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Dissolution parameters for sodium diclofenac-containing hypromellose matrix tablet

MOURAO, Samanta C.; SILVA, Cristiane da; BRESOLIN, Tania M. B.; SERRA, Cristina H. R.; PORTA, Valentina
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.99%
Sodium diclofenac (SD) release from dosage forms has been studied under different conditions. However, no dissolution method that is discriminatory enough to reflect slight changes in formulation or manufacturing process, and which could be effectively correlated with the biological properties of the dosage form, has been reported. This study sought to develop three different formulae of SD-containing matrix tablets and to determine the effect of agitation speed in its dissolution profiles. F1, F2 and F3 formulations were developed using hypromellose (10, 20 and 30%, respectively for F1, F2 and F3) and other conventional excipients. Dissolution tests were carried out in phosphate buffer pH 6.8 at 37 degrees C using apparatus 11 at 50, 75 or 100 rpm. Dissolution efficiency (DE), T(50) and T(90) were determined and plotted as functions of the variables agitation speed and hypromellose concentration. Regarding DE, F2 showed more sensitivity to variations in agitation speed than F1 and F3. Increasing hypromellose concentration reduced DE values, independent of agitation speed. Analysis of T(50) and T(90) suggests that F1 is less sensitive to variations in agitation speed than F2 and F3. Most discriminatory dissolution conditions were observed at 50 rpm. Results suggest that the comparison of dissolution performance of SD matrix tablets should take into account polymer concentration and agitation conditions. (C) 2009 Published by Elsevier B.V.; PIPG (Programa Integrado de Pos-Graduacao e Graduacao e Graduacao) of UNIVALI (Universidade do Vale do Itajai)

Estudo in vitro do efeito da adição de lauril dietilenoglicol éter sulfato de sódio nas soluções de hipoclorito de sódio sobre suas propriedades físico-químicas anteriores e posteriores à dissolução do tecido pulpar bovino; Effects of adding lauryl-diethylene-glycol-ether sodium sulfate on sodium hypochlorite's physical-chemical properties, before and after bovine pulp tissue dissolution: an in vitro analysis.

Barbin, Eduardo Luiz
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 06/08/1999 PT
Relevância na Pesquisa
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Estudou-se, in vitro, a dissolução do tecido pulpar bovino, promovida pela solução de hipoclorito de sódio nas concentrações de 0,5; 1,0; 2,5 e 5,0 por cento com e sem lauril dietilenoglicol éter sulfato de sódio analisando-se, também, o potencial hidrogeniônico (pH), a tensão superficial, a condutividade iônica e o teor de cloro, antes e depois da utilização dessas soluções. Secionava-se um fragmento da porção central da polpa de incisivos centrais inferiores de bovinos e sua massa era anotada. Para a realização do teste de dissolução, confeccionou-se um dispositivo conectado a uma bomba peristáltica que promovia a agitação da solução. Colocava-se um fragmento pulpar no interior desse dispositivo e ligava-se a bomba peristáltica. O tempo de dissolução total foi medido com um cronômetro. Usando o tempo de dissolução do fragmento de polpa e a massa deste, calculava-se a velocidade de dissolução do tecido pulpar. Concluiu-se que: a) a velocidade de dissolução dos fragmentos de polpa bovina é diretamente proporcional à concentração da solução de hipoclorito de sódio e maior sem tensoativo; b) a redução do pH, entre o início e o final do processo de dissolução pulpar, é inversamente proporcional à concentração da solução de hipoclorito de sódio...

Avaliação do perfil de dissolução de comprimidos de glibenclamida 5 mg obtidos por diferentes processos; Dissolution profile avaliation of glibenclamide 5mg tablets obtained by different processes

Zaim, Christiane Yuriko Hamai
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 14/05/2004 PT
Relevância na Pesquisa
37.02%
Fármacos pouco solúveis em água são um dos maiores desafios encontrados em formulação de comprimidos, uma vez que, se não adequadamente formulados, podem apresentar problemas de dissolução e de biodisponibilidade. O presente trabalho teve como objetivo produzir comprimidos de glibenclamida 5 mg (hipoglicemiante oral pouco solúvel) utilizando diferentes processos visando a melhoria da dissolução do fármaco e comparar a liberação in vitro (perfil de dissolução) das formulações entre si, bem como em relação ao medicamento referência no Brasil, Daonil®. Foram obtidas 19 formulações por compressão direta empregando dispersão sólida, complexação com ciclodextrina ou micronização do fármaco. Os comprimidos foram analisados quanto ao aspecto, peso médio, dureza, friabilidade, teor e eficiência de dissolução. Os resultados indicaram que, dentre os processos estudados, a utilização de complexos glibenclamida-β-ciclodextrina e glibenclamida micronizada, promoveram uma melhora da dissolução do fármaco. O superdesintegrante Explocel® promoveu significativa melhoria no perfil de dissolução em todas as formulações em que estava presente. A utilização do complexo glibenclamida-β-ciclodextrina com o Explocel® apresentou perfil de dissolução estatisticamente semelhante ao Daonil®...

Desenvolvimento e validação de ensaio de dissolução para o ritonavir cápsulas utilizando correlação in vitro-in vivo; Development and validation of dissolution test for ritonavir capsules using in vitro-in vivo correlation

Rossi, Rochele Cassanta
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
37.02%
Os testes de dissolução têm surgido no campo farmacêutico como uma ferramenta muito importante para caracterizar o desempenho de um medicamento. O ritonavir (ABT-538) é um inibidor peptidomimético tanto do HIV-1 quanto do HIV-2, sendo aprovado pelo FDA em 1996. Embora utilizado por quase dez anos, em todo o mundo, o ritonavir (cápsula mole) não está incluído em nenhuma farmacopéia ou código oficial e somente o FDA sugere uma condição para o teste de dissolução. Sendo um fármaco pouco solúvel e com uma biodisponibilidade oral em torno de 70%, o ritonavir é um candidato ao desenvolvimento de um método de dissolução baseado em uma correlação in vitro-in vivo (CIVIV). Neste trabalho, um ensaio de dissolução para ritonavir na forma farmacêutica cápsula foi desenvolvido e validado de acordo com o guia proposto pelo Fórum Farmacopéico. Diversas condições foram avaliadas, tais como, composição do meio, pH, concentração de surfactante e velocidade de agitação. O método foi desenvolvido utilizando o mesmo lote de Norvir® usado no estudo de bioequivalência e os dados in vivo foram utilizados para selecionar as melhores condições para o ensaio de dissolução, baseado em uma CIVIV. Um método seletivo por HPLC também foi desenvolvido. Para esta formulação...

Variabilidade de goethita e hematita via dissolução redutiva em solos de região tropical e subtropical; Goethite and hematite variability via reductive dissolution in soils from tropical and subtropical regions

Inda Junior, Alberto Vasconcellos; Kampf, Nestor
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
POR
Relevância na Pesquisa
37.02%
Dezenove amostras de horizontes B latossólicos, uma de B plíntico, uma de B incipiente e uma de horizonte Cr foram submetidas a dissoluções seletivas da goethita e da hematita por ditionito-citratro-bicarbonato de sódio a 20 oC em intervalos de tempo entre 5 e 3.840 minutos. O diâmetro médio do cristal (DMC), área superficial específica (ASE) e substituição do ferro por Al (substituição por Al3+) da goethita e da hematita nas amostras foram estimados, por difratometria de raios X (DRX), em subamostras não tratadas e em subamostras tratadas selecionadas ao longo das dissoluções seletivas. O controle das fases de goethita e hematita que persistiram após cada etapa da dissolução seletiva foi realizado pelo método da difratometria diferencial de raios X (DDRX). A cinética dissolutiva dos cristais foi descrita por meio da segmentação das curvas de dissolução do ferro no tempo em intervalos em que o comportamento dissolutivo foi linear. As taxas de dissolução nos diferentes segmentos lineares foram estimadas a partir do coeficiente angular da reta relativa a cada segmento. Em amostras goethíticas latossólicas, a metodologia discriminou diferentes fases de goethita (populações heterogêneas) quanto à substituição por Al3+...

Analysis of bovine pulp tissue dissolution ability by photodynamic therapy: an in vitro study

Steier,Liviu; Rossi-Fedele,Giampiero; Acauan,Monique; Bianchini,Priscila; Souza,Matheus Albino; Figueiredo,José Antônio Poli de
Fonte: Pontifícia Universidade Católica do Rio Grande do Sul Publicador: Pontifícia Universidade Católica do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 EN
Relevância na Pesquisa
37.02%
PURPOSE: To evaluate the bovine pulp tissue dissolution ability of photodynamic therapy. METHIDS: Twenty pieces of bovine pulp tissue were weighed and divided randomly into four groups (n=5), according to the cleaning protocol: G1 - distilled water (negative control), G2 - sodium hypochlorite 1% (positive control), G3 - photodynamic therapy, G4 - sodium hypochlorite 1% + photodynamic therapy. The observation of the events of dissolution was performed by two observers blinded in relation to the test using 2x magnification, recording time in minutes until complete tissue dissolution. The total observation time was 2 hours. The dissolution rate was calculated dividing the weight of the fragment pulp (mg) by the time of dissolution (mg/min). RESULTS: Only group 2 (NaOCl) was able to promote complete dissolution of pulp tissue. In the other groups there was no occurrence of complete dissolution of the samples. The mean dissolution time for samples from group 2 (NaOCl) was 1.26 mg/min. CONCLUSION: Only the sodium hypochlorite was able to dissolve the fragments of bovine pulp tissue and photodynamic therapy does not show ability to dissolve tissue.

Dissolution test optimization for meloxicam in the tablet pharmaceutical form

Oliveira,Érika de Fátima Silva; Azevedo,Roberta de Cássia Pimentel; Bonfilio,Rudy; Oliveira,Diego Borges de; Ribeiro,Gislaine Pereira; Araújo,Magali Benjamim de
Fonte: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2009 EN
Relevância na Pesquisa
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Meloxicam is a broadly used drug in the therapeutics for the osteoarthritis and rheumatoid arthritis treatments in adults, and it is available in the Brazilian market, as tablet and capsule pharmaceutical forms. The present work aimed to establish conditions for accomplishment of the dissolution test of 15 mg meloxicam tablets (A and B test products), compared with the reference product, since there is no monograph about dissolution assays for meloxicam in official summaries. To optimize the conditions several parameters were tested and, according to obtained results, the use of pH 7.5 phosphate buffer (900mL, at 37 ± 0.5ºC) as dissolution medium, paddle method (apparatus 2), stirring speed of the dissolution medium at 100 rpm and collect time of 60 minutes were considered satisfactory. The samples were quantified by UV spectrophotometric method at 362 nm. The products presented kinetics of first-order. Dissolution efficiency values were of 83.25, 83.73 and 88.10% for the A, B and reference products, respectively. Factors f1 and f2 were calculated and similarity of the tested medicines was demonstrated. The dissolution test was validated presenting selectivity, linearity, precision and accuracy within of the acceptance criteria.

Test of dissolution and comparison of in vitro dissolution profiles of coated ranitidine tablets marketed in Bahia, Brazil

Santos Júnior,Aníbal de Freitas; Barbosa,Igor Santos; Santos,Venyson Lima dos; Silva,Rangel Leal; Caetite Junior,Edimar
Fonte: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2014 EN
Relevância na Pesquisa
37.05%
Ranitidine is an antisecretory drug with H2 antagonist action useful in treating gastric and duodenal disorders. The dissolution test is used to obtain and compare dissolution profiles and establish similarities of pharmaceutical forms. The aim of this study was to compare the dissolution profiles of 150-mg coated ranitidine tablets of a reference drug (product A) and a generic (product B) and a similar (product C) drug marketed in Bahia, Brazil using a simple, fast and inexpensive ultraviolet method. Dissolution was determined using a USP type 2 apparatus at 50 rpm with 900 mL of distilled water at 37.0 ± 0.5 oC for 1h. The dissolution test was performed in compliance with the American Pharmacopoeia (USP-32). Dissolution efficiency and difference (f1) and similarity (f2) factors were calculated and evaluated. The proposed quantification methodology for drug dissolution test was validated, presenting accuracy, linearity and precision within the acceptance criteria. Products A, B and C showed dissolution efficiency values of 59.29, 73.59 and 66.67%, respectively. Factors f1 and f2 were calculated and showed that the profiles of products A, B and C were dissimilar. However, all the products released ranitidine satisfactorily, with at least 80% of the drug dissolved within 30 min.

Development of dissolution test method for a telmisartan/amlodipine besylate combination using synchronous derivative spectrofluorimetry

Anumolu,Panikumar Durga; Neeli,Sirisha; Anuganti,Haripriya; Ranganatham,Sathesh Babu Puvvadi; Satya,Subrahmanyam Chavali Venkata
Fonte: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 EN
Relevância na Pesquisa
37.04%
The dissolution process is considered an important in vitro tool to evaluate product quality and drug release behavior. Single dissolution methods for the analysis of combined dosage forms are preferred to simplify quality control testing. The objective of the present work was to develop and validate a single dissolution test for a telmisartan (TEL) and amlodipine besylate (AML) combined tablet dosage form. The sink conditions, stability and specificity of both drugs in different dissolution media were tested to choose a discriminatory dissolution method, which uses an USP type-II apparatus with a paddle rotating at 75 rpm, with 900 mL of simulated gastric fluid (SGF without enzymes) as the dissolution medium. This dissolution methodology provided good dissolution profiles for both TEL and AML and was able to discriminate changes in the composition and manufacturing process. To quantify both drugs simultaneously, a synchronous first derivative spectrofluorimetric method was developed and validated. Drug release was analyzed by a fluorimetric method at 458 nm and 675 nm for AML and TEL, respectively. The dissolution method was validated as per ICH guidance.

Analysis of bovine pulp tissue dissolution ability by photodynamic therapy: an in vitro study; Análise da capacidade de dissolução de tecido pulpar bovino através da terapia fotodinâmica: estudo in vitro

Steier, Liviu; Rossi-Fedele, Giampiero; Acauan, Monique; Bianchini, Priscila; Souza, Matheus Albino; Figueiredo, José Antônio Poli de
Fonte: EDIPUCRS; Porto Alegre Publicador: EDIPUCRS; Porto Alegre
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
37.02%
Purpose: To evaluate the bovine pulp tissue dissolution ability of photodynamic therapy. Methods: Twenty pieces of bovine pulp tissue were weighed and divided randomly into four groups (n=5), according to the cleaning protocol: G1 – distilled water (negative control), G2 – sodium hypochlorite 1% (positive control), G3 – photodynamic therapy, G4 – sodium hypochlorite 1% + photodynamic therapy. The observation of the events of dissolution was performed by two observers blinded in relation to the test using 2x magnification, recording time in minutes until complete tissue dissolution. The total observation time was 2 hours. The dissolution rate was calculated dividing the weight of the fragment pulp (mg) by the time of dissolution (mg/min). Results: Only group 2 (NaOCl) was able to promote complete dissolution of pulp tissue. In the other groups there was no occurrence of complete dissolution of the samples. The mean dissolution time for samples from group 2 (NaOCl) was 1.26 mg/min. Conclusion: Only the sodium hypochlorite was able to dissolve the fragments of bovine pulp tissue and photodynamic therapy does not show ability to dissolve tissue.; Objetivo: Avaliar a capacidade de dissolução de tecido pulpar bovino com o uso da terapia fotodinâmica. Metodologia: Vinte fragmentos de polpas bovinas foram pesados e distribuídos randomicamente em quatro grupos (n=5) de acordo com os seguintes protocolos de limpeza: G1 – água destilada (controle negativo)...

Estudo da liberação in vitro da progesterona a partir de cáspsulas de gelatina mole: desenvolvimento e validação de método de dissolução; Study of in vitro release of progesterone from cáspsulas soft gelatin: development and validation of dissolution test

BERRETTA, Mariana de Oliveira
Fonte: Universidade Federal de Goiás; BR; UFG; Mestrado em Ciências Farmacêuticas; Ciências da Saúde - Farmácia Publicador: Universidade Federal de Goiás; BR; UFG; Mestrado em Ciências Farmacêuticas; Ciências da Saúde - Farmácia
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
37.07%
Progesterone is a steroid hormone used to treat uterin disfunction, such as hemorrhage and secondary amenorrhea, contraception, hormone replacement therapy in postmenopausal women, as well as in luteal phase support cases in assisted reproduction techniques. However, it presents low oral bioavailability because of its weak water solubility and intense hepatic metabolism. So, progesterone administration is carried out, mainly, through micronized drug dispersed in oils and surfactant formulations, in soft gelatin capsules, trying to improve oral bioavailability. However, there are no official compendia notifications about dissolution methods used to evaluate progesterone release from these dosage forms. Thus, this study proposes progesterone containing soft gelatin capsules dissolution method development and validation aiming to analyze two pharmaceutical specialties (called A and B) in vitro dissolution profile commercially available. Many conditions were evaluated in the study, such as dissolution medium different compositions (pH and surfactant variations), speed of agitation and apparatus (basket, paddle). In this study, reference product A was used as model and ANOVA/Tukey tests were carried out for statistic analysis, with 95% confidence interval. Dissolution method was validated according to selectivity...

Ensaio de dissolução de fitoterápicos contendo Maytenus ilicifolia Mart ex Reiss (Celastraceae): validação de métodos para quantificação de catequina e epicatequina; Dissolution profiles of herbal medicines containing Maytenus ilicifolia Marth ex Reiss (Celastraceae)

LEAL, Ana Flavia Vasconcelos Borges
Fonte: Universidade Federal de Goiás; BR; UFG; Mestrado em Ciências Farmacêuticas; Ciências da Saúde - Farmácia Publicador: Universidade Federal de Goiás; BR; UFG; Mestrado em Ciências Farmacêuticas; Ciências da Saúde - Farmácia
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
37.04%
Maytenus ilicifolia Mart ex Reiss (Celastraceae) popularly known in Brazil as espinheirasanta is used against gastric disorders and ulcers. Quality of herbal medicines is essential to ensure the safety and efficacy of the drug. The dissolution test is an essential tool to assess the quality of herbal medicines in the solid dosage form for oral use. This work aimed to evaluate the dissolution behavior of eleven herbal medicines containing Maytenus ilicifolia, produced with powder or dry extract, purchased in local shops (Goiânia-GO, Brazil). Assay of catechin and epicatechin by high-pressure liquid chromatography (HPLC) and dissolution methods were validated and obtained results allowed the quantification of these markers with precision, accuracy and selectivity. The dissolution profiles have been determined adopting the following conditions: paddle apparatus at 75 rpm and HCl 0.1 M (900 mL at 37°C ± 0.5°C) as dissolution medium. Through the dissolution profiles it has been determined the mathematical model of release (first order), the percentage of catechin and epicatechin dissolved at 45 minutes and the efficiency of dissolution. Capsule containing powder showed rapid release of the markers in the medium (Q>85% in 12 minutes). Tests conducted to verify the quality of herbal medicines were average weight...

Zinc oxide nanoparticles in the soil environment : dissolution, speciation, retention and bioavailability.

Milani, Narges
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2012
Relevância na Pesquisa
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Zinc oxide nanoparticles (ZnO NPs) have unique physical and chemical characteristics which deviate from larger particles of the same material, due to their extremely small size, higher specific surface area and surface reactivity. The peculiar properties of ZnO NPs could potentially improve zinc (Zn) fertilizers for sustainable agriculture. This is based on the assumption that ZnO NPs provide a more soluble and bioavailable source of Zn in soil compared to micron- or millimetre- sized (bulk) ZnO particles currently used for Zn fertilizers in Zn deficient soils. However, a thorough understanding of the fate and reactions in soils and interactions of nanoparticles with plants of ZnO NPs is required prior to the recommendation for use of these novel materials. Therefore, there is a need to investigate dissolution, diffusion, transformation, partitioning and availability of manufactured ZnO NPs in soil to ensure safer and more sustainable application of ZnO NPs as a new source of Zn fertilisers for plants, and better management of their potential risks. Given inclusion of Zn in macronutrient fertilizers is the common procedure for their field application, ZnO NPs and bulk ZnO were coated onto macronutrient fertilizers (monoammonium phosphate (MAP) and urea) and dissolution kinetics...

A multi-scale approach to study silicate dissolution: Kinetic Monte Carlo simulations and experimental observations

Kurganskaya, Inna
Fonte: Universidade Rice Publicador: Universidade Rice
Relevância na Pesquisa
37.13%
Dissolution of silicate minerals is an important part of many geological processes taking place on Earth’s surface as well as in the deep crust. Weathering of rocks and soil formation, metasomatic rock alteration by hydrothermal fluids, and diagenetic transformation of sediments are controlled by dissolution reactions. Secondary pore space of natural reservoirs can be significantly altered by dissolution and the subsequent precipitation of clay minerals. As a consequence, the potential storage capacity of natural fuels, carbon dioxide, or radioactive waste, can be affected. In addition, the stability of rocks hosting potentially hazardous materials largely depends on their dissolution rates. The development of computational ab initio and Molecular Dynamics techniques drives the interest to study dissolution reactions at the molecular scale. At the same time, advanced microscopic techniques allow us to study dissolution process at the nm to micron scale and investigate spatio-temporal variations of surface reactivity. The combination of these methods has great potential for tackling fundamental questions of the mechanisms of mineral dissolution. My thesis work presents an integrated multiscale approach to studying the dissolution of silicates. The work consists of three main parts: experimental studies of the dissolving mineral surface at the micron scale...

DISSOLUTION OF TRAPPED LIGHT NON-AQUEOUS PHASE LIQUID IN THE PRESENCE OF TRAPPED GAS

Shojib, Mahmudul
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
37.07%
The dissolution of residual, or trapped, light non-aqueous phase liquid (LNAPL) is an important process that controls, in part, many LNAPL contaminated site remediation. Smear zones can be created in LNAPL source zones by water table fluctuation, trapping both residual LNAPL and gas below the water table to create a three-phase gas-LNAPL-water system. Two sets of laboratory experiments were conducted in this study to investigate the effect of trapped gas on the distribution and dissolution of trapped LNAPL. The first set involved visualization experiments where heptane was spilled in a two-dimensional (2-D) cell. Observations suggested that both heptane and air were trapped during an experiment with a large water table fluctuation, and consisted of singlets, doublets and multi-pore ganglions. Heptane was distributed as very thin films around most of the trapped air, and as discontinuous lenses, most of which were connected to air. The second set of experiments consisted of toluene dissolution experiments in short one dimensional (1-D) columns. Results showed that toluene dissolution was faster in an air-toluene-water system than in a toluene-water system. Toluene concentrations in the three-phase system were high during the early period of the dissolution...

Les effets de revêtements de surface sur la dissolution et la bioaccumulation de nanoparticules d'oxyde de zinc par l'algue unicellulaire, C. reinhardtii

Merdzan, Vladimir
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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Au cours de la dernière décennie, les nanoparticules ont connu un essor sans précédent dans plusieurs domaines. On peut retrouver ces nanoparticules dans des secteurs aussi variés tels que la médecine, l’électronique, les écrans solaires, les cosmétiques et les plastiques, pour ne nommer que ceux-là. Cette utilisation massive a eu un effet pervers sur l’environnement, sachant qu’une grande partie de ces produits se sont retrouvés inévitablement dans les milieux naturels. Plusieurs études révèlent qu’autant la présence des nanoparticules que leurs produits de dissolution sont à prendre en considération lorsque des travaux toxicologiques ou le devenir de ces matériaux sont étudiés. Il est désormais clair que les propriétés de surface de ces nanoparticules jouent un rôle central sur leur comportement dans les solutions aqueuses; que ce soit les interactions avec des organismes ou entre les particules elles-mêmes. Afin d’évaluer le devenir de nZnO, une étude sur la dissolution ainsi que la bioaccumulation a été réalisée avec l’algue modèle Chlamydomonas reinhardtii en présence de nanoparticules ayant différents enrobages. Les nanoparticules d’oxyde de zinc suivantes ont été étudiées : (i) nZnO sans enrobage (nZnO); (ii) nZnO avec enrobage d’acide polyacrylique (nZnO-PAA) et (iii) nZnO avec enrobage d’hexamétaphosphate de sodium (nZnO-HMP). La dissolution était mesurée à l’aide de trois techniques : ultrafiltration par centrifugation (CU); technique potentiométrique (scanned stripping chronopotentiometry...

Equilibrium solubility versus intrinsic dissolution: characterization of lamivudine, stavudine and zidovudine for BCS classification

Dezani,André Bersani; Pereira,Thaisa Marinho; Caffaro,Arthur Massabki; Reis,Juliana Mazza; Serra,Cristina Helena dos Reis
Fonte: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2013 EN
Relevância na Pesquisa
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Solubility and dissolution rate of drugs are of major importance in pre-formulation studies of pharmaceutical dosage forms. The solubility improvement allows the drugs to be potential biowaiver candidates and may be a good way to develop more dose-efficient formulations. Solubility behaviour of lamivudine, stavudine and zidovudine in individual solvents (under pH range of 1.2 to 7.5) was studied by equilibrium solubility and intrinsic dissolution methods. In solubility study by equilibrium method (shake-flask technique), known amounts of drug were added in each media until to reach saturation and the mixture was subjected to agitation of 150 rpm for 72 hours at 37 ºC. In intrinsic dissolution test, known amount of each drug was compressed in the matrix of Wood's apparatus and subjected to dissolution in each media with agitation of 50 rpm at 37 ºC. In solubility by equilibrium method, lamivudine and zidovudine can be considered as highly soluble drugs. Although stavudine present high solubility in pH 4.5, 6.8, 7.5 and water, the solubility determination in pH 1.2 was not possible due stability problems. Regarding to intrinsic dissolution, lamivudine and stavudine present high speed of dissolution. Considering a boundary value presented by Yu and colleagues (2004)...

Calcite dissolution by mixing waters : geochemical modeling and flow-through experiments

Sanz, E.; Ayora, C.; Carrera, J.
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //2011 ENG
Relevância na Pesquisa
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Dissolution of carbonates has been commonly predicted by geochemical models to occur at the seawater-freshwater mixing zone of coastal aquifers along a geological time scale. However, field evidences are inconclusive: dissolution vs. lack of dissolution. In this study we investigate the process of calcite dissolution by mixing waters of different salinities and pCO2, by means of geochemical modeling and laboratory experiments. Our calculations show that saturation is not always a good indicator of the real dissolution potential of the mixture. In a closed system, the maximum subsaturation occurs for mixing ratios of about 15%-salty, while the dissolved calcite is maximum for 50%. Dissolution is affected by carbonate speciation, and by the dependence of activity coefficients on salinity. Laboratory experiments confirmed a strong dependence of the dissolution on the mixing ratio and pointed out the critical role of CO2 variations at the local atmosphere. The maximum dissolution was observed for mixtures less than 17%-salty, which is attributed to the CO2 exchange between the reaction cell and the laboratory atmosphere. The reaction cell gains CO2 for mixtures less than 17%-salty and calcite dissolution is enhanced with respect to a closed system. The opposite also occurs for mixtures higher than 17% salty. Including CO2 exchange...

Comparação de perfis de dissolução da cefalexina através de estudos de cinética e eficiência de dissolução (ED%); Dissolution profile comparison of cephalexin by dissolution kinetic studies and dissolution efficiency (ED%)

Serra, Cristina Helena dos Reis; Storpirtis, Sílvia
Fonte: Universidade de São Paulo. Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo. Faculdade de Ciências Farmacêuticas
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Artigo Avaliado pelos Pares Formato: application/pdf
Publicado em 01/03/2007 POR
Relevância na Pesquisa
37.07%
O presente estudo reporta os resultados comparativos obtidos através da avaliação da cinética e da eficiência de dissolução da cefalexina a partir de dois lotes (1 e 2) de diferentes produtos contendo tal fármaco disponíveis no mercado brasileiro (A e B) sob a forma de comprimidos de liberação convencional. Os perfis de dissolução foram determinados utilizando as seguintes condições: aparato 1 (cesta, 40 mesh); 100 rpm; 900 mL de água destilada mantida a 37±0,5 °C. Amostras coletadas em: 5, 7, 10, 15, 20, 30, 40, 50 e 60 minutos e a concentração de cefalexina foi determinada por espectrofotometria UV (262 nm). A partir dos perfis de dissolução determinou-se: modelo matemático de liberação da cefalexina (primeira-ordem); porcentagem de cefalexina dissolvida em 30 minutos (Q30); constante da velocidade de dissolução (k); meia-vida de dissolução (t50%); eficiência de dissolução (ED%). Os valores Q30 obtidos indicaram que os produtos A2 e B2 se apresentaram de acordo com as especificações farmacopéicas. A comparação entre os perfis indicou diferenças estatisticamente significativa entre os produtos A2 e B1 (análise comparativa dos parâmetros cinéticos), A1 e B2 (análise comparativa pelos fatores de diferença - f1 e similaridade - f2) e B1 e B2 (análise comparativa dos parâmetros cinéticos e da ED%).; The present study reports the comparative results of the cephalexin dissolution kinetic evaluation and dissolution efficiency (ED%) considering two brands (1 and 2) of different products (A and B)...

Dissolution studies in vitro as a prognostic tool for oral absorption of modified release pharmaceutical dosage forms; A dissolução in vitro na previsão da absorção oral de fármacos em formas farmacêuticas de liberação modificada

Manadas, Rui; Pina, Maria Eugénia; Veiga, Francisco
Fonte: Universidade de São Paulo. Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo. Faculdade de Ciências Farmacêuticas
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Artigo Avaliado pelos Pares Formato: application/pdf
Publicado em 01/12/2002 POR
Relevância na Pesquisa
37.02%
The aim of the present work focused on the theoretical and practical aspects of the dissolution studies of the modified release pharmaceutical dosage forms. This paper was divided in three parts: the first refers to the classification, therapeutic interest and release of the drug; the second part presents the theory of the dissolution process, the models of drug release, dissolution systems and their validation, specifications and acceptance criteria for the dissolution studies and the factors conditioning the dissolution, release and absorption of the drug; the third part discusses the conditions in which the dissolution studies are performed and the physiological parameters making reference to the dissolution media, to the composition of the gastrointestinal tract lumen and to the hydrodynamic models.; Pretende-se com o presente trabalho abordar os aspectos teóricos e práticos dos estudos de dissolução das formas farmacêuticas sólidas orais de liberação modificada, em três partes. Na primeira parte faz-se referência à classificação, interesse terapêutico e teoria da liberação do fármaco. Na segunda parte abordam-se as teorias de dissolução, os modelos de liberação, os sistemas de dissolução e sua validação...