There are limited intravenous fosfomycin disodium (IVFOS) dosing regimens to treat carbapenem-resistant Enterobacterales (CRE) infections. This study aimed to use Monte Carlo simulation (MCS) for evaluation of IVFOS dosing regimens in critically ill patients with CRE infections. The dosing regimens in critically ill patients with various creatinine clearance were evaluated with MCS using minimum inhibitory concentration (MIC) distributions of fosfomycin against CRE clinical isolates in Thailand and the 24 h area under the plasma drug concentration–time curve over the minimum inhibitory concentration (AUC0-24/MIC) of ≥21.5 to be a target for IVFOS. The achieved goal of the probability of target attainment (PTA) and a cumulative fraction of response (CFR) were ≥90%. A total of 129 non-duplicated CRE clinical isolates had MIC distributions from 0.38 to >1024 mg/L. IVFOS 8 g every 8 h, 1 h, or 4 h infusion, could achieve approximately 90% PTA of AUC0-24/MIC target to treat CRE infections with MICs ≤ 128 mg/L. According to PTA target, an IVFOS daily dose to treat carbapenem-resistant Escherichia coli based on Clinical Laboratory Standards Institute (CLSI) breakpoints for urinary tract infections and one to treatment for CRE infections based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints were 16 g/day and 8 g/day, respectively. All dosing regimens of IVFOS against CRE achieved CFR ≤ 70%. This study proposes the IVFOS dosing regimens based on CLSI and EUCAST breakpoints for the treatment of CRE infections. However, further clinical studies are needed to confirm the results of these findings.

Limited information exists regarding the optimal dose of posaconazole delayed-release tablet for the treatment of invasive mold infection. Here, we report the case of a previously healthy 44-year-old Thai man who developed coexisting invasive pulmonary aspergillosis and mucormycosis following a car accident. He was treated with posaconazole delayed-release tablet. This report describes the pharmacokinetic/pharmacodynamic study, safety profile, and determination of the appropriate dosage of posaconazole delayed-release tablet in a patient with coexisting invasive aspergillosis and mucormycosis. Posaconazole exposure was analyzed by noncompartmental model. Ratio of area under the plasma concentration-time curve over the minimum inhibitory concentration (AUC/MIC) was applied to maximize the efficacy of posaconazole. The loading dose of 300 mg q 12 hrs was found to be potentially insufficient for achieving the AUC/MIC target for treatment of invasive mold infection with minimum inhibitory concentrations >0.01 mg/L. Early therapeutic drug monitoring to detect the drug concentration of posaconazole delayed-release tablet is necessary so that dosing adjustments can be made, as needed. In addition, a maintenance dose of either 400 or 300 mg once daily could achieve the AUC/MIC targets. These maintenance dosing regimens effectuated a successful clinical outcome with minimal adverse events.

Chloroquine (CQ) exhibited promising in vitro activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but the optimal dosage regimens remain unknown. Our objective was to explore the optimal chloroquine phosphate (CQP) dosage regimens for early achievement of virological clearance within 48-72 hours to diminish in-hospital transmission to front-line healthcare workers. A 10,000-subject Monte Carlo simulation was performed to calculate both probability of efficacy and safety attainment (PTA) using pharmacokinetic (PK) parameters obtained from the published population PK study. Dosage regimens that early achieved PTA of efficacy (PTAeff) ≥90% within 48-72 hours, while maintained PTA of toxicity (PTAtox) ≤1% were considered optimal. For the previously proposed regimens in published guidelines and clinical studies, all dosage regimens could not achieve ≥90% PTAeff, except one with the highest dosage regimen. Our simulations suggested that large amount of loading dose was required for the early achievement. We designed three dosage regimens containing high loading dose (2-3 gram per day), which early achieved ≥90% PTAeff within 48-72 hours, while also maintained ≤1% PTAtox throughout the treatment course. Further clinical studies are needed to prove the efficacy and safety of our designed regimens.