Background Nitrofurantoin is a valuable agent in the treatment of cystitis due to its activity against most common uropathogens with virtually no development of resistance since its discovery in 1953. However, it has been contraindicated in patients with creatinine clearance (CrCl) <60 mL/min, as earlier studies have suggested that it would lose its effectiveness in renal impaired patients due to inadequate urinary concentrations, thus limiting its use. Recent studies had not found nitrofurantoin to be associated with an increased risk of ineffectiveness in patients with renal impairment, although there are conflicting study results on the association between renal impairment and adverse events.

Purpose To determine if treatment of cystitis with nitrofurantoin in renal impaired patients was associated with lower cure rates and if higher rates of adverse events were observed in renal impaired patients.

Material and methods A cohort of 272 patients from Changi General Hospital treated for cystitis with nitrofurantoin from 2011 to 2014, identified from electronic hospital records, were analysed. Renal impairment was defined as CrCl <60 mL/min and non-renal impairment as CrCl ≥60 mL/min. Cure rates were based on clinical and/or microbiological cure. Clinical cure of cystitis was defined by the successful discontinuation of a course of nitrofurantoin, no other antibiotics for treatment of cystitis was prescribed 2 weeks from the start of a course of nitrofuratoin and no further documentation of cystitis symptoms. Microbiological cure was defined as a repeat negative urine culture. Adverse events associated with nitrofurantoin were also recorded. The association between cure rates and renal impairment was determined with the χ² test of independence.

Results Cure rates between patients without renal impairment and patients with renal impairment were similar (cure rates of 79.4% in non-renal impaired patients vs 79.5% in renal impaired patients, X² (1, n = 272)=0.004, p = 0.977). However, no adverse events were found to be associated with nitrofurantoin, possibly as adverse events were poorly documented.

Conclusion NItrofurantoin was able to achieve satisfactory cure rates in renal impaired patients with CrCl < 60 mL/min, although further studies in larger cohorts would have to be conducted to determine if higher rates of adverse events were observed in renal impaired patients.

References and/or Acknowledgements Changi General Hospital for kindly supporting the study

No conflict of interest.