Integration of pharmacokinetic and pharmacodynamic indices of orbifloxacin in beagle dogs after a single intravenous and intramuscular administration

Pharmacokinetics of orbifloxacin in crucian carp (Carassius auratus) after intravenous and intramuscular administration

The pharmacokinetics of orbifloxacin was studied after a single dose (7.5 mg/kg) of intravenous or intramuscular administration to crucian carp (Carassius auratus) reared in freshwater at 25°C. Plasma samples were collected from six fish per sampling point. Orbifloxacin concentrations were determined by high-performance liquid chromatography with a 0.02 μg/ml limit of detection, then were subjected to noncompartmental analysis. After intravenous injection, initial concentration of 5.83 μg/ml, apparent elimination rate constant (λ_z ) of 0.039 hr^-1 , apparent elimination half-life (T_1/2λz ) of 17.90 hr, systemic total body clearance (Cl) of 75.47 ml hr^-1  kg^-1 , volume of distribution (Vz) of 1,948.76 ml/kg, and volume of distribution at steady-state (Vss) of 1,863.97 ml/kg were determined, respectively. While after intramuscular administration, the λ_z , T_1/2λz , mean absorption time (MAT), absorption half-life (T_1/2ka ), and bioavailability were determined as 0.027 hr^-1 , 25.69, 10.26, 7.11 hr, and 96.46%, respectively, while the peak concentration was observed as 3.11 ± 0.06 μg/ml at 2.0 hr. It was shown that orbifloxacin was completely but relatively slowly absorbed, extensively distributed, and slowly eliminated in crucian carp, and an orbifloxacin dosage of 10 mg/kg administered intravenously or intramuscularly would be expected to successfully treat crucian carp infected by strains with MIC values ≤0.5 μg/ml.

Pharmacokinetic and pharmacodynamic modeling of sarafloxacin against avian pathogenic Escherichia coli in Muscovy ducks

Background

This study focused on utilizing pharmacokinetics/pharmacodynamics (PK/PD) modeling to optimize therapeutic dosage regimens of sarafloxacin against avian pathogenic Escherichia. coli O78 strain in Muscovy ducks. The ex vivo PK/PD study of sarafloxacin was conducted in Muscovy ducks after intravenous (i.v.) and oral (p.o.) administrations at a single dose of 10 mg/kg bodyweight (BW). The serum samples were analyzed by reverse phase high-performance liquid chromatography (RP-HPLC) using a fluorescence detection method. Sarafloxacin PK data were analyzed by a non-compartmental method using Winnonlin software.

Results

Calculations of the area under the concentration-time curves (AUC_0-24h) were 8.57 ± 0.59 and 8.37 ± 0.29 μg · h/ml following i.v. and p.o. administration, respectively. Elimination half-lives (t_1/2β) were 6.11 ± 0.99 h and 8.21 ± 0.64 h for i.v. injection and p.o. administration, respectively. The mean in vitro plasma protein binding of sarafloxacin was 39.3%. Integration using the sigmoid E_max model, the mean values of AUC_0-24h/MIC needed for bacteriostatic, bactericidal and bacterial eradication action were 25.4, 40.6, and 94.4 h, respectively.

Conclusions

Sarafloxacin administered at a 10 mg/kg dose may be insufficient for treatment of E. coli O78 infections with an MIC equally to or over 0.125 μg/ml. Furthermore, higher doses of sarafloxacin are required to minimize antimicrobial resistance considering the MPC theory.

Pharmacokinetics and bioavailability of orbifloxacin oral suspension in New Zealand White rabbits (Oryctolagus cuniculus)

OBJECTIVE To evaluate the pharmacokinetics and bioavailability of 2 doses of orbifloxacin in rabbits. ANIMALS 6 healthy purpose-bred adult female New Zealand White rabbits (Oryctolagus cuniculus). PROCEDURES Each of 3 rabbits received orbifloxacin at either 10 or 20 mg/kg, PO. Then, after a 1-week washout period, they received the same dose IV. Blood samples were collected from each rabbit at 0, 0.25, 0.5, 1, 2, 4, 6, 12, and 24 hours after drug administration. Plasma orbifloxacin concentration was measured with liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were determined by noncompartmental analysis for data obtained following PO administration and noncompartmental and compartmental analyses for data obtained following IV administration. RESULTS Following oral administration, the mean ± SD peak plasma orbifloxacin concentration was 1.66 ± 0.51 μg/mL for rabbits administered the 10 mg/kg dose and 3.00 ± 0.97 μg/mL for rabbits administered the 20 mg/kg dose and was attained at 2 hours after drug administration. The mean ± SD half-life of orbifloxacin in plasma was 7.3 ± 1.1 hours for rabbits administered the 10 mg/kg dose and 8.6 ± 0.55 hours for rabbits administered the 20 mg/kg dose. Mean bioavailability was 52.5% for rabbits administered the 10 mg/kg dose and 46.5% for rabbits administered the 20 mg/kg dose. CONCLUSIONS AND CLINICAL RELEVANCE Results provided pharmacokinetic properties for 2 doses (10 mg/kg and 20 mg/kg) of orbifloxacin oral suspension in rabbits. Further studies are necessary to determine the protein-binding activity of orbifloxacin in rabbits before dosages for the treatment of common pathogens in this species are recommended.

Pharmacokinetic/Pharmacodynamic Correlation of Cefquinome Against Experimental Catheter-Associated Biofilm Infection Due to Staphylococcus aureus

Biofilm formations play an important role in Staphylococcus aureus pathogenesis and contribute to antibiotic treatment failures in biofilm-associated infections. The aim of this study was to evaluate the pharmacokinetic/pharmacodynamic (PK/PD) profiles of cefquinome against an experimental catheter-related biofilm model due to S. aureus, including three clinical isolates and one non-clinical isolate. The minimal inhibitory concentration (MIC), minimal biofilm inhibitory concentration (MBIC), biofilm bactericidal concentration (BBC), minimal biofilm eradication concentration (MBEC) and biofilm prevention concentration (BPC) and in vitro time-kill curves of cefquinome were studied in both planktonic and biofilm cells of study S. aureus strains. The in vivo post-antibiotic effects (PAEs), PK profiles and efficacy of cefquinome were performed in the catheter-related biofilm infection model in murine. A sigmoid E_max model was utilized to determine the PK/PD index that best described the dose-response profiles in the model. The MICs and MBICs of cefquinome for the four S. aureus strains were 0.5 and 16 μg/mL, respectively. The BBCs (32–64 μg/mL) and MBECs (64–256 μg/mL) of these study strains were much higher than their corresponding BPC values (1–2 μg/mL). Cefquinome showed time-dependent killing both on planktonic and biofilm cells, but produced much shorter PAEs in biofilm infections. The best-correlated PK/PD parameters of cefquinome for planktonic and biofilm cells were the duration of time that the free drug level exceeded the MIC (fT > MIC, R² = 96.2%) and the MBIC (fT > MBIC, R² = 94.7%), respectively. In addition, the AUC_24h/MBIC of cefquinome also significantly correlated with the anti-biofilm outcome in this model (R² = 93.1%). The values of AUC_24h/MBIC for biofilm-static and 1-log₁₀-unit biofilm-cidal activity were 22.8 and 35.6 h; respectively. These results indicate that the PK/PD profiles of cefquinome could be used as valuable guidance for effective dosing regimens treating S. aureus biofilm-related infections.

Effects of oral orbifloxacin on fecal coliforms in healthy cats: a pilot study

The study objective was to determine the effect of oral orbifloxacin (ORB) on antimicrobial susceptibility and composition of fecal coliforms in cats. Nine cats were randomized to two groups administered a daily oral dose of 2.5 and 5.0 mg ORB/kg for 7 days and a control group (three cats per group). Coliforms were isolated from stool samples and were tested for susceptibilities to ORB and 5 other drugs. ORB concentration in feces was measured using high-performance liquid chromatography (HPLC). The coliforms were undetectable after 2 days of ORB administration, and their number increased in most cats after termination of the administration. Furthermore, only isolates of Escherichia coli were detected in all cats before administration, and those of Citrobacter freundii were detected after termination of the administration. E. coli isolates exhibited high ORB susceptibility [Minimum inhibitory concentration (MIC), ≤0.125 µg/ml] or relatively low susceptibility (MIC, 1-2 µg/ml) with a single gyrA mutation. C. freundii isolates largely exhibited intermediate ORB susceptibility (MIC, 4 µg/ml), in addition to resistance to ampicillin and cefazolin, and harbored qnrB, but not a gyrA mutation. HPLC revealed that the peaks of mean concentration were 61.3 and 141.0 µg/g in groups receiving 2.5 and 5.0 mg/kg, respectively. Our findings suggest that oral ORB may alter the total counts and composition of fecal coliform, but is unlikely to yield highly fluoroquinolone-resistant mutants of E. coli and C. freundii in cats, possibly because of the high drug concentration in feces.

Development and validation of UV spectrophotometric method for orbifloxacin assay and dissolution studies

New, simple and cost effective UV-spectrophotometric method was developed for the estimation of orbifloxacin in pharmaceutical formulation. Orbifloxacin was estimated at 290 nm in 0.5 M hydrochloric acid. Linearity range was found to be 1.0-6.0 μg mL-1. The method was tested and validated for various parameters according to main guidelines. The proposed method was successfully applied for the determination of orbifloxacin in tablets. The results demonstrated that the procedure is accurate, precise and reproducible, while being simple, economical and less time consuming. It can be suitably applied for the estimation of orbifloxacin in routine quality control and dissolution studies.

Integration of pharmacokinetic and pharmacodynamic indices of valnemulin in broiler chickens after a single intravenous and intramuscular administration

The antibacterial efficacy of valnemulin against Staphylococcus aureus was studied ex vivo in broiler chickens after intravenous and intramuscular administration at a dose of 10 mg/kg bodyweight (BW). The minimum inhibitory concentrations (MICs) of valnemulin against S. aureus strains ATCC 25923 in broth and serum were 0.12 and 1 µg/mL, respectively. The MIC50 and MIC90 of valnemulin against all susceptible S. aureus strains isolated from chickens in the test population were 0.06 and 0.12 μg/mL, respectively. Protein binding, which greatly influences the efficacy of valnemulin, was assayed by equilibrium dialysate in vitro. A high binding fraction of 86.2% was found, which seems in good agreement with the difference of bacterial susceptibility tests observed in broth and serum. The surrogate index of AUC0-24/MIC required for the lowest bacteriostatic effect, and 2 log10CFU reduction in bacterial count were 24.4 h and 38.0 h, respectively. The required daily dose of valnemulin for a bacteriostatic activity was calculated to be 15 mg/kg BW based on the MIC90 of 0.12 µg/mL. Considering the slow disposition process of valnemulin and an AUC0-24 h value of more than 10-fold obtained from diseased animals, a suggested dose of 3 mg/kg BW is sufficient to achieve a satisfactory therapeutic efficacy in infected broilers. Due to the time-dependent antibacterial characteristics of valnemulin, the recommended daily dose should be split into two or three sub-doses to achieve the highest effectiveness while diminishing the risk of development of bacterial resistance.

Determination of orbifloxacin in sheep plasma by high performance liquid chromatography with ultraviolet detection after intravenous and intramuscular administration

INTRODUCTION

Single-dose pharmacokinetics of orbifloxacin (2.5mg/kg body weight) were determined in clinically normal female Patanwadi sheep (n=6) following intravenous and intramuscular administration.

METHODS

Orbifloxacin concentrations were determined by high performance liquid chromatography with ultraviolet detection. The concentration-time data were analyzed by non-compartmental kinetic method.

RESULTS AND DISCUSSION

Following a single intravenous injection, an elimination half-life (t(1/2β)) of 8.31±0.102h. Steady-state volume of distribution (Vd(ss)) and total body clearance (Cl(B)) were 3.09±0.282L/kg and 0.158±0.006L/kg/h, respectively. Following intramuscular administration, an elimination rate constant (β), the area under the curve from zero to infinity (AUC(0-∞)) and the mean absorption time (MAT) were 0.015±0.001h(-1), 23.49±1.722μg·h/mL and 7.50±0.58h, respectively. The peak plasma concentration (C(max)) of 1.81±0.005µg/mL was achieved at 1.00±0.00h. The mean residence time (MRT) was 26.25±1.083h and the absolute bioavailability was 150.8±12.35%, respectively. Orbifloxacin could be useful for the treatment of bacterial infections in sheep that are sensitive to this drug.

Allometric scaling of orbifloxacin disposition in nine mammal species: a retrospective analysis

The objective of this study was to analyze the relationship between pharmacokinetic parameters and body weight (W) for orbifloxacin using reported pharmacokinetic data. The parameters of interest: clearance (Cl), volume of distribution at steady state (Vss) and elimination half-life were correlated across nine mammal species, including cattle, dog, rat, rabbit, goat, camel, horse, cat and sheep as a function of W using the conventional allometric equation Y = aW(b), where Y is the pharmacokinetic parameter, W is the body weight, a is the allometric coefficient (intercept) and b is the exponent that describes the relationship between the pharmacokinetic parameter and W. Our estimates (Cl=4.40 W(1.03); Vss=1.10W(1.05)) indicated that the increase in these parameters with W approximates a linear power relationship with slopes being very close to one. Overall, the results of this study indicated that it is possible to use allometry to predict pharmacokinetic variables of orbifloxacin based on W of mammal species.

Pharmacokinetic-pharmacodynamic integration of orbifloxacin in Japanese quail (Coturnix japonica) following oral and intravenous administration

The pharmacokinetics of single-dose administration of orbifloxacin were determined in Japanese quail (Coturnix japonica) at dosages of 5 mg/kg intravenous (i.v. n = 12) and 7.5 mg/kg oral (p.o.; n = 5), 10 mg/kg p.o. (n = 5), 15 mg/kg p.o. (n = 12) and 20 mg/kg p.o. (n = 5) via HPLC. Orbifloxacin minimal inhibitory concentrations (MICs) against 22 microbial isolates from various bird species were performed to calculate pharmacodynamic surrogate markers. The concentration-time data were analyzed using a naïve pooled data (NPD) approach and compartmental and noncompartmental methods. Steady-state volume of distribution (Vd(ss)) and total body clearance (Cl) after i.v. administration were estimated to be 1.27 L/kg and 0.60 L/h·kg, respectively. Following 15 and 20 mg/kg p.o. dose, bioavailability was 102% and 117%, respectively. The harmonic mean of the corresponding terminal half-lives (T(1/2) λ(z) ) across all the dose groups was 1.71 h. The C(max) /MIC(90) and AUC(0∞24) /MIC(90) for the 15 and 20 mg/kg p.o. doses were ≥5.22 and ≥8.98, and ≥25.80 and ≥39.37 h, respectively. The results of this study suggest that 20 mg/kg orbifloxacin p.o. would be a rational daily dose to treat susceptible infections in Japanese quail not intended for food consumption. For more sensitive bacterial organisms, 15 mg/kg p.o. may also be effective.