Urinary concentrations of fosfomycin after a single 3 g dose of fosfomycin to elderly nursing-home patients

Abstract

The urinary concentrations of fosfomycin in 7 elderly patients with impaired renal function (mean creatinine clearance 40 ml/min) were studied after a single oral dose of 3 g fosfomycin as the trometamol salt. Urine samples were collected as 12 h portions for 84 h. Urinary concentrations of fosfomycin were 1,383 mg/l (range 314 to 4,200 mg/l) in the first 12 h and gradually declined to 165 mg/l (range 65 to 365 mg/l) between 36 and 48 h. 37% of the oral dose was recovered in the urine unchanged after 84 h, but a wide range (15-60%) in urinary recovery was observed. The elimination half-lives in the patients (estimated from the renal excretion profile of fosfomycin) ranged between 7 and 24 h. These data suggest that the urinary levels obtained in this patient population exceed the minimum inhibiting concentration of the usual pathogens involved in uncomplicated cystitis for at least 48 h. After 24 h the urinary concentrations of fosfomycin are higher than those reported for healthy young subjects.

High interindividual variability in urinary fosfomycin concentrations in healthy female volunteers

“…When fosfomycin is administered to an elderly patient with renal impairment the elimination half-life could be longer. However, the reported half-life values are comparable with those found in the elderly, indicating that the influence of renal impairment falls within the high variation we reported [13].…”

Treatment of infections caused by multidrug-resistant Gram-negative bacteria: report of the British Society for Antimicrobial Chemotherapy/Healthcare Infection Society/British Infection Association Joint Working Party†

“…A single oral dose of 3 grams results in a plasma C max of 22-32 mg/L and a urine maximum concentration (Umax ) of 1053-445mg/L 413 The urinary concentration remains inhibitory for E. coli for at least 48 hours. In elderly patients with a mean GFR of 40mL/min concentrations after 24 hours exceeded those reported for healthy young subjects but there was considerable variation in excretion rates 414 .…”

Fosfomycin

“…Dose adjustment for both oral fosfomycin formulations is not recommended for elderly individuals with endogenous creatinine clearances of Ͼ50 ml/min per 1.73 m 2 (171). However, in elderly patients with impaired renal function (mean creatinine clearance of 40 ml/min), the fosfomycin urinary concentration was higher than that in healthy adults (205).…”