Intravenous and intramuscular pharmacokinetics of a single-daily dose of disodium-fosfomycin in cattle, administered for 3 days

Pharmacokinetics/pharmacodynamics cut-off determination for fosfomycin using Monte Carlo simulation in healthy horses

Fosfomycin (FOM) is an approved veterinary medicinal product for large animals in Japan, but Clinical breakpoint (CBP) for antimicrobial susceptibility test (AST) is not defined for animals. This study aimed at conducting a pharmacokinetics/pharmacodynamics (PK/PD) analysis to determine the PK/PD cutoff for the CBP in horses. Drug concentrations following single intravenous administration (IV) of 20 mg/kg body weight (BW) FOM in nine horses were measured using liquid chromatography/mass spectrometry. The data were modelled using a nonlinear mixed-effects model, followed by Monte Carlo simulations. A 90% probability of target attainment for a PK/PD target of the ratio of Area Under the free plasma concentration-time curve divided by the minimal inhibitory concentration (MIC) >24 hr was set as PK/PD cut-off. The PK/PD cutoff for FOM 20 mg/kg BW q12 hr IV was estimated with the MIC value of ≤16.0 mg/L, and this regimen was considered effective against E. coli (MIC90; 16.0 mg/L) in healthy horses based on the MIC90 values of the wild population. Owing to the relevance of FOM to human health, veterinarians should use q 12 hr FOM 20 mg /kg against E. coli infections with an MIC <16 µg/mL, as suggested by our PK/PD cutoff after AST.

Fosfomycin Resistance in Bacteria Isolated from Companion Animals (Dogs and Cats)

Fosfomycin is an old antibacterial agent, which is currently used mainly in human medicine, in uncomplicated Urinary Tract Infections (UTIs). The purpose of this review is to investigate the presence and the characteristics of Fosfomycin resistance in bacteria isolated from canine or feline samples, estimate the possible causes of the dissemination of associated strains in pets, and underline the requirements of prospective relevant studies. Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines were used for the search of current literature in two databases. A total of 33 articles were finally included in the review. Relevant data were tracked down, assembled, and compared. Referring to the geographical distribution, Northeast Asia was the main area of origin of the studies. E. coli was the predominant species detected, followed by other Enterobacteriaceae, Staphylococci, and Pseudomonas spp. FosA and fosA3 were the more frequently encountered Antimicrobial Resistance Genes (ARGs) in the related Gram-negative isolates, while fosB was regularly encountered in Gram-positive ones. The majority of the strains were multidrug-resistant (MDR) and co-carried resistance genes against several classes of antibiotics and especially β-Lactams, such as bla_CTX-M and mecA. These results demonstrate the fact that the cause of the spreading of Fosfomycin-resistant bacteria among pets could be the extended use of other antibacterial agents, that promote the prevalence of MDR, epidemic strains among an animal population. Through the circulation of these strains into a community, a public health issue could arise. Further research is essential though, for the comprehensive consideration of the issue, as the current data are limited.

A Real-world Study on Prescription Pattern of Fosfomycin in Critical Care Patients

Background

This study presents a real-world scenario for prescription pattern, efficacy, and safety data on the current clinical use of intravenous fosfomycin in critically ill patients in Indian settings.

Patients and methods

This was a retrospective cohort study conducted for a period of 10 months among critically ill patients admitted to hospital's critical care unit. The primary objective of the study was to analyze the prescription pattern of intravenous fosfomycin, and the secondary objective was to evaluate the safety profile and patient outcomes.

Results

A total of 309 patients were enrolled, and they were diagnosed with bacteremia (45.3%), pneumonia (15.85%), septic shock (14.24%), and urinary tract infections (UTI) (13.91%). The average dose of fosfomycin given was 11.7 ± 4.06 gm/day. The average duration of the therapy was 4.85 ± 3.59 days with a median duration of 4 days. Fosfomycin was given at 8 hourly dosing frequency to maximum (45.6%) cases. Hypokalemia was the most observed adverse event. The overall survival was seen in 55% of patients.

Conclusion

Our data suggest that UTI, infection caused by Escherichia coli, and a daily dose of >12 g were associated with better clinical outcomes. The overall survival of critically ill patients receiving fosfomycin was 55%.

How to cite this article

Zirpe KG, Mehta Y, Pandit R, Pande R, Deshmukh AM, Patil S, et al. A Real-world Study on Prescription Pattern of Fosfomycin in Critical Care Patients. Indian J Crit Care Med 2021;25(9):1055–1058.

Ex vivo penetration of fosfomycin into healthy and Lawsonia intracellularis-colonized swine intestinal mucosa

Fosfomycin (FOS) is an antibiotic used, mostly in Latin America, for the treatment of lung and enteric infections of pigs. Intracellular fluids of enterocytes can act as biophase for Lawsonia intracellularis, the causative agent of porcine proliferative enteropathy (PPE). The aim of this study was to determine whether the presence of L. intracellularis in the enterocytes modifies FOS penetration. Eight healthy pigs in growth-finishing stage were used to produce healthy (group A) and L. intracellularis-colonized (group B) intestinal explants. For both groups, treatment consisted of a 580 μg/ml concentration of calcium FOS, which was added to each explant (0.5-6 hr). For group B, the Enterisol Ileitis^® vaccine was used as source of the micro-organism. Previously to the assay, the time necessary for L. intracellularis to colonize the enterocytes was defined. Also, a PCR protocol was optimized to determine the presence of the pathogen in the explants. There were nonstatistical differences for the penetration of the antibiotic into healthy and L. intracellularis-colonized enterocytes. MIC₉₀ of FOS for L. intracellularis is unknown; nevertheless, MIC₉₀ of various antibiotics ranges between 0.125 and 128 μg/ml. FOS reaches inside the enterocyte concentrations which surpass the MICs₉₀ of other antibiotics that also act by the inhibition of cell wall synthesis; however, further studies should be carried out to determine fosfomycin MIC₉₀ for L. intracellularis to discern the usefulness of this antibiotic in the treatment of PPE.

Fosfomycin residues in colostrum: Impact on morpho-physiology and microbiology of suckling piglets

Fosfomycin is a broad-spectrum bactericidal antibiotic widely used in pig farms for the treatment of a wide variety of bacterial infections. In this study, the elimination of disodium fosfomycin in colostrum/milk of the sow and the impact of this antibiotic on the microbiota and intestinal morpho-physiology of suckling piglets were analyzed. The average amount of fosfomycin eliminated in colostrum (after administration of 15 mg/kg IM) during the first 10 hr postpartum was 0.85 μg/ml, and the mean residual amount ingested by the piglets was 0.26 mg/kg. The elimination profile of fosfomycin concentrations in colostrum occurs at a time of profound changes in the morpho-physiology of the gastrointestinal tract of the piglet. However, the studied concentrations did not produce imbalances on the microbiota or on the morpho-physiology of the gastrointestinal tract of the piglet. Concentrations of fosfomycin were maintained in the mammary gland above the MIC for more than 8 hr for pathogenic bacteria of productive importance. This would indicate that fosfomycin may be considered safe for the specific treatment of bacterial infectious processes in sows during the peri- and postpartum period. This first study with disodium fosfomycin stimulates awareness in the proper use of antimicrobials at farrowing.

Fosfomycin

The treatment of bacterial infections suffers from two major problems: spread of multidrug-resistant (MDR) or extensively drug-resistant (XDR) pathogens and lack of development of new antibiotics active against such MDR and XDR bacteria. As a result, physicians have turned to older antibiotics, such as polymyxins, tetracyclines, and aminoglycosides. Lately, due to development of resistance to these agents, fosfomycin has gained attention, as it has remained active against both Gram-positive and Gram-negative MDR and XDR bacteria. New data of higher quality have become available, and several issues were clarified further. In this review, we summarize the available fosfomycin data regarding pharmacokinetic and pharmacodynamic properties, the in vitro activity against susceptible and antibiotic-resistant bacteria, mechanisms of resistance and development of resistance during treatment, synergy and antagonism with other antibiotics, clinical effectiveness, and adverse events. Issues that need to be studied further are also discussed.

Disodium-fosfomycin pharmacokinetics and bioavailability in post weaning piglets

Disodium-fosfomycin pharmacokinetics has been studied in different species after oral, intravenous, intramuscular and subcutaneous administration. At present there are neither documented clinical experiences of the use of fosfomycin in pigs nor any published studies in weaning piglets, although it is a period of high incidence of infectious diseases. The pharmacokinetics and the bioavailability of sodium fosfomycin were studied in post weaning piglets after intravenous and intramuscular administration of 15 mg/kg of body weight. Plasma concentrations were measured by a high-performance liquid ms/ms. After IV administration the area under the fosfomycin concentration:time curve in plasma was AUC(0-12) of 120.00 ± 23.12 μg h/ml and the volume of distribution (Vd) of 273.00 ± 40.70 ml/kg. The elimination was rapid with a plasma clearance of 131.50 ± 30.07 ml/kg/h and a T(1/2) of 1.54 ± 0.40 h. Peak serum concentration (Cmax), Tmax, AUC(0-12) and bioavailability for the IM administration were 43.00 ± 4.10 μg/ml, 0.75 ± 0.00 h, 99.00 ± 0.70 μg h/ml and 85.5 ± 9.90% respectively. Different authors have determined a minimum inhibitory concentration (MIC90) ranging from 0.25 μg/ml for Streptococcus sp. and 0.5 μg/ml for Escherichia coli. Considering the above, and according to the values of plasma concentration vs time profiles observed in this study, effective plasma concentrations of fosfomycin for sensitive bacteria can be obtained following IV and IM administration of 15 mg/kg in piglets.

Pharmacokinetics of a single bolus intravenous, intramuscular and subcutaneous dose of disodium fosfomycin in horses

Pharmacokinetic parameters of fosfomycin were determined in horses after the administration of disodium fosfomycin at 10 mg/kg and 20 mg/kg intravenously (IV), intramuscularly (IM) and subcutaneously (SC) each. Serum concentration at time zero (C(S0)) was 112.21 +/- 1.27 microg/mL and 201.43 +/- 1.56 microg/mL for each dose level. Bioavailability after the SC administration was 84 and 86% for the 10 mg/kg and the 20 mg/kg dose respectively. Considering the documented minimum inhibitory concentration (MIC(90)) range of sensitive bacteria to fosfomycin, the maximum serum concentration (Cmax) obtained (56.14 +/- 2.26 microg/mL with 10 mg/kg SC and 72.14 +/- 3.04 microg/mL with 20 mg/kg SC) and that fosfomycin is considered a time-dependant antimicrobial, it can be concluded that clinically effective plasma concentrations might be obtained for up to 10 h administering 20 mg/kg SC. An additional predictor of efficacy for this latter dose and route, and considering a 12 h dosing interval, could be area under the curve AUC(0-12)/MIC(90) ratio which in this case was calculated as 996 for the 10 mg/kg dose and 1260 for the 20 mg/kg dose if dealing with sensitive bacteria. If a more resistant strain is considered, the AUC(0-12)/MIC(90) ratio was calculated as 15 for the 10 mg/kg dose and 19 for the 20 mg/kg dose.

Pharmacokinetics of disodium-fosfomycin in mongrel dogs

Pharmacokinetic variables of fosfomycin were determined after administration of buffered disodium-fosfomycin intravenously (IV), intramuscularly (IM), subcutaneously (SC) and orally (PO), in mongrel dogs, at 40 and 80 mg/kgday for three days. Renal integrity was also assessed by measuring key serum variables. Day 1, day 2 and day 3 plasma concentration vs. time profiles were undistinguishable, but there appears to be a lineal increase in serum concentrations vs. time with the dose. A non-accumulative kinetic behavior was observed after three days with both doses and most pharmacokinetic variables remain unaltered. Considering a MIC range from 1 mirog/mL to 16 microg/mL of fosfomycin in serum for sensitive bacteria, and a negligible plasma protein binding of fosfomycin (<0.5%), useful plasma concentrations can only be achieved after the SC injection of 80 mg/kg every 12h, having a C(max)=18.96+/-0.3 microg/mL; a T(1/2beta)=2.09+/-0.06 microg/mL and a bioavailability of 84-85%. No alterations were observed in serum variables of kidney-related biochemical values.

Rapid and selective liquid chromatographic/tandem mass spectrometric method for the determination of fosfomycin in human plasma

A rapid and selective liquid chromatographic/tandem mass spectrometric method for determination of fosfomycin was developed and validated. Following protein-precipitation, the analyte and internal standard (fudosteine) were separated from human plasma using an isocratic mobile phase on an Ultimate XB-CN column. An API 4000 tandem mass spectrometer equipped with Turbo IonSpray ionization source was used as detector and was operated in the negative ion mode. Multiple reaction monitoring using the precursor to product ion combinations of m/z 137-->79 and m/z 178-->91 was performed to quantify fosfomycin and fudosteine, respectively. The method was linear in the concentration range of 0.10-12.0 microg/mL using 50 microL of plasma. The lower limit of quantification was 0.10 microg/mL. The intra- and inter-day relative standard deviation over the entire concentration range was less than 10.6%. Accuracy determined at three concentrations (0.25, 1.00 and 8.00 microg/mL for fosfomycin) ranged from -1.0% to -4.2% in terms of relative error. Each plasma sample was chromatographed within 5.0 min. The method was successfully used in a bioequivalence study of fosfomycin in human plasma after an oral administration of capsules containing 1.0 g fosfomycin (approximately 1.3g calcium fosfomycin).