A bacteriostatic or bactericidal agent depending on the concentration and susceptibility of the infecting organism. Nitrofurantoin is active against some gram positive organisms such as S. aureus, S. epidermidis, S. saprophyticus, Enterococcus faecalis, S. agalactiae, group D streptococci, viridians streptococci and Corynebacterium. Its spectrum of activity against gram negative organisms includes E. coli, Enterobacter, Neisseria, Salmonella and Shigella. It may be used as an alternative to trimethoprim/sulfamethoxazole for treating urinary tract infections though it may be less effective at eradicating vaginal bacteria. May also be used in females as prophylaxis against recurrent cystitis related to coitus. Nitrofurantoin is highly stable to the development of bacterial resistance, a property thought to be due to its multiplicity of mechanisms of action.
Indication
May be used as an alternative in the treatment of urinary tract infections. May be used by females pericoitally for prophylaxis against recurrent cystitis related to coitus.
Pharmacology
Nitrofurantoin exhibits bacteriostatic or bactericidal effects by inhibiting the synthesis of DNA, RNA, protein and cell wall synthesis.
Toxicity
Acute toxicity may cause vomiting. Adverse effects include nausea and urine discolouration. Rare hepatotoxic and hypersensitivity reactions have occurred. Hemolytic anemia is a risk in patients with G6PD deficiency. Ascending polyneuropathy may occur with prolonged therapy or in patients with low creatinine clearance.
Affected Organisms
Gram negative and gram positive bacteria
Biotransformation
Partially metabolized in liver to aminofurantoin.
Absorption
Readily absorbed in GI tract primarily in small intestine. Enhanced by food or delayed gastric emptying via enhanced dissolution rate of the drug.