Missed detection of significant positive and negative shifts in gentamicin assay: implications for routine laboratory quality practices.

INTRODUCTION: A product recall was issued for the Roche/Hitachi Cobas Gentamicin II assays on 25th May 2016 in Australia, after a 15 - 20% positive analytical shift was discovered. Laboratories were advised to employ the Thermo Fisher Gentamicin assay as an alternative. Following the reintroduction of the revised assay on 12th September 2016, a second reagent recall was made on 20th March 2017 after the discovery of a 20% negative analytical shift due to erroneous instrument adjustment factor. MATERIALS AND METHODS: The practices of an index laboratory were examined to determine how the analytical shifts evaded detection by routine internal quality control (IQC) and external quality assurance (EQA) systems. The ability of the patient result-based approaches, including moving average (MovAvg) and moving sum of outliers (MovSO) approaches in detecting these shifts were examined. RESULTS: Internal quality control data of the index laboratory were acceptable prior to the product recall. The practice of adjusting IQC target following a change in assay method resulted in the missed negative shift when the revised Roche assay was reintroduced. While the EQA data of the Roche subgroup showed clear negative bias relative to other laboratory methods, the results were considered as possible 'matrix effect'. The MovAvg method detected the positive shift before the product recall. The MovSO did not detect the negative shift in the index laboratory but did so in another laboratory 5 days before the second product recall. CONCLUSIONS: There are gaps in current laboratory quality practices that leave room for analytical errors to evade detection.

Once versus twice daily gentamicin dosing for infective endocarditis: a randomized clinical trial.

OBJECTIVES: The aim of this randomized study was to investigate the effects of once versus twice daily gentamicin dosing on renal function and measures of infectious disease in a population with infective endocarditis (IE). METHODS: Seventy-one IE patients needing gentamicin treatment according to guidelines were randomized to either once (n = 37) or twice daily (n = 34) doses of gentamicin. Kidney function (glomerular filtration rate, GFR) was measured with an isotope method ((51)Cr-EDTA) at the beginning of treatment and at discharge. Treatment efficacy was assessed by C-reactive protein (CRP) time to half-life, mean CRP and leukocytes. RESULTS: Baseline GFR was similar in the two groups. Both groups displayed a significant fall in GFR from admission to discharge. The mean decrease in GFR was as follows: with once daily gentamicin, 17.0% (95% confidence interval 7.5-26.5), and with twice daily gentamicin, 20.4% (95% confidence interval 12.0-28.8). However, there was no significant difference in the GFR decrease between the once and twice daily regimens (p = 0.573). No difference in infection parameters was demonstrated between the two dosing regimens. CONCLUSIONS: A twice daily gentamicin dosing regimen is neither less nephrotoxic nor more efficient than a once daily regimen in the treatment of IE patients. When indicated, gentamicin may therefore also be administered as a single-dose regimen in the treatment of IE patients.

Antimicrobial activity of the methanolic extracts and compounds from Treculia obovoidea (Moraceae).

The crude extract from Treculia obovoidea was subjected to purification by repeated chromatography. Eight compounds were isolated from Treculia obovoidea and identified as Psoralen (1), Bergapten (2), 7-methoxycoumarin (3), 7-hydroxycoumarin (4), 4,2',4'-trihydroxychalcone (5), 4,2',4'-trihydroxy-3-prenylchalcone (6), 3-hydroxy-4-methoxybenzoic acid (7) and O-[3-(2,2-dimethyl-3-oxo-2H-furan-5-yl) butyl] bergaptol (8). These compounds together with the extract were tested for their antimicrobial activity against Gram-positive bacteria (six species), Gram-negative bacteria (12 species) and three Candida species using micro-dilution methods for the determination of the minimal inhibition concentration (MIC) and the minimal microbicidal concentration (MMC). The MIC values obtained with the crude extracts varied from 78.12 to 156.25 microg/ml against 17 (80.95%) of the 21 tested microorganisms. All the isolated compounds showed selective activity. The antimicrobial activity of this plant as well as that of compounds 6 and 8 is being reported for the first time. The obtained results provide promising baseline information for the potential use of these crude extract as well as some of the isolated compounds in the treatment of bacterial and fungal infections.

Multivariate analysis of nuclear magnetic resonance data--characterization of critical drug substance quality of gentamicin sulfate.

Fourteen gentamicin sulfate lots collected from international markets showed high quantities of impurities (approximately 30% of studied lots). 1H NMR spectroscopy as a primary analytical method was applied in order to validate the quantification results obtained from micellar electrokinetic chromatography method (MEKC). In this study, 1H NMR data of 46 gentamicin sulfate drug substance lots were used to classify the lots by means of principal component analysis (PCA) of 14 1H NMR-signals in the 5.0-6.0 ppm region. Three main groups could be classified: high purity (3 lots), average quality (28 lots) and low purity (14 lots); one lot proved to be atypical. The 14 normalized signal heights in the 5.0-6.0 ppm region are predictive for purity quality according to a partial least squares (PLS)-model with sum of all impurities as Y-variable (measured by MEKC).

Development and validation of a novel LC/ELSD method for the quantitation of gentamicin sulfate components in pharmaceuticals.

The equivalent response of evaporative light scattering detector (ELSD) for compounds of similar structure is exploited to develop an LC/ELSD method for the simultaneous quantitation of the four main components of gentamicin sulfate, using as external standard the one main component kanamycin. A C18 column was used along with a mobile phase consisting of H2O (containing 35.4 microg/ml of trichloroacetic acid and 0.89 microl/ml of trifluoroacetic acid)-methanol-acetonitrile (990:5:5, v/v/v), in an isocratic mode at 1.1 ml/min. Parameters of ELSD were 50 degrees C for evaporation temperature and 3.0 bar for pressure of carrier gas (N2). A logarithmic calibration curve was obtained for sulfate (tR = 1.9 min) from 4.2 to 150 microg/ml (r > 0.994) with a precision of 0.18%R.S.D. Kanamycin and the four gentamicin components (C(1a), C2, C(2a) and C1) were eluted at 3.2, 4.6, 5.9, 7.1 and 8.7 min, respectively, with good resolution (Rs > 1.5). Logarithmic calibration curve was obtained for each component (r > 0.99) with statistically equal slopes varying from 2.457 to 2.558. The mass range of total gentamycin was 35-240 microg/ml. The proposed method was applied for the determination of gentamicin components and sulfate in raw materials and pharmaceutical formulations (injection, drops and cream) without any pretreatment except cream, for which liquid-liquid extraction was required. Recovery from standard addition experiments in commercial formulations was 99-100% regarding total gentamicin and 89-108% regarding individual components, with a precision (%RSD, n = 4) 0.7-5.8%.

New combination for the therapy of canine otitis externa. II. Efficacy in vitro and in vivo.

A new, effective drug combination was developed for the therapy of canine otitis externa (OE) by taking into consideration the microorganisms most frequently isolated from dogs affected with OE, their combination, their drug sensitivity and the type and incidence of ear canal inflammation. The antimycotic active ingredient of the combination is ketoconazole, its antibacterial component is gentamicin sulphate, while its antiphlogistic constituent is mazipredone hydrochloride. Based upon the results of in vitro pharmacodynamic tests, the antifungal activity of the combination is superior to that of ketoconazole used alone at the same concentration. A total of 210 dogs affected with OE were treated with the combination: 94.2 per cent of them became clinically symptomless and microbiologically negative in an average of 8.5 days. No adverse reactions were observed in connection with the use of the drug combination. The therapeutic results can be attributed to the high antifungal efficacy of the combination demonstrated in vitro and to the favourable properties of the solvent mixture.

Parámetros Usados en la Prescripción de Amicacina y Gentamicina en la Unidad Pediátrica de un Hospital de Tercer Nivel / Parameters Used in the Prescription of Amikacin and Gentamicin in the Pediatric Unit of a Third-Level Hospital

Se estudió retrospectiva y descriptivamente un grupo de 105 historias clínicas de pacientes pediátricos hospitalizados y con indicación de administración de un aminoglucósido en la Unidad de Pediatría de la Clínica Henrique De La Vega de la ciudad de Cartagena (Colombia), durante el año de 1994. Se evaluó el número de pacientes que recibieron la dosis ideal del aminoglucósido con base en la edad, peso, talla, función renal (calculada con base en la creatinina sérica) y niveles séricos de aminoglucósidos. Sólo en nueve casos (8.57 por ciento) se determinó la creatinina sérica inicial, de los cuales cinco (4.76 por ciento) tuvieron dosificación adecuada y dos insuficiente (1.91 por ciento). Los 96 restantes recibieron dosis empírica y sólo en 20 casos (19.04 por ciento) se usó el aminoglucásido con intervalo de 24 h. En ningún caso se reportaron niveles séricos del aminoglucósido, ni se utilizó dosis de carga. De los resultados se deduce que en esta clínica no se toma en cuenta la depuración de creatinina para la dosificación del aminoglucósido, como tampoco se controlan los niveles séricos de los mismos, que son indispensables para una buena vigilancia farmacológica

Comparative in-vitro antibacterial activity of two brands of antibiotics against clinical isolates of some bacterial genera.

Six brands of ampicillin and four of gentamicin were compared for their in-vitro antibacterial activity against clinical isolates of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The minimum inhibitory concentrations obtained for each brand against each bacterial isolate compared very well with one another, and the kinetics of bactericidal activity showed that the brands of each antibiotic possessed similar activity against the clinical isolates tested.

Interlot variability in gentamicin and tobramycin concentration and its possible significance.

Aminoglycoside therapy is routinely monitored at many institutions. It is widely known that serum concentrations of gentamicin and tobramycin may differ markedly among patients receiving the same doses of these drugs. One possible source of this variability may be interlot variation in the concentration of these drugs in commercial preparations. A study was designed to evaluate inter- and intralot variation in gentamicin and tobramycin concentrations at the labeled concentrations of 10 and 40 mg/ml. Multiple samples from six to 10 lots of commercially available gentamicin sulfate injection (Elkins-Sinn, Inc.) and tobramycin sulfate injection (Eli Lilly & Co.) were studied at each concentration. The actual percentage concentration of gentamicin in various lots ranged from 101 to 134% of the labeled concentrations; the actual percentage range was 101-109% at 10 mg/ml and 102-134% at 40 mg/ml labeled concentration. The actual percentage concentration of tobramycin in various lots ranged from 103 to 122% of labeled concentration; the actual percentage range was 107-117% at 10 mg/ml and 103-122% at 40 mg/ml labeled concentration. The intralot variation was less than 4% for both drugs at two concentrations. Based on these results, an 80-mg dose may in fact contain 107 mg of gentamicin or 98 mg of tobramycin. This may be clinically important in the care of patients and may at least in part explain the large variation in serum concentrations and difficulty in prediction of dosage requirements from routine monitoring. Furthermore, the available literature on pharmacokinetics, efficacy, and toxicity has not considered this interlot variation in aminoglycoside concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of manufacturer lot number on pharmacokinetic manipulation of gentamicin serum concentrations.

A prospective, randomized trial was performed to study the impact of lot variation on pharmacokinetic manipulation of serum gentamicin concentrations. Twenty patients receiving gentamicin were randomized prospectively into two groups. Group I patients had blood samples obtained before and after two doses during their hospital regimen using gentamicin from the same lot number. Group II patients had the samples obtained around two doses using different lot numbers of gentamicin. Pharmacokinetic parameters were calculated assuming a one-compartment model and were compared between the initial and subsequent set of serum concentrations. For Group I, the gentamicin distribution volume (Vd) did not differ (mean change, -0.007 L/kg, or mean absolute percentage change, 20.8%). Group II also did not have a significant mean change in Vd (0.023 L/kg, or mean absolute percentage change, 18.7%). The gentamicin Vd did not appear to change over time whether gentamicin was administered using identical or differing lot numbers.

Enzymatic inactivation of residual gentamicin after membrane filtration.

RESIDUAL GENTAMICIN ON A MILLIPORE MEMBRANE WAS INACTIVATED BY MODIFICATION WITH TWO DIFFERENT ENZYMES: gentamicin adenylyltransferase and 3-N-acetyltransferase. Both modifications allowed the growth of susceptible strains of Escherichia coli and Bacillus subtilis.

Control of the composition of gentamicin sulphate by proton magnetic resonance spectrometry.

The proportions of the main components present in gentamicin sulphate complex, gentamicins C1, C1a and C2, can be monitored by 1H nuclear magnetic resonance (nmr) spectrometry. The method depends on measurement of the peak heights of signals for N-methyl and C-methyl groups present in all three components and of those present in C1 and C2 only, followed by calculation of peak height ratios to control composition within acceptable limits. The precision and reproducibility of the method have been established through two collaborative studies each involving seven laboratories. In the second study, with an improved procedure, the mean variance between laboratories with 10 samples was 3.4 X 10(-4) for the N-methyl ratio of the peak at delta 2.75 to that at delta 2.95, and 1.25 X 10(-3) for the C-methyl ratio of the peak at delta 1.25 to that at delta 1.35. Within laboratories the mean variance for triplicate determinations was 7.4 X 10(-5) and 8.9 X 10(-5) respectively. The data presented here form the experimental basis for the test controlling the composition of gentamicin sulphate in the British Pharmacopoeia 1973: Addendum 1975, and for the introduction into the British Pharmacopoeia of nmr spectrometry as an analytical technique. The reference standards and all batches of gentamicin sulphate intended for therapeutic use in the United Kingdom examined by this procedure comply with the limits laid down.

Standardization of a preparative ultracentrifuge method for quantitative determination or protein binding of seven antibiotics.

A preparative ultracentrifuge method was standardized for determination of quantitative binding of cephalothin, cefamandole, cefazolin, cefaclor, erythromycin, gentamicin, and chloramphenicol to human serum proteins. At achievable in vivo concentrations, serum binding was 78.5% for cephalothin, 79.9% for cefamandole, 88.5% for cefazolin, 23.5% for cefaclor, 41.9% for erythromycin, 22.7% for gentamicin, and 59.5% for chloramphenicol. Techniques that use semipermeable cellophane or diaflow membranes, cross-linked dextran, inhibition of bacterial growth, protein precipitation, or liquid partitioning all have inherent problems with either the ligand or the antibiotic adversely interacting with the experimental apparatus. Ultracentrifugation provides a rapid, reproducible technique for protein-binding determinations of the classes of antibiotics described.

International standards and international reference preparations: amphotericin B, vancomycin, capreomycin, cefalotin, demethylchlortetracycline, gentamycin, gramicidin S, kanamycin and kanamycin B, lincomycin, lymecycline, methacycline, paromomycin, rifamycin SV, ristocetin and ristocetin B, spiramycin, and triacetyloleandomycin.

Each of the preparations described here was obtained and evaluated at the request of a WHO Expert Committee on Biological Standardization. Unless otherwise stated, a standard procedure was used to distribute the material into individual ampoules. The procedure was as follows. Upon receipt by the National Institute for Medical Research (NIMR), London, materials were stored temporarily in the dark at a temperature of -10 degrees C or lower, and protected from moisture. At a convenient time they were brought back to room temperature, mixed, and distributed into individual neutral glass ampoules so that each ampoule contained 50-100 mg of powder. If it was known that the material was light-sensitive non-actinic glass ampoules were used. After exhaustive drying in vacuum over phosphorus(V) oxide, the ampoules were either constricted (up to 1963) or fitted with capillary leak plugs, dried for a further period under the same conditions, filled with dry nitrogen, and sealed by fusion of the glass. The total drying period varied from 8 to 38 days according to the nature of the material. After they had been tested for leaks, the ampoules were stored in the dark at -20 degrees C.