Effect of Renal Function on Urinary Recovery of Orally Administered Nitrofurantoin

The urinary recovery of nitrofurantoin after a single 100-mg oral dose was studied in subjects with varying renal function. Almost all uremic patients excreted little or no drug in the urine during a 10-hour collection period. Recovery of drug in the urine appeared to be linearly related to creatinine clearance. The highest concentration of drug recovered during any collection period in uremic patients was inadequate to inhibit organisms commonly found in urinary-tract infections. A small group of subjects with impaired renal function, given 100 mg daily, failed to excrete detectable amounts of drug even after five days of treatment. Three azotemic patients receiving 400 mg per day for several days excreted small amounts of drug in the urine. In view of these and other studies, it is recommended that nitrofurantoin be contraindicated in azotemic patients.