Consequently, many patients who are treated with nitrofurantoin capsules (macrocrystals) are predisposed to persistence or reappearance of bacteriuria. Nitrofurantoins lack the broader tissue distribution of other therapeutic agents approved for urinary tract infections. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. To reduce the development of drug-resistant bacteria and maintain the effectiveness of nitrofurantoin capsules (macrocrystals) and other antibacterial drugs, nitrofurantoin capsules (macrocrystals) should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. Nitrofurantoin is not indicated for the treatment of pyelonephritis or perinephric abscesses. Nitrofurantoin capsules (macrocrystals) are specifically indicated for the treatment of urinary tract infections when due to susceptible strains of Escherichia coli, enterococci, Staphylococcus aureus, and certain susceptible strains of Klebsiella and Enterobacter species. NOTE: Some strains of Enterobacter species and Klebsiella species are resistant to nitrofurantoin.įor specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for this drug, please see. However, the efficacy of nitrofurantoin in treating clinical infections due to these microorganisms has not been established in adequate and well-controlled trials.Ĭoagulase-negative staphylococci (including StaphylococcusĮpidermidis and Staphylococcus saprophyticus) NOTE: While nitrofurantoin has excellent activity against Enterococcus faecalis, the majority of Enterococcus faecium isolates are not susceptible to nitrofurantoin.Īt least 90 percent of the following microorganisms exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for nitrofurantoin. Nitrofurantoin has been shown to be active against most strains of the following bacteria both in vitro and in clinical infections (see Indications and Usage):Īerobic and facultative Gram-positive microorganisms:Īerobic and facultative Gram-negative microorganisms: Cross-resistance with antibiotics and sulfonamides has not been observed, and transferable resistance is, at most, a very rare phenomenon. Development of Resistanceĭevelopment of resistance to nitrofurantoin has not been a significant problem since its introduction in 1953. The clinical significance of this finding is unknown. Interactions with Other AntibioticsĪntagonism has been demonstrated in vitro between nitrofurantoin and quinolone antimicrobials. The broad-based nature of this mode of action may explain the lack of acquired bacterial resistance to nitrofurantoin, as the necessary multiple and simultaneous mutations of the target macromolecules would likely be lethal to the bacteria. Nitrofurantoin is bactericidal in urine at therapeutic doses. As a result of such inactivations, the vital biochemical processes of protein synthesis, aerobic energy metabolism, DNA synthesis, RNA synthesis, and cell wall synthesis are inhibited.
Nitrofurantoin is reduced by bacterial flavoproteins to reactive intermediates which inactivate or alter bacterial ribosomal proteins and other acromolecules. The mechanism of the antimicrobial action of nitrofurantoin is unusual among antibacterials. Nitrofurantoin is a nitrofuran antimicrobial agent with activity against certain Gram-positive and Gram-negative bacteria. Unlike many drugs, the presence of food or agents delaying gastric emptying can increase the bioavailability of nitrofurantoin (macrocrystals), presumably by allowing better dissolution in gastric juices. It is highly soluble in urine, to which it may impart a brown color.įollowing a dose regimen of 100 mg four times a day for 7 days, average urinary drug recoveries (0 to 24 hours) on day 1 and day 7 were 37.9% and 35.0%. Blood concentrations at therapeutic dosage are usually low.
The absorption of nitrofurantoin (macrocrystals) is slower and its excretion somewhat less when compared to nitrofurantoin. Nitrofurantoin (macrocrystals) is a larger crystal form of nitrofurantoin. The 50 mg and 100 mg capsules also contain FD&C Yellow No. Inactive Ingredients: Each capsule contains D&C Yellow # 10, FD&C Blue # 1, FD&C Blue # 2, FD&C Red # 40, gelatin, iron oxide black, lactose anhydrous, magnesium stearate, pregelatinized corn starch, sodium lauryl sulfate, talc and titanium dioxide.