List of products in the National Drug Code with proprietary name . Nitrofurantoin is an antibiotic used to treat or prevent certain bladder infections. It works by stopping the growth of bacteria. This antibiotic treats only bacterial infections. It will not work for viral infections (such as common cold, flu). Using any antibiotic when it is not needed can cause it to not work for future infections. This medication should not be used in infants younger than 1 month old (see also Precautions section). This drug should not be used to treat infections outside the bladder (including kidney infections such as pyelonephritis or perinephric abscesses).