High-performance liquid chromatographic determination of netilmicin in guinea-pig and human serum by fluorodinitrobenzene derivatization with spectrophotometric detection

Development of Sٍٍensitive Spectrofluorimetric Methods for Determining Netilmicin Based on Selective Condensation Reactions of its Amine Moiety with each Acetylacetone/Formaldehyde and Ninhydrin/Phenylacetaldehyde Reagents

Netilmicin is an aminoglycoside antibiotic used to treat infections caused by a broad spectrum of Gram-negative and Gram-positive bacteria and is pharmaceutically formulated in ophthalmic dosage forms. In this study, two spectrofluorimetric approaches were designed and developed to switch-on the fluorescence activity of NTC. The first method, or Hantzsch (HNZ) method, was relied on measuring the generated fluorescence intensity upon the condensation of NTC with acetylacetone and formaldehyde (Hantzsch reaction) at λ_emis=483 nm/λ_excit=425.5 nm. While the second fluorometric method (NHD method) was relied on measuring the generated fluorescence intensity upon the condensation of NTC with ninhydrin/phenylacetaldehyde at λ_emis=482.2 nm/λ_excit=385.8 nm. The reaction conditions for the two approaches were well investigated and optimized. The selectivity study for the methods was investigated by determining NTC in the presence of the co-formulated drug (dexamethasone) and pharmaceutical excipients. The validation for two approaches was performed based on ICH guidelines, and ranges of linearity were 0.1-1.2 and 1.5-6.0 µg/mL, while LOD values were 0.039 and 0.207 µg/mL for the HNZ method and the NHD method, respectively. Finally, NTC has been determined in different ophthalmic preparations by the proposed approaches with adequate recovery values.

Advances in antibiotic measurement

Antibiotics are most commonly prescribed drugs in clinical practice. Therapeutic drug monitoring of these medications is typically associated with a select group of antibiotics such as aminoglycosides and vancomycin. Outside this group, other antibiotics such as chloramphenicol and antituberculosis agents may also require monitoring. Due to their wide therapeutic index, other classes of antibiotics such as penicillins, cephalosporin, sulfonamides, quinolones, and macrolides do not generally require routine therapeutic drug monitoring. Determination of serum or plasma concentration of these drugs, however, may be beneficial in those patients with compromised renal function. As can be expected, immunoassays for routine monitoring of aminoglycosides and vancomycin have been developed and are widely commercially available. Tests for other antibiotics, due to their infrequent use and low clinical application, are generally limited to in-house developed methods.

Characterization of impurities in sisomicin and netilmicin by liquid chromatography/mass spectrometry

The characterization of unknown impurities present in netilmicin and sisomicin by liquid chromatography (LC) coupled with mass spectrometry (MS) is described. The volatile ion-pairing agent trifluoroacetic acid (TFA) was used for the retention of the main compounds and their impurities on a reversed-phase (RP) C18 column, because they are highly hydrophilic and basic compounds. The method showed good separation between netilmicin and its four potential related substances prescribed in the European Pharmacopoeia, which were identified by comparison of their retention times with those of the reference substances. Furthermore, in total 16 unknown impurities in a netilmicin sample and six in a sisomicin sample with unknown identity were detected. The structures of the unknown compounds were deduced based on comparison of fragmentation patterns with those of the reference substances investigated in LC/MSn experiments by the use of electrospray ion trap mass spectrometry.

Adsorptive stripping voltammetric determination of netilmicin in the presence of formaldehyde

A linear sweep adsorptive stripping voltammetric method for the determination of netilmicin in the presence of formaldehyde has been proposed for the first time. In the presence of 3.0 x 10(-3) g ml(-1) formaldehyde, netilmicin exhibits a sensitive cathodic peak at -1.30 V (vs. the saturated calomel electrode, SCE) in a medium of Britton-Robinson buffer (pH 8.7) with a scan rate of 100 mV s(-1) after a preconcentration period of 120 s at -1.10 V (vs. SCE). The peak current showed a linear dependence on the netilmicin concentration over the range 4.2 x 10(-9)-1.0 x 10(-7) g ml(-1). The achieved limits of detection and quantitation were 1.0 x 10(-10) and 3.3 x 10(-10) g ml(-1) netilmicin, respectively. It was deduced from the experiments that the amine-aldehyde condensation product formed between netilmicin and formaldehyde is mainly responsible for the appearance of the peak. The electrochemical behavior of netilmicin in the presence of formaldehyde has been studied. The method was applied to the direct determination of netilmicin in injectable formulations and spiked human urine and serum samples.

Shelf lives of aseptically prepared medicines—stability of netilmicin injection in polypropylene syringes

There is no published information on the stability of netilmicin solutions in prefilled syringes. The purpose of this study was to evaluate the stability of netilmicin in polypropylene syringes and to determine the optimum validated shelf life so that they may be prepared in bulk in appropriately licensed facilities. The syringes containing netilmicin 10 or 100mg/ml were stored at 7 degrees C, room temperature in the light (RTL) and 25 degrees C/60% relative humidity for up to 300 days. Netilmicin concentration was determined by reversed phase high performance liquid chromatography (RP-HPLC) of the isoindole derivative formed with o-phthalaldehyde (OPA). The shelf lives were calculated using the maximum rate method applied to the netilmicin analytical data. At 7 degrees C 10 and 100mg/ml solutions were stable for 90 days falling to 30 days at 25 degrees C and 60% RH. At RTL the 10mg/ml solution was stable for 9 days.

Aminoglycoside antibiotics--two decades of their HPLC bioanalysis

Several reviews have been published on high-performance liquid chromatographic (HPLC) methods for the determination of aminoglycoside antibiotics (aminoglycosides) in biological fluids [e.g. Nilsson-Ehle, I. (1983). J. Liq. Chromat. 6: 251]. Of these, the paper by Maitra et al. [(1979a). Clin. Chem. 25: 1361.] briefly summarizes the early 2-3 years of experience on HPLC assaying of amikacin, gentamicin, netilmicin and tobramycin in body fluids. The reviews by Nilsson-Ehle, I. [(1983). J. Liq. Chromat. 6: 251] and by Miner, D. J. [(1985). Antibiotics. In Therapeutic Drug Monitoring and Toxicology by Liquid Chromatography, (Wong S. H. Y., ed.), ch. 10, p. 269. Marcel Dekker, New York and Basel.] devoted to the monitoring of antibiotics, also evaluated the first 6-8 years of the application of HPLC assays for the aminoglycosides amikacin, gentamicin, netilmicin, sisomicin and tobramycin. This report presents a great majority of the HPLC assay methods published during the last two decades for determining practically a dozen different aminoglycoside antibiotics in body fluids, particularly in the serum or plasma, and in urine.

Determination of netilmicin sulfate by liquid chromatography with pulsed electrochemical detection

The determination of netilmicin sulfate by liquid chromatography using a column packed with poly (styrene-di-vinylbenzene) and pulsed electrochemical detection on a gold electrode is described. The mobile phase consisted of an aqueous solution containing 35 g 1-1 of sodium sulfate, 0.5 g 1-1 of sodium octanesulfonate, 10 ml 1-1 of tetrahydrofuran and 50 ml 1-1 of 0.2 M phosphate buffer (pH 3.0). The total analysis time was not more than 25 min. The effects of the different chromatographic parameters on this selection were also investigated. When a number of commercial samples of netilmicin sulfate was analyzed using this method, eight different components were separated, three of which were of unknown identities.

Analysis of isepamicin in human plasma by radioimmunoassay, microbiologic assay, and high-performance liquid chromatography

Plasma concentrations of isepamicin, a new aminoglycoside antibiotic, were determined by radioimmunoassay (RIA), microbiological assay (MA), and high-performance liquid chromatography (HPLC) in healthy volunteers after administration of 7.5 mg/kg intramuscular dosages once daily for 10 days. Plasma samples were collected on days 1, 7, and 10. The limit of quantitation (LOQ) was 0.1 microg/ml for HPLC and RIA and 0.5 microg/ml for MA. The HPLC and RIA yielded superimposable plasma concentration-time curves, whereas the plasma concentrations obtained with MA appeared to be 20% to 30% lower. Regression analysis indicated good correlations among the three assays, with coefficients of correlation measuring 0.935 to 0.960 for RIA compared with HPLC, 0.925 to 0.945 for MA compared with HPLC, and 0.920 to 0.945 for RIA compared with MA.

Comparison of a fluorescence polarization immunoassay of netilmicin in plasma, peritoneal dialysate, and urine with a high-performance liquid chromatographic method

The quantitative analysis of netilmicin in plasma, peritoneal dialysate, and urine using the fluorescence polarization immunoassay (FPIA) of the Abbott TDx system is compared with the modified high-performance liquid chromatography (HPLC) method of Peng et al., which was chosen as a reference. Using the least square method, we found that the results of the FPIA (y) correlated well with those obtained with HPLC (x). The three regression equations for the plasma, peritoneal dialysate, and urine samples, respectively, were y = 0.71x + 0.44 with r = 0.88 and n = 45; y = 0.94x + 1.22 with r = 0.93 and n = 95; and y = 0.92x + 0.70 with r = 0.93 and n = 61. The corresponding mean errors (FPIA-HPLC) with their 95% confidence intervals were -0.19 (-0.38 to -0.02), 0.69 (-0.42 to 1.81), and -0.13 (-1.13 to 0.87) microgram/ml. According to results of the Wilcoxon matched-pairs signed-ranks test, these errors did not represent a significant bias. The FPIA is thus suitable for analyzing netilmicin in the three biological fluids studied except when dialysate is contaminated with Amuchina. In this case, HPLC should be used.

Prophylactic mezlocillin-netilmicin combination in permanent transvenous cardiac pacemaker implantation: a single-center, prospective, randomized study

A prospective, randomized study was carried out in order to assess the efficacy and safety of the mezlocillin-netilmicin combination in the prophylaxis of first permanent transvenous cardiac pacemaker implantation. Five hundred and fifty-two consecutive patients were randomly administered either 2 g mezlocillin and 200 mg netilmicin both as an i.v. bolus before implantation or 2g mezlocillin before and then 6 and 12 hours after surgery and 200 mg netilmicin before and then 12 hours after implantation. No adverse events were seen. Neither pocket nor electrode infections were observed in the 457 subjects still alive (mean follow-up: 29.2 months) or in patients who died after 1 year of follow-up (mean follow-up: 20.1 months) or before this time (mean follow-up: 4.7 months). The serum and pocket concentrations of mezlocillin and netilmicin at the end of surgery were found to be adequate to cover microorganisms that most often cause infections, including methicillin-resistant staphylococci.