Determination of neomycin in plasma and urine by high-performance liquid chromatography. Application to a preliminary pharmacokinetic study

Pharmacokinetics of neomycin sulfate after intravenous and oral administrations in swine

The aminoglycoside antibiotic neomycin, which is used to treat external or internal bacterial infections, is primarily administered in veterinary medicine as a sulfate salt. However, no information is available on the pharmacokinetic characteristics and absolute availability of neomycin sulfate after intravenous (i.v.) and oral (p.o.) administrations in swine. Here, these parameters were studied in swine after i.v. and p.o. doses of single 15 mg/kg body weight doses. The blood samples were assessed using ultra-high-performance liquid chromatography-tandem mass/mass spectrometry (UPLC-MS/MS) and pharmacokinetic parameters were analyzed using a non-compartmental model. In swine, after the p.o. administration, the elimination half-life, mean residue time from t0 to the last collection point, mean maximum concentration, mean time to reach maximum concentration and area under concentration-time curve from t0 to the last collection point values were 12.43 ± 7.63 h, 10.25 ± 4.32 h, 0.11 ± 0.07 μg/ml, 1.92 ± 0.97 h and 1.23 ± 0.78 μg·h/ml, respectively, whereas after the i.v. administration, the values were 5.87 ± 1.12 h, 6.07 ± 0.49 h, 15.80 ± 1.32 μg/ml, 0.30 ± 0.38 h and 76.14 ± 3.52 μg·h/ml, respectively. The absolute bioavailability of neomycin sulfate B was 4.84%±0.03.

Using existing drugs as leads for broad spectrum anthelmintics targeting protein kinases

As one of the largest protein families, protein kinases (PKs) regulate nearly all processes within the cell and are considered important drug targets. Much research has been conducted on inhibitors for PKs, leading to a wealth of compounds that target PKs that have potential to be lead anthelmintic drugs. Identifying compounds that have already been developed to treat neglected tropical diseases is an attractive way to obtain lead compounds inexpensively that can be developed into much needed drugs, especially for use in developing countries. In this study, PKs from nematodes, hosts, and DrugBank were identified and classified into kinase families and subfamilies. Nematode proteins were placed into orthologous groups that span the phylum Nematoda. A minimal kinome for the phylum Nematoda was identified, and properties of the minimal kinome were explored. Orthologous groups from the minimal kinome were prioritized for experimental testing based on RNAi phenotype of the Caenorhabditis elegans ortholog, transcript expression over the life-cycle and anatomic expression patterns. Compounds linked to targets in DrugBank belonging to the same kinase families and subfamilies in the minimal nematode kinome were extracted. Thirty-five compounds were tested in the non-parasitic C. elegans and active compounds progressed to testing against nematode species with different modes of parasitism, the blood-feeding Haemonchus contortus and the filarial Brugia malayi. Eighteen compounds showed efficacy in C. elegans, and six compounds also showed efficacy in at least one of the parasitic species. Hypotheses regarding the pathway the compounds may target and their molecular mechanism for activity are discussed.

Parasitic nematode infection is a large global health and economic problem, infecting around 2 billion people and costing $100 billion in crops and livestock. People in developing countries often live on one dollar per day, so treatments cannot be expensive, therefore using pre-existing drugs as lead compounds provides an economical way to begin to develop affordable treatments. Protein kinases were chosen as the focus of this work due to the large number of pre-existing drugs that target them and their important role in regulating almost all activities in the cell. Herein we describe a set of protein kinases conserved in diverse nematode species and experimental screening results of pre-existing drugs that target these kinases. The compounds that show in vitro efficacy in both C. elegans and parasitic nematodes, H. contortus or B. malayi have potential to be optimized further. These compounds have potential to provide accessible treatment to people in developing countries, as well as improving the health of livestock and boosting food production globally.

SPR sensing of small molecules with modified RNA aptamers: detection of neomycin B

We have studied how the modification of the RNA aptamer evolved against neomycin B at 2' position of ribose with a methyl group influences the affinity of the interaction. Using surface plasmon resonance (SPR) and faradaic impedance spectroscopy (FIS) an affinity constant in the muM range was calculated. The results showed that the modification of the aptamer does not significantly alter the affinity of the aptamer for the antibiotic. This finding opens up the possibility of designing modified RNA aptamers resistant to endonucleases without variation of the analytical features. In addition to this, we propose a competitive assay for the detection of neomycin B using SPR as a transduction technique. A range of quantification between 10 nM and 100 microM was obtained, which shows the feasibility of detecting small molecules using aptamers with high sensitivity.

Development of enzyme-linked immunosorbent assay (ELISA) for the detection of neomycin residues in pig muscle, chicken muscle, egg, fish, milk and kidney

A colorimetric competitive direct enzyme-linked immunosorbent assay (ELISA) method was developed using polyclonal antibody to determine neomycin residues in food of animal origin. No cross-reactivity of the antibody was observed with other aminoglycosides. The limit of detection of the method was 0.1μg/kg. A simple and efficient sample extraction method was established with recoveries of neomycin ranged from 75% to 105%. The detection limits were 5μg/kg(l) in pig muscle, chicken muscle, fish and milk, 10μg/kg in kidney and 20μg/kg in egg, respectively. Chemiluminescence assay was developed for detecting neomycin residues in pig muscle and chicken muscle. The limit of detection of the method was 0.015μg/kg, and the detection limits were 1.5μg/kg in pig muscle and 6μg/kg in chicken muscle. The ELISA tests were validated by HPLC, and the results showed a good correlation (r(2)) which was greater than 0.9.

Determination of neomycin and bacitracin in human or rabbit serum by HPLC–MS/MS

The method for the simultaneous determination of neomycin and bacitracin in human or rabbit serum was developed by using ion pairing reversed phase chromatography and tandem mass spectrometry (MS/MS) detection with electrospray (ESI) in positive mode. Both substances elute under these conditions at the same time and also kanamycin as internal standard elutes almost at the same time. The sample preparation was simple-only using 0.1 mL serum by protein precipitation with acetonitrile. Neomycin and bacitracin were detected as two-fold charged ions as well as the internal standard. The calibration range of these quite difficult detectable substances was 0.2-50 microg/mL of serum. The method was validated for both human or rabbit serum. The inter batch precision of quality control samples in human serum for neomycin ranged from 4.46% to 8.99% and for bacitracin from 6.85% to 11.17%. The inter batch accuracy for neomycin ranged from 98.7% to 100.7% and for bacitracin from 99.2% to 103.0%. At lower limit of quantitation (LLOQ) level of 0.2 microg/mL inter batch precision in human serum for neomycin was 12.05% and for bacitracin 11.91%, whereas accuracies were 99.9% for neomycin and 102.7% for bacitracin. Bench top stability in human or rabbit serum was given over three freeze thaw cycles and 4h at room temperature. The method can be considered to be specific and recoveries for sample preparation were high.

Rapid analysis of native neomycin components on a portable capillary electrophoresis system with potential gradient detection

A simple method based on capillary electrophoresis with potential gradient detection was developed to separate and detect neomycin components within 4 min without a derivatization step. Satisfactory separation and good repeatability were obtained using a separation buffer composed of 1 mM ammonium citrate (pH 3.5). The linearity of the method ranged from 10 to 1000 ppm with a limit of detection for neomycin B of about 7 ppm. After a simple dilution and filtering pretreatment step, neomycin components in three real samples were successfully analyzed without any major interference. Due to its simplicity and reliability, this method could provide an excellent alternative to the assays currently listed in U.S. and European Pharmacopoeia. The experiments were performed on a portable capillary electrophoresis system and, hence, the method can be readily applied to field analysis and point-of-care testing. Figure Photo of portable CE-P2-PGD system.

Rapid and sensitive determination of aminoglycoside antibiotics in water samples using a strong cation-exchange chromatography non-derivatisation method with chemiluminescence detection

A simple and sensitive chemiluminescence (CL) detection approach was developed for the direct analysis of aminoglycoside antibiotics in water samples following strong cation-exchange chromatographic (SCX-HPLC) separation. This detection system, which eliminates the need for sample derivatisation, is based on the inhibitory effect of aminoglycosides on the CL reaction between luminol and hydrogen peroxide catalysed by copper(II). As the operational and chemical variables that affect the CL signal were optimised, ionic strength and the Triton X-100 micelles turned out to be the keys to obtain maximum CL efficiency. Aminoglycosides were successfully separated in 10 min on a SCX column using a mobile phase consisting of an aqueous solution containing 5.0 x 10(-3)mol/l sodium acetate and 0.65 mol/l sodium chloride at pH 6.1. Sample volumes of 50 ml were preconcentrated by passage through a weakly acidic IRC-50 exchange column. Limits of detection from 0.7 to 10 microg/l and relative standard deviations from 2.7 to 5.4% were thus obtained. The proposed method surpasses other chromatographic alternatives in terms of the limit of detection, sample requirements for analysis and cost.

Development of ELISA and immunochromatographic assay for the detection of neomycin

BACKGROUND

Reliable analytical methods are required to monitor neomycin residue levels in the livestock products. In particular, a more simple and rapid detection method is required in the veterinary fields.

METHODS

Competitive direct ELISA and immunochromatographic assay were developed using monoclonal antibody to detect neomycin in the animal plasma and milk.

RESULTS

No cross-reactivity of the antibody was observed with other aminoglycosides based on competitive direct ELISA methods, indicating that the antibody is highly specific for neomycin. Based on the standard curves, the detection limits were determined to be 6.85 ng/ml in PBS, 3.61 ng/ml in plasma, and 2.73 ng/ml in milk, respectively. Recoveries of neomycin from spiked plasma and milk at levels of 50-200 ng/ml ranged from 87% to 108%. Concentration of intramuscularly injected neomycin was successfully monitored in the rabbit plasma through competitive direct ELISA. Immunochromatographic method was also developed using colloidal gold-conjugated monoclonal antibody. Through this method, the detection limits were estimated to be about 10 ng/ml of neomycin in PBS, plasma, and milk.

CONCLUSIONS

Immunochromatographic assay developed in this study is suitable for the simple screening of neomycin residues in the veterinary field. Observed positives can be confirmed using a more sensitive laboratory method such as competitive direct ELISA.

Analysis of neomycin sulfate and framycetin sulfate by high-performance liquid chromatography using evaporative light scattering detection

A rapid and simple method for the determination of main components and related substances of both neomycin sulfate and framycetin sulfate by HPLC and evaporative light scattering detection (ELSD) is described. The method was also used to determine the neomycin B and the sample sulfate content. Detection and quantitation of aminoglycoside antibiotics are problematic because of the lack of UV absorbing chromophore. The use of a universal detector avoids the need for sample derivatization or use of specific detector based on pulsed amperometry described to be difficult in routine assays. Separation was performed with a Polaris C18 150 mm x 4.6 mm i.d., 3 microm reversed-phase column with a solution of 170mM trifluoroacetic acid (TFA) mobile phase at a flow rate of 0.2 mL/min. The chromatographic parameters were optimized with the help of experimental design software. Mass spectrometry (MS) was employed to confirm the ELSD profile. The final method was validated using methodology described by the International Conference of Harmonization in the field of Active Pharmaceutical Ingredients. Commercial samples of different sources were analyzed and results were in good agreement with specifications of the European Pharmacopoeia.

Enhancement of evaporative light scattering detection in high-performance liquid chromatographic determination of neomycin based on highly volatile mobile phase, high-molecular-mass ion-pairing reagents and controlled peak shape

In the frame of the development of a novel HPLC-ELSD (evaporative light scattering detection) method for the determination of the aminoglycoside antibiotic neomycin sulfate, the influence of mobile phase composition and peak broadening on ELSD response was evaluated. ELSD response was enhanced by: (a) increase of mobile phase volatility (solvents examined: water, acetonitrile, methanol and acetone), (b) increase of molecular mass of ion-pairing species [acidic reagents tested: formic, acetic, trifluoroacetic, trichloroacetic and heptafluorobutyric acid (HFBA)], and (c) decrease of peak width and asymmetry obtained by controlling the concentration of the ion-pairing acidic reagent (HFBA). Utilizing a Waters ODS-2 C18 Spherisorb column, evaporation temperature of 45 degrees C and nitrogen pressure of 3.5 bar, the optimized mobile phase was water-acetone (50:50), containing 11.6 mM HFBA, in an isocratic mode at a rate of 1.0 ml/min. Neomycin was eluted at 4.9 min, with asymmetry factor 1.3. Logarithmic calibration curve was obtained from 2 to 50 microg/ml (r > 0.9997). Limit of detection (LOD) was 0.6 microg/ml and R.S.D. = 1.7% (n = 3, 3.3 microg/ml). In raw materials, the simultaneous determination of sulfate (LOD = 3 microg/ml, R.S.D. = 1.7%, r> 0.9998) and of minor impurities was feasible. The developed method was also applied for the determination of neomycin in pharmaceutical formulations (powder, aerosol and cream) without any interference from excipients (recovery from spiked samples ranged from 99 to 102%) and a %R.S.D. of <2.1 (n = 3). The HPLC-ELSD method was also found applicable in the determination of neomycin in animal feeds (LOQ=0.2%) without any interference from the feed matrices.

Determination of neomycin by LC–tandem mass spectrometry using hydrophilic interaction chromatography

A specific, and automated method was developed to quantitate neomycin in human serum. Samples were prepared with an automated solid phase extraction (SPE). The hydrophilic interaction chromatography (HILIC) was used for additional sample cleanup and baseline separation. The analyte neomycin was detected with electrospray ionisation tandem mass spectrometry (ESI-MS-MS). Using a volume of 500 microl biological sample the lower limit of quantification was 100 ng/ml. The described HILIC-MS-MS method is suitable for clinical and pharmcokinetical investigations of neomycin.

Sample preparation for residue determination of gentamicin and neomycin by liquid chromatography

The effect of sample preparation on the determination of gentamicin and neomycin residues in animal tissues was investigated. The extract was mixed with an ion-pair reagent and applied to an octadecyl cartridge. The cartridges were washed with buffer followed by water, and analytes were eluted with ion-pair buffer-acetonitrile mixture. The aminoglycosides were derivatized with 9-fluorenylmethyl chloroformate prior to liquid chromatography using a reversed-phase column and fluorescence detection. Under the conditions applied neomycin was fully separated from all the gentamicin compounds. The highest recoveries of gentamicin and neomycin from spiked tissues were obtained using trichloroacetic acid after initial extraction with phosphate-buffered saline. No interfering peaks from endogenous compounds of matrix were noted at the elution position of the analytes. An intra-laboratory validation of the whole procedure was performed. The calibration graphs were linear from 0.1 to 1.0 mg/kg for gentamicin, and from 0.2 to 1.0 mg/kg for neomycin. Limits of detection were 0.05 mg/kg and 0.10 mg/kg for gentamicin and neomycin, respectively. Limits of quantitation for gentamicin and neomycin were 0.1 and 0.20 mg/kg muscle, liver or kidney tissue, respectively. Recoveries of gentamicin spiked at levels of 0.1 mg/kg porcine tissues ranged from 76 to 86%. Recoveries of neomycin spiked at levels of 0.2 mg/kg porcine tissues ranged from 77 to 83%. The validated procedure was used to determine gentamicin concentrations in porcine tissue after dosing with gentamicin at a level of 5 mg/kg body mass.

Determination of paromomycin in human plasma and urine by reversed-phase high-performance liquid chromatography using 2,4-dinitrofluorobenzene derivatization

A sensitive high-performance liquid chromatographic method for the determination of paromomycin in human plasma and urine was developed. Paromomycin was quantitated following pre-column derivatization with 2,4-dinitrofluorobenzene (DNFB). The chromatographic separation was carried out on a C18 column at 50 degrees C using a mobile phase consisting of 64% methanol in water adjusted to pH 3.0 with phosphoric acid. The eluents were monitored by UV detection at 350 nm. The linearity of response for paromomycin was demonstrated at concentrations from 0.5 to 50 microg/ml in plasma and 1 to 50 microg/ml in urine. The relative standard deviation of the assay procedure is less than 5%.

Linkup of a fast protein liquid chromatography system with a stirred thermostated cell for sterile preparation of liposomes by the proliposome-liposome method: application to encapsulation of antibiotics, synthetic peptide immunomodulators, and a photosensitizer

The proliposome-liposome method is based on the conversion of the initial proliposome preparation into a liposome dispersion by dilution with the aqueous phase. This technique is characterized by an extremely high entrapment efficiency and is suitable for the encapsulation of a wide range of drugs with different water and alcohol solubility. A description of a home-made stirred thermostated cell and its linkup with an FPLC system for a rapid and automated preparation of multilamellar liposomes under strictly controlled conditions (temperature, dilution rate, and schedule) is presented. The highly reproducible procedure yields multilamellar liposomes with a high encapsulation efficiency for various drugs. Carboxyfluorescein, as a model hydrophilic compound, was entrapped with an efficiency of 81 +/- 2%. The antibiotics neomycin and gentamycin were entrapped with efficiencies of 65 and 69%, respectively. Synthetic immunomodulators adamantylamide dipeptide, muramyl dipeptide, and beta-D-GlcNAc-norMurNAc-L-Abu-D-isoGln were entrapped with efficiencies of 87, 62, and 85%, respectively. The photosensitizer mesotetra-(parasulfophenyl)-porphin was entrapped with an efficiency of 65%. The cell has been designed for laboratory-scale preparation of liposomes (300-1000 mg of phospholipid per run) in a procedure taking less than 90 min. The method can be readily scaled up and linked with secondary processing methods, such as pressure extrusion through polycarbonate filters.

Sensitive high-performance liquid chromatographic assay for aminoglycosides in biological matrices enables the direct estimation of bacterial drug uptake

Following the development of a sensitive high-performance liquid chromatographic (HPLC) assay for gentamicin in biological matrices, the utility of this assay for the determination of other clinically important aminoglycosides (neomycin, netilmicin and sisomicin) in bacterial culture media or plasma is demonstrated. The high sensitivity of the assay enables direct measurement of the aminoglycoside content of bacterial cells cultured in the presence of unlabelled drug.

Determination of neomycin sulfate by liquid chromatography with pulsed electrochemical detection

The determination of neomycin sulfate by liquid chromatography using a column packed with a poly(styrenedivinylbenzene) co-polymer and pulsed electrochemical detection on a gold electrode is described. The mobile phase consisted of an aqueous solution containing 70 g/l of sodium sulfate, 1.4 g/l of sodium 1-octanesulfonate and 50 ml/l of a 0.2 M phosphate buffer (pH 3.0). Sodium hydroxide was added post-column. The influence of the different chromatographic parameters on the separation was investigated. The method shows good linearity and repeatability and is stability indicating. A number of commercial samples was analyzed using this method and the results were compared with results obtained with the European Pharmacopoeia method and a previously described thin-layer chromatographic method.

Disposition and bioavailability of neomycin in Holstein calves

The disposition and absorption kinetics of neomycin were studied in healthy ruminating dairy calves (n = 6), approximately 3-months-old. The calves were treated with single intravenous (i.v.) (12 mg/kg), intramuscular (i.m.) (24 mg/kg), oral (p.o.) (96 mg/kg) and repeated p.o. (96 mg/kg, b.i.d., 15 1/2 days) doses of neomycin. A 3-week rest period was allowed between treatments A and B, and B and C. Baseline and serial venous blood samples were collected from each calf. Plasma concentrations of neomycin were determined by a high performance liquid chromatography procedure. The resulting data were evaluated by using compartmental pharmacokinetic models and nonlinear least squares regression analysis. The mean of some selected parameters were t1/2 lambda 3 7.48 +/- 2.02 h, Clt = 0.25 +/- 0.04 L/h/kg, Vd(ss) = 1.17 +/- 0.23 L/kg, and MRT = 4.63 +/- 0.87 h for the i.v. data and t1/2 = 11.5 +/- 3.8 h, MRTabs = 0.960 +/- 1.001 h, F = 127 +/- 35.2%, and Clt/F = 0.199 +/- 0.047 L/h/kg for the i.m. data, respectively. Only one calf absorbed neomycin to any significant degree (F = 0.0042) after a single p.o. dose. Selected mean parameters determined after repeated oral dosing were: F = 0.45 +/- 0.45%, Cmax = 0.26 +/- 0.37 microgram/ml, and tmax = 2.6 +/- 2.9 h. Terminal half-lives determined for the i.v. and i.m. treatments were considerably longer than those reported previously in the literature.