Cefoxitin-Serum Creatinine Interference in a Patient With Nontuberculous Mycobacteria Ventriculomeningitis

Cefoxitin is a second-generation cephamycin antibiotic, which at concentrations ≥100 µg/mL is known to modestly interfere, for up to 2 hours post-infusion, with serum creatinine measurement via the traditional Jaffe-based assay. We report a case of a severe serum creatinine elevation while utilizing cefoxitin as a component of an antimicrobial regimen in a critically ill patient with Mycobacterium abscessus ventriculomeningitis. Our results, both via patient serum analysis and a cefoxitin spiking experiment, demonstrate interference despite the utilization of improved modern Jaffe-based assays. In fact, the cefoxitin-creatinine interference may be clinically relevant at concentrations 3 times lower than that listed in the package insert and may display more than a modest interference at typical therapeutic concentrations.