Pharmacokinetic profile of fosfomycin trometamol (Monuril)

The kinetics of fosfomycin in serum and in urine was studied in 5 healthy volunteers after intravenous administration of disodium fosfomycin and after oral administration of trometamol fosfomycin at 50 mg/kg. The presence of secondary peaks in serum kinetics, more evident after oral administration, requires the use of a compartmental model with enterohepatic recirculation to which all the data of each subject were simultaneously fitted. The following values of the various pharmacokinetic parameters were calculated: central volume 10.6 +/- 0.92 liters; bioavailability 0.58 +/- 0.04; delay time in the recirculation 2.00 +/- 0.92 h; half-life 2.43 +/- 0.31 h; total clearance 8.3 +/- 1.6 l/h; urinary clearance 7.0 +/- 0.9 l/h; peak level 32.1 +/- 3.0 micrograms/ml; time of the peak 2.2 +/- 0.44 h. The fosfomycin concentration in urine remains above 1,000 micrograms/ml for 12 h and above 100 micrograms/ml for 48 h. The oral kinetics of fosfomycin is dose-dependent, as shown by serum and urine kinetics in other 4 volunteers after oral administration of 2, 3, 4 and 5 g; the fraction of the dose excreted by urine goes from 50% for 2 g to 22% for 5 g.