SAN DIEGO – Oral fosfomycin, a drug used for more than 4 decades to treat urinary tract infections in women, has gained a new life as a promising treatment for chronic prostatitis.
In the largest patient series reported to date, a 6-week course of fosfomycin resulted in an 85% clinical cure rate in 20 men with chronic prostatitis due to multidrug-resistant pathogens, Dr. Ilias Karaiskos reported at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
This is a most welcome development because chronic prostatitis is a common condition and Escherichia coli – the number-one pathogen – is becoming increasingly resistant to fluoroquinolones, long considered the first-line therapy. The quinolone resistance issue is of particular concern because most other antibiotics lack the pharmacokinetics required to penetrate the prostate gland, explained Dr. Karaiskos of Hygeia General Hospital in Athens.
A recent study by other investigators showing that fosfomycin penetrates the prostate and achieves potentially therapeutic levels (Clin Infect Dis. 2014 Feb;58:e101-5) inspired Dr. Karaiskos and coworkers to conduct their open 20-patient trial. Participants averaged 2.25 prior episodes of prostatitis.
Urine cultures showed that the most common pathogen was indeed E. coli, and that 15 of the 20 strains were resistant to fluoroquinolones. Most strains were also resistant to minocycline and trimethoprim-sulfamethoxazole. However, all strains were sensitive to fosfomycin (Monurol).
Dosing of fosfomycin in the study was 3 g once daily for the first week, then 3 g every 48 hours for the next 5 weeks.
Seventeen of 20 patients experienced clinical cure, defined as resolution of all symptoms plus absence of any evidence of inflammation upon follow-up imaging of the prostate by transrectal ultrasound or MRI upon treatment completion after 6 weeks of fosfomycin. Two patients failed to respond, and one discontinued treatment due to diarrhea.
Diarrhea was the most common treatment-emergent adverse event, affecting 5 of 20 patients. In most instances, diarrhea subsided when the dosing intervals were extended.
Further studies are needed to clarify the best fosfomycin dosing regimen for chronic prostatitis, Dr. Karaiskos said. For uncomplicated urinary tract infections the drug is typically given in a single megadose.
Dr. Karaiskos reported having no financial conflicts regarding this study, conducted free of commercial support.