Some pharmacokinetic parameters of pefloxacin in lactating goats

Oral Bioavailability and Plasma Disposition of Pefloxacin in Healthy Broiler Chickens

The pharmacokinetics of pefloxacin after single 10 mg/kg BW intravenous (IV) and oral doses were studied in healthy broiler chickens. For 24 h, serial blood samples were obtained after IV and oral administration. Concentrations of pefloxacin and its major metabolite N-demethyl pefloxacin (norfloxacin) were measured by use of high-performance liquid chromatography. The plasma concentrations–time data were found to fit a two-compartment open model. For pefloxacin, the elimination half-life (t_½β) was 8.44 ± 0.48 and 13.18 ± 0.82 h after IV and oral administration, respectively. After single oral dose, pefloxacin was rapidly absorbed with an absorption half-life (t_½a) and T_MAX of 0.87 ± 0.07 and 2.01 ± 0.12 h, respectively. Maximum plasma concentration (C_MAX) was 4.02 ± 0.31 µg/mL. Oral bioavailability of pefloxacin was found to be 70 ± 2%. Pefloxacin was converted to N-demethyl pefloxacin (norfloxacin). This metabolite represented 5% of the parent drug plasma concentrations. The maximal plasma concentration (C_MAX) of N-demethyl pefloxacin (norfloxacin) was calculated as 0.19 ± 0.01 mg/mL. The t_½β of N-demethyl pefloxacin after oral pefloxacin administration was 10.93 ± 0.80 h. The results indicate that an oral dose of 10 mg pefloxacin/kg BW, every 24 h, should be effective in treatment of the most systemic infections in poultry.

Pharmacokinetics, milk penetration and PK/PD analysis by Monte Carlo simulation of marbofloxacin, after intravenous and intramuscular administration to lactating goats

The main objectives of this study were (i) to evaluate the serum pharmacokinetic behaviour and milk penetration of marbofloxacin (MFX; 5 mg/kg), after intravenous (IV) and intramuscular (IM) administration in lactating goats and simulate a multidose regimen on steady-state conditions, (ii) to determine the minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) of coagulase negative staphylococci (CNS) isolated from caprine mastitis in Córdoba, Argentina and (iii) to make a PK/PD analysis by Monte Carlo simulation from steady-state pharmacokinetic parameters of MFX by IV and IM routes to evaluate the efficacy and risk of the emergence of resistance. The study was carried out with six healthy, female, adult Anglo Nubian lactating goats. Marbofloxacin was administered at 5 mg/kg bw by IV and IM route. Serum and milk concentrations of MFX were determined with HPLC/uv. From 106 regional strains of CNS isolated from caprine mastitis in herds from Córdoba, Argentina, MICs and MPCs were determined. MIC₉₀ and MPC₉₀ were 0.4 and 6.4 μg/ml, respectively. MIC and MPC-based PK/PD analysis by Monte Carlo simulation indicates that IV and IM administration of MFX in lactating goats may not be adequate to recommend it as an empirical therapy against CNS, because the most exigent endpoints were not reached. Moreover, this dose regimen could increase the probability of selecting mutants and resulting in emergence of resistance. Based on the results of Monte Carlo simulation, the optimal dose of MFX to achieve an adequate antimicrobial efficacy should be 10 mg/kg, but it is important take into account that fluoroquinolones are substrates of efflux pumps, and this fact may determine that assumption of linear pharmacokinetics at high doses of MFX may be incorrect.

Pharmacokinetics and milk penetration of difloxacin after a long-acting formulation for subcutaneous administration to lactating goats

The single-dose disposition kinetics of difloxacin were determined in clinically normal lactating goats (n=6) after intravenous (IV) and subcutaneous (SC) administration and subcutaneous administration of a long-acting poloxamer 407 gel formulation (P407). Difloxacin concentrations were determined by HPLC with fluorescence detection. Minimum inhibitory concentrations of difloxacin against 14 strains of Staphylococcus aureus isolated from mastitic goats' milk in Spain were determined to compute pharmacodynamic surrogate markers. The concentration-time data were analyzed by compartmental and noncompartmental pharmacokinetic methods. Following SC and P407 administration, difloxacin achieved maximum milk concentrations of 1.34+/-0.12 and 2.97+/-1.18 mg/L, respectively, at 4.00+/-0.00 h (SC) and 3.60+/-0.89 h (P407) after administration. The absolute bioavailabilities after SC and P407 administration were 81.74+/-15.60% and 72.58+/-20.45%, respectively. Difloxacin penetration from the blood into the milk was good and high concentrations were found in milk secretions. From these data, a 15 mg/kg dose of difloxacin P407 would appear to be effective against Staphylococcus aureus isolated from mastitic goats' milk with minimum inhibitory concentrations <or=0.25mg/L.

Disposition kinetics of moxifloxacin in lactating ewes

The present study was planned to investigate the plasma disposition kinetics and the pattern of moxifloxacin elimination in the milk of lactating ewes (n=6) following a single intravenous (IV) bolus or intramuscular (IM) injections at a dosage of 5 mg/kg in all animals. A crossover study was carried out in two phases separated by 21 days. Plasma and milk samples were collected serially for 72 h and moxifloxacin concentrations were assayed using high performance liquid chromatography with fluorescence detection. A two-compartment open model best described the decrease of moxifloxacin concentration in the plasma after IV injection. The disposition after IM administration moxifloxacin was best described by a one-compartment model. Following IV administration, the distribution half-life (t(1/2alpha)) was 0.22+/-0.02 h. The elimination half-life was 1.77+/-0.23 h. The volume of distribution at steady state (V(dss)) was 0.84+/-0.12L/kg, the total body clearance (Cl(tot)) was 0.34+/-0.04 L/h/kg and the area under the curve (AUC) was 14.74+/-2.16 microg h/mL. Following IM administration, the mean T(max), C(max), t(1/2el) and AUC values for plasma data were 1.45+/-0.02 h, 2.21+/-0.27 microg/mL, 2.68+/-0.19 h and 14.21+/-2.35 microg h/mL. The IM bioavailability was 96.35+/-17.23% and the in vitro protein binding of moxifloxacin ranged from 32-37%. Penetration of moxifloxacin from the blood into milk was rapid and extensive, and the moxifloxacin concentrations in milk exceeded those in plasma from 1h after administration. The kinetic values AUC(milk)/AUC(plasma) and C(maxmilk)/C(maxplasma) ratios indicated a wide penetration of moxifloxacin from the bloodstream to the mammary gland. The in vitro minimum inhibitory concentration (MIC) of moxifloxacin for Mannheimia haemolytica was found to be 0.035 microg/mL.

Approaches for application of sub and supercritical fluid extraction for quantification of orbifloxacin from plasma and milk: application to disposition kinetics

Since its extensive development in the early 1980s, SFE has attracted considerable attention as a sample-preparation procedure. However, other different sample preparation procedures, including precipitation, liquid- and/or solid-phase extraction in biological fluids, also remain in use. In this investigation, SFE was introduced to isolate and identify orbifloxacin from plasma and milk. Four parameters, including the temperature and the pressure of supercritical fluid, modifier ratios, and dynamic extraction time, were evaluated and optimized to obtain the best yield of the analyte from the biological fluids. Determinations of the orbifloxacin (OBFX) in the extracts were carried out using HPLC-FLD. The optimum conditions of the extraction process that yielded the maximum analyte extraction efficiencies were 150 degrees C vs. 60 degrees C, 250 kg cm(-2), 30% vs. 35% methanol, and 40 min vs. 20 min, for plasma and milk, respectively. The linearity of the calibration curves as well as the instrument LODs/LOQs were evaluated. Good linearity (at least r(2) > or = 0.999) of the calibration curves was obtained over the range from 0.2 to 0.01 microg mL(-1). The method showed a good recovery rate (74.2-127.73%) and precision (RSDs: 1.64-20%). The instrumental LOD and LOQ values were 0.004 microg mL(-1) vs. 0.01 microg mL(-1) or 0.006 microg mL(-1) vs. 0.02 microg mL(-1), for plasma and milk, respectively. The method was successfully applied to estimate the pharmacokinetic variables of orbifloxacin in lactating does. To the best of our knowledge, this is the first time that SFE has been applied to isolate an antimicrobial agent from biological fluids. This method is promising for clinical applications and for pharmacokinetic studies of various pharmaceuticals in biological fluids.

Effect of trikatu pretreatment on the pharmacokinetics of pefloxacin administered orally in mountain Gaddi goats

The pharmacokinetics of orally administered pefloxacin were studied to evaluate the bio-enhancing effect of the herbal bio-enhancer, trikatu, in mountain Gaddi goats (n = 6). The findings of the study revealed a decreased plasma concentration (p > 0.05) of pefloxacin following trikatu administration during the absorption phase (10, 15, 20 min post pefloxacin administration). In contrast, the plasma concentrations of pefloxacin were significantly higher at 4, 6, 8 and 12 h (during the elimination phase) of the pefloxacin administration. The findings of the investigation revealed higher values for the area under the curve, the area under the first moment of the plasma drug concentration time curve, the mean residential time, the total duration of pharmacological action and bioavailability. Trikatu treatment, however, significantly reduced the elimination half life (t 1/2 beta) and zero time intercept of the elimination phase. The apparent volume of distribution based on the total area under the plasma drug concentration curve [(Vd(area)] and the apparent volume of distribution based on the zero time plasma concentration intercept of the elimination phase [Vd(B)] were significantly higher in trikatu treated animals indicating a better penetration of the drug. Based on the MIC of 0.8 microg/ml of pefloxacin, a priming dose of 6.0 mg/kg and a maintenance dose of 2.21 mg/kg is required to be administered at 8 h intervals. For practical purposes in goats this would mean a priming dose of 6 mg/kg and a maintenance dose of 2 mg/kg given by the oral route, to be repeated at 8 h intervals.

Pharmacokinetics and Milk Penetration of Orbifloxacin After Intravenous, Subcutaneous, and Intramuscular Administration to Lactating Goats

The single-dose disposition kinetics of orbifloxacin were determined in clinically normal lactating goats (n = 6) after intravenous, subcutaneous, and intramuscular administration of 2.5 mg of orbifloxacin/kg of body weight. Orbifloxacin concentrations were determined by HPLC with fluorescence detection. The concentration-time data were analyzed by compartmental and noncompartmental kinetic methods. Steady-state volume of distribution and clearance of orbifloxacin after intravenous administration were 1.13 +/- 0.08 L/kg and 0.40 +/- 0.11 L/h x kg, respectively. Following subcutaneous and intramuscular administration, orbifloxacin achieved maximum plasma concentrations of 1.85 +/- 0.20 and 1.66 +/- 0.14 mg/L at 1.25 +/- 0.22 and 0.87 +/- 0.38 h, respectively. The absolute bioavailabilities after subcutaneous and intramuscular routes were 108.96 +/- 17.61% and 105.01 +/- 15.61%, respectively. Orbifloxacin penetration from the blood into the milk was rapid and showed high levels of concentrations in milk secretion. From this data, orbifloxacin could have success against susceptible mastitis pathogens in goats.

Pharmacokinetics and milk penetration of moxifloxacin after intramuscular administration to lactating goats

The pharmacokinetics of moxifloxacin was studied following intramuscular administration of 5mg/kg to healthy lactating goats (n=6). Moxifloxacin concentrations were determined by high performance liquid chromatography assay with fluorescence detection. The moxifloxacin plasma concentration versus time data could best be described by a one-compartment model. The plasma moxifloxacin clearance (Cl) was mean standard deviation (+/-SD) 0.49+/-0.14 L/h kg. The apparent volume of distribution (V(z)) was 0.83+/-0.20 L/kg. The terminal half-life (t(1/2 lambda z)) was 1.31+/-0.64 h. Moxifloxacin penetration from blood to milk was rapid and the high AUC(milk)/AUC(plasma) and C(max-milk)/C(max-plasma) ratios reached indicated a good penetration of moxifloxacin into the milk.

Pharmacokinetics and milk penetration of difloxacin after intravenous, subcutaneous and intramuscular administration to lactating goats

The single-dose disposition kinetics of difloxacin were determined in clinically normal lactating goats (n = 6) after intravenous (i.v.), subcutaneous (s.c.) and intramuscular (i.m.) administration of 5 mg/kg. Difloxacin concentrations were determined by high performance liquid chromatography with fluorescence detection. The concentration-time data were analysed by compartmental and noncompartmental kinetic methods. Steady-state volume of distribution (V(ss)) and total body clearance (Cl) of difloxacin after i.v. administration were estimated to be 1.16 +/- 0.26 L/kg and 0.32 +/- 0.05 L/h x kg respectively. Following s.c. and i.m. administration difloxacin achieved maximum plasma concentrations of 1.33 +/- 0.25 and 1.97 +/- 0.40 mg/L at 3.37 +/- 0.36 and 1.79 +/- 1.14 h respectively. The absolute bioavailabilities after s.c. and i.m. routes were 90.16 +/- 11.99% and 106.79 +/- 13.95% respectively. Difloxacin penetration from the blood into the milk was extensive and rapid, and the drug was detected for 36 h after i.v. and s.c. dosing, and for 72 h after i.m. administration.

Pharmacokinetics and milk penetration of moxifloxacin after intravenous and subcutaneous administration to lactating goats

The pharmacokinetics of moxifloxacin was studied following intravenous (IV) and subcutaneous (SC) administration of 5 mg/kg to healthy lactating goats (n = 6). Moxifloxacin concentrations were determined by high performance liquid chromatography assay with fluorescence detection. The moxifloxacin plasma concentration versus time data after IV administration could best be described by a two compartment open model. The disposition of SC administered moxifloxacin was best described by a one-compartment model. The plasma moxifloxacin clearance (Cl) for the IV route was 0.43 +/- 0.02 L/kg (mean +/- SE). The steady-state volume of distribution (Vss) was 0.79 +/- 0.08 L/kg. The terminal half-life (t1/2lambdaz) was 1.94 +/- 0.41 and 2.98 +/- 0.48 h after IV and SC administration, respectively. The absolute bioavailability was 96.87 +/- 10.27% after SC administration. Moxifloxacin penetration from blood to milk was quick for both routes of administration and the high AUCmilk/AUCplasma and Cmax-milk/Cmax-plasma ratios reached indicated a wide penetration of moxifloxacin into the milk. From these data, it appears that a 5 mg/kg SC dose of moxifloxacin would be effective in lactating goats against bacterial isolates with MIC < or = 0.20 microg/mL in plasma and MIC < or = 0.40 microg/mL in milk.