A new method for the determination of nitrofurantoin in urine.

Nitrofurantoin is presently used as an antibacterial agent for the urinary tract of both man and animals. A new, quantitative procedure for the determination of this drug in urine consistsof direct extraction of the nonionized form of the drug by the use of nitromethane, addition of an alkaline reagent to the extract to produce a visible color, and determination of the nitrofurantoin concentration by spectrophotometry. The method hasa sensitivity of 5 mg./L., with recoveriesof 99-101% and a standard curve that is linear to 100 mg./L. Results indicate that the method measuresnitrofurantoin alone, and not its metabolites, in rat, dog,and humanurine.