Is There a Potential of Misuse for Quetiapine? Literature Review and Analysis of the European Medicines Agency/European Medicines Agency Adverse Drug Reactions' Database

Purpose/Background A recent years' increase in both prescribing and availability of second-generation antipsychotics (SGAs) has been observed. According to the literature, typically made up by case studies/series, quetiapine seems to be the most commonly misused SGA, with both intranasal and intravenous intake modalities having been described. Another SGA that has been anecdotally reported to be misused is olanzapine. For these molecules, both a previous history of drug misuse and being an inmate have been described as factors associated with misuse. Hence, while providing here an updated literature review of the topic, we aimed at assessing all cases of quetiapine misuse/abuse/dependence/withdrawal as reported to the European Medicines Agency's EudraVigilance (EV) database; this was carried out in comparison with the reference drug olanzapine. Methods All spontaneous, European Medicines Agency database reports relating to both quetiapine (2005-2016) and olanzapine (2004-2016) misuse/abuse/dependence/withdrawal issues were retrieved, and a descriptive analysis was performed. Results From the EV database, 18,112 (8.64% of 209,571) and 4178 (7.58% of 55,100) adverse drug reaction reports of misuse/abuse/dependence/withdrawal were associated with quetiapine and olanzapine, respectively. The resulting proportional reporting ratio values suggested that the misuse/abuse-, dependence-, and withdrawal-related adverse drug reactions were more frequently reported for quetiapine (1.07, 1.01, and 5.25, respectively) in comparison with olanzapine. Conclusions Despite data collection limitations, present EV data may suggest that, at least in comparison with olanzapine, quetiapine misuse may be a cause for concern.