted a regression analysis with DDD per day as a function of possible explanatory variables.
The number of users filling at least two prescriptions of quetiapine per year increased from 584 in 2004 to 8506 in 2015 and the mean dose declined from 1.58 DDD per day (SD 8.00) to 0.48 DDD per day (SD 2.27). The latter is much lower than recommended for treatment of psychoses. In 2015, 60.1% of the 8506 quetiapine users did not seek reimbursement for the treatment of a major psychiatric disorder and only 2.6% of the patients were prescribed 1 DDD or more per day and reimbursed in accordance with the drug's primary indication, psychosis. A reported diagnosis of psychosis was not associated with higher quetiapine doses.
In 2015, the pattern of quetiapine dispensing in Norway most likely reflects predominant off-label use. This is unsettling considering poorly documented effects in non-psychotic disorders, profound side effects, significant toxicity and growing concern regarding abuse.