Simple determination of urine cefazolin concentration in pediatric patients with urinary tract infections using high‐performance liquid chromatography

Recently, global health concerns regarding increasing multidrug resistance have arisen. This study aimed to develop a simple, inexpensive and rapid high‐performance liquid chromatography–ultraviolet (HPLC–UV) method for determining urinary concentrations of a first‐generation cephem antibiotic in pediatric patients with urinary tract infections (UTIs). HPLC–UV was used to analyze urinary cefazolin concentrations at a detection wavelength of 254 nm. The assay used contained 10‐fold diluted urine with an internal standard (cephapirin). The standard calibration curve for cefazolin was linear in the concentration range of 31.25–500 μg/ml (r2 > 0.999). The retention times of cefazolin and the internal standard were 4.2 and 4.9 min, respectively. The within‐ and between‐day coefficients of variation were in the concentration ranges 1.2–15.2 and 5.5–19.2%, respectively. The urinary cefazolin concentration of a pediatric patient with a UTI was 1,476.6 μg/ml, which was over 700‐fold higher than the minimum inhibitory concentration of cefazolin (≤2 μg/ml). The developed method is applicable to the confirmation of appropriate use for UTI treatment as therapeutic drug monitoring of cefazolin. Therefore, the findings of this study may contribute to the appropriate use of antibiotics to prevent antimicrobial resistance in pediatric patients with UTIs.