Preparation and application of a carbon paste electrode modified with multi-walled carbon nanotubes and boron-embedded molecularly imprinted composite membranes.

An innovative electrochemical sensor was fabricated for the sensitive and selective determination of tinidazole (TNZ), based on a carbon paste electrode (CPE) modified with multi-walled carbon nanotubes (MWCNTs) and boron-embedded molecularly imprinted composite membranes (B-MICMs). Density functional theory (DFT) calculations were carried out to investigate the utility of template-monomer interactions to screen appropriate monomers for the rational design of B-MICMs. The distinct synergic effect of MWCNTs and B-MICMs was evidenced by the positive shift of the reduction peak potential of TNZ at B-MICMs/MWCNTs modified CPE (B-MICMs/MWCNTs/CPE) by about 200 mV, and the 12-fold amplification of the peak current, compared with a bare carbon paste electrode (CPE). Moreover, the coordinate interactions between trisubstituted boron atoms embedded in B-MICMs matrix and nitrogen atoms of TNZ endow the sensor with advanced affinity and specific directionality. Thereafter, a highly sensitive electrochemical analytical method for TNZ was established by different pulse voltammetry (DPV) at B-MICMs/MWCNTs/CPE with a lower detection limit (1.25 × 10-12 mol L-1) (S/N = 3). The practical application of the sensor was demonstrated by determining TNZ in pharmaceutical and biological samples with good precision (RSD 1.36% to 3.85%) and acceptable recoveries (82.40%-104.0%).

One-pot synthesis of three-dimensional Mn3O4 microcubes for high-level sensitive detection of head and neck cancer drug nimorazole.

We described a three-dimensional Mn3O4 microcubes (3D-Mn3O4MCs) synthesised via a facile hydrothermal route for the determination of nimorazole (NMZ), an important drug that used in the treatment of head and neck cancer. The 3D-Mn3O4 MCs possess large active area and high conductivity, and 3D-Mn3O4 MCs film modified screen-printed carbon electrode (3D-Mn3O4MCs/SPCE) was fabricated which displayed excellent electrocatalytic ability towards NMZ. Under optimised working conditions, the modified electrode responded linearly to NMZ in the 0.025-8060µM concentration range and the detection limit was 6nM. A rapid, sensitive, selective, reproducible, and durable sensor was described. The practical feasibility of the sensor was demonstrated in human serum and NMZ tablet samples. The obtained results revealed the potential real-time applicability of the sensing device in biological analysis and pharmaceutical formulations.

In vivo and real time determination of ornidazole and tinidazole and pharmacokinetic study by capillary electrophoresis with microdialysis.

The aim of this study was to develop a rapid and sensitive method for in vivo and real time monitoring unbound ornidazole (ONZ) and tinidazole (TNZ) in rabbit blood using capillary electrophoresis coupled with microdialysis. The UV wavelength was set at 214 nm and all separations were performed in 20 mM Tris-H3PO4 (pH 1.5) buffer. Microdialysis probes were perfused at 4 microl/min resulting in relative recoveries of 33.1+/-3.6% and 34.8+/-3.3% (n=3) for ONZ and TNZ, respectively. The linearity was studied in the concentration range of 1.0-412 microg/ml for ONZ and 1.0-520 microg/ml for TNZ. The detection limits were 0.7 microg/ml for ONZ and 0.6 microg/ml for TNZ (S/N=3). All separation could be achieved within 15 min. This method has been successfully applied to the pharmacokinetic study of ONZ and TNZ in rabbit blood.

Validated HPLC method for the determination of tinidazole in human serum and its application in a clinical pharmacokinetic study.

A high performance liquid chromatographic (HPLC) method for the determination of tinidazole in human serum using metronidazole as internal standard (IS) is described. Protein precipitation is used for the preparation of sample. Mobile phase consisting of 0.002 M phosphate buffer, methanol and acetonitrile mixture (85:7.5:7.5/v/v/v) was used at a flow rate of 1 ml/min on a C18 column. The eluate was monitored using an UV/Vis detector set at 320 nm. Ratio of peak area of analyte to IS was used for quantification of serum samples. The absolute recovery was greater than 95% over a concentration range of 0.5 to 30 micrograms/ml and the limit of quantitation was 0.05 microgram/ml. The intra-day relative standard deviation (RSD) measured at 0.5, 5, 15 and 30 micrograms/ml ranged from 0.36 to 6.14%. The inter-day RSD ranged from 1.14 to 4.21%. The method is simple, sensitive and has been successfully used in a pharmacokinetic study conducted in healthy human volunteers.

Assay of tinidazole in human serum by high-performance thin-layer chromatography--comparison with high-performance liquid chromatography.

Determination of tinidazole in human serum by high-performance thin-layer chromatography (HPTLC) is presented. It includes use of 10 x 10 cm plates coated with silica gel 60 and chloroform-acetonitrile-acetic acid (60 + 40 + 2) as mobile phase. Quantitation was performed by densitometry at 320 nm. The linearity (1-10 ng), precision (6%), reproducibility (5%), recovery (96%), and detection limit (1 mg/L) of tinidazole determination by HPTLC were comparable with corresponding method parameters by reversed-phase HPLC. A satisfactory correlation was found between the 2 analytical methods. The procedure was used to quantitate tinidazole in patient sera.

Simple and sensitive method for determination of metronidazole in human serum by high-performance liquid chromatography.

A simple and sensitive HPLC method for determination of metronidazole in human plasma has been developed. A step of freezing the protein precipitate allowed an efficient separation of aqueous and organic phases minimizing the noise level and improved therefore the limit of quantitation (10 ng ml(-1) using 1 ml of plasma sample). The separation of compounds was performed on a RP 18 column with acetonitrile-aqueous 0.01 M phosphate solution (15:85, v/v) as mobile phase. Detection was performed by UV absorbance at 318 nm. Metronidazole was well resolved from the plasma constituents and internal standard. An excellent linearity was observed between peak-height ratios plasma concentrations over a concentration range of 0.01 to 10 microg ml(-1). Within-day and between-day precision (expressed by relative standard deviation) and accuracy (mean error in per cent) did not exceed 4% between 1 and 10 microg ml(-1) and 8.3 and 7.2% respectively for the limit of quantitation. The method is suitable for bioavailability and pharmacokinetic studies in humans.

Direct assay of tinidazole in human serum by micellar liquid chromatography.

A liquid chromatographic procedure for the direct determination of tinidazole in human serum is presented. It includes the use of a micellar mobile phase consisting of SDS (5.10(-2) M): propan-1-ol; (94:6, v/v) and a mu Bondapak CN column with UV detection at 320 nm. No solvent extraction or deproteinization are necessary. The linearity (0.1-10 mg L), the precision (3%), the reproducibility (1.3%), the recovery (99%), and the detection limit (0.1 mg L) in the tinidazole determination are comparable and sometimes greater than the corresponding tinidazole parameters when deproteinization and conventional reversed-phase HPLC are used. One hundred injections of serum samples do not affect the column life. The procedure is applied to ascertain the pharmacokinetics of 10 mg/kg of tinidazole.

A liquid chromatography assay for the study of serum and gastric juice metronidazole concentrations in the treatment of Helicobacter pylori.

Metronidazole is an important component of combination antimicrobial therapies used in the eradication of Helicobacter pylori, a recognized cause of gastritis and duodenal ulcer. Studies are needed to understand which pharmacokinetic factors determine the success of metronidazole therapy and what role drug monitoring plays. Such studies require a rapid, accurate assay for small volumes of sample, including gastric juice, over a 200-fold range of concentrations. Using an isocratic high-performance liquid chromatography (HPLC) method, with an 8-min run time and protein precipitation of samples, metronidazole could be measured reliably to as low as 0.5 mg/L in 100 microliters samples of serum, gastric juice, or saliva. Standard curves for serum and gastric juice were linear between 0.5 and 50 mg/L. Within-day coefficients of variation (CVs) (n = 5 at six concentrations) ranged from 1.1 to 4.8% over this range and the between-day CV (n = 7 days) was 5.8%. Neither omeprazole nor common gastroenteric and cardiac medications interfered with this assay. A pilot study, done in four healthy volunteers given intravenous metronidazole 500 mg before and after 7 days of omeprazole therapy, found metronidazole to be present in higher concentrations in gastric juice and saliva than in serum 2 h after intravenous administration. The range and accuracy of the assay proved to be suitable for carrying out pharmacokinetic studies at clinically used doses of the drug.

Disposition of metronidazole in hens (Gallus gallus) and quails (Coturnix coturnix japonica): pharmacokinetics and whole-body autoradiography.

Hens were given single intravenous or oral doses (30 mg/kg body weight) of metronidazole and the plasma concentrations of the drug were determined by high-performance liquid chromatography (HPLC) at intervals from 10 min to 24 h after drug administration. Pharmacokinetic variables were calculated by the Lagrange algorithm technique. The elimination half-life (t1/2 beta) after the intravenous injection was 4.2 +/- 0.5 h, the volume of distribution (Vd(ss) 1.1 +/- 0.2 L/kg and the total body clearance (ClB) 131.2 +/- 20 mL/h.kg. Oral bioavailability of the metronidazole was 78 +/- 16%. The plasma maximum concentration (Cmax) 31.9 +/- 2.3 micrograms/mL was reached 2 h after the oral administration and the oral elimination half-life (t1/2 beta) was 4.7 +/- 0.2 h. The binding of metronidazole to proteins in hen plasma was very low (less than 3%). Whole body autoradiography of [3H] metronidazole in hens and quails showed an even distribution of labelled material in various tissues at short survival intervals (1-4 h) after oral or intravenous administration. A high labelling was seen in the contents of the small and large intestines. In the laying quails a labelling was also seen in the albumen and in a ring in the periphery of the yolk at long survival intervals. Our results show that a concentration twofold above the MIC is maintained in the plasma of hens for at least 12 h at an oral dose of 30 mg/kg metronidazole.

Short-term sucralfate administration does not alter the absorption of metronidazole in healthy male volunteers.

BACKGROUND: An oral triple therapy using sucralfate instead of a bismuth to eradicate Helicobacter pylori has yielded worse results than those obtained with conventional oral triple therapies. To date, the effect of sucralfate on the pharmacokinetics of nitroimidazolic compounds used in triple therapy such as with metronidazole is unknown. The aim of this study was to investigate the effect of a 5-day administration period of sucralfate (2 g b.i.d.) on metronidazole pharmacokinetics. METHODS: Fourteen healthy male volunteers were selected. The study had an open randomized 2-period crossover design with a 14-day washout period between the phases. The plasma concentration of metronidazole and its hydroxy-metabolite were measured by reverse-phase HPLC with ultraviolet detection. RESULTS: No statistically significant difference was observed in any of the pharmacokinetic parameters studied in the absence and presence of sucralfate. CONCLUSION: Our results clearly indicate that short-term treatment with sucralfate in healthy volunteers does not alter the extent or the rate of metronidazole absorption, and does not affect metronidazole clearance.

Concentrations of tinidazole in gingival crevicular fluid and plasma in dogs after multiple dose administration.

Tinidazole 15 mg/kg was administered to eight Beagle dogs with gingivitis or periodontitis twice daily for 3 days. Tinidazole concentrations in blood and gingival crevicular fluid (GCF) were measured 1, 3, 6 and 9 h after the morning dose each day. The concentration of tinidazole was determined by high performance liquid chromatography (HPLC). The mean concentration of tinidazole in GCF for each dog ranged from 6.05 to 9.32 micrograms/mL at different time points after the first dose, and on the first day the highest concentration was observed 6 h after the drug administration. Tinidazole concentrations were 34 +/- 4%-72 +/- 9% (mean +/- SEM) of simultaneous plasma concentration. At steady-state, on the third treatment day, the mean tinidazole concentrations in GCF ranged from 6.68 to 13.1 micrograms/mL, i.e. 44 +/- 6%-75 +/- 25% of the corresponding concentrations in plasma. Tinidazole concentration in GCF exceeded the MIC values for putative path-ogenic periodontal bacteria and it is concluded that, when indicated, tinidazole could be used for chemotherapy of periodontitis in dogs.

Determination of nitroimidazole residues in poultry tissues, serum and eggs by high-performance liquid chromatography.

A simple high-performance liquid chromatographic (HPLC) method was developed for determination of dimetridazole and metronidazole residues in poultry muscle, liver, serum and eggs. The drug residues were extracted from tissues and egg samples with acetonitrile followed by solid-phase extraction clean-up and HPLC analysis with photodiode array detector. Serum samples were treated with trichloroacetic acid, centrifuged and analysed without further clean-up. The detection limits were 2 ng/g and 5 ng/mL of analysed tissue (egg) and serum samples, respectively. Average recoveries for spike levels of 10 and 20 ng/g ranged from 82 to 94%, and coefficients of variation were below 10%.

Electron-capture gas chromatographic assays of 5-nitroimidazole class of antimicrobials in blood.

Sensitive and selective electron-capture gas chromatographic methods for the determination of N-1-substituted 5-nitroimidazole class of antiprotozoals from blood are described. Metronidazole, secnidazole and ornidazole having a hydroxyl function in the N-1 substitution, were converted to their respective trimethylsilyl derivatives before chromatography on an OV-11 column. Tinidazole and satranidazole, devoid of the hydroxy group but containing a sulphur atom in the molecule, were chromatographed as such on the same stationary phase. Blood levels as low as 50 ng/ml for all the 5-nitroimidazoles have been measured with good precision. The methods can be readily utilized for pharmacokinetic studies.

[Study of serum concentrations and urinary excretion of secnidazole after oral administration in man. Comparison with tinidazole]. / Etude des taux sériques et de l'élimination urinaire du secnidazole après administration orale chez l'homme. Comparaison avec le tinidazole.

Secnidazole, a derivative of 5-nitro imidazole exhibits trichomonacid, amoebicid and antimicrobial properties; it has been studied in view of its biological fate in healthy volunteers (man and woman) comparatively with tinidazole. Both products were administered orally to the same volunteers at the single dose level of 2 g. The seric concentrations and the pharmacokinetic profile were determined up to the 72nd hour after drug administration. The whole urinary excretion (unchanged product + metabolites) during the same period was determined in percent of the administered dose level. Secnidazole is particularly different from tinidazole owing to its slower blood clearance. The apparent average half-life in the ten volunteers (5 men and 5 women) is about 17 hours for secnidazole and 13 hours for tinidazole. However, for both drugs, a difference between men and women was demonstrated: in female volunteers, the decrease in blood concentrations occurs a little quicker than in male volunteers. Regarding urinary excretion, it is also a little greater in female volunteers than in male volunteers.

Metabolism of 5-isopropyl-1-methyl-2-nitro-1H-imidazole. Identification of some urinary metabolites in the dog.

The metabolism of 5-isopropyl-1-methyl-2-nitro-1H-[2-14C] imidazole in dogs has been investigated after oral administration of 50 mg/kg. Three main metabolites, still containing the nitro group and accounting for about 50% of the total radiocarbon, together with a small amount of the unchanged drug, were isolated from the urine within 48 hr. The structures were determined by mass, infrared, and nuclear magnetic resonance spectroscopy. The biotransformations giving rise to the metabolites isolated involve the isopropyl chain of the molecule, either at the tertiary carbon atom or at one of the two methyl groups, or both. Thus, the metabolic behavior of this 2-nitroimidazole derivative appears to be similar to that previously demonstrated for the class of the isomeric 5-nitroimidazoles.