Determination of meloxicam in human plasma administrated with four drugs by LC method: application to a pilot bioavailability study

The development and validation of a simple and accurate method by HPLC-UV to quantify meloxicam (MLX) in human plasma and its application to comparative bioavailability study between MLX formulation and manipulated meloxicam + prednisone + cyclobenzaprine + diacerein + hidroxychloroquine is described. MLX and the internal standard (piroxicam) were extracted from plasma using protein precipitation. Chromatographic separation of meloxicam, piroxicam, other active ingredients, diacerein metabolite (Rhein) and plasma interferents was achieved with a C18 column, using a mobile phase of 20 mM sodium Hydrogen pH 3.0 and acetonitrile, with detection at 360 nm and retention times of 4.7, 3.7 and 4.1 min, respectively. The method was linear over the concentration range of 50 to 3000 ng/mL, meloxicam and piroxicam had an average recovery from plasma of 96 and 97 %, respectively. The precision and accuracy (intra-, inter-day) were less than 6 %. The method was successfully applied to a pilot pharmacokinetic study.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Simultaneous spectrophotometric determination of lamivudine and zidovudine in fixed dose combinations using multivariate calibration

The simultaneous determination of two or more active components in pharmaceutical preparations, without previous chemical separation, is a common analytical problem. Published works describe the determination of AZT and 3TC separately, as raw material or in different pharmaceutical preparations. In this work, a method using UV spectroscopy and multivariate calibration is described for the simultaneous measurement of 3TC and AZT in fixed dose combinations. The methodology was validated and applied to determine the AZT+3TC contents in tablets from five different manufacturers, as well as their dissolution profile. The results obtained employing the proposed methodology was similar to methods using first derivative technique and HPLC

High-performance liquid chromatographic determination of fluconazole in plasma and its application to a bioequivalence study

A sensitive and accurate HPLC-UV method for the quantification of fluconazole (FNZ) in human plasma has been developed. The sample was prepared by liquid–liquid extraction (LLE) of FNZ from plasma using ethyl acetate. Nevirapine (NVP) was used as internal standard. The chromatographic retention times of FNZ and NVP were 3.4 and 5.7 min, respectively. The lower limit of quantitation (LLOQ) was 0.5 μg/mL, and no interferences were detected in the chromatograms. The HPLC-UV method was validated by evaluating its intra-day and inter-day precisions and accuracies in a linear concentration range between 0.5 and 8.0 μg/mL. The method was developed, validated and successfully applied to bioequivalence studies involving the oral administration of a single 150 mg FNZ capsules in healthy Brazilian male volunteers.Colegio de Farmacéuticos de la Provincia de Buenos Aire

In vitro performance of fluticasone/salmeterol pressurized metered dose inhaler in combination with three different valved holding chambers

Spacer devices are used to optimize airway aerosol deposition from pressurized metered-dose inhalers (pMDI). The in vitro performance of the combination fluticasone/salmeterol pMDI alone and connected to 3 different valved holding chambers (VHC) was compared by measuring impactor entry port (“throat”) deposition and fine particle dose (FPD) of each medication. Salmeterol (SX) and Fluticasone (FP) throat deposition was reduced over 90 % by all VHC compared to pMDI alone (p < 0,001). The FPD obtained from pMDI alone and connected to VHCs Vortex®, AeroChamber Plus® and Able Spacer® for Salmeterol (25 μg nominal dose) were 12.2 ± 0.7, 12.5 ± 0.5, 11.6 ± 0.8, and 7.9 ± 0.9 μg, respectively. For Fluticasone (125 μg nominal dose) the FPD were 42.5 ± 2.6, 36.3 ± 3.1, 39.8 ± 2.4, and 22.8 ± 3.5 μg, respectively. There were no statistical differences in FPD between devices, except for AbleSpacer® that delivered a lower FPD for both drugs (p < 0.001).Colegio de Farmacéuticos de la Provincia de Buenos Aire

Determination of Escitalopram in Human Plasma by High Performance Liquid Chromatography-Tandem Mass Spectrometry

A rapid (3.0 min) and sensitive (LLOQ 0.5 ng/mL) analytical method for the quantitation of Escitalopram (ETP) in human plasma is described. The method is based on High-Performance Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) using paroxetine as internal standard (I.S.). Sample preparation involved precipitation extraction with acetonitrile. The chromatographic separation was achieved on a ACE C18 (125 x 4,6 mm) reversed-phase column and a mobile phase containing acetonitrile/water (60:50 v/v, add 0.2 % formic acid), in isocratic conditions. The target analytes were transferred into a triple quadrupole mass spectrometer equipped with an electrospray ionization source for mass detection. The ion transitions selected for MRM detection were: m/z 325.2 > 109.2 and 330.0 > 192.0 for ETP and I.S., respectively. The assay was linear in the concentration range of 0.5-50 ng/mL. The mean recovery for ETP was 97.69 %. Intra- and inter-day precision (R.S.D.) were < 10.5 % and <8.2 %, respectively and the accuracy (R.E.) was in the range ± 12.23 %. The method was successfully applied to a single oral dose pharmacokinetics study in 28 healthy Brazilian human volunteers.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is  < 2000 mm yr⁻¹ (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall  < 2000 mm yr⁻¹

&lt;b&gt;Desenvolvimento e validação de método analítico para quantificação de diclofenaco de dietilamônio em pele humana por cromatografia líquida de alta eficiência&lt;/b&gt;

Foi desenvolvido e validado neste estudo um método analítico para quantificação de diclofenaco de dietilamônio em pele humana por cromatografia líquida de alta eficiência, segundo a Resolução 899/2003 da Agência Nacional de Vigilância Sanitária (ANVISA). Empregou-se cromatografia em fase reversa com coluna C18 150 x 4,6 mm, 5 µm Shimpack®, à temperatura de 40 ºC e fase móvel, constituída por mistura de acetonitrila e tampão fosfato de sódio 20 mM pH 3,0 (70:30, v/v) com fluxo de 1,2 mL min-1. Os analitos foram detectados por UV a 280 nm e o método foi especifico, preciso, exato, robusto e linear no intervalo de 0,05 a 20 µg mL-1 (R2 = 0,998), mostrando que pode ser utilizado em estudos de penetração cutânea in vitro tendo como modelo de membrana a pele humana. &lt;i&gt;Palavras-chave&lt;/i&gt;: Diclofenaco dietilamônio. Retenção cutânea. Validação. &lt;b&gt;ABSTRACT&lt;/b&gt; &lt;i&gt;Development and validation of an analytical method for quantitation of diclofenac diethylamine in human skin by high performance liquid chromatography&lt;/i&gt; An analytical method has been developed and validated for the quantitation of diclofenac diethylamine (DDA) in human skin by high performance liquid chromatography (HPLC), in accordance with Regulation 899/2003 of the National Sanitary Surveillance Agency (ANVISA). The HPLC column was a reversed-phase Shimpack® C18, with a 5 µm particle bed, measuring 150 x 4.6 mm i.d., eluted isocratically at 40C with 20 mM sodium phosphate buffer (pH 3.0):acetonitrile (30:70, v/v), the mobile phase flowing at 1.2 mL min-1. Analytes were measured by a UV detector set at 280 nm. The results revealed that the method was specific, precise, accurate, robust and linear (R2=0.998) in the range from 0.05 to 20 µg mL-1. Therefore, it can safely be used to assess DDA in vitro penetration of human skin in kinetic studies. &lt;i&gt;Keywords&lt;/i&gt;: Diclofenac diethylamine. Human skin retention. Validation

Determination of phenytoin in human plasma by a validated liquid chromatography method and its application to a bioequivalence study

A sensitive and specific method based on liquid chromatography was developed and validated for the determination of phenytoin in human plasma using phenobarbital as internal standard. The drugs were extracted from plasma by liquid-liquid extraction and separated isocratically on a Phenomenex Synergi MAX-RP C12 column (150x 4.6 mm i.d.), with water: acetonitrile: methanol(58.8:15.2:26, v/v/v) as mobile phase. Detection was carried out using photodiode array detector set at 205 nm. The chromatographic separation was obtained within 12 min and was linear in the concentration range of 50-2500 ng/mL (r2 = 0.9999). The method was successfully applied for the bioequivalence study of two tablet formulations (test and reference) of phenytoin 100 mg after single oral dose administration to 28 healthy human volunteers. The 90% confidence intervals were calculated for the Cmax, AUC(0-t) and AUC(0-∞), giving values between 99.97–118.40% demonstrating the bioequivalence of the two formulations.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Validação de metodologia analítica para doseamento de soluções de lapachol por CLAE Validation of the analytical methodology for evaluation of lapachol in solution by HPCL

<abstract language="eng">Lapachol is a naphthoquinone found in several species of the Bignoniaceae family possessing mainly anticancer activity. The present work consists of the development and validation of analytical methodology for lapachol and its preparations. The results here obtained show that lapachol has a low quantification limit, that the analytical methodology is accurate, reproducible, robust and linear over the concentration range 0.5-100 µg/mL of lapachol