Emilio García-Quetglas

Rapid liquid chromatographic assay for the determination of acetaminophen in plasma after propacetamol administration: application to pharmacokinetic studies

A simple method for the rapid estimation of acetaminophen in plasma is described here. p-Propionamidophenol was used as internal standard. The assay involved a single ethyl acetate extraction and liquid chromatographic analysis at a wavelength of 242 nm using a reversed-phase encapped column, with a mobile phase of acetonitrile and 0.005 M potassium dihydrogen phosphate adjusted at pH 3.00. The limit of quantitation of acetaminophen by this method was 0.05 microg ml(-1), only 0.1 ml of the plasma sample was required for the determination. The calibration graph was linear from 0.05 to 100 microg ml(-1). Intra and inter-day precision (CV) did not exceed 8.93%. Mean recoveries of 90.31% with a CV of 1.38% were obtained. Applicability of the method was demonstrated by a pharmacokinetic study in normal volunteers who received 2 mg propacetamol.

Development and validation of a sensitive method for the determination of ganciclovir in human plasma samples by reversed-phase high-performance liquid chromatography.

A rapid, sensitive, specific liquid chromatographic method has been developed for the determination of therapeutic levels of ganciclovir in human plasma. Plasma (1 ml) and acyclovir (I.S.) were treated with 50% trichloroacetic acid. The supernatant was neutralized with 2 M NaOH and purified with chloroform. The aqueous phase (80 microl) was analyzed by a 3-microm Hypersil ODS C18 column with 0.04 M triethylamine-0.1 M sodium dihydrogen phosphate monohydrate as the mobile phase (1 ml/min) and ultraviolet detection at 254 nm. Calibration was linear from 50 to 10000 ng/ml. Intra- and inter-day C.V. did no exceed 6.65%. The detection limit was about 10 ng/ml.

Rapid Determination of Ranitidine in Human Plasma by High-Performance Liquid Chromatography

SummaryAn HPLC method has been developed for the quantification of rantidine in plasma for pharmacokinetic studies. Metoclopramide was used as internal standard. The method uses a simple and rapid sample clean-up procedure involving single-step extraction with organic solvent to extract ranitidine from plasma. After evaporation and reconstitution the samples are chromatographed on a 250 mm×4 mm base-stable reversed-phase column with 0.05 M ammonium acetate-acetonitrile, 75∶25 (v/v) as mobile phase and UV detection at 313 nm. The calibration graph was linear for quantities of ranitidine between 10 and 2000 ng mL−1. Intra- and inter-dayCV did not exceed 11.64%. The quantitation limit was 10 ng mL−1 for human plasma. The applicability of this method for pharmacokinetic studies of ranitidine after oral administration are described. Approximately 90 samples can be processed in 24 h.

High-performance liquid chromatographic assay for simultaneous determination of tramadol and its active metabolite in human plasma. Application to pharmacokinetic studies

SummaryA sensitive liquid chromatographic assay for the quantitative determination of the opioid analgesic tramadol and its active metabolite is described. Fluconazole was used as internal standard. The assay involved a singletert-butyl methyl ether extraction and LC analysis with fluorescence detection. Chromatography was at 30°C pumping an isocratic mobile phase of acetonitrile-water (19∶81, v/v) containing 0.06M NaH2PO4 and 0.05M triethylamine, adjusted to pH 7.90, at 1 mL min−1 through a reversed-phase, 250×4 mm base-stable column. The limit of quantitation of tramadol and its active metabolite was 1 ng mL−1, only 0.5 mL plasma sample was required for the determination. The calibration curve was linear from 1–1000 ng mL−1. Intra and inter-day precision (C.V.) did not exceed 10%. Mean recoveries of 96.38% for tramadol and 96.62% forO-demethyltramadol with CVs of 0.43% and 1.46% were obtained. Applicability of the method was demonstrated by a pharmacokinetic study on normal volunteers who received 100 mg tramadol intravenously.

A sensitive method for the determination of gemfibrozil in human plasma samples by RP-LC

A sensitive high-performance liquid chromatographic assay for the quantitative determination of gemfibrozil is described in this work. Ibuprofen was used as internal standard. The assay involved a single cyclohexane extraction and LC analysis with fluorescence detection. Chromatography was performed at 40 degrees C on a Hypersil ODS column. The mobile phase was a mixture of a solution of phosphoric acid 0.4% and acetonitrile (45:55). The method was validated. The detection limit of this method was 0.025 microg ml(-1); only 0.5 ml of the plasma sample was required for the determination. The calibration graph was linear from 0.05 to 0.5 microg ml(-1) and required a cubic equation from 0.5 to 30 microg ml(-1). Intra and inter-day precision (C.V.) did no exceed 15%. Mean recoveries were of 90.15+/-6.9% (C.V.s<8%) for gemfibrozil and 93.10% for ibuprofen Applicability of the method was demonstrated by a pharmacokinetic study in normal volunteers who received gemfibrozil by oral route.

Granulicatella adiacens breast implant-associated infection

The 1st reported case of breast implant-associated infection due to Granulicatella adiacens, formerly known as nutritionally variant streptococci, Streptococcus adiacens, and Abiotrophia adiacens is presented. Microbiology and previously reported cases of infections by this organism are reviewed.

Determination of ketorolac enantiomers in plasma using enantioselective liquid chromatography. Application to pharmacokinetic studies

SummaryA direct HPLC method for quantification of the (R) and (S) enantiomers of ketorolac in human plasma for pharmacokinetics studies has been developed. Naproxen sodium [S(+) enantiomer] was used as an internal standard. Plasma samples (1 mL) were vortexed for 30 sec with methyltert-butyl ether, followed by centrifugation at 2000 g for 8 min. The aqueous phase was acidified (pH 1) by adding 1 mL of 2N HCl and back-extracted with 5 mL methyltert-butyl ether. The organic phase was evaporated, and the residue was dissolved in 200 μL of mobile phase. 25 μL were chromatographed on a α1-acid glycoprotein column (Chiral-AGP, 100×4 mm I.D.), using a mobile phase with 8.5% propan-2-ol in phosphate buffer (0.09M NaH2PO4.H2O, 0.01M Na2HPO4, 0.002M Dimethyloctylamine; pH 5.5). Calibration range was 20–20000 ng mL−1 for (R)- and (S)-ketorolac. The LOQ was 5 ng mL−1 for both enantiomers. The sensitivity could be extended to 1 ng mL−1 with the same precison by increasing the injection volume to 100 μL.The method is reproducible, accurate, and stereospecific. The inter-assay and intra-assay CVs were <11.40% and <9.30% for (R)- and (S)-ketorolac respectively. Under the conditions employed, no racemization was observed.

Farmacología de los azoles

Azole antifungals have different pharmacokinetic characteristics: complete oral absorption for Voriconazole, and to a lesser extent for fluconazole. The absorption of posaconazole and itraconazole increases with food intake. All of them have high tissue distribution with low plasma concentrations, especially low in the case of posaconazole and itraconazole. Posaconazole and itraconazole have high plasmatic protein binding and consequently both have a very low free fraction. Elimination of azole antifungals is through a metabolic pathway with CYP450 isoenzymes, and has a non linear pharmacokinetics with a high risk of interation with other drugs since azoles have the ability of CYP450 isoenzymes inhibition. Possibly the parameter that defines more precisely their efficacy is AUIC with an optimum value near 20, although cut-off values must be defined since some azoles may have difficulty to reach this value.

Determination of cisapride in human plasma by high-performance liquid chromatography

SummaryAn HPLC method has been developed for the quantification of cisapride in plasma for pharmacokinetic studies. Clebopride was used as internal standard. Plasma samples were extracted at alkaline pH withtert-butyl methyl ether. The organic phase was then extracted with sulphuric acid to eliminate endogenous interferences, and cisapride and the internal standard were then extracted at alkaline pH intotert-butyl methyl ether. After evaporation oftert-butyl methyl ether, the residue was analysed by HPLC. Chromatography was performed at 20°C on a 250mm×4mm i.d. reversed-phase column selective for basic compounds. The isocratic mobile phase was 48∶52 (v/v) acetonitrile-water containing 0.05 M potassium dihydrogen phosphate and 0.04 M triethylamine, adjusted to pH 5.5; the flow rate was 1 mL min−1. Cisapride and the internal standard were detected by ultraviolet monitoring at 276 nm. The calibration graph was linear for quantities of cisapride from 1 to 200 ng mL−1. Intra- and inter-day precision (CV) did not exceed 13.98%. The limit of quantitation (LOQ) was 0.68 ng mL−1 for human plasma. The applicability of the method has been demonstrated in a pharmacokinetic study of normal volunteers who received 10 mg cisapride orally.

Fosfomicina trometamol. Dosis múltiples como pauta larga en el tratamiento de las infecciones urinarias bajas

Introduccion El tratamiento de las infecciones urinarias del tracto inferior no complicadas se realiza con pautas de tratamiento cortas. En otras circunstancias no esta tan clara la pauta que hay que seguir. Cuando la infeccion urinaria del tracto inferior no se produce en una mujer joven, la recomendacion terapeutica es la utilizacion de antibioticos durante al menos 7 dias, y son las quinolonas y el cotrimoxazol los antibioticos utilizados con mayor frecuencia. Pero debido al porcentaje de resistencias de los microorganismos implicados en este tipo de infecciones, es aconsejable evaluar otras pautas de tratamiento, de forma que habria que evaluar, entre otros, el uso de antibioticos con un menor indice de resistencias como fosfomicina trometamol, en periodos de tratamiento mas largos que el uso tan extendido en dosis unica. Metodos Desde los datos de eliminacion urinaria de fosfomicina obtenidos en voluntarios sanos en un estudio previo, se han simulado las concentraciones de este antibiotico en orina tras la administracion de 2 dosis. Se ha calculado el intervalo mas idoneo para mantener concentraciones urinarias por encima del punto de corte de Escherichia coli para fosfomicina (16 mg/l), uno de los microorganismos implicados con mayor frecuencia en este tipo de infecciones. Resultados Las concentraciones de fosfomicina en orina se mantienen por encima del punto de corte durante 161 h cuando se administran 2 dosis de 3 g de fosfomicina trometamol separadas 72 h. Este supone un tiempo de eficacia del 96% en un periodo total de 7 dias. Conclusion La pauta teorica, desde el punto de vista farmacocinetico, para conseguir concentraciones de fosfomicina en orina por encima del punto de corte de E. coli es la administracion de 2 dosis de 3 g de fosfomicina trometamol separadas 72 h.