Nitrofurantoin, along with the branded versions Macrobid and Macrodantin, is an antibacterial agent. Macrobid is largely used for UTI treatment, specifically acute uncomplicated urinary tract infections (acute cystitis) caused by susceptible strains of Escherichia coli and Staphylococcus saprophyticus. Nitrofurantoin should only be used in the treatment or prevention of infections that are strongly suspected or proven to be caused by bacteria. As Macrobid, nitrofurantoin is found as a hard gelatin capsule shell containing nitrofurantoin 100 mg (nitrofurantoin macrocrystals and nitrofurantoin monohydrate). After administration, some nitrofurantoin can be found unchanged in the urine over 24 hours. Nitrofurantoin works by inactivating specific molecules such as ribosomal proteins in the target bacteria, impairing a number of metabolic processes. Additionally, bacterial resistance to nitrofurantoin is low. Macrobid is often prescribed as one 100mg capsule every 12 hours for seven days.