Simultaneous determination of FLZ and its metabolite (M1) in human plasma and urine by UHPLC‐MS/MS: Application to a pharmacokinetic study

Abstract

HighlightsA rapid and sensitive UHPLC‐MS/MS method was developed for the simultaneous determination of FLZ and M1.The method was fully validated and successfully applied to a first‐in‐human clinical study.The PK profiles and excretory fraction in urine were obtained in Chinese healthy subjects for the first time. Abstract FLZ is a novel anti‐Parkinson’s disease candidate drug. The main active metabolite is FLZ O‐dealkylation (M1) in preclinical studies. A reliable ultra‐high‐performance liquid chromatography‐tandem mass spectrometry (UHPLC‐MS/MS) quantitation method was developed for the simultaneous determination of FLZ and M1 with low limits of quantitation in human plasma (0.1 ng/mL) and urine (0.5 ng/mL). The plasma and urine samples were both purified by full‐automatic solid phase extraction (SPE) method with ensured high extraction recovery and little matrix effect for both analytes, and then separated on a BEH C18 column (2.1 × 50 mm, 1.7 &mgr;m). Detection and quantification were performed using an electrospray ionization (ESI) source in positive mode by multiple reaction monitoring (MRM). The precursor to product ion transitions were monitored at m/z 450.3+→313.2+ for FLZ, m/z 436.3+→299.1+ for M1, m/z 462.6+→142.0+ for [D12]‐FLZ (internal standard of FLZ) and m/z 447.2+→125.2+ for [D11]‐M1 (internal standard of M1), respectively. This method showed good linearity, accuracy, precision and stability in the range of 0.1–100 ng/mL in plasma and 0.5–500 ng/mL in urine of two analytes. Finally, the developed method was successfully applied to a pharmacokinetic research in Chinese healthy volunteers after oral administration of FLZ tablets.