Quetiapine fumarate (Seroquel®) is an atypical antipsychotic dibenzothiazepine derivative. Due to its extensive hepatic metabolism and low level of unchanged excretion (< 1%) the routine toxicological drug-screening analyses of urine often leads to false negative results. In the present study, we report that a newly identified metabolite of quetiapine, N-desalkylquetiapine, can be used as an indicative marker of quetiapine-intake in urine using common GC-MS screening procedure. The structure of the mentioned metabolite was solved from the mass-spectrum obtained and the quetiapine presence was proved by consequent HPLC plasma analysis.
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