The effect of different grades polymer blends on release profiles of diclofenac sodium from hydrophilic matrices.

An attempt was made to design matrix tablet of diclofenac sodium by using various grades of hydroxypropyl methyl cellulose (HPMC E50, E15 and E300LV). The effect of hydrophilic polymers was studied on release characteristics of the diclofenac matrix tablet. Dicalcium phosphate and magnesium stearate were used as an excipients. Tablets were prepared by direct compression method. The in vitro dissolution test carried out for 12 hrs using USP dissolution apparatus II at 50 rpm in 900ml phosphate buffer pH 6.8. Statistically significant difference was found among the drug release profile from different matrices. The tablet evaluation parameters of hardness, friability, thickness, content uniformity were founded within the limit. At a fixed polymer level, drug release from the higher viscosity grades E50 was slower as compared to the lower viscosity grades (E300LV and E15). Tablet prepared with HPMC E50 is more release retardant. As the drug to polymer ratio increased drug release decreased. The dissolution study revealed that maximum retardation of the drug was obtained by highest viscosity grade HPMC at higher concentrations. The release of the model drug from these HPMC matrix tablets was prolonged.

Mecanismos generales de cesión de principios activos a partir de matrices monolíticas hidrofílicas preparadas con éteres de celulosa / Overall mechanisms that rule the active pharmaceutical ingredient’s delivery process from hydrophilic matrices elaborated with ether cellulose

Las matrices hidrofílicas son uno de los sistemas de liberación controlados más empleados a escala mundial. El reconocido éxito global de este tipo de sistemas está ligado a su manufactura por medio de tecnología convencional para la obtención de comprimidos, además de su bajo costo. Estos sistemas han sido objeto de investigación desde hace ya algunas décadas, mediante el uso de técnicas como la creación de imágenes a partir de resonancia magnética, calorimetría de barrido diferencial y la espectroscopia dieléctrica de baja frecuencia, entre otras. Varios autores han estudiado los diferentes estados del agua dentro de una matriz, así como el estado y los cambios en los estados de los materiales en el tiempo, con el fin de estudiar los mecanismos de cesión de los activos a partir de las matrices, así como para buscar modelos matemáticos que describan la evolución de la concentración en el tiempo. En la actualidad se cuenta con modelos matemáticos de gran utilidad que permiten identificar dichos mecanismos a partir de un análisis de los parámetros de los modelos y que conducen finalmente a predecir la velocidad de liberación a partir de estos sistemas.

The hydrophilic matrices are one of the most used controlled delivery systems in the world, due to the simple technology and low cost. A number of publications, over the last decades, have reported investigations in regard with the mechanisms of drug release from hydrophilic matrices. Nevertheless, the mechanisms of drug release from these systems continue to be a matter of debate. Differential scanning calorimetry, low frequency dielectric spectroscopy and nuclear magnetic resonance have been used to examine the distribution of water within ether cellulose matrices, as well as to describe the state of the materials inside the device. The objective is to study the release and hydration rate of hydrophilic matrices in order to contribute to the rationalization of the design of these controlled release systems through mathematical modeling and to obtain a better knowledge of the processes that occur during the release of the drug.

Dissolução de comprimidos e péletes de liberação prolongada empregando-se os métodos da pá e Bio-Dis / Dissolution of sustained release tablets and pellets using the paddlle and Bio-Dis methods

Matrizes hidrofílicas de diclofenaco sódico e de cetoprofeno foram preparadas por meio de compressão direta ou granulação úmida seguida de compressão, utilizando-se hipromelose para modular a dissolução do fármaco. Foram também obtidos péletes de liberação prolongada de cetoprofeno, mediante extrusão-esferonização e revestimento, em leito fluidizado, com Kollicoat® EMM 30D. Um planejamento fatorial 22 foi usado para elucidar os efeitos de variáveis de formulação sobre os perfis de liberação do fármaco a partir dos sistemas em estudo, determinados empregando-se os métodos da pá e/ou Bio-Dis. No caso dos comprimidos matriciais, os efeitos do grau de viscosidade e concentração de hipromelose foram investigados. Para os péletes, avaliou-se os efeitos da granulometria e ganho de peso em revestimento. A influência do pH sobre a liberação do fármaco a partir dos sistemas preparados foi também estudada, usando-se meios de dissolução com pH 1,2-7,2. Os métodos ANOVA e teste de Tukey (comparação estatística entre porcentuais de fármaco dissolvido e/ou eficiência de dissolução), f1, f2 e Weibull foram usados para caracterizar e comparar os perfis de dissolução. O grau de viscosidade e concentração de hipromelose influenciaram a liberação de diclofenaco sádico e cetoprofeno a partir das matrizes em estudo, sendo a concentração do polímero o fator principal que governou o processo. A granulação alterou os perfis de dissolução de cetoprofeno em relação às matrizes obtidas por compressão direta, diminuindo a velocidade e modificando o mecanismo de liberação. No caso dos péletes, o ganho de peso em revestimento foi o parâmetro que exerceu maior efeito sobre a liberação do cetoprofeno, enquanto a granulometria apenas influenciou os perfis de dissolução dás formulações com maior ganho de peso em revestimento. A liberação do fármaco a partir dos sistemas em estudo aumentou com a elevação do pH, o que ocorreu devido à solubilidade pH-dependente do cetoprofeno e diclofenaco sódico.

Diclofenac sodium and ketoprofen hydrophilic matrices were prepared by direct compression or wet granulation followed by compression, using hypromellose to modulate the drug dissolution. Sustained release ketoprofen pellets were also obtained by extrusion-spheronization and fluidized bed coating with Kollicoat® EMM 30D. A 22 factorial design has been used to elucidate the effects of formulation variables on the drug release profiles from the systems in study, determined using the paddle method and Bio-Dis. In the case of matrix tablets, the effects of the viscosity grade and concentration of hypromellose were investigated. For the pellets, the effects of granulometry and weight gain were evaluated. The influence of the pH value on the drug release from the prepared systems was also studied, using pH 1,2-7,2 dissolution media. ANOVA and Tukey's test (statistical comparison between percentages of drug dissolved and/or dissolution efficiency), f1, f2 and Weibull methods were used to characterize and compare the dissolution profiles. The concentration and viscosity grade of hypromellose influenced the ketoprofen and diclofenac sodium release from the studied matrices, being the polymer concentration the main factor that has governed the process. Granulation has modified the dissolution profiles of ketoprofen in relation to the matrices obtained by direct compression, reducing the rate and modifying the mechanism of drug release. In the pellets case, weight gain was the main factor that has influenced the ketoprofen release, while ganulometry has only influenced the dissolution profiles of the formulation with the highest weight gain. Drug release from the systems under study increased with the increase of the pH value of the medium because of the diclofenac sodium and ketoprofen pH-dependent solubility.