Pharmacokinetics, plasma protein binding and bioavailability of moxifloxacin in Muscovy ducks after different routes of administration

Simultaneous determination of three iridoid glycosides of Rehmannia glutinosa in rat biological samples using a validated hydrophilic interaction-UHPLC-MS/MS method in pharmacokinetic and in vitro studies

The purpose of this study was to develop a method for simultaneous analysis of aucubin, catalpol, and geniposide, which are representative iridoid glycoside constituents of Rehmannia glutinosa, in rat plasma, urine, and feces using hydrophilic interaction ultra high-performance liquid chromatography with tandem mass spectrometry. The three components were separated using 10 mmol/L aqueous ammonium formate containing 0.01% (v/v) formic acid and acetonitrile as a mobile phase by gradient elution at a flow rate of 0.2 mL/min, equipped with a Kinetex^® HILIC column (50 × 2.1 mm, 2.6 μm). Quantitation of this analysis was performed on a triple quadrupole mass spectrometer employing electrospray ionization and operated in multiple reaction monitoring mode. The chromatograms showed high resolution, sensitivity, and selectivity with no interference with plasma constituents. In all three iridoid glycosides, both the intra- and interbatch precisions (coefficient of variation %) were less than 4.81%. The accuracy was 96.56-103.55% for aucubin, 95.23-106.21% for catalpol, and 94.50-104.16% for geniposide. The developed analytical method satisfied the criteria of international guidance and was successfully applied to pharmacokinetic studies including oral bioavailability of aucubin, catalpol, and geniposide, and their urinary and fecal excretion ratios after oral or intravenous administration to rats. The new method was also applied to measure plasma protein binding ratios in vitro.

Risk assessment for humans using physiologically based pharmacokinetic model of diethyl phthalate and its major metabolite, monoethyl phthalate

Diethyl phthalate (DEP) belongs to phthalates with short alkyl chains. It is a substance frequently used to make various products. Thus, humans are widely exposed to DEP from the surrounding environment such as food, soil, air, and water. As previously reported in many studies, DEP is an endocrine disruptor with reproductive toxicity. Monoethyl phthalate (MEP), a major metabolite of DEP in vivo, is a biomarker for DEP exposure assessment. It is also an endocrine disruptor with reproductive toxicity, similar to DEP. However, toxicokinetic studies on both MEP and DEP have not been reported in detail yet. Therefore, the objective of this study was to evaluate and develop physiologically based pharmacokinetic (PBPK) model for both DEP and MEP in rats and extend this to human risk assessment based on human exposure. This study was conducted in vivo after intravenous or oral administration of DEP into female (2 mg/kg dose) and male (0.1-10 mg/kg dose) rats. Biological samples consisted of urine, plasma, and 11 different tissues. These samples were analyzed using UPLC-ESI-MS/MS method. For DEP, the tissue to plasma partition coefficient was the highest in the kidney, followed by that in the liver. For MEP, the tissue to plasma partition coefficient was the highest in the liver. It was less than unity in all other tissues. Plasma, urine, and fecal samples were also obtained after IV administration of MEP (10 mg/kg dose) to male rats. All results were reflected in a model developed in this study, including in vivo conversion from DEP to MEP. Predicted concentrations of DEP and MEP in rat urine, plasma, and tissue samples using the developed PBPK model fitted well with observed values. We then extrapolated the PBPK model in rats to a human PBPK model of DEP and MEP based on human physiological parameters. Reference dose of 0.63 mg/kg/day (or 0.18 mg/kg/day) for DEP and external doses of 0.246 μg/kg/day (pregnant), 0.193 μg/kg/day (fetus), 1.005-1.253 μg/kg/day (adults), 0.356-0.376 μg/kg/day (adolescents), and 0.595-0.603 μg/kg/day (children) for DEP for human risk assessment were estimated using Korean biomonitoring values. Our study provides valuable insight into human health risk assessment regarding DEP exposure.

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.

Plasma and Tissue Disposition of Moxifloxacin in Japanese Quail ( Coturnix japonica )

Plasma disposition and depletion of moxifloxacin were investigated in Japanese quail ( Coturnix japonica ) after single intravenous, intramuscular, and oral administration of 5 mg/kg and after intramuscular and oral administration of 5 mg/kg q24h for 5 consecutive days, respectively. Drug concentrations in plasma and tissues were measured by high-performance liquid chromatography with fluorescence detection. After intravenous injection, plasma drug concentration-time curves were best described by a 2-compartment open model. The decline in plasma drug concentration was biexponential with half-lives of 0.3 hours and 2.18 hours for distribution and elimination phases, respectively. Steady-state volume of distribution and total body clearance after intravenous administration were estimated to be 1.12 L/kg and 0.41 L/h per kilogram, respectively. After intramuscular and oral administration of moxifloxacin at the same dose, the peak plasma concentrations were 2.14 and 1.94 μg/mL and were obtained at 1.4 and 1.87 hours, respectively, and the elimination half-lives were 2.56 and 1.97 hours, respectively. The systemic bioavailabilities were 92.48% and 87.94%, respectively. Tissue levels after intramuscular and oral administration were highest in liver and kidneys, respectively, and decreased in the following order: plasma, lungs, and muscle. Moxifloxacin concentrations after intramuscular and oral administration were below the detection limit of the assay in tissues and plasma after 120 hours.

Determination of geniposide in adjuvant arthritis rat plasma by ultra-high performance liquid chromatography tandem mass spectrometry method and its application to oral bioavailability and plasma protein binding ability studies

A specific, sensitive and high throughput ultra-high performance liquid chromatography-electrospray ionization tandem mass spectrometric method (UHPLC-ESI-MS/MS) was established and validated to assay geniposide (GE), a promising anti-inflammatory drug, in adjuvant arthritis rat plasma: application to pharmacokinetic and oral bioavailability studies and plasma protein binding ability. Plasma samples were processed by de-proteinised with ice-cold methanol and separated on an ACQUITY UPLC™ HSS C18 column (100 mm × 2.1mm i.d., 1.8 μm particle size) at a gradient flow rate of 0.2 mL/min using acetonitrile-0.1% formic acid in water as mobile phase, and the total run time was 9 min. Mass detection was performed in selected reaction monitoring (SRM) mode with negative electro-spray ionization includes the addition of paeoniflorin (Pae) as an internal standard (IS). The mass transition ion-pair was followed as m/z 387.4 → 122.4 for GE and m/z 479.4 → 449.0 for IS. The calibration curves were linear over the concentration range of 2-50,000 ng/mL with lower limit of quantification of 2 ng/mL. The intra-day and inter-day precisions (RSD, %) of the assay were less than 8.4%, and the accuracy was within ± 6.4% in terms of relative error (RE). Extraction recovery, matrix effect and stability were satisfactory in adjuvant arthritis rat plasma. The UHPLC-ESI-MS/MS method was successfully applied to a pharmacokinetic study of GE after oral administration of depurated GE at 33, 66, 132 mg/kg and intravenous injection at 33, 66, 132 mg/kg in adjuvant arthritis (AA) rats. In addition, it was found that GE has rapid absorption and elimination, low absolute bioavailability, high plasma protein binding ability in AA rats after oral administration within the tested dosage range. It suggested that GE showed slow distribution into the intra- and extracellular space, and the binding rate was not proportionally dependent on plasma concentration of GE when the concentration of GE was below 5.0 μg/mL.

Comparative Pharmacokinetics of Levofloxacin in Healthy and Renal Damaged Muscovy Ducks following Intravenous and Oral Administration

The pharmacokinetics aspects of levofloxacin were studied in healthy and experimentally renal damaged Muscovy ducks after single intravenous (IV) and oral (PO) dose of 10 mg kg⁻¹ bwt. Following IV administration, elimination half-life (t_1/2(β)) and mean residence time (MRT) were longer in renal damaged ducks than in healthy ones. Total clearance (Cl_tot) in renal damaged ducks (0.20 L kg⁻¹ h⁻¹) was significantly lower as compared to that in healthy ones (0.41 L kg⁻¹ h⁻¹). Following PO administration, the peak serum concentration (C_max) was higher in renal damaged than in healthy ducks and was achieved at maximum time (t_max) of 2.47 and 2.05 h, respectively. The drug was eliminated (t_1/2(el)) at a significant slower rate (3.94 h) in renal damaged than in healthy ducks (2.89 h). The pharmacokinetic profile of levofloxacin is altered in renal damaged ducks due to the increased serum levofloxacin concentrations compared with that in clinically healthy ducks. Oral administration of levofloxacin at 10 mg kg⁻¹ bwt may be highly efficacious against susceptible bacteria in ducks. Also, the dose of levofloxacin should be reduced in renal damaged ducks. Pharmacokinetic/pharmacodynamic integration revealed significantly higher values for C_max/MIC and AUC/MIC ratios in renal damaged ducks than in healthy ones, indicating the excellent pharmacokinetic characteristics of levofloxacin in renal damaged ducks.