In routine care, nitrofurantoin is frequently prescribed for patients with low estimated glomerular filtration rate, but the safety and effectiveness of this practice remain uncertain. 8 Two recent retrospective studies suggested that the effectiveness of nitrofurantoin is no different between those with and those without reduced kidney function 9, 10 however, both studies included a limited number of patients with estimated glomerular filtration rate below 40 mL/min per 1.73 m 2. 5, 6Ī recent review suggested that the drug be avoided only for those with estimated glomerular filtration rate below 40 mL/min per 1.73 m 2. 7 However, this recommendation remains controversial, as the supporting evidence originates from studies with small sample sizes (< 20 patients with reduced creatinine clearance) and outcomes of drug concentration in the urine, rather than treatment success. 5, 6 Therefore, nitrofurantoin is not recommended for patients with estimated glomerular filtration rate below 60 mL/min per 1.73 m. 4 The renal elimination of nitrofurantoin is reduced in patients with low estimated glomerular filtration rate, which can increase the risk of treatment failure for urinary tract infection and possibly also the risk of adverse events caused by elevated blood concentrations of the drug. 3 Reduction in the estimated glomerular filtration rate is common among older adults, and over 25% of those 65 years of age or older have an estimated glomerular filtration rate less than 60 mL/min per 1.73 m 2. 1, 2 Therapeutic concentrations of nitrofurantoin are achieved only in the urine, and the drug is eliminated primarily by glomerular filtration, with some secretion through the renal tubules.
Nitrofurantoin is a first-line antibiotic commonly used to treat uncomplicated urinary tract infection, and an estimated 25 million prescriptions are filled worldwide each year.