Development of a dosing-adjustment tool for fluoroquinolones in osteoarticular infections: The Fluo-pop study.

Fluoroquinolones efficacy depend on both the drug exposure and the level of drug resistance of the bacteria responsible for the infection. Specifically for the Staphylococcus species, which is the microorganism mainly involved in osteoarticular infections (OAI), in-vitro data reported that an AUC/MIC ratio above 115 h maximizes drug efficacy. However, data on OAI patients are lacking and a simple approach to access AUCs is still a clinical issue. We conducted a prospective, single-center study in 30 OAI patients hospitalized in the Rennes University Hospital to model ofloxacin pharmacokinetics and to define a limited sampling strategy (LSS) suitable for ofloxacin and levofloxacin treatments. Modeling was conducted with the Monolix software. The final model was externally validated using levofloxacin data. Monte-Carlo simulations were used to evaluate the probability of target attainment (PTA) of different dosing regimens. Two hundred and ninety-seven (297) ofloxacin concentrations were available for the pharmacokinetic modeling. Ofloxacin pharmacokinetics was best described using a bicompartmental model with a first order elimination, and a transit compartment model absorption. CKD-EPI and sex explained half of ofloxacin pharmacokinetic variability. For LSS, the 0, 1 h and 3 h sampling scheme resulted in the best approach both for BID and TID dosages (R2 adjusted = 91.1% and 95.0%, outliers = 4.8% and 5.0%, respectively). PTA allows choosing the best drug and dosage according to various hypotheses. A simple 3-sample protocol (pre-dose, 1 h after intake and 3 h after intake) to estimate ofloxacin and levofloxacin AUC allows optimal drug dosage for the treatment of osteoarticular infections.

Susceptibility breakpoint for Danofloxacin against swine Escherichia coli.

BACKGROUND: Improper use of antimicrobials results in poor treatment and severe bacterial resistance. Breakpoints are routinely used in the clinical laboratory setting to guide clinical decision making. Therefore, the objective of this study was to establish antimicrobial susceptibility breakpoints for danofloxacin against Escherichia coli (E.coli), which is an important pathogen of digestive tract infections. RESULTS: The minimum inhibitory concentrations (MICs) of 1233 E. coli isolates were determined by the microdilution broth method in accordance with the guidelines in Clinical and Laboratory Standards Institute (CLSI) document M07-A9. The wild type (WT) distribution or epidemiologic cutoff value (ECV) was set at 8 µg/mL with statistical analysis. Plasma drug concentration data were used to establish pharmacokinetic (PK) model in swine. The in vitro time kill test in our study demonstrated that danofloxacin have concentration dependent activity against E.coli. The PK data indicated that danofloxacin concentration in plasma was rapidly increased to peak levels at 0.97 h and remained detectable until 48 h after drug administration. The pharmacodynamic cutoff (COPD) was determined as 0.03 µg/mL using Monte Carlo simulation. To the best of our knowledge, this is the first study to establish the ECV and COPD of danofloxacin against E.coli with statistical method. CONCLUSIONS: Compared to the COPD of danofloxacin against E.coli (0.03 µg/mL), the ECV for E.coli seemed reasonable to be used as the final breakpoint of danofloxacin against E.coli in pigs. Therefore, the ECV (MIC ≤8 µg/mL) was finally selected as the optimum danofloxacin susceptibility breakpoint for swine E.coli. In summary, this study provides a criterion for susceptibility testing and improves prudent use of danofloxacin for protecting public health.

Pharmacokinetic/pharmacodynamic evaluation of marbofloxacin as a single injection for Pasteurellaceae respiratory infections in cattle using population pharmacokinetics and Monte Carlo simulations.

Population pharmacokinetic of marbofloxacin was investigated with 52 plasma concentration-time profiles obtained after intramuscular administration of Forcyl® in cattle. Animal's status, pre-ruminant, ruminant, or dairy cow, was retained as a relevant covariate for clearance. Monte Carlo simulations were performed using a stratification by status, and 1000 virtual disposition curves were generated in each bovine subpopulation for the recommended dosage regimen of 10 mg/kg as a single injection. The probability of target attainment (PTA) of pharmacokinetic/pharmacodynamic (PK/PD) ratios associated with clinical efficacy and prevention of resistance was determined in each simulated subpopulation. The cumulative fraction of response (CFR) of animals achieving a PK/PD ratio predictive of positive clinical outcome was then calculated for the simulated dosage regimen, taking into account the minimum inhibitory concentration (MIC) distribution of Pasteurella multocida, Mannheimia haemolytica, and Histophilus somni. When considering a ratio of AUC0-24 hr /MIC (area under the curve/minimum inhibitory concentration) greater than 125 hr, CFRs ranging from 85% to 100% against the three Pasteurellaceae in each bovine subpopulation were achieved. The PTA of the PK/PD threshold reflecting the prevention of resistances was greater than 90% up to MPC (mutant prevention concentration) values of 1 µg/ml in pre-ruminants and ruminants and 0.5 µg/ml in dairy cows.

Clinical pharmacokinetics and pharmacodynamic target attainment of pazufloxacin in prostate tissue: Dosing considerations for prostatitis.

The present study examined the clinical pharmacokinetics of pazufloxacin in prostate tissue and estimated the probability of target attainment for tissue-specific pharmacodynamic goals related to treating prostatitis using various intravenous dosing regimens. Patients with prostatic hypertrophy received prophylactic infusions of pazufloxacin (500 mg, n = 23; 1000 mg, n = 25) for 0.5 h prior to transurethral prostate resection. Drug concentrations in plasma (0.5-5 h) and prostate tissue (0.5-1.5 h) were measured by high-performance liquid chromatography and used for subsequent noncompartmental and three-compartmental analysis. Monte Carlo simulation was performed to evaluate the probability of target attainment of a specific minimum inhibitory concentration (MIC) in prostate tissue: the proportion that achieved both area under the drug concentration over time curve (AUC)/MIC = 100 and maximum concentration (Cmax)/MIC = 8. Prostatic penetration of pazufloxacin was good with mean Cmax ratios (prostate tissue/plasma) of 0.82-0.99 and for AUC, 0.80-0.98. The probability of reaching target MIC concentrations in prostate tissue was more than 90% for dosing schedules of 0.25 mg/L for 500 mg every 24 h (500 mg daily), 0.5 mg/L for 500 mg every 12 h (1000 mg daily), 1 mg/L for 1000 mg every 24 h (1000 mg daily), and 2 mg/L for 1000 mg every 12 h (2000 mg daily). Importantly, the 2000 mg daily regimen of pazufloxacin produced a profile sufficient to have an antibacterial effect in prostate tissue against clinical isolates of Escherichia coli and Klebsiella pneumonia with MIC values less than 2 mg/L.

Pharmacokinetic and pharmacodynamic evaluations of a 10 mg/kg enrofloxacin intramuscular administration in bearded dragons (Pogona vitticeps): a preliminary assessment.

Enrofloxacin (E) is commonly used in veterinary medicine. It is necessary to perform pharmacokinetic/dynamic studies to minimize the selection of resistant mutants of bacteria and extend the efficacy of antimicrobial agents. Eight healthy adult Pogona vitticeps were assigned into two groups of equal size and treated with a single intramuscular injection of E at 10 mg/kg. Blood samples were withdrawn at different scheduled times for each group, and rectal swabs were collected. E and ciprofloxacin (active metabolite) blood concentrations were quantified by an HPLC validated method, while the in vitro antimicrobial susceptibility was evaluated by the Kirby-Bauer disc diffusion susceptibility test. The pharmacokinetic profiles of E gave similar pharmacokinetic parameters irrespective of the collection time schedule. Bacteria isolation showed the presence of both E. coli, Salmonella enterica subspecies enterica and subspecies 3a, Proteus spp., and Pseudomonas spp. The majority of isolated colonies were sensitive to E, but the treatment did not reduce the number of bacteria in faeces. Results suggest that E is able to reach blood concentrations high enough to kill susceptible bacteria (MIC < 0.9 µg/mL), but at the same time does not significantly affect intestinal bacteria.

Assessment of 8-methosypsoralen, lomefloxacin, sparfloxacin, and Pirfenidone phototoxicity in Long-Evans rats.

Phototoxicity has a strong impact on drug development. Although several animal models have been developed to quantitatively assess human risks, none have been validated for standardized use. In this study, we validated an in vivo phototoxicity model using Long-Evans (LE) rats treated with 4 well-known phototoxic drugs, namely 8-methoxypsoralen, lomefloxacin, sparfloxacin, and pirfenidone. Daily macroscopic observations of skin and eyes, ophthalmological examinations 4 days after dosing, and blood sampling for toxicokinetics (TKs) were performed after exposure of treated animals to ultraviolet, and dose-dependent eye and/or skin reactions were noted for all compounds. Margins of safety were calculated when possible and correlated well with known relative phototoxicity of the 4 compounds. We conclude that the present in vivo phototoxicity assay using LE rats with TK analysis can be used to quantitatively predict the risk of pharmaceutical phototoxicity in humans.

Gemifloxacin mesylate (GFM): dissolution test based on in vivo data.

Gemifloxacin mesylate (GFM) is a synthetic, broad-spectrum, fluoroquinolone antibacterial agent. It is different from other class members because it achieves adequate plasma concentrations to inhibit both topoisomerase IV and gyrase. The aim of this study was to develop and validate a dissolution test for GFM in coated tablets, using a simulated absorption profile based on in vivo data obtained from the literature. The fraction and percentage of the dose absorbed were calculated using model-dependent Loo-Riegelman approach for two compartments. The best in vitro dissolution profile was obtained using 900 mL of pH 6.0 phosphate buffer as a dissolution medium at 37 °C ± 0.5 °C and paddles at 50 rpm. The in vitro dissolution samples were analyzed using a liquid chromatography method, and the validation was performed according to USP 34 (2011). The method showed specificity, precision, accuracy, robustness and linearity. Under these conditions, a level-A in vitro-in vivo correlation was suggested (r = 0.9926). The prediction errors were calculated to determine the validity and accuracy of the suggested correlation. The dissolution test can be used to evaluate the dissolution profile of GFM-coated tablets and minimize the number of bioavailability studies as part of new formulation development.

Estimating marbofloxacin withdrawal time in broiler chickens using a population physiologically based pharmacokinetics model.

Residue depletion of marbofloxacin in broiler chicken after oral administration at 5 mg/kg/day for three consecutive days was studied in this study. The areas under the concentration-time curve from 0 h to ∞ (AUC0-∞ s) of marbofloxacin in tissues and plasma were used to calculate tissue/plasma partition coefficients (PX s). Based on PX s and the other parameters derived from published studies, a flow-limited physiologically based pharmacokinetics (PBPK) model was developed to predict marbofloxacin concentrations, which were then compared with those derived from the residue depletion study so as to validate this model. Considering individual difference in drug disposition, a Monte Carlo simulation included 1000 iterations was further incorporated into the validated model to generate a population PBPK model and to estimate the marbofloxacin residue withdrawal times in edible tissues. The withdrawal periods were compared to those derived from linear regression analysis. The PBPK model presented here successfully predicted the measured concentrations in all tissues. The withdrawal times in all edible tissues derived from the population PBPK model were longer than those from linear regression analysis, and based on the residues in kidney, a withdrawal time of 4 days was estimated for marbofloxacin after oral administration at 5 mg/kg/day for three consecutive days. It was shown that population PBPK model could be used to accurately predict marbofloxacin residue withdrawal time in edible tissues in broiler chickens.

Approved medication of water with enrofloxacin to treat turkey colibacillosis: assessment of efficacy using a PK/PD approach.

The efficacy of administering enrofloxacin at 10mg/kg in medicated water to turkeys was evaluated by applying a PK/PD approach to the kinetic parameters obtained after oral pulsed administration and to the MIC values of avian pathogenic Escherichia coli (APEC) strains isolated from commercial turkey flocks. The kinetic parameters of enrofloxacin were evaluated in 10 healthy and 10 colisepticemic turkeys that received the drug dissolved in medicated water at 89 µg/mL and 71 µg/mL, respectively, for 10h/day for 5 days. Blood samples were collected for 24h from all turkeys on the last day of treatment, and the serum was analysed by HPLC with fluorimetric detection. The mean AUC (7374.53±1067.64 h ng/mL and 7656.95±1460.61 h ng/mL) and C(max) values (673.09±186.18 ng/mL and 543.50±68.75 ng/mL) obtained for healthy and sick turkeys were not significantly different. High-level resistance was observed in 30.3% of strains, 40.5% exhibited intermediate resistance, and only 29.2% were susceptible; the MIC(50) and MIC(90) values were 1mg/L and 32 mg/L, respectively. The PK/PD parameters C(max)/MIC(50) (0.67 and 0.54 for healthy and sick turkeys, respectively) and AUC/MIC(50) (7.37 and 7.66) were lower than the efficacy breakpoints reported for fluoroquinolones. These results indicate that authorised dosage of enrofloxacin used in pulsed medicated water administration could be ineffective against more than the 70% of circulating APEC strains, indicating the need to test the drug susceptibility of APEC prior to administering the drug and adopting a more convenient medication schedule for mass treatment.

Role of mixed ion channel effects in the cardiovascular safety assessment of the novel anti-MRSA fluoroquinolone JNJ-Q2.

BACKGROUND AND PURPOSE: JNJ-Q2, a novel broad-spectrum fluoroquinolone with anti-methicillin-resistant Staphylococcus aureus activity, was evaluated in a comprehensive set of non-clinical and clinical cardiovascular safety studies. The effect of JNJ-Q2 on different cardiovascular parameters was compared with that of moxifloxacin, sparfloxacin and ofloxacin. Through comparisons with these well-known fluoroquinolones, the importance of effects on compensatory ion channels to the cardiovascular safety of JNJ-Q2 was investigated. EXPERIMENTAL APPROACH: JNJ-Q2 and comparator fluoroquinolones were evaluated in the following models/test systems: hERG-transfected HEK293 cells sodium channel-transfected CHO cells, guinea pig right atria, arterially perfused rabbit left ventricular wedge preparations and in vivo studies in anaesthetized guinea pigs, anaesthetized and conscious telemetered dogs, and a thorough QT study in humans. KEY RESULTS: The trend for effects of JNJ-Q2 on Tp-Te, QT, QRS and PR intervals in the non-clinical models and the plateau in QTc with increasing plasma concentration in humans are consistent with offsetting sodium and calcium channel activities that were observed in the non-clinical studies. These mixed ion channel activities result in the less pronounced or comparable increase in QTc interval for JNJ-Q2 compared with moxifloxacin and sparfloxacin despite its greater in vitro inhibition of I(Kr). CONCLUSIONS AND IMPLICATIONS: Based on the non-clinical and clinical cardiovascular safety assessment, JNJ-Q2 has a safe cardiovascular profile for administration in humans with comparable or reduced potential to prolong QT intervals, compared with moxifloxacin. The results demonstrate the importance of compensatory sodium and calcium channel activity in offsetting potassium channel activity for compounds with a fluoroquinolone core.

In vivo and ex vivo assessment of the interaction between ivermectin and danofloxacin in sheep.

The impact of an efflux pump-related interaction between ivermectin and danofloxacin on their intestinal transport (ex vivo) and disposition kinetics (in vivo) was assessed. Eighteen male Corriedale sheep were randomly assigned to one of three groups. Animals in Group A received 0.2mg/kg ivermectin by SC injection, those in Group B were given 6 mg/kg danofloxacin SC on two occasions 48 h apart and those in Group C were treated with both compounds at the same rates. Plasma concentrations of ivermectin and danofloxacin were measured by HPLC using fluorescence detection. Ex vivo intestinal drug transport activity was measured by the use of the Ussing chamber technique. Plasma concentrations of ivermectin in the first 6 days after injection tended to be higher in Group C than Group A. Contemporaneous treatment with ivermectin significantly increased systemic exposure to danofloxacin (AUC values were 32-35% higher) and prolonged the elimination half-life of danofloxacin (40-52% longer). Ex vivo, incubation with ivermectin significantly decreased the efflux transport of rhodamine 123, a P-glycoprotein substrate, in sheep intestine, but no significant effect of danofloxacin on transport activity was observed. Evaluation of the interaction of danofloxacin with the breast cancer resistance protein (BCRP) showed that pantoprazole and ivermectin significantly decreased danofloxacin secretion in the rat intestine. Thus, the ivermectin-induced reduction of danofloxacin efflux transport observed in this study may involve BCRP activity but the involvement of P-glycoprotein cannot be ruled out.

Validated liquid chromatographic-fluorescence method for the quantitation of gemifloxacin in human plasma.

A highly selective, sensitive and rapid high performance liquid chromatographic method has been developed and validated to quantify gemifloxacin in human plasma. The gemifloxacin and internal standard (ciprofloxacin) were extracted by ultrafiltration technique followed by injection into chromatographic system. Chromatographic separation was achieved on a reversed phase C(18) column with a mobile phase of acetonitrile:0.1% trifluoroacetic acid (20:80, v/v) using isocratic elution (at flow rate 1 mL min(-1)). The analytes were detected at 269 and 393 nm for excitation and emission, respectively. The assay exhibited a linear range of 25-5000 ng mL(-1) for gemifloxacin in human plasma. The lower limit of detection was 10 ng mL(-1). The method was statistically validated for linearity, accuracy, precision and selectivity following FDA guidelines. The intra- and inter-assay coefficients of variation did not exceed 7.6% deviation of the nominal concentration. The recovery of gemifloxacin from plasma was greater than 97.0%. Stability of gemifloxacin in plasma was excellent with no evidence of degradation during sample processing (auto-sampler) and at least 3 months storage in a freezer at -70 °C. This validation method is applied for clinical study of the gemifloxacin in human volunteers.

Highly sensitive spectrofluorimetric determination of lomefloxacin in spiked human plasma, urine and pharmaceutical preparations.

A sensitive, simple and selective spectrofluorimetric method was developed for the determination of lomefloxacin in biological fluids and pharmaceutical preparations. The method is based on the reaction between the drug and 4-chloro-7-nitrobenzodioxazole in borate buffer of pH 8.5 to yield a highly fluorescent derivative that is measured at 533 nm after excitation at 433 nm. The calibration curves were linear over the concentration ranges of 12.5-625, 15-1500 and 20-2000 ng/mL for plasma, urine and standard solution, respectively. The limits of detection were 4.0 ng/mL in plasma, 5.0 ng/mL in urine and 7.0 ng/mL in standard solution. The intra-assay accuracy and precision in plasma ranged from 0.032 to 2.40% and 0.23 to 0.36%, respectively, while inter-assay accuracy and precision ranged from 0.45 to 2.10% and 0.25 to 0.38%, respectively. The intra-assay accuracy and precision estimated on spiked samples in urine ranged from 1.27 to 4.20% and 0.12 to 0.24%, respectively, while inter-assay accuracy and precision ranged from 1.60 to 4.00% and 0.14 to 0.25%, respectively. The mean recovery of lomefloxacin from plasma and urine was 98.34 and 98.43%, respectively. The method was successfully applied to the determination of lomefloxacin in pharmaceuticals and biological fluids.

Flow-injection chemiluminescence determination of enrofloxacin using the Ru(phen)3(2+)-Ce(IV) system and central composite design for the optimization of chemical variables.

The main purpose of this study was to develop an inexpensive, simple, rapid and sensitive chemiluminescence (CL) method for the determination of enrofloxacin (ENRO) using a flow-injection system. This method is based on rapid reduction of Ru(phen)(3)(3+), which is produced in the reaction between Ru(phen)(3)(2+) and acidic Ce(IV) by ENRO, producing strong CL. A central composite design (CCD) was used for optimization of the chemical variables. Regression analysis of the data from the CCD demonstrated that a second-order polynomial model is an adequate description of the surface over the factor limits studied. Optimization using CCD gave approximately four-fold better results than the single-factor-at-a-time method. Under optimal experimental conditions, the CL response was proportional to the concentration of ENRO over a wide range (0.008-3.6 microg/mL) with a correlation coefficient of 0.9986 and a detection limit of 0.003 microg/mL (3sigma). The relative standard deviation for 11 repeated determinations of 0.14 microg/mL ENRO was 4.2%. This method was successfully applied to the analysis of commercial formulations, spiked plasma and spiked poultry tissue. Sample analyses showed good recovery percentages for drugs and spiked plasma (95.1-103.9%). Recovery percentages for spiked poultry tissue were in the range 77.6-87.3%. The minimum sampling rate was 100 samples/h.