Silver nanoparticles for the visual detection of lomefloxacin in the presence of cystine

A novel optical sensors for lomefloxacin based on the plasma resonance properties of silver nanoparticles (AgNPs) for the first time. The hydrogen bonds and electrostatic force between the lomefloxacin and AgNPs could induce the change in color and absorption spectra of AgNPs suspension, which provided a theoretical basis for the optical detection of lomefloxacin. In addition, we made the AgNPs-lomefloxacin detection system reach the critical point of discoloration by adding cystine to improve the sensitivity. Furthermore, the influence of some factors such as temperature, reaction time and pH on the AgNPs-lomefloxacin detection system was investigated. The results of UV-vis spectra showed that the absorption ratio (A₅₂₀/A₃₉₅) was linear with the concentration of lomefloxacin in the range from 0.2 to 5 μmol/L with linear coefficients of 0.991. The proposed method can be applied to detecting lomefloxacin with an ultralow detection limit of 0.6 μmol/L without any complicated instruments and complex pretreatment. The selectivity of AgNPs-lomefloxacin detection system is proved excellent by comparing with other ions and analytes in urine. The method in our study is appropriate to be used to monitor quantitatively entecavir in human urine owing to its rapid response rate, visible color changes, wide linear range and excellent selectivity.

New spectrophotometric/chemometric assisted methods for the simultaneous determination of imatinib, gemifloxacin, nalbuphine and naproxen in pharmaceutical formulations and human urine

In this paper, novel univariate and multivariate regression methods along with model-updating technique were developed and validated for the simultaneous determination of quaternary mixture of imatinib (IMB), gemifloxacin (GMI), nalbuphine (NLP) and naproxen (NAP). The univariate method is extended derivative ratio (EDR) which depends on measuring every drug in the quaternary mixture by using a ternary mixture of the other three drugs as divisor. Peak amplitudes were measured at 294nm, 250nm, 283nm and 239nm within linear concentration ranges of 4.0-17.0, 3.0-15.0, 4.0-80.0 and 1.0-6.0μgmL^-1 for IMB, GMI, NLP and NAB, respectively. Multivariate methods adopted are partial least squares (PLS) in original and derivative mode. These models were constructed for simultaneous determination of the studied drugs in the ranges of 4.0-8.0, 3.0-11.0, 10.0-18.0 and 1.0-3.0μgmL^-1 for IMB, GMI, NLP and NAB, respectively, by using eighteen mixtures as a calibration set and seven mixtures as a validation set. The root mean square error of predication (RMSEP) were 0.09 and 0.06 for IMB, 0.14 and 0.13 for GMI, 0.07 and 0.02 for NLP and 0.64 and 0.27 for NAP by PLS in original and derivative mode, respectively. Both models were successfully applied for analysis of IMB, GMI, NLP and NAP in their dosage forms. Updated PLS in derivative mode and EDR were applied for determination of the studied drugs in spiked human urine. The obtained results were statistically compared with those obtained by the reported methods giving a conclusion that there is no significant difference regarding accuracy and precision.

Delafloxacin Pharmacokinetics in Subjects With Varying Degrees of Renal Function

Delafloxacin, a fluoroquinolone, has activity against gram-positive organisms including methicillin-resistant Staphylococcus aureus and fluoroquinolone-susceptible and -resistant gram-negative organisms. This study was conducted to determine delafloxacin pharmacokinetics after a single intravenous infusion or oral dose administration in subjects with varying degrees of renal function. The study was an open-label, parallel-group crossover study in subjects with normal renal function or with mild, moderate, or severe renal impairment. Subjects received 300 mg delafloxacin intravenously, placebo intravenously, and 400 mg delafloxacin orally in 3 periods separated by ≥14-day washouts. Blood and urine pharmacokinetic parameters were calculated using noncompartmental methods. Delafloxacin total clearance decreased with decreasing renal function, with a corresponding increase in AUC0-∞ . After intravenous administration, mean total clearance was 13.7 and 7.07 L/h, and mean AUC0-∞ was 22.6 and 45.0 μg·h/mL in normal and severe renal subjects, respectively. Mean renal clearance as determined by urinary excretion was 6.03 and 0.44 L/h in normal and severe renal impairment subjects, respectively. Total clearance exhibited linear relationships to eGFR and CLCR . Similar observations were found after oral administration of delafloxacin. Single doses of delafloxacin 300 mg intravenously and 400 mg orally were well tolerated in all groups. In conclusion, renal insufficiency has an effect on delafloxacin clearance; a dosing adjustment for intravenous dosing is warranted for patients with severe renal impairment (eGFR < 30 mL/min).

Colorimetric recognition of pazufloxacin mesilate based on the aggregation of gold nanoparticles

A novel colorimetric nanomaterial-assisted optical sensor for pazufloxacin mesilate was proposed for the first time. Pazufloxacin mesilate could induce the aggregation of glucose-reduced gold nanoparticles (AuNPs) through hydrogen-bonding interaction and electrostatic attraction, leading to the changes in color and absorption spectra of AuNPs. The effect of different factors such as pH, the amount of AuNPs, reaction time and reaction temperature was inspected. Under the optimum condition, UV-vis spectra showed that the absorption ratio (A670/A532) was linear with the concentration of pazufloxacin mesilate in the range from 9×10(-8) mol L(-1) to 7×10(-7) mol L(-1) with a linear coefficient of 0.9951. This method can be applied to detecting pazufloxacin mesilate with an ultralow detection limit of 7.92×10(-9) mol L(-1) without any complicated instruments. Through inspecting other analytes and ions, the anti-interference performance of AuNP detection system for pazufloxacin mesilate was excellent. For its high efficiency, rapid response rate as well as wide linear range, it had been successfully used to the analysis of pazufloxacin mesilate in human urine quantificationally.

Silver nanoparticles enhanced flow injection chemiluminescence determination of gatifloxacin in pharmaceutical formulation and spiked urine sample

Silver nanoparticles have been utilized for the enhanced chemiluminogenic estimation of fluoroquinolone antibiotic gatifloxacin. It has been found that the weak chemiluminescence intensity produced from the reaction between calcein and KMnO4 can further be strengthened by the addition of silver nanoparticles in the presence of gatifloxacin. This phenomenon has been exploited to the quantitative determination of gatifloxacin. Under the optimum experimental conditions, the calibration curves are linear over the range of 8.9×10(-9)-4.0×10(-6) M, while the limits of detections were found to be 2.6×10(-9) M with correlation coefficient value (r(2)) 0.9999. The relative standard deviation calculated from six replicate measurements (1.0×10(-4) M gatifloxacin) was 1.70%. The method was applied to pharmaceutical preparations and the results obtained were in reasonable agreement with the amount labeled on the formulations. The proposed method was also used for the determination of gatifloxacin in spiked urine samples with satisfactory results. No interference effects from some common excipients used in pharmaceutical preparations have been found.

High performance liquid chromatography coupled with resonance Rayleigh scattering for the detection of three fluoroquinolones and mechanism study

A reliable and versatile high performance liquid chromatography coupled with resonance Rayleigh scattering method was established for the determination of three fluoroquinolones, including levofloxacin, norfloxacin and enrofloxacin in water sample and human urine sample. In pH 4.4-4.6 Britton-Robinson buffer medium, the fluoroquinolones separated by high performance liquid chromatography could react with erythrosine to form 1:1 ion-association complexes, which could make contributions to the great enhancement of RRS. The resonance Rayleigh scattering signal was recorded at λex=λem=330 nm. The resonance Rayleigh scattering spectral characteristics of the drugs and the experimental conditions such as pH, detection wavelength, erythrosine concentration, flow rate, the length of reaction tube were studied. Quantum chemistry calculation, Fourier transform infrared spectroscopy and absorption spectroscopy were used to discuss the reaction mechanism. The recoveries of samples added standard ranged from 97.53% to 102.00%, and the relative standard deviation was below 4.64%. The limit of detection (S/N=3) of 0.05-0.12 μg mL(-1) was reached, and the linear regression coefficients were all above 0.999. The proposed method was proved as a simple, low cost and high sensitivity method.

On the performance of multiway methods for simultaneous quantification of two fluoroquinolones in urine samples by fluorescence spectroscopy and second-order calibration strategies

In the present work, the analytical performance of three multi-way algorithms has been evaluated. The proposed analytical problem was the simultaneous determination of moxifloxacin and ciprofloxacin in human urine samples using fluorescence spectroscopy. Parallel factor analysis (PARAFAC), self-weighted alternating trilinear decomposition (SWATLD) and unfolded partial least squares combined with the residual bilinearization procedure (U-PLS/RBL) have been compared, regarding their ability to solve the proposed problem. In this study, "second-order advantage" was also exploited for the mentioned algorithms through different calibration strategies. The three-way data was obtained via fluorescence spectroscopy, so that excitation-emission matrices (EEM) of the samples were recorded as the analytical signals. The accuracy and precision of each individual algorithm for analyzing the drugs in urine samples were compared using root mean square error of prediction (RMSEP), recovery and elliptical joint confidence region (EJCR) plots. The results revealed that each of the three algorithms could be applied for determination of moxifloxacin and ciprofloxacin, despite different EEM subsets and calibration strategies. However, better analytical performances were observed through PARAFAC and U-PLS/RBL modeling for MOX and CIP, respectively. So, by coupling the multi-way decomposition algorithms with fluorescence spectroscopy, a main part of preliminary sample preparation steps can be eliminated and experimental procedure might be significantly simplified, while achieving desirable analytical performance.

Well-defined nanostructured surface-imprinted polymers for highly selective magnetic separation of fluoroquinolones in human urine

The construction of molecularly imprinted polymers on magnetic nanoparticles gives access to smart materials with dual functions of target recognition and magnetic separation. In this study, the superparamagnetic surface-molecularly imprinted nanoparticles were prepared via surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization using ofloxacin (OFX) as template for the separation of fluoroquinolones (FQs). Benefiting from the living/controlled nature of RAFT reaction, distinct core-shell structure was successfully constructed. The highly uniform nanoscale MIP layer was homogeneously grafted on the surface of RAFT agent TTCA modified Fe3O4@SiO2 nanoparticles, which favors the fast mass transfer and rapid binding kinetics. The target binding assays demonstrate the desirable adsorption capacity and imprinting efficiency of Fe3O4@MIP. High selectivity of Fe3O4@MIP toward FQs (ofloxacin, pefloxacin, enrofloxacin, norfloxacin, and gatifloxacin) was exhibited by competitive binding assay. The Fe3O4@MIP nanoparticles were successfully applied for the direct enrichment of five FQs from human urine. The spiked human urine samples were determined and the recoveries ranging from 83.1 to 103.1% were obtained with RSD of 0.8-8.2% (n = 3). This work provides a versatile approach for the fabrication of well-defined MIP on nanomaterials for the analysis of complicated biosystems.

Gatifloxacin Pharmacokinetics in Healthy Men and Women

The sex-based pharmacokinetics of gatifloxacin were investigated. Healthy subjects (6 men, 6 women) received a single oral dose of gatifloxacin 400 mg. Blood and urine samples were collected, and gatifloxacin concentrations were determined by high-performance liquid chromatography. Pharmacokinetic parameters were estimated by fitting appropriate models to the serum concentration-time data using ADAPT II. Linear regression analysis was used to determine the influence of sex and weight on the oral clearance (CL(s)/F) and apparent steady-state volume of distribution (V(ss)/F) of gatifloxacin. Women had a significantly smaller V(ss)/F compared to men (93.5 +/- 21.3 L vs 128.8 +/- 16.2 L, P = .009); however, there was no significant difference when normalized for total body weight (TBW) or lean body weight (LBW). Neither CL(s)/F nor peak serum concentration (C(max)) was significantly different between sexes, although C(max) was 25% higher in women (P = .06). Regression analyses revealed that TBW (R(2) = .63) and LBW (R(2) = .65) were strong predictors of V(ss)/F. Given the smaller V(ss)/F, women may have slightly higher maximum concentrations, but these differences are unlikely to have clinical significance.

Determination of enrofloxacin by room-temperature phosphorimetry after solid phase extraction on an acrylic polymer sorbent

A phosphorimetric method was developed to enable the determination of enrofloxacin using photochemical derivatization which was used to both improve detection limits and to minimize the uncertainty of measurements. Phosphorescence was induced on cellulose containing TlNO(3). Absolute limit of detection at the ng range and linear analytical response over three orders of magnitude were achieved. A metrological study was made to obtain the combined uncertainty value and to identify that the precision was mainly affected by the changing of substrates when measuring the signal from each replicate. Pharmaceutical formulations containing enrofloxacin were successfully analyzed by the method and the results were similar to the ones achieved using a HPLC method. A solid phase extraction on an acrylic polymer was optimized to separate enrofloxacin from interferents such as diclofenac and other components from biological matrices, which allowed the successful use of the method in urine analysis.

Quantification of sparfloxacin in pharmaceutical dosages and biological samples

A simple and fast method for spectrophotometric determination of sparfloxacin using p-dimethyl-aminobenzaldehyde (DMAB) has been developed. A yellow coloured product formed from reaction between sparfloxacin and DMAB as a result of condensation reaction at room temperature. The maximum absorbance was found at 392 nm with molar absorptivity of 4.9 × 10(3) L mol(-1) cm(-1). All parameters for the reaction, as concentration of DMBA reagent, molarity of sulphuric acid, and reaction temperature were studied. Under the conditions studied, a linear relationship between absorbance of the condensation product and concentration of sparfloxacin in the range of 2.0-80.0 μg mL(-1) was found with good correlation coefficient (0.9997). The limits of detection (LOD) and quantification (LOQ) for the proposed method were found to be 0.22 and 0.75 μg mL(-1) respectively. The repeatability and accuracy (model) of the method was studied at three different concentrations of sparfloxacin and found with value of relative standard deviation less than 2.0%. The method was found selective for determination of sparfloxacin in the presence of commonly used excipients in dosage forms. The developed method was validated statistically and applied successfully to the analysis of the drug in pure form, pharmaceutical preparations, and spiked blood plasma and urine samples with good accuracy (real) and precision. The percentage recovery was found from 99.0-100.0% with relative standard deviation less than 1%. The results of the proposed method were compared statistically with the results of literature HPLC method.

[The use of fluoroquinolones in bacterial urinary tract infections in cats]

Older cats (>10 years) with FLUTD (Feline Lower Urinary Tract Disease) symptoms are often affected by urinary tract infections. In most of these cats organ diseases (e.g. chronic renal failure, diabetes mellitus) or iatrogenic factors (immunosuppressive drugs, indwelling catheter) are found that clearly predispose cats to this kind of infection. From a diagnostic point of view, urinalysis and urine culture are the most important tools in detecting bacteriuria. The microbiological spectrum is thereby comparable to that found in dogs, revealing Escherichia ( E. ) coli but also Staphylococcus spp. and Enterococcus spp./ Streptococcus spp. Antibiotic therapy should be based on the results of susceptibility testing. If this kind of information is not available, drug selection has to be decided on an empirical basis unless it is a complicated urinary tract infection. Preferred antibiotics should have a high renal excretion rate and thus ensure therapeutically effective drug levels in the urine. In this respect, the fluoroquinolones belong to the group of appropriate drugs to be used in cats. The relevance of therapeutical drug concentrations achievable in the urine is discussed for the example of marbofloxacin, a third-generation fluoroquinolone. New pharmacokinetic data showed that marbofloxacin concentrations of ≥2µg/ml are maintained in the urine of healthy cats for 72 and 103 hours after administration of 2 and 4mg/kg BW s.c., respectively.

Plasma and urine concentrations of marbofloxacin following single subcutaneous administration to cats

The pharmacokinetic properties of marbofoxacin, a third generation fluoroquinolone, were investigated in 12 healthy adult cats after single subcutaneous (SC) administration of 2 mg/kg BW (Part I, n=8 cats) and 4 mg/kg BW (Part II, n=4 cats). In each part of the study blood and urine samples were collected before treatment and thereafter for 5 days. The plasma and urine concentrations of marbofloxacin were determined by HPLC with UV detection. Pharmacokinetic calculations were performed for each treated animal using an open one-compartment-model with first-order elimination after SC dosing. Marbofloxacin in plasma (means): Maximum concentrations (Cmax) of about 1.2 and 3.0 microg/ml were measured 2.3 and 4 hours (tmax) after dosing of 2 and 4 mg/kg BW, respectively. Elimination from the body was low with a total clearance (Cl/F) of approximately 0.1 l/h/kg for both dosages. The half-life (t 1/2) for this process was calculated with 8-10 hours. AUC increased almost proportional when doubling the dose, i.e., 19.77 +/- 6.25 microg * h/ml (2 mg/kg BW) and 51.26 +/- 11.83 microg * h/ml (4 mg/kg BW). Plasma kinetics measured were in accordance with data from literature. Marbofloxacin in urine (means): Maximum drug concentrations were detected 4 and 8 hours after dosing with 70 microg/ml (2 mg/kg BW) and 160 microg/ml (4 mg/kg BW), respectively. Inhibitory effects of the urinary matrix on the antimicrobial activity of the drug were taken into account when performing PK/PD calculations. However, a concentration-dependent bactericidal activity (Cmax/MIC > 8-10) which is claimed for fluoroquinolones was sufficiently met with focus on Escherichia (E.) coli (MIC90 0.5 microg/ml). In the same matrix a threshold value of 1.0 microg/ml was undercut 82 and 116 hours after SC dosing, respectively. Hence, a time-dependent bacteria killing kinetic (T > MIC) which may be of relevance for some Gram-positive germs like Staphylococcus spp. (MIC90 1.0 microg/ml) should be covered, too.

Influence of a five-day vegetarian diet on urinary levels of antibiotics and phthalate metabolites: a pilot study with "Temple Stay" participants

Diet is purported to be means of exposure to many environmental contaminants. The purpose of this study is to understand the influence of dietary change on the levels of exposure to several environmental chemicals - in particular, antibiotics and phthalates. For this purpose, we examined the extent to which short-term changes in diet influenced the inadvertent exposure levels to these chemicals in an adult population. We recruited participants (n=25) of a five-day 'Temple Stay' program in Korea and collected urine samples before and after the program. We also conducted a questionnaire survey on participants' dietary patterns prior to their participation. During the program, participants followed the daily routines of Buddhist monks and maintained a vegetarian diet. Urinary levels of three antibiotics and their major metabolites, metabolites of four major phthalates, and malondialdehyde (MDA) as an oxidative stress biomarker were analyzed. The frequency and levels of detection for antibiotics and phthalates noticeably decreased during the program. Urinary MDA levels were significantly lower than before program participation (0.16 versus 0.27mg/g creatinine). Although the exposure to target compounds might be influenced by other behavioral patterns, these results suggest that even short-term changes in dietary behavior may significantly decrease inadvertent exposure to antibiotics and phthalates and hence may reduce oxidative stress levels.

Determination of ofloxacin and gatifloxacin by mixed micelle-mediated cloud point extraction-fluorimetry combined methodology

A cloud point extraction process using mixed micelle of the anionic surfactant sodium dodecyl sulfate (SDS) and the non-ionic surfactant polyoxyethylene(7.5)nonylphenylether (PONPE 7.5) to extract two fluoroquinolone antimicrobial agents, ofloxacin and gatifloxacin, from aqueous media was investigated. The method is based on the mixed micelle-mediated extraction of fluoroquinolones in the presence of NaCl as an inducing agent in phase separation, followed by spectrofluorimetric determination. The effect of different variables such as pH, PONPE7.5 concentration, SDS concentration, NaCl concentration, cloud point temperature, and time was investigated, and optimum conditions were established. At optimum conditions, the rectilinear calibration graphs were obtained in the concentration range of 0.1-150 and 0.1-250ngmL(-1) for ofloxacin and gatifloxacin, and the limits of detection were 0.04 and 0.06ngmL(-1), respectively. The proposed procedure was applied successfully for the detection of the investigated drugs in their pharmaceutical dosage forms, in spiked plasma, spiked urine, and urine samples, with good precision and accuracy.

Micelle-enhanced and terbium-sensitized spectrofluorimetric determination of gatifloxacin and its interaction mechanism

A terbium-sensitized spectrofluorimetric method using an anionic surfactant, sodium dodecyl benzene sulfonate (SDBS), was developed for the determination of gatifloxacin (GFLX). A coordination complex system of GFLX-Tb(3+)-SDBS was studied. It was found that SDBS significantly enhanced the fluorescence intensity of the complex (about 11-fold). Optimal experimental conditions were determined as follows: excitation and emission wavelengths of 331 and 547nm, pH 7.0, 2.0x10(-4)moll(-1) terbium (III), and 2.0x10(-4)moll(-1) SDBS. The enhanced fluorescence intensity of the system (DeltaI(f)) showed a good linear relationship with the concentration of GFLX over the range of 5.0x10(-10) to 5.0x10(-8)moll(-1) with a correlation coefficient of 0.9996. The detection limit (3sigma) was determined as 6.0x10(-11)moll(-1). This method has been successfully applied to the determination of GFLX in pharmaceuticals and human urine/serum samples. Compared with most of other methods reported, the rapid and simple procedure proposed in the text offers higher sensitivity, wider linear range, and better stability. The interaction mechanism of the system is also studied by the research of ultraviolet absorption spectra, surface tension, solution polarity and fluorescence polarization.

Determination of norfloxacin and enrofloxacin by solid-phase microextraction/high-performance liquid chromatography

A solid-phase microextraction (SPME) method followed by separation with high-performance liquid chromatography and subsequent UV detection was developed for the determination of norfloxacin and enrofloxacin. The simple and sensitive preconcentration technique uses 280 nm wavelength in mobile phase of citrate buffer (0.01 M), pH 3.8, prepared in water (A) and acetonitrile (B), with composition of the mobile phase A:B, 40:60, at a flow rate of 1.0 mL/min. A C18 reversed-phase analytical column (5 microm) was selected as separation medium for the technique. To obtain optimum extraction efficiency, several parameters relating to SPME were investigated. The method was linear over the range of 10-100 ng/mL for norfloxacin and enrofloxacin with a correlation coefficient (R2) value of 0.9972 and 0.9980 for norfloxacin and enrofloxacin, respectively. Using the SPME method, the detection limits (signal-to-noise ratio = 3) are 0.17 and 0.12 ng/mL for norfloxacin and enrofloxacin, respectively.

Fluorescence probe enhanced spectrofluorimetric method for the determination of gatifloxacin in pharmaceutical formulations and biological fluids

A spectrofluorimetry for the determination of gatifloxacin (GFLX) was developed based on the strong fluorescence of gatifloxacin after adding fluorescence probe yttrium in buffer solution (pH 7.0) and various factors of influencing fluorescence have been researched. Under the optimum conditions, the liner range was 4.00x10(-8) to 1.00x10(-6)gmL(-1) and the detection limit is 3.36x10(-9)gmL(-1) (correlation coefficient r=0.9997), respectively. The relative standard deviation was 1.1% for 11 measurements of 5.6x10(-7)gmL(-1) gatifloxacin standard solution. The mechanism of sensitizing effect of probe was discussed. The proposed method has been successfully applied to determine real samples and the obtained results are in good agreement with the results of HPLC.

Separation of seven fluoroquinolones by microemulsion electrokinetic chromatography and application to ciprofloxacin, lomefloxacin determination in urine

A simple, reliable microemulsion electrokinetic chromatography (MEEKC) method is developed for the simultaneous separation of seven fluoroquinolones (FQs). The best separation is achieved in a carrier electrolyte containing 1% (v/v) heptane, 100 mmol/L sodium dodecyl sulfate (SDS), 10% (v/v) 1-butanol, and 8 mmol/L phosphate-sodium tetraborate buffer at pH 7.30. The proposed method was directly applied to the determination of ciprofloxacin (CPF) and lomefloxacin (LMF) in urine samples of subjects administered either with CPF or LMF.

Evaluation of gatifloxacin pharmacokinetics and pharmacodynamics in severely ill adults in a medical Intensive Care Unit

A prospective, open-label study investigated the steady-state pharmacokinetics of gatifloxacin in 20 adult patients in a medical Intensive Care Unit (ICU). Twelve patients had normal or moderately impaired renal function (creatinine clearance (CrCL) >or=40 mL/min) and received gatifloxacin 400 mg intravenously once daily. Eight patients had CrCL<40 mL/min and received 200 mg doses. Gatifloxacin plasma and urine concentrations were determined by validated high-performance liquid chromatography. Mean+/-standard deviation gatifloxacin elimination half-life (t(1/2)), systemic clearance and volume of distribution in patients with CrCL>or=40 mL/min were 10.8+/-1.5h, 156+/-29 mL/min and 1.8+/-0.2 L/kg, respectively. Maximum and minimum serum concentrations (C(max) and C(min)) and area under the serum concentration-time curve from 0-24 h (AUC(0-24)) in these patients were 4.77+/-0.76 mg/L, 1.08+/-0.28 mg/L and 44.4+/-9.2 mgh/L, respectively. Observed t(1/2), C(max) and AUC(0-24) following 200 mg doses in patients with poor renal function (CrCL<40 mL/min) were 18.2+/-3.3 h, 2.85+/-0.76 mg/L and 36.6+/-3.4 mgh/L, respectively. Statistically significant (P<0.05) increase in AUC(0-24) and decreases in t(1/2) and clearance (total and renal) were observed in ICU patients administered intravenous gatifloxacin compared with previous data in healthy volunteers. Pharmacodynamic evaluation by Monte Carlo simulation indicated that approved gatifloxacin dosage regimens appear to be adequate for most pathogens (minimum inhibitory concentration (MIC) <or=0.5 microg/mL) associated with community-acquired infections in severely ill ICU patients; less susceptible pathogens (MIC>or=1 microg/mL) do not appear to be optimally treated with currently approved doses.

Plasma Concentrations, Pharmacokinetics and Urinary Excretion of Gatifloxacin after Single Intravenous Injection in Buffalo Calves

The pharmacokinetics and urinary excretion of gatifloxacin were investigated after a single intravenous injection of 4 mg/kg body weight in buffalo calves. The therapeutic plasma drug concentration was maintained for up to 12 h. Gatifloxacin rapidly distributed from blood to tissue compartments, which was evident from the high values of the distribution rate constant, alpha1 (11.1 +/- 1.06 h(-1)) and the rate constant of transfer of drug from central to peripheral compartment, k12 (6.29 +/- 0.46 h(-1)). The area under the plasma drug concentration-time curve and apparent volume of distribution were 17.1 +/- 0.63 (microg.h)/ml and 3.56 +/- 0.95 L/kg, respectively. The elimination half-life (t (1/2 beta)), total body clearance (ClB) and the ratio of drug present in tissues and plasma (T/P) were 10.4 +/- 2.47 h, 235.1 +/- 8.47 ml/(kg.h) and 10.1 +/- 2.25, respectively. About 19.7% of the administered drug was excreted in urine within 24 h. A satisfactory intravenous dosage regimen for gatifloxacin in buffalo calves would be 5.3 mg/kg at 24 h intervals.

Determinations of fluoroquinolones and nonsteroidal anti-inflammatory drugs in urine by extractive spectrophotometry and photoinduced spectrofluorimetry using multivariate calibration

Multivariate calibration methods are chemometric tools that may be applied to the analysis of spectroscopic data with multichannel detection. Two procedures, based on spectrophotometric and fluorimetric signals, are reported for the simultaneous determination of two fluoroquinolones (ciprofloxacin and ofloxacin) and two nonsteroidal anti-inflammatory drugs (diclofenac and mefenamic acid) using first- and second-order multivariate calibration methods. In the spectrophotometric method, an extractive procedure into chloroform using trioctylmethylammonium chloride-adogen as counter ion was optimized, with the object of extracting the analytes from urine samples and eliminating matrix interferences. After separation, the absorption spectrum of the organic phase was used as the analytical signal in a partial least squares method. A photoinduced spectrofluorimetric (PIF) method using excitation-emission fluorescence matrices, is proposed, to apply three-way chemometric calibration, with the aim of analyzing ofloxacin, ciprofloxacin, and diclofenac in urine samples without the previous extractive sample-cleaning step. For both procedures, recoveries around 100% were found for all the analytes. However, the PIF three-way chemometric method provides the most sensitive and selective procedure as the urine interferences are modulated using the three-way chemometric technique.

On-line sample cleanup and chiral separation of gemifloxacin in a urinary solution using chiral crown ether as a chiral selector in microchip electrophoresis

In chiral capillary electrophoresis of primary amine enantiomers using (+)-18-crown-6-tetracarboxylic acid (18C6H4) as a chiral selector, the presence of alkaline metal ions in the sample solution as well as in the run buffer is undesirable due to their strong competitive binding with 18C6H4. A channel-coupled microchip electrophoresis device was designed to clean up alkaline metal ions from a sample matrix for the chiral analysis of amine. In the first channel, the metal ions in the sample were monitored by indirect detection using quinine as a chromophore and drained to the waste. In the second separation channel, gemifloxacin enantiomers, free of the alkaline metal ions, were successfully separated using only a small amount of the chiral selector (50 microM 18C6H4).

Spectrofluorimetric and micelle-enhanced spectrofluorimetric determination of gatifloxacin in human urine and serum

A spectrofluorimetric method to determine gatifloxacin has been developed and applied to the quantification of this fluoroquinolone in spiked human urine and serum. The native fluorescence of gatifloxacin allow the determination of 0.040-0.700 micro gmL(-1) of this molecule in aqueous solution containing acetic acid-sodium acetate buffer (pH 3.5), with lambda(exc)=292 nm and lambda(em)=484 nm. Micelle-enhanced fluorescence led to 75% higher analytical signals in presence of 12 mM sodium dodecyl sulphate, which allow the determination of 0.020-0.450 microg mL(-1) fluoroquinolone with lambda(exc)=292 nm and lambda(em)=470 nm. Both methods were successfully applied to gatifloxacin determination in spiked human urine and serum.

Electrochemical Adsorptive Behavior of Some Fluoroquinolones at Carbon Paste Electrode

Cyclic voltammetry and differential pulse voltammetry were used to explore the adsorption behavior of three antibacterial agents at a carbon paste electrode. The drugs were accumulated on a carbon paste electrode, and a well-defined oxidation peak was obtained in acetate buffer (pH 5.0). The adsorptive stripping response was evaluated as a function of some variables such as the scan rate, pH and accumulation time. A simple, precise, inexpensive and sensitive voltammetric method has been developed for the determination of the cited drugs (Lomefloxacin (LFX), Sparfloxacin hydrochloride (SFX), and Gatifloxacin (GFX)). A linear calibration was obtained from 2 x 10(-7) M to 4 x 10(-5) M for LFX, 2 x 10(-7) M to 6 x 10(-5) M for SFX, and GFX. The limits of detection (LOD) were 4.2 x 10(-7), 7 x 10(-7) and 6.6 x 10(-7) M, while the limits of quantification (LOQ) were 1.4 x 10(-6), 2.3 x 10(-6) and 2.2 x 10(-6) M for LFX, SFX, and GFX, respectively. The R. S. D. of five measurements at the 1 x 10(-6) M level were 0.4, 0.5 and 0.3 for LFX, SFX and GFX, respectively. The method was applied to the determination of LFX, SFX and GFX in dilute urine samples and dosage forms, and compared with the HPLC method.

Possible involvement of P-glycoprotein in renal excretion of pazufloxacin in rats

The present study aims to investigate whether pazufloxacin, a new quinolone antimicrobial agent, is a substrate for P-glycoprotein in vitro, and whether it is excreted from kidney by P-glycoprotein and/or multidrug resistance-associated protein (Mrp2) in vivo. The in vitro experiments showed that the intracellular accumulation of pazufloxacin in adriamycin-resistant human chronic myelogenous leukemia cells (K562/ADR) overexpressing P-glycoprotein was significantly lower than that in human chronic myelogenous leukemia cells (K562/S) not expressing P-glycoprotein. When rats received an intravenous injection of pazufloxacin in combination with or without cyclosporine, cyclosporine significantly delayed the disappearance of pazufloxacin from plasma and decreased the systemic clearance and volume of distribution at steady state of pazufloxacin to 50% and 70% of the corresponding control values, respectively. Renal handling experiments revealed that the renal clearance of pazufloxacin was 75% of that corresponding to the systemic clearance, suggesting that the main route of pazufloxacin elimination is the kidney. Cyclosporine significantly increased the steady-state concentration of pazufloxacin in plasma by decreasing the tubular secretion clearance and glomerular filtration rate. These results suggest the possibility that pazufloxacin is excreted into the urine via P-glycoprotein. No significant differences in the renal and tubular secretion clearances of pazufloxacin were observed between normal rats and Eisai hyperbilirubinemic rats (EHBR), which have a hereditary deficiency in Mrp2, indicating the lack of the involvement of Mrp2 in the renal excretion of pazufloxacin. Sparfloxacin, a P-glycoprotein substrate, also significantly decreased the renal and tubular secretion clearances of pazufloxacin, suggesting that pazufloxacin and sparfloxacin share the same transporters, including P-glycoprotein. The present study at least suggests that pazufloxacin is excreted into the urine via P-glycoprotein and some active drug transporters other than Mrp2.

False-Positive Urine Opiate Screening Associated with Fluoroquinolone Use

OBJECTIVE:

To review the literature regarding false-positive urine opiate screens associated with the use of fluoroquinolones.

DATA SOURCES:

Literature was identified using MEDLINE (1966—February 2004), EMBASE, and all EBM Reviews with the terms quinolones, substance abuse detection, opiates, cross-reactions, false-positive reactions, and each fluoroquinolone. Article references were also reviewed.

DATA SYNTHESIS:

Various settings utilize the practice of screening for drugs of abuse, such as opiates. These screening procedures can impact aspects of one's life, such as employment; therefore, accuracy is of the utmost importance. Two clinical trials were evaluated which showed that certain fluoroquinolone antibiotics cross-react with some of the commonly used urine opiate screening immunoassays. This suggests the importance of verifying positive results in instances where one's livelihood can be affected.

CONCLUSIONS:

Fluoroquinolones can cause false-positive urine opiate screens. Clinicians should be aware of this potential interaction and may need to verify positive results.

Simultaneous determination of cefepime and grepafloxacin in human urine by high-performance liquid chromatography

A liquid chromatographic method with UV detection for simultaneous determination of cefepime and grepafloxacin has been developed. The method uses a C18 column, equipped with a pre-column of the same material, and acetonitrile-0.1 M phosphoric acid/sodium hydroxide buffer (pH 3.0)-0.01 M n-octylamine (pH 3.0) as mobile phase in gradient mode. Mobile flow rate and sample volume injected were 1.3 mL min(-1) and 20 microL, respectively. Detection wavelengths were 259 nm for cefepime and 278 nm for grepafloxacin. The retention times were 4.03 min for cefepime and 8.85 min for grepafloxacin, with detection limits of 1.0 and 1.1 microg mL(-1), respectively. The method was applied to the determination of both antibiotics in spiked samples of human urine.

Urinary concentrations and bactericidal activities of newer fluoroquinolones in healthy volunteers

Eleven healthy male subjects participated in a crossover study to compare the urine concentrations and bactericidal activities of newer fluoroquinolones against common uropathogens. Each volunteer received a single oral dose of gatifloxacin (400 mg), levofloxacin (250 mg), moxifloxacin (400 mg) and trovafloxacin (200 mg), and a urine sample was obtained at 2, 6, 12 and 24 h after the dose. Urine concentrations were highest with gatifloxacin and levofloxacin and lowest with trovafloxacin. Each drug concentration was studied against a levofloxacin susceptible and moderately-susceptible strain of Escherichia coli (minimal inhibitory concentration, MICs: 0.125 and 4 mg/l), K. pneumoniae (MICs: 0.125 and 4 mg/l), Pseudomonas aeruginosa (MICs: 0.5 and 4 mg/l) and Enterococcus faecalis (MICs: 0.25 and 4 mg/l). The duration of urine bactericidal activity (UBA) was based upon the median bactericidal titre at each time period. Both gatifloxacin and levofloxacin exhibited prolonged (> or = 6 h) UBA against all of the study isolates. Moxifloxacin exhibited prolonged UBA against both isolates of E. coli, K. pneumoniae and E. faecalis but not against either strain of P. aeruginosa. Prolonged UBA was not observed for trovafloxacin against the moderately-susceptible strains with the exception of E. faecalis. Furthermore, UBA was not observed for trovafloxacin against the susceptible strain of P. aeruginosa. Although these newer fluoroquinolones exhibited similar in vitro activity against these uropathogens, only those compounds with the highest urinary concentrations (gatifloxacin and levofloxacin) produced prolonged UBA against both strains of P. aeruginosa. The findings from this study suggest that both microbiological activity and urinary concentrations are important parameters to consider when choosing a fluoroquinolone for empirical treatment of urinary tract infections (UTIs).

Urinary bactericidal activity, urinary excretion and plasma concentrations of gatifloxacin (400 mg) versus ciprofloxacin (500 mg) in healthy volunteers after a single oral dose

In an open randomised double-crossover study 12 volunteers (six men, six women) received a single oral dose of gatifloxacin (400 mg) or ciprofloxacin (500 mg) to assess urinary bactericidal activity (in eight intervals up to 120 h) and pharmacokinetic (PK) parameters (up to 36 h). Plasma concentrations and urinary excretion were determined by HPLC with fluorescence detection, and urinary bactericidal titers (UBT) by microdilution-method, using antibiotic-free urine of each volunteer. The mean maximum plasma concentration of gatifloxacin was 3.35 mg/l and that of ciprofloxacin 2.12 mg/l. The mean (median) cumulative renal excretion of the parent drug was for gatifloxacin 81 (83)% of the administered dose within 120 h and for ciprofloxacin 43 (45)%. The UBTs, i.e. the highest two-fold dilution (antibiotic-free urine as diluent) of urine still being bactericidal, were determined for an Escherichia coli ATCC reference strain and nine clinical uropathogens with the following MICs (mg/l) for gatifloxacin/ciprofloxacin (microdilution, MHB): E. coli ATCC 25922 (0.008/0.008); E. coli 523 (0.06/0.06); Klebsiella pneumoniae 1058 (0.03/0.016); Proteus mirabilis 524 (0.125/0.016); Pseudomonas aeruginosa 561 (1/0.125); Enterococcus faecalis strains 60 an 55 (0.5/1 and 8/32); Staphylococcus aureus strains 248 and 596 (both 0.03/0.125) and S. saprophyticus Ho94 (0.125/0.25). The median UBTs measured within the first 6h for gatifloxacin were between 1:16 and 1:>or=1024 for the Gram-negative strains including P. aeruginosa and between 1:8 and 1:>or=1024 for the five Gram-positive strains. The median UBTs for ciprofloxacin were between 1:64 and 1:>or=1024 for the Gram-negative strains (incl P. aeruginosa) and between 1:1.5 and 1:768 for the five Gram-positive strains. The UBTs up to 12 < 0.05 h showed no difference (P<0.05 ) for both E. coli strains, but ciprofloxacin was superior to gatifloxacin against Klebsiella, Proteus and Pseudomonas strains and gatifloxacin was superior to ciprofloxacin against all Gram-positive strains. For the UBTs at 12-24 h, gatifloxacin was generally superior to ciprofloxacin, but showed no difference in the Proteus and Pseudomonas strains. The areas under the UBT-time-curve (AUBT) up to 120 h showed statistically significant (P ) differences between both quinolones in favour of gatifloxacin against 8 of 10 strains tested, no difference for P. mirabilis and significantly higher activity of ciprofloxacin against P. aeruginosa. In conclusion, gatifloxacin and ciprofloxacin had overall comparable initial urinary bactericidal activity with some differences for specific pathogens, some times in favour of gatifloxacin (Gram-positives) and some times of ciprofloxacin (usually Gram-negatives), suggesting that for empiric therapy a single oral dose of gatifloxacin (400mg) would be clinically equivalent to ciprofloxacin (500 mg) twice daily-in agreement with the results of a clinical study in complicated UTI performed previously [Int. J. Antimicrob. Agents (2004)].

Evaluation of the effect of cephalexin and enrofloxacin on clinical laboratory measurements of urine glucose in dogs

OBJECTIVE

To determine the effects of cephalexin and enrofloxacin on results of 4 commercially available urine glucose tests in dogs.

ANIMALS

6 healthy adult female dogs.

PROCEDURE

In a crossover design, cephalexin (22 and 44 mg/kg [10 and 20 mg/lb], p.o., q 8 h) or enrofloxacin (5 and 10 mg/kg [2.3 and 4.5 mg/lb], p.o., q 12 h) was administered to dogs for 1 day. Urine samples were tested for glucose at 0, 6, and 24 hours after drug administration. In vitro, dextrose was added to pooled glucose-negative canine urine samples containing either no antimicrobial or known concentrations of either antimicrobial; urine samples were then tested for glucose.

RESULTS

In vivo, false-positive results were obtained by use of a tablet test in the presence of both antimicrobials and by use of a strip test in the presence of cephalexin. In vitro, false-positive results were obtained with the tablet test at the highest urine concentration of cephalexin (2,400 microg/mL) and with a strip test at the highest concentration of enrofloxacin (600 microg/mL). Enrofloxacin in urine samples containing dextrose caused the urine glucose tests to underestimate urine glucose concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

Cephalexin and enrofloxacin at dosages used in clinical practice may result in false-positive or false-negative urine glucose results, and care should be taken when using urine as a basis for identifying or monitoring diabetic animals.

Differential Involvement of Multidrug Resistance-Associated Protein 1 and P-Glycoprotein in Tissue Distribution and Excretion of Grepafloxacin in Mice

The involvement of multidrug resistance-associated protein 1 (Mrp1) and P-glycoprotein (mdr1) in the tissue distribution and excretion of grepafloxacin (GPFX), a fluoroquinolone antibiotic, was investigated using gene-deficient mice [mdr1a(-/-), mdr1a/1b(-/-), and mrp1(-/-)]. The plasma concentration-time profile of GPFX in mrp1(-/-) was nearly identical to that in mrp1(+/+), whereas that in mdr1a/1b(-/-) was higher than that in mdr1a/1b(+/+). The urinary clearance of GPFX in mdr1a/1b(-/-) was lower than that in mdr1a/1b(+/+), suggesting that the urinary excretion of GPFX is at least partially mediated by mdr1. The tissue-to-plasma concentration ratios during the beta-phase (K(p beta),) was significantly higher in the heart, trachea, kidney, spleen, and brown fat of mrp1(-/-) than those in mrp1(+/+). In MRP1-transfected LLC-PK1 cells, the efflux of GPFX after preloading into the cells was higher than that observed in the parent cell lines. These results suggest that GPFX is a substrate of MRP1 and that its distribution to these tissues might be limited by Mrp1. On the other hand, a higher K(p beta), and of GPFX in mdr1a(-/-) mdr1a/1b(-/-) compared with mdr1a/1b(+/+) was observed only in the brain. GPFX was efficiently distributed to the lung parenchyma cells and pulmonary airspaces, including the epithelial lining fluid and macrophages that are the pharmacological target of GPFX, although the contribution of Mdr1 and Mrp1 to such distribution seems to be minor. Thus, the present findings reveal that the disposition of GPFX is at least in part governed by these two ABC transporters and that both Mrp1 and Mdr1 are involved in the limited distribution of GPFX to the distinct tissues, including pharmacological and/or toxicological targets by an active efflux mechanism.

Determination of fluoroquinolones in human urine by liquid chromatography coupled to pneumatically assisted electrospray ionization mass spectrometry1

The fluoroquinolones are synthetic antimicrobial agents widely used in human and veterinary medicine. The aim of this work was to develop a method of characterization and determination of three widely used fluoroquinolones (norfloxacin, ciprofloxacin and ofloxacin) in human urine by liquid chromatography (LC) coupled to pneumatically assisted electrospray ionization (ESI) mass spectrometry (MS). For this purpose, the operational parameters of the electrospray interface were optimized in order to obtain the best signal stability and the highest sensitivity of the fluoroquinolones. The three fluoroquinolones studied and enrofloxacin, used as internal standard, were extracted from human urine samples by solid-phase extraction (SPE) and the previously established LC-UV method was successfully coupled with the MS system. The mass spectra obtained provide adequate information for identification purposes. Quality parameters were determined and satisfactory results were obtained. Likewise, the method detection limit was about 10 ng ml(-1) for the three fluoroquinolones studied employing selected-ion monitoring mode.

Determination of gatifloxacin in human serum and urine by high-performance liquid chromatography with ultraviolet detection

A simple and sensitive HPLC method for the determination of gatifloxacin concentrations in human serum and urine was developed and validated. Serum proteins were removed by ultrafiltration through a filtering device after adding a displacing agent. Urine samples were diluted with mobile phase prior to injection. Separation was achieved with a C18 reverse-phase column and gatifloxacin concentrations were determined using ultraviolet detection. The quantitation limits of the assay were 100 ng/ml in serum and 1.0 microg/ml in urine. The assay method was successfully applied to a pharmacokinetic study of gatifloxacin in healthy volunteers.

Pharmacoknetic study of diclofenac and its interaction with enrofloxacin in buffalo calves

A comparative pharmacokinetic study of diclofenac (1 mg/kg, i.v.) when given alone or in combination with enrofloxacin (4 mg/kg, i.v.) in five buffalo calves was carried out by using HPLC. The study revealed that the plasma concentrations of diclofenac were significantly lower (p<0.05) in combined administration of diclofenac with enrofloxacin (0.042 to 3 h), whereas significantly higher (p<0.05) levels of plasma drug concentrations were observed in later period (8 to 24 h). In urine, significantly lower (p<0.05) drug concentrations of diclofenac were observed from 0.167 to 1.5 h, whereas significantly higher (p<0.01) urine drug concentrations were observed in later period (4 to 48 h) when diclofenac was given in combination with enrofloxacin as compared to when diclofenac was given alone. Various kinetic parameters like A, Cpo and beta were significantly lower (p<0.05) whereas t1/2 beta, AUMC, MRT and various volume of distribution (VdC, VdB, Vdarea and VdSS) were significantly higher in combined administration of diclofenac with enrofloxacin as compared to when diclofenac was given alone (p<0.05).

[Study on the direct determination of lomefloxacin in urine by derivative-synchronous fluorescence]

The LMX fluorescence properties at various pH of media were studied. The experiments indicated that LMX fluorescence emission wavelength is red shifted 40 nm at pH value of 3.3. The background interference was eliminated effectively. Under this condition, a new method for the determination of lomefloxacin in human urine by derivative-synchronous fluorescence has been developed. The linear equation of LMX can be obtained as dF/d lambda = -6.642c-24.143, of which the correlation coefficient is 0.9996. When concentrations of LMX were within the range of 0.35-28.10 mg.L-1, there exists a good linear relationship between the concentration and fluorescence intensity of LMX. The detection limit was 0.35 mg.L-1. The average recoveries of LMX were 97%-104% and the RSD were 0.83%-1.62%.

Tissue concentrations of enrofloxacin and ciprofloxacin in anesthetized dogs following single intravenous administration

Concentrations of enrofloxacin and its active metabolite, ciprofloxacin, were detected in tissues following single intravenous administration of 20 mg/kg to four anesthetized dogs. Two hours after treatment, serum samples were collected, animals were euthanized, and tissues were collected from each dog. Solid tissues were homogenized, and both enrofloxacin and ciprofloxacin were detected using high-performance liquid chromatography. Enrofloxacin was detected in all tissues examined; the highest concentrations were found in the gall bladder, urine, bile, stomach, and liver. Concentrations in the cerebral cortex, cerebrospinal fluid, skin, and prostate were 5.7, 5.3, 9.2, and 23.5 microg/ml, respectively. Tissues for which the concentration of enrofloxacin was 4 microg/ml or lower included the trachea, articular cartilage, aqueous humor, fat, and tendon. An inhibitory quotient of 8 or more was achieved for enrofloxacin in the majority of tissues studied. Ciprofloxacin was detected in 29 of 40 tissues examined.