Issue 33 July 2011
2. Urinary infections: Old is Gold.

    The progressing indications of antibiotic resistance to trimethoprim-sulfamethoxazole (TMP-SMX) and quinolones has made uncomplicated urinary tract infection (UTI) a nightmare to treat recently. The alternative treatment method according to many experts now is the resurrection of the venerable antibiotic nitrofurantoin as a first-line treatment for uncomplicated cystitis.

    Mayo Clinic researchers constructed a decision tree, which included costs of the drugs and of complications to analyze the costs of common empirical antibiotic choices for uncomplicated UTI at different community levels of drug resistance.

    When 3-day courses of TMP-SMX or a fluoroquinolone were compared with a standard 5-day course of nitrofurantoin, the model indicated that nitrofurantoin became the most cost-effective option when the community's level of TMP-SMX resistance exceeded 17% and its quinolone resistance exceeded 12%. (Below these levels, the 3-day drug with the least resistance was favoured.) Recent surveys indicate that TMP-SMX resistance exceeds 15% everywhere in the U.S. and exceeds 40% in some areas; fluoroquinolone resistance is as high as 20% in some regions.

    This is the second major shout-out for nitrofurantoin this year. Earlier, the Infectious Diseases Society of America endorsed it as a first-line treatment for cystitis (JW Infect Dis Feb 23 2011) not because of cost, but for efficacy and ecology: Minimal resistance to this drug has developed among Enterobacteriaceae, and, because ingested drug largely stays in the urine, little resistance is likely to evolve. Clinicians should keep this old standby in mind. However, they also should remind themselves of its potential toxicity, which includes idiosyncratic pneumonitis and hemolysis in glucose-6-phosphate dehydrogenase-deficient patients; in addition, the drug is contraindicated when creatinine clearance is <60 mL/minute.


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