Population Pharmacokinetics of a Novel Oral Fosfomycin Prophylactic Scheme in the Plasma and Prostate of Patients Undergoing Endoscopic Surgery for Benign Prostatic Hyperplasia

Background and objective: Fosfomycin trometamol may be a valuable option for antimicrobial prophylaxis before urological surgery for benign prostatic hyperplasia. The objective is to develop a population pharmacokinetic model of a novel oral fosfomycin prophylactic scheme in the plasma and prostate of patients undergoing endoscopic surgery for benign prostatic hyperplasia. Methods: One- and two-compartment plasma pharmacokinetic models were fitted to fosfomycin plasma data, and different plasma-prostate linked models were tested by means of non-linear mixed effects modelling. Monte Carlo simulation was used to obtain 1000-subject concentration-time profiles of fosfomycin in the prostate. Probabilities of target attainment ≥ 90% of an area under the plasma concentration-time curve/minimum inhibitory concentration (MIC) > 83.3 and of a 70%t > MIC in the prostate were considered as optimal. Cumulative fractions of response against both wild-type and extended-spectrum beta-lactamase-producing Escherichia coli were calculated. Results: A total of 104 patients, each providing a pair of plasma and prostate concomitant samples were included in the study. A one-compartment pharmacokinetic model was used to describe plasma fosfomycin concentration. Fosfomycin plasma-prostate relationships were adequately described by a direct response model with a power function. Simulations showed that fosfomycin disposition in the prostate was closely related to that in plasma. Optimal probabilities of target attainments were ensured against Enterobacterales having an MIC up to 0.5-1 mg/L in the 12 h vulnerable period after completing the prophylactic scheme. Conclusion: A prophylactic regimen of two doses of oral fosfomycin trometamol 3 g 12 h apart before undergoing prostatic surgery may grant effective concentrations in the prostatic tissue of patients for a 12 h vulnerable period.