Antibacterial activity
Nitrofurantoin has been shown to have good activity against:

E. coli
Staphylococcus saprophyticus
Coagulase negative staphylococci
Enterococcus faecalis
Staphylococcus aureus
Streptococcus agalactiae
Citrobacter species
Klebsiella species
Bacillus subtilis speciesIt is used in the treatment of infections caused by these organisms.Many or all strains of the following genera are resistant to nitrofurantoin:
Enterobacter
Proteus
PseudomonasAntibiotic susceptibility testing should always be performed to further elucidate the resistance profile of the particular strain of bacteria causing infection. Special populations
Pregnancy
Nitrofurantoin is pregnancy category B in the United States and pregnancy category A in Australia. It is one of the few drugs commonly used in pregnancy to treat UTIs. It however should not be used in late pregnancy due to the potential risk of hemolytic anemia in the newborn. Newborns of women given this drug late in pregnancy had a higher risk of developing neonatal jaundice.Evidence of safety in early pregnancy is mixed as of 2017. The American College of Obstetricians and Gynecologists states that while they can be used in the first trimester other options may be preferred. They remain a first line treatment in the second trimester. A 2015 meta analysis found no increased risk from first trimester use in cohort studies that was a slight increase of malformations in case control studies. Available forms
There are two formulations of nitrofurantoin:

Macrocrystals - (Macrodantin, Furadantin) – 25, 50, or 100 mg capsules – taken once every 6 hours
Monohydrate/macrocrystals - (Macrobid) – 100 mg capsules – taken once every 12 hours or 2 times a day (written on prescriptions as BID, which is the last part of the trade name MacroBID).
Stasis dermatitis refers to the skin changes that occur in the leg as a result of "stasis" or blood pooling from insufficient venous return; the alternative name of varicose eczema comes from a common cause of this being varicose veins.Insufficient venous return results in increased pressure in the capillaries with the result that both fluid and cells may "leak" out of the capillaries. This results in red cells breaking down, with iron containing hemosiderin possibly contributing to the pathology of this entity. Symptoms
Stasis dermatitis may be characterized by:

Skin that appears thin, brown and tissue-like, with possible skin lesions (macule or patches), red spots, superficial skin irritation and/or darkening and/or thickening of the skin at the ankles or legs
Weak skin may ulcerate in some areas and legs, ankles, or other areas may become swollen
Open sores, ulcers
Itching and/or leg pains
Sometimes pain may persist from swollen tissues and may feel like "stabbing" or "needle pricks"If skin continues to deteriorate and breaks down, a venous ulcer (also known as a stasis ulcer) may form. Without proper wound care, open cracks predispose patients for the entry of a bacterial infection, causing cellulitis in the leg. Diagnosis
Stasis dermatitis is diagnosed clinically by assessing the appearance of red plaques on the lower legs and the inner side of the ankle. Stasis dermatitis can resemble a number of other conditions, such as cellulitis and contact dermatitis, and at times needs the use of a duplex ultrasound to confirm the diagnosis or if clinical diagnosis alone is not sufficient.