Determination of norfloxacin by fluorescence in the presence of different antacids: quantification of analytical interferences

Review of Properties and Analytical Methods for the Determination of Norfloxacin

The first-generation quinolones have their greatest potency against Gram-negative bacteria, but newly developed molecules have exhibited increased potency against Gram-positive bacteria, and existing agents are available with additional activity against anaerobic microorganisms. Norfloxacin is a broad-spectrum antimicrobial fluoroquinolone used against Gram-positive and Gram-negative organisms (aerobic organisms). There are different analytical methods available to determine norfloxacin applied in quality control of this medicine in order to ensure its effectiveness and safety. The authors present an overview of the fourth generation of quinolones, followed by the properties, applications, and analytical methods of norfloxacin. These results show several existing analytical techniques that are flexible and broad-based methods of analysis in different matrices. This article focuses on bionalytical and pharmaceutical quality-control applications, such as thin-layer chromatography, microbiological assay, spectrophotometry, capillary electrophoresis (CE), and high-performance liquid chromatography (HPLC).

Development and validation of a rapid turbidimetric assay to determine the potency of norfloxacin in tablets

Norfloxacin is one of the first commercially available (and most widely used) fluoroquinolone antibiotics. This paper reports the development and validation of a simple, sensitive, accurate and reproducible turbidimetric assay method to quantify norfloxacin in tablets formulations in only 4 hours. The bioassay is based on the inhibitory effect of norfloxacin upon the strain ofStaphylococcus epidermidis ATCC 12228 IAL 2150 used as test microorganism. The assay was performed 3x3 parallel lines like, three tubes for each concentration of reference substance and three tubes for each sample concentration. The results were treated statistically by analysis of variance and were found to be linear (r2 = 0.9999) in the selected range of 25-100 μg mL-1; precise (intra-assay: relative standard deviation (RSD) = 1.33%; inter-assay: RSD = 0.21%), accurate (100.74%) and robust with RSD lower than 4.5%. The student's t-test showed no statistically significant difference between the proposed turbidimetric method and an HPLC method previously validated. However the turbidimetric assay can be used as a valuable alternative methodology for the routine quality control of this medicine, complementary to other physical-chemical methods.

Determination of norfloxacin in human urine by capillary electrophoresis with electrochemiluminescence detection

A fast and sensitive approach that can be used to detect norfloxacin in human urine using capillary electrophoresis with end-column electrochemiluminescence (ECL) detection of Ru(bpy)(3)(2+) is described. The separation column was a 75-microm i.d. capillary. The running buffer was 15 mmol L(-1) sodium phosphate (pH 8.2). The solution in the detection cell was 50 mmol L(-1) sodium phosphate (pH 8.0) and 5 mmol L(-1) Ru(bpy)(3)(2+). The ECL intensity varied linearly with norfloxacin concentration from 0.05 to 10 micromol L(-1). The detection limit (S/N=3) was 0.0048 micromol L(-1), and the relative standard deviations of the ECL intensity and the migration time for eleven consecutive injections of 1.0 micromol L(-1) norfloxacin (n=11) were 2.6% and 0.8%, respectively. The method was successfully applied to the determination of norfloxacin spiked in human urine without sample pretreatment. The recoveries were 92.7-97.9%.

Validation of a novel HPLC sorbent material for the determination of ten quinolones in human and veterinary pharmaceutical formulations

A novel sorbent material of ultrapure silica gel provided with novel State of the Art Bonding- and Endcapping Technology commercially available under the name PerfectSil Target (250 x 4 mm, ODS-3, 5 microm, by MZ-Analysentechnik, Germany) was used and validated for the sensitive HPLC determination of ten quinolone antibiotics: enoxacin, ofloxacin, norfloxacin, ciprofloxacin, danofloxacin (DAN), enrofloxacin (ENR), sarafloxacin, oxolinic acid (OXO), nalidixic acid (NAL), and flumequine. The analytical column validation was performed in terms of separation efficiency, precision, and peak asymmetry. The separation was achieved at ambient temperature using a mobile phase of TFA (0.1%)-CH3OH-CH3CN delivered under the optimum gradient program, at a flow rate of 1.2 mU/min. Photodiode array detection was used and eluant was monitored at 275 nm. For the quantitative determination caffeine (7.5 ng/microL) was used as internal standard. The achieved LODs were 0.03 ng/microL per 50 microL injected volume for OXO, 0.1 ng/microL for DAN, ENR, and NAL, and 0.2 ng/microL for the remaining six studied quinolones. The method was validated in terms of interday (n = 6) and intraday (n = 5) precision and accuracy. The proposed method was successfully applied to the analysis of pharmaceutical formulations destined either for human or for veterinary use.

Residues of selected antibiotics in water and mud from shrimp ponds in mangrove areas in Viet Nam

In recent years, antibiotics have been used widely in intensive shrimp culture and this may lead to their contamination of the environment. Surveys on residues of trimethoprim (TMP), sulfamethoxazole (SMX), norfloxacin (NFXC) and oxolinic acid (OXLA) in water and mud in shrimp ponds in mangrove areas were conducted in the north as well as in south of Viet Nam in July and August, 2002. The results show that these antibiotics are found in all samples in both shrimp ponds and surrounding canals. The highest concentrations of TMP, SMX, NFXC and OXLA are 1.04, 2.39, 6.06, and 2.50 ppm in water samples; and 734.61, 820.49, 2615.96, 426.31 ppm (based on wet mud weight), respectively. The comparison of antibiotics residues between study sites and types of shrimp ponds will be discussed in this paper. The results also suggest that antibiotics residues may cause harmful effect on ecosystems in the study sites.

Kinetic spectrophotometric method for the determination of norfloxacin in pharmaceutical formulations

A simple and sensitive kinetic spectrophotometric method is described, based on the oxidation of norfloxacin with alkaline potassium permanganate. The reaction is followed spectrophotometrically by measuring the rate of change of absorbance at 603 nm. The initial rate and fixed time (at 3 min) methods are utilized for constructing the calibration graphs to determine the concentration of the drug. The calibration graphs are linear in the concentration ranges 2.0-20 microg ml(-1) and 1.0-20 microg ml(-1) using the initial rate and fixed time methods, respectively. The results are validated statistically and through recovery studies. The method has been successfully applied to the determination of norfloxacin in commercial dosage forms. Statistical comparison of the results with the reference method shows excellent agreement and indicates no significant difference in accuracy and precision.

Influence of pharmacotechnical design on the interaction and availability of norfloxacin in directly compressed tablets with certain antacids

Norfloxacin is a fluorquinolone that can interfere with antacids that contain aluminum and magnesium salts by complexation and modification of its solubility, which reduces its absorption and may lead to therapeutic failures. The purpose of this work was to evaluate the effect of the pharmaceutical design on this interaction and to develop a formulation of norfloxacin tablets in which this process could be avoided. Norfloxacin tablets were designed in 28 formulations. The interaction was studied in terms of in vitro dissolution behavior (USP 23, apparatus 2) in simulated gastric fluid with different doses of four commercially available antacid preparations. It was observed that dissolution rates were markedly reduced in the presence of all antacids studied. This phenomenon was practically avoided with some formulations of norfloxacin tablets in which a disintegrant (sodium starch glycolate or crospovidone) was included. These results indicated that the chelation among metal ions and norfloxacin could be affected by the delivering ability of the drug in the tablet. It was demonstrated that the pharmacotechnical design could modify an interaction process. Some formulations of tablets, in which the reduced dissolution rates in the presence of nonsystemic antacids in vitro was practically avoided, were developed by direct compression.

Validation of a high-performance liquid chromatographic method for the determination of norfloxacin and its application to stability studies (photo-stability study of norfloxacin)

The development and validation study of a sensitive, rapid, reproducible, easy and precise reversed-phase high-performance liquid chromatographic assay for norfloxacin (NFLX) samples from photo-stability of solid dosage forms, without using gradient elution, extraction methods and without using counter-ion has been carried out. The method showed excellent linearity (r2> or =0.999) in the range 1-20 microg ml(-1) using a Lichrosorb-RP-8 column (10 microm, 20 cm x 4.6 mm) and UV-detection (278 nm) at ambient temperature. This method showed good efficiency for the analysis of photodegraded NFLX samples, and was applied to study the photo-stability of NFLX tablets under different conditions (direct sun light, ultraviolet light and fluorescent light). It was proven that the use of a disintegrant can increase the photo-stability of the NFLX in the tablets. This effect was studied in directly compressible tablets with microcrystalline cellulose (MCC) and mannitol for direct compression.

Modification of fluorescent properties of norfloxacin in the presence of certain antacids

Modification of the fluorescent properties of norfloxacin samples in the presence of different antacids in terms of dissolution rates has been reported in a previous paper. The formation of chelates with Al3+ and Mg2+ ions has been previously suggested as a mechanism of interaction. In the present paper, the chelation was studied with different types and amounts of antacids and the stability of the non-absorbable chelates with each antacid was studied. Six dose fractions of each antacid were used in samples with the same norfloxacin concentration (9 microg ml(-1)). All samples were measured using both UV/Vis-spectrophotometry and spectrofluorimetry, and compared to a standard solution of norfloxacin (10 microg ml(-1)) without antacids, used as a reference in the calibration of the spectrofluorimeter. The results showed that the fluorescence signal features remarkable differences depending on the kind and the concentration of antacid, as well as on the time of contact. It was found that increasing amounts of antacids increased the fluorescence signal of norfloxacin samples. The evolution of the fluorescence signal in function of the antacid concentration showed a maximum and a posterior decrease. It was observed that, for a higher concentration of antacid in the medium, a higher signal was obtained and lower stability of the compound norfloxacin-antacid was observed. The data obtained strongly indicated that the binding of Al3+ and Mg2+ ions to the carboxylic groups of norfloxacin produced non-absorbable chelates. This effect might reduce the drug bioavailability.

The effect of photodegradation on the fluorescent properties of norfloxacin: (photodegradation and fluorescence of norfloxacin)

Norfloxacin (NFLX), a broad spectrum antibacterial quinolone, is a very thermostable but photosensitive drug, especially in solution leading to the formation of an ethylenediamine degradate. The modification of the fluorescent properties of NFLX in acid solution after exposure to fluorescent light and the degradation mechanisms were studied. Two analytical methods were previously developed and validated for NFLX, ultraviolet spectrophotometry (UV) and spectrofluorimetry (FL). Data obtained using both methods in the analysis of remaining NFLX in terms of percent recoveries revealed that there was no statistically significant modifications of the UV signal and of the recoveries obtained by the method. However, an important increase of the fluorescent signal after light exposure of NFLX solutions appeared, which led to an increase of the average recovery up to 270% over 15 months. Using a previously validated HPLC method for the photostability studies of NFLX, a loss of 5% with respect to the initial drug amount was observed. The study of UV and fluorescence spectra evidenced the formation of the degradation product, which induced significant modification of the fluorescent properties of NFLX samples. These results clearly indicated that FL analysis definitively is the method of choice and can be used to study the photodegradation of NFLX.