Mungkhunthod S.Prommas S.Puangpetch A.Paholpak P.Nakkam N.Sukasem C.Tassaneeyakul W.Vannaprasaht S.Mahidol University2026-01-292026-01-292025-10-01Journal of the Medical Association of Thailand Vol.108 (2025) , S92-S10001252208https://repository.li.mahidol.ac.th/handle/123456789/114089Background: Quetiapine (QTP) is an atypical antipsychotic drug that is widely used to treat psychiatric patients. N-desalkylquetiapine (NQTP) is the major and active metabolite. Objective: The present study aimed to develop and validate a method for measuring QTP and NQTP concentrations in human plasma by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Materials and Methods: Plasma samples were processed using liquid-liquid extraction, and the analytes were separated on a C18 column. The analysis was conducted using a triple quadrupole tandem mass spectrometer with a mobile gradient phase consisting of 0.1% formic acid in 10 mM ammonium formate and 100% acetonitrile. The total run time was 6 min. Results: The calibration curves for QTP and NQTP were in a linear range of 2.0 to 600.0 ng/ml. The within-run and between-run precision for QTP was 10.29% and 11.16%, whereas those for NQTP were 8.21% and 12.87%, respectively. The within-run and between-run accuracy for QTP was <111.74%, <100.34%, <110.53%, and <104.11% for NQTP, respectively. The lower limit of detection for QTP and NQTP was 2.0 ng/ml. Conclusion: An LC-MS/MS method for measuring QTP and NQTP levels in human plasma was validated and successfully applied to measure these analytes in psychiatric patients.MedicineArticleSCOPUS10.35755/jmedassocthai.2025.S02.S92-S1002-s2.0-10502789459424081981