Five-day courses of nitrofurantoin are equivalent clinically and microbiologically to a three-day course of trimethoprim-sulfamethoxazole (TMP-SMX) for acute uncomplicated cystitis in women, researchers report. The finding could enable clinicians to slow the emergence of microbial resistance to fluoroquinolones, which frequently are used as an alternative to TMP-SMX. Though TMP-SMX is the preferred regimen for acute cystitis, it is often contraindicated because of resistance or allergy. In many regions of the country, resistance turns up in >20% of women.

Nitrofurantoin has been used for more than 50 years for uncomplicated cystitis. It remains active against most uropathogens, but its popularity is hindered by a recommended seven-day regimen and concerns about efficacy and tolerance. Few studies have evaluated the drug, especially when used short-term. The new study helps fill that gap.

Kalpana Gupta, MD, MPH, and her colleagues at the University of Washington School of Medicine in Seattle randomly assigned 338 women (aged 18-45 years) with acute uncomplicated cystitis to receive either nitrofurantoin 100 mg twice daily for five days or one double-strength TMP-SMX tablet twice daily for three days. Clinical cure was achieved in 79% of the TMP-SMX group and 84% of the nitrofurantoin group. Clinical and microbiologic cure rates at the first follow-up visit were equivalent. The researchers concluded that a five-day course of nitrofurantoin “should be considered an effective fluoroquinolone-sparing alternative for the treatment of acute cystitis in women” (Arch Intern Med. 2007;164:2207-2212).

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