Multiple-Dose Oral Fosfomycin for Treatment of Complicated Urinary Tract Infections in the Outpatient Setting

BACKGROUND: Few published studies exist to describe the off-label use of multiple-dose fosfomycin for outpatient treatment of complicated urinary tract infections (UTI). The purpose of this study was to characterize the patients, infections, drug susceptibilities, and outcomes of multiple-dose fosfomycin episodes for outpatient UTI treatment. METHODS: This retrospective study evaluated patients who received an outpatient prescription for multiple-dose fosfomycin between July 1999 and June 2018. Multiple-dose fosfomycin prescriptions dispensed for UTI prophylaxis were excluded. The primary outcome was clinical resolution (complete resolution of signs and symptoms) of infection within 30 days. Secondary outcomes included descriptions of antibiotics and cultures before and after treatment, 30-day bacteriologic resolution (posttreatment urine culture <10(3) colony-forming units of the original pathogen), and 90-day healthcare utilizations for UTI or pyelonephritis. Data were analyzed using descriptive statistics. RESULTS: Of 171 multiple-dose fosfomycin treatment episodes, the most common regimen was 1 dose every 3 days, mean duration of 6.1 days. Clinical resolution occurred in 115 of 171 (67.3%) episodes, and bacteriologic resolution occurred in 37 of 76 (48.7%) episodes with posttreatment cultures. Most patients used antibiotics or had urine cultures before treatment (81.9% and 97.7%, respectively). Additional antibiotic use, urine cultures, and healthcare utilizations within 90 days posttreatment occurred in 51.5%, 66.1%, and 24.6% of patients, respectively. CONCLUSIONS: For treating complicated UTI with multiple-dose fosfomycin, clinical resolution occurred in 2 of 3 treatment episodes and bacteriologic resolution occurred in one-half of treatment episodes. Future research is necessary to determine the relative efficacy and safety and optimal dosing regimen, duration, and population for UTI treatment with multiple-dose fosfomycin.