Application of non-linear angle synchronous spectrofluorimetry to the determination of complex mixtures of drugs in urine: a comparative study.

Synchronous fluorescence spectroscopy (SFS) is a rapid, sensitive and non-destructive method suitable for the analysis of multifluorophoric mixtures. In this study non linear variable angle synchronous spectrofluorimetry was applied to the determination of three fluoroquinololes in urine. Although this technique provides very good results, total resolution of multicomponent mixtures is not always achieved when the spectral profiles strongly overlap. Partial least-squares regression (PLS-1) was utilized to a develop calibration model that related synchronous fluorescence spectra to the analytical concentration of fluoroquinolones in the presence of urine. The same multicomponent mixture was determined using excitation emission matrix fluorescence (EEMF) along with N-way partial least squares regression (N-PLS and U-PLS). The determination was carried out in micellar medium 0.01 M with a pH of 4.8 provided by 0.2 M sodium acetate/acetic acid buffer. A central composite design was selected to obtain a calibration matrix of 25 standards plus a blank sample. The proposed methods were validated by application to a test set of synthetic samples. The results show that SFS with PLS-1 is a better method compared to EEMF with N-PLS or U-PLS because of the low RMSEP values of the former.

A simple chromatographic method for determining norfloxacin and enoxacin in pharmacokinetic study assessing CYP1A2 inhibition.

We developed a simple assay method for the determination of serum and urine norfloxacin and enoxacin using reversed-phase high-performance liquid chromatography and perchloric acid precipitation for sample pre-treatment. Optimized conditions can permit detection of norfloxacin and enoxacin in the same chromatogram, so either compound can be used as an internal standard for another determinant. Supernatants of the precipitated samples were analyzed by the octadecylsilyl silica-gel column under ambient temperature and an ultraviolet wavelength of 272 nm. A mobile phase solvent consisting of 20 mm sodium dihydrogenphosphate (pH 3.0) and acetonitrile (85:15, v/v) was pumped at a flow rate of 1.0 mL/min. The calibration curves for norfloxacin and enoxacin at a concentration of 62.5-1000 ng/mL for serum and 250-4000 ng/mL for urine were linear (r > 0.9997). The recoveries of norfloxacin and enoxacin from serum and urine were >94% with the coefficient of variations (CV) <5%. The CVs for intra- and inter-day assay of norfloxacin and enoxacin were <4.2 and <5.5%, respectively. This method can be applied to the pharmacokinetic study of norfloxacin and enoxacin after repeated administration to assess changes in CYP1A2 activity in healthy subjects.

Simultaneous determination of tetracaine, proline, and enoxacin in human urine by CE with ECL detection.

A simple, fast, and sensitive capillary electrophoresis method was developed for the simultaneous determination of tetracaine, proline, and enoxacin in human urine with electrochemiluminescence (ECL) detection. The effects of experimental conditions including the mode of applied voltage signal, the potential of working electrode, pH value, the flow rate of carrier of solution, the concentration of Ru(bpy)(3)(2+), and the ECL intensity of the drugs were investigated in detail. Parameters related to the separation and detection were investigated and optimized. Under optimized conditions, the proposed method displayed a linear range from 0.4 to 100 microg/mL for tetracaine, 0.2 to 80 microg/mL for proline, and 0.1 to 100 microg/mL for enoxacin. Their limits of detection were 0.08, 0.06, and 0.02 microg/mL, respectively. A baseline separation for tetracaine, proline, and enoxacin was achieved within 10 min. Developed method was successfully applied to determine tetracaine, proline, and enoxacin in human urine.

Determination of enoxacin and ofloxacin by capillary electrophoresis with electrochemiluminescence detection in biofluids and drugs and its application to pharmacokinetics.

A novel and sensitive method for the simultaneous determination of enoxacin and ofloxacin has been established using capillary electrophoresis (CE) coupled with electrochemiluminescence (ECL) detection based on the ECL enhancement of tri(2,2-bipyridyl)ruthenium(II). The conditions for sample solvent type, CE separation and ECL detection were investigated systematically. The analytes were well separated and detected within 7 min. The limits of detection (S/N = 3) of enoxacin and ofloxacin are 9.0 x 10(-9) and 1.6 x 10(-8) mol/L, respectively. The precisions (RSD%) of intraday and interday are less than 2.1 and 4.0%, respectively. The limits of quantitation (S/N = 10) of enoxacin and ofloxacin are 3.2 x 10(-7) and 5.4 x 10(-7) mol/L in human urine samples and 4.1 x 10(-7) and 6.9 x 10(-7) mol/L in human serum samples, respectively. The recoveries of enoxacin and ofloxacin at different concentration levels in human urine, serum and eye drop samples are between 94.0 and 106.7%. The proposed method was successfully applied to the determination of the enoxacin and ofloxacin in human urine, serum and eye drop samples and the monitoring of pharmacokinetics of ofloxacin in human body.

Exploring Mn-doped ZnS quantum dots for the room-temperature phosphorescence detection of enoxacin in biological fluids.

While most research works focus on the development of quantum dots (QDs)-based fluorescence sensors, much less attention is paid to the phosphorescence properties of QDs and their potential for phosphorescence detection. In this work, the phosphorescence property of Mn-doped ZnS QDs is explored to develop a novel room-temperature phosphorescence (RTP) method for the facile, rapid, cost-effective, sensitive, and selective detection of enoxacin in biological fluids. The Mn-doped ZnS QDs-based RTP method reported here does not need the use of deoxidants and other inducers and allows the detection of enoxacin in biological fluids without interference from autofluorescence and the scattering light of the matrix. The Mn-doped ZnS QDs offer excellent selectivity for detecting enoxacin in the presence of the main relevant metal ions in biological fluids, biomolecules, and other kinds of antibiotics. Quenching of the phosphorescence emission due to the addition of enoxacin at 1.0 microM is unaffected by 5000-fold excesses of Na (+) and 10000-fold excesses of K (+), Mg (2+), and Ca (2+). Amino acids such as tryptophan, histidine, and l-cysteine at 1000-fold concentration of enoxacin do not affect the detection of enoxacin. Glucose does not affect the detection at 10000-fold concentration of enoxacin. Typical coadministers (mainly other types of antibiotics) such as ceftezole, cefoperazone, oxacillin, and kalii dehydrographolidi succinas are permitted at 50-, 10-, 100-, and 50-fold excesses, respectively, without interference with the detection of enoxacin. The precision for 11 replicate detections of 0.4 microM enoxacin is 1.8% (RSD). The detection limit for enoxacin is 58.6 nM. The recovery of spiked enoxacin in human urine and serum samples ranges from 94 to 104%. The developed Mn-doped ZnS QDs-based RTP method is employed to monitor the time-dependent concentration of enoxacin in urine from a healthy volunteer after the oral medication of enoxacin. The investigation provides evidence that doped QDs are promising for RTP detection in further applications.

HPLC determination of enoxacin, ciprofloxacin, norfloxacin and ofloxacin with photoinduced fluorimetric (PIF) detection and multiemission scanning: application to urine and serum.

The fluorescence emission of the fluoroquinolones enoxacin (ENO), ciprofloxacin (CIPRO), norfloxacin (NOR) and ofloxacin (OFLO) notably increased by UV irradiation during few minutes, in ethanolic-water medium. An HPLC method has been developed, for the determination of these fluoroquinolones, based in the separation of the formed irradiation photoproducts. Optimization of the analytical wavelengths has been carried out by fast multiemission scanning fluorescence detection. The highest sensitivity has been found when measuring at emission wavelengths of 407 and 490 nm, for ENO and OFLO, respectively, and at 444 nm for both NOR and CIPRO (exciting at 277 nm). According to the criterium of Clayton, using 0.05 as false positive and false negative error assurance probabilities, detection limits of 7.3, 6.0, 6.3 and 14.5 ng/mL, for ENO, NOR, CIPRO and OFLO, respectively, have been found. Urine and serum samples have been successfully analyzed, with recovery values ranging among 99-97% and 98-103%, for urine and serum, respectively.

[Determination of enoxacin in urine by synchronous fluorimetry].

The effect of metal ions on uhe fluorescence spectra of enoxacin was studied in detail. It has been found that aluminum can enhance the fluorescence intensity of enoxacin remarkably in the buffer solution of NaH2 PO4-Na2B4O7 with pH 6.3. A new method using synchronous fluorimetry has been developed for the determination of enoxacin in human urine. The synchronous fluorescence intensity of Al/ENX system is linearly proportional to the concentration of ENX in the concentration range of 0.04-1.0 microg x mL(-1). The detection limit, calculated according to IUPAC recommendations, was 0.018 microg x mL(-1). The precision of the method was established by repeated assays (n = 12) using 0.4 microg x mL(-1) solution of ENX, and the relative standard deviation was 3.1%. The method was satisfactorily applied to the determination of enoxacin in human urine samples. The recovery was within the range of 95%-105%.

Selective separation and simultaneous determination of trace levels of five types of fluorinated quinolone drugs by thin-layer chromatography/fluorescence densitometry.

This paper reports the determination of trace levels of 5 types of fluorinated quinolone drugs, i.e., ciprofloxacin, norfloxacin, enoxacin, pefloxacin, and ofloxacin, by thin-layer chromatography (TLC)/fluorescence densitometry. The new analytical method uses 2-step TLC development, selective separation, and simultaneous determination of the 5 drugs. The method was also applied to the determination of recoveries of standards of the 5 drugs in plasma and urine samples. The results show that the method has a wide linear range, high repeatability, and good stability.

[Terbium sensitized chemiluminescence of enoxacin].

AIM: To determine the enoxacin by means of terbium sensitized chemiluminescence in pharmaceutical preparations as well as urine samples. METHODS: Through six-way injection valve Ce4+, H2SO3, Tb3+ and enoxacin (ENX) standard solutions were injected into the flow system in a certain order, the chemiluminescence signal was detected by weak luminescence analyzer. RESULTS: The chemiluminescence intensity was linearly related to the concentration of ENX in the range of 2.0 x 10(-9)-6.0 x 10(-8) mol.L-1 with a detection limit of 4.0 x 10(-10) mol.L-1. Relative standard deviation was less than 1.6% (n = 11). CONCLUSION: It provides a sensitive rapid, simple and accuracy measurement of enoxacin for the pharmacokinetic studies.

Distribution kinetics of enoxacin and its metabolite oxoenoxacin in excretory fluids of healthy volunteers.

The distribution kinetics of enoxacin and its main metabolite oxoenoxacin in excretory fluids was investigated in 11 healthy volunteers. A single intravenous dose of 428 mg of enoxacin was given as a 1-h infusion. Serial samples of plasma, urine, saliva, nasal secretions, tears, and sweat were drawn and analyzed for enoxacin and oxoenoxacin by reversed-phase high-pressure liquid chromatography. Large differences in the concentration-time profiles of the excretory fluids analyzed were observed. Nasal secretions exhibited the highest enoxacin exposure, as assessed by the area under the concentration-time curve. Excretory fluid/plasma area under the concentration-time curve ratios were found to be 1.67 +/- 0.36 for nasal secretions, 0.76 +/- 0.28 for saliva, 0.25 +/- 0.07 for sweat, and 0.23 +/- 0.11 for tears. The elimination half-life of enoxacin from sweat (8.27 +/- 2.63 h) was significantly longer than that for plasma (5.10 +/- 0.46 h). Oxoenoxacin was detected in urine and saliva and exhibited a higher renal clearance and a lower saliva exposure than the parent compound. In contrast to that of the metabolite, distribution of enoxacin in saliva was found to be time and pH dependent. In conclusion, our study revealed considerable differences in the distribution kinetics of enoxacin among various excretory sites. Because of distinct acidic and basic properties, the anionic oxometabolite significantly differs from the zwitterionic parent compound in its distribution characteristics.

Prevention of subsequent urinary tract infections in women by the use of anti-adherence antimicrobial agents: a double-blind comparison of enoxacin with co-trimoxazole.

A prospective, double-blinded crossover study was carried out to test whether a brief course of antibiotic therapy could eliminate bacteria adherent to uroepithelial cells and thus prolong the interval between urinary tract infections (UTIs). Thirty-two women with frequent Gram-negative urinary tract infections were randomized to receive either co-trimoxazole or enoxacin twice a day for 10 days to treat their UTI. Their urines were collected for 30 days after the onset of their UTI and quantitatively analyzed for bacteria, antibiotics, and bacteria adherent to uroepithelial cells (UECs). A subsequent infection caused the patient to be treated with the alternative antibiotic. A third infection terminated the study. Both regimens were indistinguishable in the rate of elimination of bacteria and in their inhibition of bacterial adherence to UECs for up to five days after stopping treatment. The interval between infections was inversely correlated with the number of adherent bacteria per UEC 30 days after the onset of the first UTI. Both regimens were equally effective in preventing subsequent UTI and the effect of 10 days therapy on the inhibition of bacterial adherence to UEC's did not extend beyond five days after stopping treatment.

Pharmacokinetics of enoxacin and its oxometabolite following intravenous administration to patients with different degrees of renal impairment.

Enoxacin is a fluorinated quinolone with potential clinical use in the treatment of serious infections. Twenty-three patients (age, 19 to 87 years) with different degrees of renal function, including a group undergoing chronic hemodialysis, received enoxacin (400 mg) by intravenous infusion (1 h). Blood samples were collected before infusion; at the end of infusion; and at 5, 10, 20, 30, 45, 60, 90, and 120 min and 3, 4, 6, 12, 18, 24, 48, and 72 h after infusion. Enoxacin and oxoenoxacin concentrations were measured by high-pressure liquid chromatography. Pharmacokinetic parameters (mean +/- standard deviation) were calculated by using a noncompartmental PK model according to creatinine clearances (in milliliters per minute). Total clearance of enoxacin decreased from 4.95 +/- 1.16 ml/min per kg in the group with normal creatinine clearance to 0.76 +/- 0.21 ml/min per kg in the patients with severe renal failure (creatinine clearance, less than 15 ml/min), whereas the elimination half-life increased from 4.5 +/- 1.0 to 20 +/- 5 h, respectively. The elimination of oxoenoxacin (the main metabolite of enoxacin) in urine was markedly decreased when creatinine clearance was less than 15 ml/min. Hemodialysis removed an insignificant amount of enoxacin and oxoenoxacin. These data indicate that as creatinine clearance falls below 30 ml/min, the daily enoxacin dose should be reduced by half. During prolonged administration of enoxacin to patients with creatinine clearances of less than 30 ml/min, the accumulation of oxoenoxacin might lead to unexpected side effects.

Enoxacin penetration into human prostatic tissue.

Concurrent enoxacin concentrations in serum and prostatic tissue were determined in 14 patients. The mean ratios of enoxacin concentration in tissue over concentration in serum were 1.4 +/- 0.2 (standard error of the mean). The levels in serum and prostatic tissue were above the MICs for most urinary pathogens.

The absorption and disposition of enoxacin in healthy subjects.

Enoxacin is a new orally active, synthetic broad-spectrum antibacterial drug of the fluorinated quinolone class. The pharmacokinetics and renal handling of this drug have not been thoroughly investigated, in particular, with specific analytical methodology. Sixteen healthy, young subjects received a single 400-mg oral dose of enoxacin after an overnight fast and multiple blood samples and all urine were collected for 33 hours. Enoxacin in plasma and urine and oxo-enoxacin in urine were determined by a high-performance liquid chromatographic method. Enoxacin was absorbed rapidly, with tmax values ranging from 0.5 to 2.5 hours. The variability in the AUC values of 35% was reduced to 23% when variations in body weight were taken into consideration. The terminal half-life ranged from 4.2 to 6.8 hours and the unbound fraction in plasma was 0.33 +/- 0.07. In urine, 44 +/- 9% of the dose was recovered as unchanged enoxacin and 5.4 +/- 3.9% as oxo-enoxacin; there was no evidence of conjugates of enoxacin in urine. Renal clearance of enoxacin was 230 +/- 92 mL/min, with 17 +/- 8% of this being due to glomerular filtration and 83 +/- 8% being due to tubular secretion. These data indicate that the major potential drug interactions affecting enoxacin disposition are likely with drugs competing for renal proximal tubular secretion and hepatic elimination. These conclusions regarding enoxacin are likely to be applicable to the fluorinated quinolones in general.