Application of the Gurnham Equation in Characterizing the Compressibility of Fonio and Sweet Potato Starches and their Paracetamol Tablet Formulations

Background: A number of empirical relationships have been proposed to describe the compaction of pharmaceutical materials, among them are the Heckel, Kawakita and Gurnham equations.Objective: To characterize the compressibility of fonio, sweet potato and corn starches and their paracetamol formulations using the Gurnham and Kawakita equations, and to determine the complementarity of these equations.Materials and Methods: Starches were extracted from fonio (Digitaria exilis) grains and sweet potato (Ipomea batatas) tubers and modified by acid hydrolysis for 96 h. Paracetamol formulations containing 2.5–10.0 %w/w starch binders were prepared by wet granulation. Packing and compaction properties of native and modified starches and their formulations were determined using tapping procedures. The data obtained was analyzed using the Gurnham and Kawakita equations.Results: The ranking for Gurnham compressibility, c, for the starches was sweet potato>corn>fonio, which was inversely related to the ranking for Kawakita maximum volume reduction, a and angle of internal flow, θ. There was no clear-cut pattern in the Gurnham compressibility of paracetamol formulation probably due to its multicomponent nature. There was correlation between c, a and θ for all the starches with the modified starches exhibiting higher compressibility than native starches. There appeared to be no correlation between c and Kawakita compressibility index, b.Conclusion: The Gurnham equation appeared useful in characterising compressibility in single component systems and could be used along with Kawakita functions, to gain a better understanding of the deformation of powdered materials under pressure.Keywords: Compressibility, Gurnham equation, Kawakita function, Fonio starch, sweet potato starc

Powder properties of binary mixtures of chloroquine phosphate with lactose and dicalcium phosphate

A study was conducted on the packing and cohesive properties of chloroquine phosphate in binary mixtures with lactose and dicalcium phosphate powders. The maximum volume reduction due to packing as expressed by the Kawakita constant, a, and the angle of internal flow, &#952;, were the assessment parameters. The individual powders were characterized for their particle size and shape using an optical microscope. Binary mixtures of various proportions of chloroquine phosphate with lactose and dicalcium phosphate powders were prepared. The bulk and tapped densities, angles of repose and internal flow, as well as compressibility index of the materials were determined using appropriate parameters. The calculated and determined values of maximum volume reduction for the binary mixtures were found to differ significantly (PRealizou-se estudo das propriedades de empacotamento e de coesão do fosfato de cloroquina em misturas binárias com lactose e fosfato dicálcico em pó. O volume máximo de redução devido ao empacotamento, segundo expresso pela constante de Kawakita, a, e o ângulo de fluxo interno, &#952;, foram os parâmetros de avaliação. Os pós individuais foram caracterizados por seu tamanho e forma de partículas, utilizando microscópio óptico. Prepararam-se misturas binárias de várias proporções de fosfato de cloroquine e lactose e fosfato dicálcico em pó. As densidades de bulk and tapped, os ângulos de repouso e de fluxo interno e o índice de compressibilidade dos materiais foram determinados utilizando-se parâmetros apropriados. Os valores calculados e determinados do volume máximo de redução para as misturas binárias mostraram-se significativamente diferentes (P< 0,05), sendo o traçado de Kawakita mais confiável na determinação das propriedades de empacotamento. O tipo de diluente influenciou as propriedades de fluxo das misturas com fosfato dicálcico, dando resultados previsíveis, enquanto as misturas contendo lactose mostraram-se anômalas com relação ao fluxo. A caracterização das propriedades de empacotamento e de coesão das misturas binárias de cloroquina com lactose e fosfato dicálcico seria útil na produção de pós, comprimidos, cápsulas e outros sistemas de liberação de fármacos contendo esses pós com propriedade de fluxo desejada e previsível

Influence of binder type and process parameters on the compression properties and microbial survival in diclofenac tablet formulations

The influence of binder type and process parameters on the compression properties and microbial survival in diclofenac tablet formulations were studied using a novel gum from Albizia zygia. Tablets were produced from diclofenac formulations containing corn starch, lactose and dicalcium phosphate. Formulations were analyzed using the Heckel and Kawakita plots. Determination of microbial viability in the formulations was done on the compressed tablets of both contaminated and uncontaminated tablets prepared from formulations. Direct compression imparted a higher plasticity on the materials than the wet granulation method. Tablets produced by wet granulation presented with a higher crushing strength than those produced by the direct compression method. Significantly higher microbial survival (pA influência do tipo de ligante e os parâmetros do processo de propriedades de compressão e sobrevivência microbiana em comprimidos de diclofenaco foram estudados utilizando uma nova goma de Albizia zygia. Os comprimidos foram produzidos a partir de formulações de diclofenaco contendo amido de milho, lactose e fosfato bicálcico. As formulações foram analisadas usando os gráficos de Heckel e Kawakita. A determinação da viabilidade microbiana nas formulações foi feita nos comprimidos contaminados e não contaminados preparados a partir de formulações. A compressão direta confere maior plasticidade dos materiais do que o método de granulação úmida. Comprimidos produzidos por granulação úmida apresentaram maior força de esmagamento do que aqueles produzidos pelo método de compressão direta. Observou-se sobrevivência significativamente maior (p<0,05) em formulações preparadas por compressão direta. A sobrevivência percentual dos esporos de Bacillus subtilis diminuiu com o aumento da concentração do agregante. O estudo mostrou que a goma de Albizia é capaz de conferir maior plasticidade aos materiais e apresentou maior redução da contaminação microbiana nas formulações. O método de compressão direta produziu comprimidos com viabilidade reduzida de contaminantes microbianos

Characterization and evaluation of acid-modified starch of Dioscorea oppositifolia (Chinese yam) as a binder in chloroquine phosphate tablets

Chinese yam (Dioscorea oppositifolia) starch modified by acid hydrolysis was characterized and compared with native starch as a binder in chloroquine phosphate tablet formulations. The physicochemical and compressional properties (using density measurements and the Heckel and Kawakita equations) of modified Chinese yam starch were determined, and its quantitative effects as a binder on the mechanical and release properties of chloroquine phosphate were analyzed using a 2³ full factorial design. The nature (X1), concentration of starch (X2) and packing fraction (X3) were taken as independent variables and the crushing strength-friability ratio (CSFR), disintegration time (DT) and dissolution time (t80) as dependent variables. Acid-modified Chinese yam starch showed a marked reduction (p<0.05) in amylose content and viscosity but increased swelling and water-binding properties. The modified starch had a faster onset and greater amount of plastic flow. Changing the binder from native to acid-modified form led to significant increases (p<0.05) in CSFR and DT but a decrease in t80. An increase in binder concentration and packing fraction gave similar results for CSFR and DT only. These results suggest that acid-modified Chinese yam starches may be useful as tablet binders when high bond strength and fast dissolution are required

Physical and Release Properties of Metronidazole Suppositories

Purpose: A study was made of the effects of some bases and adjuvants on the physical and release properties of metronidazole suppositories with a view to providing more information for the optimization of the rectal formulation of metronidazole. Method: Suppositories (1g) containing 200mg of metronidazole each were prepared in witepsol (H15 and E75) and polyethylene glycol (PEG 2850 and 4650) bases, using different concentrations of Tween 80, sodium salicylate and methylcellulose as adjuvants. The setting time, solidification point and melting range of the suppositories were determined, along with their crushing strength, disintegration time and the time for 80% of metronidazole to be released from the suppositories (t80). Results: The ranking of setting time for the suppositories was witepsol H15 > PEG 2850 > witepsol E75 > PEG 4650, while the ranking of solidification point, melting range, crushing strength, disintegration time and the time for 80% of metronidazole to be released from the suppositories (t80) was the reverse of that for setting time. Optimal concentrations of Tween 80 and sodium salicylate were observed for the suppository formulations. Using Kitazawa plots, all formulations showed two dissolution rate constants, k1 and k2 intersecting at time t1, with formulations containing 5 to 20 % w/w of methylcellulose exhibiting a third dissolution rate constant, k3 intersecting with k2 at time t2. Conclusion: The physical and release properties of metronidazole suppositories are influenced considerably by the bases and adjuvants employed. Tween 80 and sodium salicylate can probably be used to formulate only immediate-release suppositories while methylcellulose can be useful for sustained-release metronidazole suppositories. Some insight into these inferences can be obtained from parameters derived from Kitazawa plots

Physical and Release Properties of Metronidazole Suppositories

Purpose: A study was made of the effects of some bases and adjuvants on the physical and release properties of metronidazole suppositories with a view to providing more information for the optimization of the rectal formulation of metronidazole. Method: Suppositories (1g) containing 200mg of metronidazole each were prepared in witepsol (H15 and E75) and polyethylene glycol (PEG 2850 and 4650) bases, using different concentrations of Tween 80, sodium salicylate and methylcellulose as adjuvants. The setting time, solidification point and melting range of the suppositories were determined, along with their crushing strength, disintegration time and the time for 80% of metronidazole to be released from the suppositories (t80). Results: The ranking of setting time for the suppositories was witepsol H15 > PEG 2850 > witepsol E75 > PEG 4650, while the ranking of solidification point, melting range, crushing strength, disintegration time and the time for 80% of metronidazole to be released from the suppositories (t80) was the reverse of that for setting time. Optimal concentrations of Tween 80 and sodium salicylate were observed for the suppository formulations. Using Kitazawa plots, all formulations showed two dissolution rate constants, k1 and k2 intersecting at time t1, with formulations containing 5 to 20 % w/w of methylcellulose exhibiting a third dissolution rate constant, k3 intersecting with k2 at time t2. Conclusion: The physical and release properties of metronidazole suppositories are influenced considerably by the bases and adjuvants employed. Tween 80 and sodium salicylate can probably be used to formulate only immediate-release suppositories while methylcellulose can be useful for sustained-release metronidazole suppositories. Some insight into these inferences can be obtained from parameters derived from Kitazawa plots