Detection and Quantitation of Lomefloxacin and Pefloxacin Residues in the Organ Tissues and Eggs of Laying Hens.

Lomefloxacin (LOM) and pefloxacin (PEF) are synthetic antibiotics that have been used in the treatment of infectious diseases in both human and animals. In the People's Republic of China, the use of LOM and PEF in livestock has been prohibited because of the concern that the residues of these drugs may pose a risk to public health. Despite this prohibition, these drugs are still being used in the poultry industry illegally, and so far there has been no systematic study of the persistence of LOM and PEF residues in chickens. In this study, laying hens were treated with a daily dose (10 mg/kg of body weight) of LOM or PEF for five consecutive days, and the drug residues in various tissues and eggs were determined over a 15-day period after the last drug administration. The highest LOM and PEF residual concentrations were found in the tissues 4 h after the last drug administration, and concentrations gradually decreased over time. Plasma had the lowest and liver had the highest residual concentrations throughout the 15-day study period. At the end of the 15 days, 3.64 ± 0.74 µg/kg LOM and 1.78 ± 0.28 µg/kg PEF were detected in the liver, with slightly lower residual concentrations in the kidney. No LOM or PEF residue was detected in the ovarian follicle, plasma, and muscle at the end of the 15 days. In eggs, the depletion rate of LOM was slower than that of PEF. LOM and PEF residues were detected in whole eggs for up to 10 and 8 days, respectively, after drug administration ceased. These findings suggest that the liver and, to a lesser extent, the kidney may be the sites where LOM or PEF residues would persist. This information can be a reliable reference for governmental agencies with respect to the screening of LOM and PEF residues in food products derived from laying hens.

Interspecies scaling of excretory amounts using allometry - retrospective analysis with rifapentine, aztreonam, carumonam, pefloxacin, miloxacin, trovafloxacin, doripenem, imipenem, cefozopran, ceftazidime, linezolid for urinary excretion and rifapentine, cabotegravir, and dolutegravir for fecal excretion.

1. Interspecies allometry scaling for prediction of human excretory amounts in urine or feces was performed for numerous antibacterials. Antibacterials used for urinary scaling were: rifapentine, pefloxacin, trovafloxacin (Gr1/low; <10%); miloxacin, linezolid, PNU-142300 (Gr2/medium; 10-40%); aztreonam, carumonam, cefozopran, doripenem, imipenem, and ceftazidime (Gr3/high; >50%). Rifapentine, cabotegravir, and dolutegravir was used for fecal scaling (high; >50%). 2. The employment of allometry equation: Y = aW(b) enabled scaling of urine/fecal amounts from animal species. Corresponding predicted amounts were converted into % recovery by considering the respective human dose. Comparison of predicted/observed values enabled fold difference and error calculations (mean absolute error [MAE] and root mean square error [RMSE]). Comparisons were made for urinary/fecal data; and qualitative assessment was made amongst Gr1/Gr2/Gr3 for urine. 3. Average correlation coefficient for the allometry scaling was >0.995. Excretory amount predictions were largely within 0.75- to 1.5-fold differences. Average MAE and RMSE were within ±22% and 23%, respectively. Although robust predictions were achieved for higher urinary/fecal excretion (>50%), interspecies scaling was applicable for low/medium excretory drugs. 4. Based on the data, interspecies scaling of urine or fecal excretory amounts may be potentially used as a tool to understand the significance of either urinary or fecal routes of elimination in humans in early development.

Experimental and theoretical studies on the molecular properties of ciprofloxacin, norfloxacin, pefloxacin, sparfloxacin, and gatifloxacin in determining bioavailability.

The aim of this investigation is to identify, by in silico and in vitro methods, the molecular determinants, e.g., solubility in an aqueous medium and lipophilic properties, which have an effect on the bioavailability of five selected fluoroquinolones. These properties were estimated by analysis of the electrostatic potential pattern and values of free energy of solvation as well as the partition coefficients of the studied compounds. The study is based on theoretical quantum-chemical methods and a simple experimental shake-flask technique with two immiscible phases, n-octanol and phosphate buffer. The solvation free energy values of compounds in both environments appeared to be negative. The wide range of electrostatic potential from negative to positive demonstrates the presence of dipole-dipole intermolecular interactions, while the high electron density at various sites indicates the possibility of hydrogen bond formation with solvent molecules. High partition coefficient values, obtained by summing the atomic contributions, did not take various correction factors into account and therefore were not accurate. Theoretical partition coefficient values based on more accurate algorithms, which included these correction factors (fragmental methods), yielded more accurate values. Theoretical methods are useful tools for predicting the bioavailability of fluoroquinolones.

Superparamagnetic surface molecularly imprinted nanoparticles for water-soluble pefloxacin mesylate prepared via surface initiated atom transfer radical polymerization and its application in egg sample analysis.

The novel superparamagnetic surface molecularly imprinted Fe3O4@MIP nanoparticles for water-soluble pefloxacin mesylate (PEF-M) were prepared via surface initiated atom transfer radical polymerization (si-ATRP). The binary mixture of methanol and water was selected as the polar solvents for fabricating PEF-M imprinted MIPs. The Fe3O4@MIP exhibited high saturation magnetization of 41.4 emu/g leading to the fast separation. The adsorption behaviors indicated that the Fe3O4@MIP nanoparticles possessed specific recognition and high affinity towards template PEF-M in aqueous media. Moreover, Fe3O4@MIP nanoparticles were directly used to selectively enrich PEF-M from egg samples. By RP-HPLC analysis, the recoveries of PEF-M were obtained as 92.8-96.5% with relative standard division of 2.4-4.0%.

[Molecular transport mechanism of pefloxacin mesylate binding with transferrin].

The binding mechanism between pefloxacin mesylate (PM) and transferrin (Tf) was explored using spectral experiment combined with molecular modeling techniques. The binding parameters and thermodynamic functions of PM-Tf solution system were measured at different temperatures. The effect of PM on molecular conformation of Tf was investigated and the interaction mechanism was also discussed. The results showed that dynamic quenching mechanism occurs with PM binding to Tf. The value of binding distances (r) is low, which indicates the occurrence of energy transfer. The drug had conformational effect on Tf, which resulted in changes of hydrophobic environment of the binding domain in Tf. According to the obtained thermodynamic parameters, the main interaction force between PM and Tf is attributed to hydrophobic bonding. The results of molecular modeling revealed that hydrophobic and hydrogen bonds are main binding forces in the PM-Tf system. These results were in accordance with spectral experiments. The research results have given a better theoretical reference for the study of pharmacological mechanism between protein and quinolone.

In vitro selection of allosteric ribozymes.

In vitro selection techniques offer powerful and versatile methods to isolate nucleic acid sequences with specific activities from huge libraries. The present protocol describes an in vitro selection strategy for the de novo selection of allosteric self-cleaving ribozymes responding to virtually any drug of choice. We applied this method to select hammerhead ribozymes inhibited specifically by doxycycline or pefloxacin in the sub-micromolar range. The selected ribozymes can be converted into classical aptamers via insertion of a point mutation in the catalytic center of the ribozyme.

Concentration-time courses of pefloxacin in plasma and milk of lactating she-camels (Camelus dromedarius).

Using the microbial inhibition test, the single-dose pharmacokinetics of pefloxacin mesylate dehydrate were studied in six clinically normal lactating she-camels (Camelus dromedarius) after intravenous (IV) and intramuscular (IM) administration of 10 mg/kg body weight (bwt). Blood and milk samples were collected intermittently for a 48 h period, and the pharmacokinetic variables were calculated using compartmental and non-compartmental analytical methods.The plasma course of pefloxacin was best resolved to a two-compartment open model after IV administration and a two-compartment open model with first-order absorption after IM administration. Pefloxacin exhibits a long elimination-phase disposition half-life (t1/2beta) of 4.89 +/- 1.12 h after IV injection and 5.73 +/- 1.42 h after IM administration. The mean volume of distribution at steady state (Vdss) and total body clearance (Cl(tot)) values after IV dosing were 1.18 +/- 0.45 I/kg and 0.21 +/- 0.10 I/kg/h, respectively. The observed peak plasma level (Cmax) of 3.6 +/- 0.1 microg/ml was rapidly attained at 0.75 h (the time of maximum concentration Tmax) after IM administration. The areas under the concentration versus time curves (AUCs) were 44.18 +/- 9.68 microg x h/ml and 29.42 +/-6.49 microg x h/ml after IV and IM administration, respectively. The absolute bioavailability (F%) obtained after IM administration was 71.59 +/- 12.45%. Milk was penetrated quickly, with a mean peak level of 3.24 +/- 0.17 microg/ml occurring at 1.0 h. The elimination half-life was significantly shorter after IV versus IM administration (4.21 +/- 0.84 h versus 5.32 +/- 0.67 h, respectively). Ultimately, pefloxacin could be useful for treatment of udder infections in she-camels after specific assessment of susceptible microorganisms.

Binding interactions of pefloxacin mesylate with bovine lactoferrin and human serum albumin.

The binding of pefloxacin mesylate (PFLX) to bovine lactoferrin (BLf) and human serum albumin (HSA) in dilute aqueous solution was studied using fluorescence spectra and absorbance spectra. The binding constant K and the binding sites n were obtained by fluorescence quenching method. The binding distance r and energy-transfer efficiency E between pefloxacin mesylate and bovine lactoferrin as well as human serum albumin were also obtained according to the mechanism of Förster-type dipole-dipole nonradiative energy-transfer. The effects of pefloxacin mesylate on the conformations of bovine lactoferrin and human serum albumin were also analyzed using synchronous fluorescence spectroscopy.

Pharmacokinetics and tissue residues of pefloxacin and its metabolite norfloxacin in broiler chickens.

1. The pharmacokinetics of pefloxacin and its active metabolite norfloxacin were investigated in chickens after a single oral administration of pefloxacin at a dosage of 10 mg/kg. To characterise the residue pattern, another group of chickens was given 10 mg of pefloxacin/kg body once daily for 4 d by oral route; the tissue concentrations of pefloxacin and norfloxacin were determined at 1, 5 and 10 d after the last administration of the drug. 2. The concentrations of pefloxacin and norfloxacin in plasma and tissues were determined by HPLC assay. The limit of detection for pefloxacin and norfloxacin was 0.03 microg/ml in plasma or microg/g in tissue. 3. The plasma concentration-time data for pefloxacin and norfloxacin were characteristic of a one-compartment open model. The elimination half-life, maximum plasma drug concentration, time to reach maximum plasma drug concentration and mean residence time of pefloxacin were 8.74 +/- 1.48 h, 3.78 +/- 0.23 microg/ml, 3.33 +/- 0.21 h and 14.32 +/- 1.94 h, respectively, whereas the respective values of these variables for norfloxacin were 5.66 +/- 0.81 h, 0.80 +/- 0.07 microg/ml, 3.67 +/- 0.21 h and 14.44 +/- 0.97 h. 4. Pefloxacin was metabolised to norfloxacin to the extent of 22%. 5. The concentrations of pefloxacin (microg/g) 24 h after the fourth dose of the drug declined in the following order: liver (3.20 +/- 0.40) > muscle (1.42 +/- 0.18) > kidney (0.69 +/- 0.04) > skin and fat (0.06 +/- 0.02). Norfloxacin was also detectable in all the tissues analysed except muscle. No drug and/or its metabolite was detectable in tissues except skin and fat 5 d after the last administration. The concentrations of pefloxacin and norfloxacin in skin and fat 10 d after the last dose of pefloxacin were 0.04 +/- 0.02 and 0.03 +/- 0.01 microg/g, respectively.

Spectroscopic and voltammetric studies of pefloxacin bound to calf thymus double-stranded DNA.

Spectral and electrochemical studies have been carried out on the interaction of pefloxacin with calf thymus double-stranded dsDNA. The voltammetric behavior of pefloxacin was investigated at glassy carbon, carbon paste and dsDNA-modified carbon paste electrodes using cyclic voltammetry. Pefloxacin was oxidized, yielding one irreversible oxidation peak. The modification of the carbon paste surface with dsDNA allowed an accumulation process to take place for pefloxacin such that higher sensitivity was achieved compared with the bare surface. The response was characterized with respect to ionic strength, accumulation time, pefloxacin concentration, and other variables. The stripping differential pulse voltammetric response showed a linear calibration curve in the range 1.0 x 10(-7)-1.0 x 10(-5) mol l(-1) with a detection limit of 5.0 x 10(-8) mol l(-1) at the dsDNA modified electrode. The method was applied to the direct determination of pefloxacin in diluted urine samples.

Evidence of active efflux in resistance to ciprofloxacin and to ethidium bromide by Mycoplasma hominis.

The uptake of fluoroquinolones was characterized for the fluoroquinolone-susceptible strain PG21 of Mycoplasma hominis. Accumulation of fluoroquinolones appeared to occur by passive diffusion. Addition of arginine as the energizer significantly reduced the uptake of fluoroquinolones, suggesting the presence of an energy-dependent efflux process. Reserpine and orthovanadate, two multidrug pump inhibitors, increased significantly the ciprofloxacin (CIP) uptake. In contrast, such a strong effect was not observed for moxifloxacin and pefloxacin uptakes. Two ethidium bromide (EtBr)-resistant strains, selected in vitro, showed a resistance profile compatible with a multidrug-resistant phenotype, with increased MICs for the hydrophilic fluoroquinolones, CIP and norfloxacin, EtBr, and acriflavine. Taking the EtBr-resistant strain RB1La as a model, a significant decrease of the CIP and EtBr uptakes was observed compared to the reference strain PG21. In the presence of reserpine and orthovanadate, both inhibitors of ATP-dependent efflux pumps, the CIP uptake increased significantly, reaching approximately the same level as that of the susceptible strain. Similar results were obtained with EtBr uptake and efflux experiments. Our data suggest the presence of an active efflux system, possibly an ABC-type efflux pump, implicated in the resistance to CIP and unrelated compounds like EtBr in the human mycoplasma M. hominis.

In vitro selection of allosteric ribozymes: theory and experimental validation.

In vitro selection techniques offer powerful and versatile methods to isolate nucleic acid sequences with specific activities from huge libraries. We describe an in vitro selection strategy for the de novo selection of allosteric self-cleaving ribozymes responding to pefloxacin and other quinolone derivatives. Within 16 selection cycles, highly sensitive clones responding to drug levels in the sub-micromolar range were obtained. The morpholine moiety of the quinolone derivatives was required for inhibition of the self-cleavage of the selected ribozymes: modifications of the aromatic system were tolerated better than modifications of the morpholine ring. We also present a theoretical model that analyzes the predicted fraction of ribozymes with a given binding constant and cleavage rate recovered after each selection cycle. This model precisely predicts the actual experimental values obtained with the selection procedure. It can thus be used to determine the optimal conditions for an in vitro selection of an allosteric ribozyme with a desired dissociation constant and cleavage rate for a given application.

Effects of pefloxacin on urinary and salivary concentrations of isoniazid in six healthy female volunteers.

The effects of pefloxacin (PFC), a fluoroquinolone antibiotic, on the urinary and salivary concentrations of Isoniazid (INH) were investigated in six healthy female volunteers 19 to 30 years of age. The presence of PFC increased the rate and extent of INH absorption and the rate of its excretion in the urine and saliva. There was an increase in the excretion rate constant (K) and a reduction in the half-life (t1/2) of INH in the presence of PFC. Four of the volunteers had t(1/2) values in the range of 1.55 to 2.43 hours and were considered to be fast acetylators, whereas two subjects with a t(1/2) in the range of 3.36 to 4.41 hours were considered to be slow acetylators. Concurrent administration of INH and PFC may lead to an increased INH toxicity based on the results of the present study.

Energy-dependent accumulation of fluoroquinolones in quinolone-resistant Klebsiella pneumoniae strains.

The intracellular accumulation of norfloxacin and pefloxacin in Klebsiella pneumoniae was evaluated. The roles of lipopolysaccharide, capsule, and outer membrane proteins were not important for the intrabacterial accumulation of fluoroquinolones in isogenic strains with known outer membrane alterations. In fluoroquinolone-resistant clinical isolates also expressing GyrA alterations, an active efflux leading to decreased accumulation of the drugs enhanced their resistance to these agents.

Evidence for an efflux pump in multidrug-resistant Campylobacter jejuni.

Mechanisms of drug resistance in Campylobacter jejuni were investigated. Mutant strains 34PEFr, which was resistant to pefloxacin (128-fold increase in the MIC), and 34CTXr, which was resistant to cefotaxime (32-fold increase in the MIC) and which was derived from the susceptible parent 34s, were obtained by serial passages on pefloxacin and cefotaxime gradient plates, respectively. Both mutants showed cross-resistance to erythromycin, chloramphenicol, tetracycline, beta-lactams, and quinolones. While the quinolone resistance of strain PEFr could be explained by a mutation at codon 86 of the gyrA gene, the multidrug resistance phenotype of both strains was further investigated. Accumulation of pefloxacin, ciprofloxacin, and minocycline was measured by fluorometry and was found to be lower in the mutant strains than in the parent strain. Preincubation of the cells with carbonyl cyanide m-chlorophenylhydrazone, however, completely abolished this difference. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of outer membrane preparations from both mutant strains showed overexpression of two proteins of 55 and 39 kDa which were absent from the outer membranes of the wild-type strain. These results indicate that in C. jejuni 34PEFr and 34CTXr, multidrug resistance is associated with an efflux system with a broad specificity.

Multiple-dose pharmacokinetics of pefloxacin in patients with hepatocellular deficiency.

Multiple-dose pharmacokinetics of pefloxacin were evaluated in 25 patients with hepatocellular insufficiency. The severity of liver disease was graded A, B or C according to the Child-Pugh classification. Pharmacokinetic parameters evaluated in patients on day 1 of treatment were compared with those computed in 11 healthy volunteers (the control group) after a single dose. Blood samples were taken at frequent intervals after drug administration and assayed by high performance liquid chromatography. The mean age of patients with liver impairment was slightly greater (59.5 years, range 33 to 81 years) than that of the control group (46.7 years, range 42 to 51 years). In the patients with liver disease, the mean (+/- SD) half-life of elimination, although highly variable, was significantly longer (46.3 +/- 42.5 hours) than in the control group (11.3 +/- 3.5 hours, p < 0.001). The total clearance was significantly decreased (1.76 +/- 1.31 L/h vs 6.03 +/- 2.99 L/h in the control group). In groups B and C of the Child-Pugh classification, total body clearance was about 30% of normal values. Elimination half-life increased by 200% in group B and 373% in group C compared with values in healthy volunteers. Intergroup differences (group B vs group C of the Child-Pugh classification) were not statistically significant. The minimum concentrations inhibiting 90% of Gram-negative strains (MIC90) were exceeded by plasma pefloxacin concentrations throughout treatment. For most patients, trough plasma concentrations were above 2 mg/L and peak plasma concentrations averaged 8.5 mg/L. Large inter- and intraindividual variations in the elimination half-life, total clearance and volume of distribution were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Pefloxacin and immunity: cellular uptake, potentiation of macrophage phagocytosis and intracellular bioactivity for Klebsiella pneumoniae.

Antibiotic potentiation of host defence mechanisms may be of potential clinical importance in the outcome of infections. Therefore the effect of pefloxacin upon the interaction of in vitro of human macrophages with Klebsiella pneumoniae, by assays of antibiotic cellular uptake, bacterial phagocytosis and intracellular killing, was examined. The results indicated that pefloxacin was well concentrated by phagocytes at all the concentrations tested. The uptake proceeded rapidly and was not affected either by cell viability or physiological environmental temperature. Synergistic phagocytosis and intracellular killing of K. pneumoniae was observed in the presence of macrophages and subinhibitory concentrations (one-half MIC) of pefloxacin. Pretreatment of bacteria with pefloxacin led to an increase in both bacterial uptake and microbicidal activity of phagocytes. Exposure of the macrophages to pefloxacin did not affect any phagocyte functions.

Effect of pefloxacin on microorganism: host cell interaction.

Recent evidence indicates that certain antibiotics affect bacterial adherence and phagocyte-micro-organism interactions. These interactions are important in the early stages of bacterial pathogenesis, that is, attachment to mucosal surfaces and invasion. Among the antibiotics of interest in this field are the fluoroquinolones. Sub-MICs of pefloxacin can alter the ability of Gram-positive cocci (Staphylococcus aureus, Enterococcus faecalis) and Gram-negative bacilli (Escherichia coli) to adhere to different eukaryotic cells (uroepithelial and buccal cells) and to fibrin-platelet matrices. The mechanism by which pefloxacin reduces adhesion is not completely understood. However in the case of Esch. coli, the inhibition of haemagglutination and adherence corresponds to: (1) a decrease in production of fimbriae; (2) changes in the composition of outer membrane proteins; and (3) an effect on partition coefficient (carried out with the PEG/dextran system) which can be attributed to changes in electric and/or hydrophobic properties of the Esch. coli surface. The first step of phagocytosis is represented by adherence of opsonized bacteria to the membrane receptors of phagocytes. Consequently, the action of pefloxacin on phagocytosis is also of importance. Pretreatment of bacteria (Staph. aureus, Ent. faecalis, Esch. coli and Legionella pneumophila) with 1/4 the MIC of pefloxacin leads to an increase in uptake of the different strains by phagocytes (polymorphonuclear leucocytes and macrophages). Exposure of the phagocytes to 10 mg/l of pefloxacin enhances phagocytosis of strains that have not been pretreated. Finally, entry of antibiotics into phagocytic cells is a prerequisite for activity against intracellular organisms. The concentration of pefloxacin by polymorphs and macrophages is high (intracellular concentration/extracellular concentration = 5-10). Such findings correlate well with the intracellular activity of pefloxacin, demonstrated with guinea pig macrophages and different bacteria (Staph. aureus, L. pneumophila).