URINARY CONCENTRATIONS OF FOSFOMYCIN AFTER A SINGLE 3G DOSE OF FOSFOMYCIN TO ELDERLY NURSING-HOME PATIENTS

The urinary concentrations of fosfomycin in 7 elderly patients with im paired renal function (mean creatinine clearance 40 ml/min) were studi ed 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 concen trations of fosfomycin were 1,383 mg/l (range 314 to 4,200 mg/l) in th e 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 wa s 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 p opulation exceed the minimum inhibiting concentration of the usual pat hogens involved in uncomplicated cystitis for at least 48 h. After 24 h the urinary concentrations of fosfomycin are higher than those repor ted for healthy young subjects.