Effect of seven fluoroquinolones on the determination of serum creatinine by the picric acid and enzymatic methods

OBJECTIVE: To investigate in vitro the interaction of seven fluoroquinolone antibiotics with the determination of serum creatinine by the picric acid and enzymatic methods. DESIGN: This blind, in vitro study assayed duplicate serum samples for creatinine by the picric acid and enzymatic methods with averaged spiked concentrations of 2.71, 13.56, 27.12, and 108.47 mumol/L of ciprofloxacin, fleroxacin, lomefloxacin, ofloxacin, 1-ofloxacin, sparfloxacin, and temafloxacin. Cefoxitin (in concentrations of 233.9, 1169.6, 1754.4, and 2339.2 mumol/L) was used as a positive control for the picric acid assay. SETTING: University-affiliated hospital, Department of Pharmaceutical Services and Clinical Chemistry section of the Department of Pathology. MAIN OUTCOME MEASURE: The serum creatinine samples spiked with the seven substituted fluoroquinolones and cefoxitin were assayed by both the picric acid and enzymatic assays. Statistical analysis compared the spiked samples with blank serum by Student's t-test and concentration ranges were compared by analysis of variance. A statistically significant interference with serum creatinine was p < 0.05. RESULTS: None of the substituted fluoroquinolones interfered significantly with the determination of serum creatinine by either method. Cefoxitin significantly interfered with the determination of serum creatinine by the picric acid method. CONCLUSIONS: Fluoroquinolones do not interfere with the determination of serum creatinine by either the picric acid or enzymatic method.