On the application of the Heckel and Kawakita equations to powder compaction

Multivariate data analysis to evaluate commonly used compression descriptors

Numerous studies elucidated material behavior based on compression analyses. Especially compressibility, compactibility and tabletability were in the focus of these investigations. In the present study, a comprehensive multivariate data analysis was performed using principal component analysis method. Twelve pharmaceutically used excipients were selected for direct compression tableting and subsequent evaluation of several compression analyses. Material properties, tablet properties, tableting parameters and parameters from compression analyses were used as input variables. The materials could successfully be grouped using principal component analysis. Of the tableting parameters, the compression pressure showed the greatest influence on the results. The tabletability was found to be the most important compression analysis in the material characterization. Compressibility and compactibility only played a minor role in the evaluation. Some important insights have been gained for a deeper understanding of the tableting process using the multivariate approach to evaluate the variety of compression data.

Preparation and Characterization of Co-Processed Mannitol and Sorbitol Using NanoCrySP Technology

Particle engineering of excipients, at sub-particulate level using co-processing, can provide high functionality excipients. NanoCrySP technology has been recently explored as a novel approach for the generation of nanocrystalline solid dispersion of poorly soluble drugs, using spray drying process. The purpose of the present study was to generate co-processed mannitol and sorbitol (SD-CSM) using NanoCrySP technology having similar composition to commercial co-processed excipient (Compressol® SM, CP). The characterization of excipients was performed to evaluate their various physicomechanical properties. The sub-micron crystallite size of sorbitol in the matrix of mannitol was determined using the Williamson-Hall equation and Halder-Wagner equation. The reduction in crystallite size of sorbitol and mannitol, lower melting point, and lower heat of fusion of SD-CSM could be responsible for excellent compactibility, better tabletability, and comparable compressibility with respect to CP. This was confirmed by the compressibility-tabletability-compactibility (CTC) profile and Heckel plot analysis. Overall, SD-CSM generated using NanoCrySP technology improved functionalities of excipients over CP and would be useful for direct compression application.

Preparation and optimization of multi-functional directly compressible excipient: an integrated approach of principal component analysis and design of experiments

Developing a new excipient and obtaining its market approval is an expensive, time-consuming, and complex process. The application of a multivariate analytical approach - principal component analysis (PCA) - in combination with the design of experiments (DoE) approach can make the process of developing co-processed excipient cost-effective and rapid. The present investigation was aimed to demonstrate the applicability of the DoE approach and PCA in developing a co-processed excipient by using the spray drying technique. The preliminary studies suggested a significant effect of inlet air temperature (X ₁) and polymer ratio [chitosan chlorhydrate (CC): mannitol - X ₂) on critical product characteristics so they were selected as independent variables in 3² full factorial design. The result of regression analysis suggested a significant effect of both independent variables on all response variables. The PCA of practically obtained value suggested a strong effect of all the selected response variables on the model. The prepared co-processed excipient had better tableting properties compared to the physical mixture of excipients and was able to accommodate more than 80% drug without compromising the flow property and compressibility. The present investigation successfully proved the applicability PCA and DoE approach as an effective and rapid tool for optimizing process parameters and formulation composition for preparing a directly compressible co-processed excipient.

Characterization and evaluation of the performance of different calcium and magnesium salts as excipients for direct compression

The performance of a series of inorganic salts as direct compression excipients was systematically evaluated. The physical-chemical and technological properties of the different salts were investigated in terms of crystalline/amorphous state, morphology, granulometry, apparent/tapped density, specific surface area, flowability, compressibility, dilution and distribution coefficients. To achieve a comprehensive evaluation of the performance of the different salts, the data obtained by the various analyses were normalized, giving a score to each excipient for each evaluated property/parameter. Statistical elaboration (JMP software) of the full dataset provided a final ranking of the powders based on their effectiveness as direct compression excipients. The salt emerged as the best was used to prepare direct-compression tablets, using cefixime as model drug, by modifying the composition of marketed tablets. A significant improvement of the mechanical properties of the new tablets was observed, compared to the marketed ones, with a crushing strength increase of over 30%, without variations of the drug dissolution profile. Even though the resulted ranking cannot have an absolute value, being the behavior of the different excipients susceptible to the kind of drug and other formulation excipients, the proposed approach can provide a useful model for a systematic evaluation and comparison of potentially similar excipients.

Compression characteristics of agglomerated food powders: Effect of agglomerate size and water activity Características de la compresión de alimentos en polvo: Efecto del tamaño del aglomerado y del contenido de humedad

The stability of food agglomerates is very important for keeping optimal instant properties as well as flow characteristics. Compression tests have been proven not only to be useful tools in char acterizing attrition, but also excellent descriptors for powder flowability. The purpose of this work was to study the effects of particle size and water activity ( a w) on the compression characteristics of selected agglomerated food powders, and then to identify suitable mathematical models by using a non-linear regression program for predicting the compression characteristics of food agglomerates when partial attrition takes place. Three agglomerated food powders - non-fat milk, low fat milk and instant coffee - were classified by size into five or six fractions with a set of RX-29 sieve screens. Each fraction was conditioned at three aw levels, placed in a cylindrical compression cell, and compressed with a piston attached to the crosshead of a TA-XT2 texture analyser. The crosshead speed was 1 mm/s in all tests and the maximum force applied was 245 N. Particle size was found to play a significant role in compression tests in that the greater the particle size, the greater the volume reduction. It was easier to compress the low aw samples, but in all tests changing aw did not significantly affect compression characteristics. Sone's two- parameter model accurately described the combination of compaction and attrition when compres sion pressure did not exceed a certain level, while Peleg's double-exponential model with four parameters best fitted the compression data.

Design of salbutamol EOP tablets from pharmacokinetics parameters

Salbutamol elementary osmotic pump (EOP) tablets were developed, and fundamental variables affecting their release characteristics were evaluated. The effects of film thickness and compression force on drug release from the tablets containing fixed amount of sodium chloride used as osmogent were evaluated. The core tablets were directly compressed at four compression forces and coated with 3% wt/vol cellulose acetate in acetone to levels of 2%, 3%, and 4% wt/wt. Coated tablets were drilled with CO2 laser beam to form drug delivery orifice of approximately 400 microm in diameter. The drug release was found to follow zero order fashion. The release rate decreased with the increased film thickness and was not affected by the compression force or porosity. The tablets coated to 3% and 4% levels exhibited the release rates within the range calculated from pharmacokinetic data. To illustrate the effect of osmogent content, the tablets were prepared at four osmogent levels and compressed at a constant compression force. The core tablets were coated to a level of 3% wt/wt. The release rate was initially increased with osmogent content and then decreased. At higher osmogent contents, the drug fraction in soluble component was decreased and resulted in the reduction of drug release. In conclusion, film thickness and osmogents played important roles in drug release from EOP tablets.

Pressure susceptibility of polymer tablets as a critical property: a modified Heckel equation

The pressure susceptibility (chip), which is defined as the decrease of porosity (epsilon) under pressure was investigated. Of special interest are compacts obtained at very low pressures, because of the transition between the state of a powder and the state of a tablet. This range was found to be critical in respect to a diverging pressure susceptibility. Above a critical porosity (epsilonc) or below the corresponding relative density (rhoc), no pressure susceptibility can be defined, because of no rigid structure exists. To take this into account, a simple function was proposed for the pressure susceptibility: chip approximately 1/(epsilonc - epsilon). This proposal leads to a new porosity vs pressure relationship. The new model was compared to the Heckel equation that involves a constant pressure susceptibility. Various polymers were tested from "out of die" measurements, and the new relationship was found superior to the Heckel equation. As a conclusion, the pressure susceptibility exhibits a curvature that can be called critical at low relative densities. Consequently, a better understanding evolves as to why the Heckel equation is not valid at low pressures. The new model has proven to be adequate for polymer tablets but, so far it is not clear whether other substances exhibit the same performance. Especially tableting materials exhibiting brittle fracture will be of interest considering their importance in compaction technology.