Cefoxitin falsely elevates creatinine levels
A. J. Saah, T. R. Koch and G. L. Drusano
Cefoxitin sodium has been found to act like creatinine in assays for
creatinine used by many hospitals. Our in vitro results show that cefoxitin
causes an apparent rise in the serum creatinine level; the magnitude of the
increase depends on the assay method and the concentration of cefoxitin.
Results varied from 1.5 to more than 8.5 times the normal serum creatinine
level. Published data from studies of human volunteers show the same
effect. In patients with normal renal function, the serum creatinine test
is reliable two to four hours following cefoxitin infusion and in mild to
moderate renal failure (glomerular filtration rate greater than 30 mL/min),
six to eight hours. In severe renal failure, the serum creatinine
determination is unreliable. Measurement of urinary creatinine employs
similar assays, thus making estimation of creatinine clearance unreliable
when the patient is receiving cefoxitin.
