The toxicology and comorbidities of fatal cases involving quetiapine

The use of quetiapine in Australia has increased rapidly in recent years. Anecdotal and post-marketing surveillance reports indicate an increase in quetiapine misuse in prisons as well as an increase in its availability on the black-market. This study examined a cohort of quetiapine-associated deaths occurring in Victoria, Australia, between 2001 and 2009, to determine the prevalence of deaths associated with this drug and to determine whether misuse represents a legitimate concern. Case details were extracted from the National Coronial Information System. There were 224 cases with an average age of 43 years of age (range 15–87 years). The cause of death was mostly drug toxicity (n = 114, 51 %), followed by natural disease (n = 60, 27 %), external injury (n = 31, 14 %) and unascertained causes (n = 19, 8 %). Depression and/or anxiety were common, observed in over a third of the cohort (80 cases, 36 %). About 20 % of cases did not mention a psychiatric diagnosis at all which raises the question of whether quetiapine had been prescribed correctly in these cases. Cardiovascular disease was the most commonly reported illness after mental disease. Quetiapine ranged in concentration from the limit of reporting (0.01 mg/L) to 110 mg/L. The median concentration of quetiapine was much lower in the natural disease deaths (0.25 mg/L) compared with drug caused deaths (0.7 mg/L). The most commonly co-administered drug was diazepam in 81 (36 %) cases. There were a small number of cases where quetiapine contributed to a death where it had not apparently been prescribed, including the death of a 15 year old boy and one of a 34 year old female. Overall, misuse of quetiapine did not appear to be a significant issue in this cohort; use of the drug only occasionally led to fatalities when used in excess or concomitantly with interacting drugs. However, considering that it is a recent social concern, it is possible that analysis of cases post 2009 would reveal more cases of quetiapine abuse. Close monitoring of quetiapine is therefore advised to prevent adverse outcomes, particularly in vulnerable populations such as substance abusers.