β‐Cyclodextrin‐Functionalized Gold Nanoparticles/Poly(L‐cysteine) Modified Glassy Carbon Electrode for Sensitive Determination of Metronidazole

A simple electrochemical method was developed to determine metronidazole based on β‐cyclodextrin‐functionalized gold nanoparticles/poly(L ‐cysteine) modified glassy carbon electrode (β‐CD‐GNPs/poly(L ‐cys)/GCE). The electropolymerized film of poly(L ‐cys) provides a stable matrix for the fabrication of a sensing interface. β‐CD‐GNPs can form inclusion complexes with metronidazole and act as a modifier with catalytic function. The modified electrode exhibited excellent electrocatalytic activity towards metronidazole. The reaction of metronidazole at the modified electrode was an irreversible process controlled by diffusion. Under optimum experimental conditions, the logarithm of catalytic currents shows a good linear relationship with that of the metronidazole concentration in the range of 0.1–600 µmol/L with a low detection limit of 14 nmol/L. In addition, the modified electrode exhibited satisfactory stability, sensitivity and reproducibility, and could be applied to the determination of metronidazole in an injection solution.     

Preparation and evaluation of topical microemulsion system containing metronidazole for remission in rosacea

The aim of this study was to prepare a topical water-in-oil type microemulsion containing metronidazole and to compare its effectiveness with a commercial gel product in the treatment of rosacea. A pseudo-ternary phase diagram (K(m)=2:1) was constructed using lecithin/butanol/isopropyl myristate/water. The microemulsion was chosen from the microemulsion region in the phase diagram. The formulation was a water-in-oil type microemulsion (droplet size: 11.6 nm, viscosity: 457.3 mPa·s, conductivity: 1.5 μs/cm, turbidity: 6.89 NTU) and the addition of the metronidazole did not alter the properties of the system. The release experiment showed that the release rate of metronidazole from the commercial gel product was higher than that of the microemulsion. Stability experiments showed that the metronidazole microemulsion remained stable for at least 6 months; none of the characteristic properties of the microemulsion had changed, the system retained its clarity and there was no sign that crystallization of metronidazole has occurred. Microemulsion was compared to a gel product in a randomized, double-blind, baseline-controlled, split-face clinical trial for the treatment of patients. After the 6-week treatment period there was a statistically significant difference in reduction of the main symptoms of rosacea. Of the patients treated with the microemulsion, 17% experienced complete relief from inflammatory lesions, and 50% from erythema. The microemulsion resulted in complete relief in 38% of the patients with telangiectasia while the commercial product did not provide any relief of telangiectasia symptoms. In conclusion, the microemulsion containing metronidazole was found to be more effective in reducing the symptoms of rosacea compared to the commercial gel product.     

Pharmacokinetics of metronidazole in rat blood,brain and bile studied by microdialysis coupled to microbore liquid chromatography

Metronidazole is a synthetic nitroimidazole-derived antibacterial and antiprotozoal agent used for the treatment of infections involving gram-negative anaerobes. The aim of this study is to develop an in vivo microdialysis with microbore high-performance liquid chromatographic system for the pharmacokinetic study of metronidazole in rat blood, brain and bile. In addition, to investigate the disposition mechanism of metronidazole, the P-glycoprotein modulator and cytochrome P450 inhibitor were concomitantly administered. Separation of metronidazole from various biological fluids was applied to a microbore reversed-phase ODS 5 microm (150 x 1 mm I.D.) column. Its mobile phase consists of an acetonitrile-50 mM monosodium phosphate buffer (pH 3.0) containing 0.1% triethylamine (10:90, v/v) with a flow-rate of 0.05 ml/min. The UV detector wavelength was set at 317 nm. The results suggest that metronidazole penetrates the blood-brain barrier (BBB) and goes through hepatobiliary excretion. However, these pathways of BBB penetration and hepatobiliary excretion of metronidazole may not be related to the P-glycoprotein.     

Thermal stability of metronidazole drug and tablets

TG and DSC data were used to determine the thermal parameters of metronidazole drug and tablets. Three tablets A, B and C were analysed. The TG curves of metronidazole drug and tablets A and B displayed five and C four thermal decomposition processes, respectively. Analysis of the DSC data pointed to chemical interactions between metronidazole drug and the excipients of tablets, suggested by alterations in the melting point of metronidazole. The rate constants obtained from the isothermal TG data presents following sequence of the thermal stability: tablet A>tablet C>metronidazole drug>tablet B. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study on metronidazole distribution in rectal cancer tissue using application method of administration in experiment in vivo

The distribution of metronidazole in rectal cancer tissue using application method of administration was studied. A comparative evaluation of pharmacokinetic parameters of metronidazole accumulation in the tissues depending on the concentration of the drug in the application mixture was carried out. The generalized actual data on metronidazole distribution in tissue samples (341 sample) obtained during 31 surgery are presented.     

Macromolecular prodrugs. V. Simultaneous determination of high-molecular-weight dextran metronidazole monosuccinate ester prodrugs and the hydrolysis products metronidazole and the corresponding monosuccinate ester on nucleosil diol

A high-performance size-exclusion chromatography procedure using Nucleosil Diol has been developed which provides the simultaneous determination of macromolecular dextran metronidazole monosuccinate ester prodrugs and the hydrolysis products metronidazole and metronidazole monosuccinate. Various factors influencing the chromatographic behaviour of the compounds are discussed. Baseline separation of the three substances was achieved within 8 min by using a 0.05 M phosphate buffer pH 7.5 eluent at a flow-rate of 2 ml min-1. The detection limit at 320 nm for a conjugate with a degree of substitution of 4.61 was found to be 3.5 micrograms ml-1.     

用荧光光谱和共振光散射光谱研究甲硝唑与牛血清白蛋白的相互作用

用荧光光谱和共振光散射光谱对甲硝唑与牛血清白蛋白的作用进行了对比研究, 测定了该反应的结合常数、结合位点数. 探讨了甲硝唑对牛血清白蛋白荧光和共振光散射猝灭的机理． 利用热力学参数确定了分子间的作用力性质；根据非辐射能量转换机制, 确定了甲硝唑-牛血清白蛋白间的结合距离. 采用同步荧光技术考察了甲硝唑对牛血清白蛋白构象的影响．     

LOW-TEMPERATURE TRAPPING OF EARLY PHOTOINTERMEDIATES OF α-ISORHODOPSIN

Abstract— a-Isorhodopsin, an artificial visual pigment with a 9- cis -4,5-dehydro-5,6-dihydro(a)retinal chromophore, was photolyzed at low temperatures and absorption difference spectra were collected as the sample was warmed. A bathorhodopsin (Batho)-like intermediate absorbing at ca 495 nm was detected below 55 K, a blue-shifted intermediate (BSI)-like intermediate absorbing at ca 453 nm was observed when the temperature was raised to 60 K and a lumirhodopsin (Lumi)-like intermediate absorbing at ca 470 nm was found when the sample was warmed to 115 K. Photointermediates from this pigment were compared to those of native rhodopsin and 5,6-dihydroisorhodopsin. As in native rho-dopsin, Batho is the first intermediate detected in a-isorhodopsin, though unlike native rhodopsin at low temperatures BSI is observed prior to Lumi formation. a-Isorhodopsin behaves similarly to 5,6-dihydroisorhodopsin, with the same early intermediates observed in both artificial visual pigments lacking the C₅-C₆ double bond. The transition temperature for BSI formation is higher in a-isorhodopsin, suggesting an interaction involving the chromophore ring in BSI formation. The transition temperature for Lumi formation is similar for these two pigments as well as for native rhodopsin, suggesting comparable changes in the protein environment in that transition.     

Design,synthesis and biological evaluation of quinazolin-4(3H)-one Schiff base conjugates as potential antiamoebic agents

In an effort to develop novel antiamoebic scaffolds having better efficacy than the standard drug metronidazole (IC₅₀ = 1.80 μM) used against Entamoeba histolytica, quinazolin-4(3H)-one Schiff base conjugates were synthesized and evaluated against HM1: IMSS strain of E. histolytica. Out of the thirteen compounds (S2-S14), six compounds (S2, S3, S4, S5, S6 and S11) were found to be better inhibitors than metronidazole and showed low cytotoxicity on HeLa cells, a cervical cancer cell line. The structure of intermediate compound S1 was confirmed by crystal structure studies.     

一种新的甲硝唑荧光光纤传感器的研制

将1,4-二(苯并(噁)唑-1',3'-基-2')苯(BBOB)包埋在增塑的聚氯乙烯膜中,研制了一种新的荧光猝灭型甲硝唑光纤传感器.猝灭机制包括甲硝唑的初级内滤效应和甲硝唑与BBOB形成电荷转移复合物两种作用.传感器可逆性好,响应时间小于30s,响应线性范围是4.00×10^-6～1.00×10^-4mol/L,检测限为1.00×10^-6mol/L,对1.00×10^-4mol/L甲硝唑的相对偏差为0.82%(n=10).常见的无机离子、药物不影响甲硝唑的测定,对商品制剂中甲硝唑的测定结果与药典法一致.     

Efficient and selective separation of metronidazole from human serum by using molecularly imprinted magnetic nanoparticles

Magnetic molecularly imprinted nanoparticles were prepared through surface‐initiated reversible addition fragmentation chain transfer polymerization by using metronidazole as a template. The molecularly imprinted magnetic nanoparticles were characterized by attenuated total reflection Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, transmission electron microscopy, X‐ray diffraction, and vibrating sample magnetometry. The adsorption characteristics were also investigated and the kinetics of the adsorption of metronidazole on the imprinted nanoparticles were described by the second‐order kinetic model with the short equilibrium adsorption time (30 min). The adsorption isotherm was well matched with the Langmuir isotherm in which the maximum adsorption capacity was calculated to be 40.1 mg/g. Furthermore, the imprinted magnetic nanoparticles showed good selectivity as well as reusability even after six adsorption–desorption cycles. The imprinted magnetic nanoparticles were used as a sorbent for the selective separation of metronidazole from human serum. The recoveries of metronidazole from human serum changed between 97.5 and 99.8% and showed similar sensitivity as an enzyme‐linked immunoassay method. Therefore, the molecularly imprinted magnetic nanoparticles might have potential application for the selective and reliable separation of metronidazole from biological fluids in clinical applications.     

Novel Metronidazole Membrane Sensor Based on a 2,6‐(p‐N,N‐Dimethylaminophenyl)‐4‐Phenylthiopyrylium Perchlorate

A novel PVC‐based membrane sensor based on 2,6‐(p‐N,N‐dimethylaminophenyl)‐4‐phenylthiopyrylium perchlorate (DAPP) is described. The electrode exhibits a sub‐Nernstian response to 1‐(beta‐hydroxyethyl)‐2‐methyl‐5‐nitroimidazole (metronidazol) over a relatively wide concentration range (1.0 × 10^?1 to 1.0 × 10^?5 M) with a detection limit of 8.0 × 10^?6 M. The best performance was obtained with the membrane containing 30% poly (vinyl chloride), 50% dibutyl phthalate, 7% DAPP and 13% oleic acid. It has a fast response time (< 30 s) and can be used for at least four weeks without any major deviation. The proposed sensor revealed very good selectivity for metronidazole over a wide variety of common cations, anions and amino acids and could be used in the pH range of 6.0–7.5. It was successfully used for direct determination of metronidazole in an oral synthetic antiprotozoal as an antibacterial agent, in metronidazole tablets, and metronidazole injections and metronidazole gels.     

Electrochemical reduction and voltammetric determination of metronidazole at a nanomaterial thin film coated glassy carbon electrode

Simple and sensitive electrochemical method for the determination of metronidazole, based on a nanostructured film coated glassy carbon electrode (GCE), is described. Multi-walled carbon nanotubes (MWNT) was dispersed into water in the presence of a hydrophobic surfactant to give very stable and homogeneous MWNT suspension, and a MWNT-film coated GCE was achieved via evaporating solvent. Metronidazole yields a well-defined reduction peak whose potential is −0.71 V at the MWNT-film coated GCE in pH 9.0 Britton-Robinson buffer. Compared with bare GCE, the MWNT-film modified GCE significantly enhances the reduction peak current of metronidazole. All the experimental parameters were optimized for the determination of metronidazole. The detection limit is 6×10⁻⁹ mol/l at 2 min accumulation. This method has been successfully used to determine metronidazole in the drugs. Furthermore, results obtained by the proposed method have been compared with spectrophotometric method.     

Development of thermogravimetric method for quantitative determination of metronidazole

The objective of this work was to develop and validate a fast and reproducible method to determine the concentration of metronidazole in drug substance and tablets. The samples were analyzed by dynamic thermogravimetry, using 10, 20, 40, 60 and 80°C min^–1 heating rates in nitrogen and in nitrogen with synthetic air. Obtained data were used in the Antoine and Langmuir equations in order to have the pressure curves. Vapor pressure curves of drug and tablet of metronidazole were evaluated using the mathematical indexes of difference factor, f ₁, and similarity factor, f ₂, to compare their profiles. The data showed that there is no significant difference between the vapor pressure profiles of drug and tablet of metronidazole in both environmental conditions, which confirms that the process is really vaporization. The concentration of metronidazole was determined in the raw material and tablets of the drug.     

Application of Central Composite Design to the Optimization of HPLC Analysis of Nitroimidazoles

Abstract

A 2 factor central composite design is used to study the effects of acetonitrile concentration and eluent pH on the retention and resolution of metronidazole and tinidazole on a C-18 column. The equations obtained have been used to predict the composition of an eluent for an optimum separation. The assay developed has been applied to the quantitation of metronidazole in human plasma following simple protein precipitation. The detection limit at 320nm for metronidazole is 0.01μg/mL. Using this assay a relative bioavailability study of two commercial metronidazole tablets in ten healthy volunteers has been performed.     

ENHANCEMENT OF UV-INDUCED SKIN CARCINOGENESIS BY AZATHIOPRINE: ROLE OF PHOTOCHEMICAL SENSITISATION

Abstract The phototoxicity of various drugs (chlorpromazine (CPZ), metronidazole (MET), 8-methoxypsoralen (8-MOP), azathioprine (AZA) and the azathioprine metabolites, 6-mercaptopurine (6-MP), methylnitrothio-imidazole (MNTI), methylnitroimidazole (MNI)) was determined in hairless (Skh-hrl) mice exposed to a light source with broad emission (290–700 nm). Chlorpromazine, MET, 8-MOP, AZA, MNI and 6-MP were phototoxic, as determined by the oedematous response of skin, at doses comparable to those used clinically.
The effects of long-term drug therapy and UV radiation on skin carcinogenesis were then determined. Chlorpromazine and MET, and to a lesser extent AZA, MNTI and 6-MP, enhanced photocarcinogen-esis. In each case, both the tumour yield and the proportion of malignant:benign skin tumours were increased. The results of this study imply that prolonged treatment of mice with low-level phototoxins predisposes to photocarcinogenesis.     

Non-destructive determination of metronidazole powder by using artificial neural networks on short-wavelength NIR spectroscopy

The present study aimed at providing a new method in sight into short-wavelength near-infrared (NIR) spectroscopy of in pharmaceutical quantitative analysis. To do that, 124 experimental samples of metronidazole powder were analyzed using artificial neural networks (ANNs) in the 780-1100 nm region of short-wavelength NIR spectra. In this paper, metronidazole was as active component and other two components (magnesium stearate and starch) were as excipients. Different preprocessing spectral data (first-derivative, second-derivative, standard normal variate (SNV) and multiplicative scatter correction (MSC)) were applied to establish the ANNs models of metronidazole powder. The degree of approximation, a new evaluation criterion of the networks was employed to prove the accuracy of the predicted results. The results presented here demonstrate that the short-wavelength NIR region is promising for the fast and reliable determination of major component in pharmaceutical analysis.     

The effect of methylcellulose on metronidazole release from polyacrylic acid hydrogels

Topical treatment of acne rosacea, a chronic condition characterized by recurrent course for many years, is primarily based on metronidazole preparations. The aim of this study was to evaluate the effect of various acrylic acid polymers, in composition with methylcellulose on metronidazole release rate from hydrogels proposed for the treatment of acne rosacea. Viscosity and release studies using "Paddle over Disk" system with semipermeable membrane of MWCO 3500 were performed. Compositions of Carbopol 971P and methylcellulose revealed an increase in viscosity with increasing concentration of methylcellulose in the range of 17200-26166 mPa.s. In all the examined formulations, the release process was characterized by a two-stage course. Among bipolymeric formulations, the highest first-stage release rate of 9.18 x 10(-3) min(-1) was determined for the gel consisting of 2.00% Carbopol 980NF with 1.00% methylcellulose. The second-stage release rates ranged between 2.88 x 10(-3) and 8.00 x 10(-3) min(-1). Two-stage release course can thus be attributed to metronidazole distribution into two compartments of hydrogel matrix. Proposed gels, with similar rheological properties, may be used for ex vivo and in vivo studies to obtain a suitable drug activity of metronidazole in the treatment of acne rosacea.     

ON THE TWO FORMS OF INTERMEDIATE M OF BACTERIORHODOPSIN

Abstract— The decay time course of intermediate M of bacteriorhodopsin was investigated by flash spectrophotometry. The decay was composed of two exponentials showing the existence of two forms of intermediate absorbing around 410 nm. The two were very different in kinetic character whereas the absorption spectra were almost the same. The relative yield of the two components was a function of the intensity of the exciting flash and the slower component disappeared when the flash intensity was made very small. A model based on the trimeric cluster structure of bacteriorhodopsin is proposed.