ObjectivesCefazolin, a first generation cephalosporin β-lactam antibiotic, is commonly used for prophylaxis during cesarean delivery, and in treatment of pulmonary infections and many surgical procedures. The aim of this work was to develop a simple, fast and accurate liquid-chromatography-mass spectrometry method for determination of serum cefazolin. MethodsMass spectrometric analyses were performed using an Shimadzu LC-20-AD (Kyoto, Japan) coupled with a ABSCIEX API 3200 triple quadrupole mass spectrometer (USA) equipped with an electrospray ion source (ESI) operating in positive mode. ResultsThe standard curves for cefazolin was linear within the range of 0.39-200 µg/ml. Total run time was 5 minutes. Chromatographic separation was performed on a C18 column (4.6×50 mm, 5 µm, Phenomenex Luna) with a mobile phase consisting of 1% formic acid in water and MeOH (10:90, V/V) at a flow rate of 0.8 ml/min.  DiscussionSerum cefazolin measurement can be easily performed by LC-MS/MS system to identify the risk of the patients with therapeutic drug monitoring. This method performs this drug analysis with high throughput. ConclusionsExact determination of cefazolin provides reliable levels in clinical studies to avoid toxic effects. KeywordsAntibiotic levels, mass spectrometry, cefazolin, toxicity.  Acknowledgments: No conflict of interest