Akademik Veri Yönetim Sistemi
34th International Symposium on Pharmaceutical and Biomedical Analysis (PBA2024), Geneve, İsviçre, 9 - 12 Eylül 2024, ss.99
One of the psychiatric diseases that researchers have focused on is schizophrenia (SCZ). It has been
reported that about one percent of the world's population suffers from this disease. The disturbance of
brain development due to genetic, environmental, and neurobiological factors influences the
emergence of SCZ. Pharmacotherapy is the cornerstone of the treatment of SCZ. The efficacy of
clozapine as a treatment for SCZ has been substantiated by evidence, establishing it as the most
effective antipsychotic medication for this condition. Its selection as a leading pharmaceutical option
can be attributed to its enzymatic activity. Clozapine (CLZ) is known to be metabolized by cytochrome
P450 (CYP) enzymes to form N-desmethylclozapine (DCLZ). CLZ and caffeine are both primarily
metabolized by the CYP1A2 enzyme. Studies have indicated that caffeine has an inhibitory effect on
clozapine metabolism. Therefore, the consumption of caffeine may increase clozapine levels in the
plasma by inhibiting the CYP1A2 enzyme. In the case of smoking, polycyclic aromatic hydrocarbons in
cigarettes are thought to be the inducers of the CYP1A2 enzyme. As a result of the induction, smokers
require higher clozapine doses than non-smokers to reach the recommended, or therapeutic, level of
clozapine. This study aimed to expand previous findings on schizophrenia by examining the amount of
CLZ and its metabolite DCLZ in the plasma of individuals with schizophrenia. The research is designed
to examine the relationship between exogenous substances, including drugs, and their metabolites in
patients who consume caffeine and nicotine. Analytes selected for analysis include CLZ, caffeine,
nicotine, and its metabolites (paraxanthine, theobromine, theophylline, and cotinine). The method
development was conducted using a high-performance liquid chromatography (HPLC) system with an
EVO C18 analytical column (250mm x 4.6mm, 5µm). The injection volume, column temperature, and
flow rate were optimized. The pH of the buffer was also optimized. Finally, the gradient method was
applied with 0.1% H3PO4 buffer (pH 4) (A), methanol (B), and acetonitrile (C). The flow rate was set to
1 mL/min, and the column temperature was set to 20 °C. The detector wavelength was adjusted to 260
nm. The validated chromatographic method was in accordance with the ICH guidelines. Instrumental
calibration curves were constructed using standard solutions for all the analytes. The developed
method is appropriate for the detection of each analyte at a concentration of 0.1 µg/mL, with the
exception of nicotine, which can be detected at a minimum concentration of 0.25 µg/mL. The R2 values
were greater than 0.99, indicating that the developed HPLC method can be used for the determination
of the analytes and their metabolites from biological samples after the development of an efficient
extraction methodology.