A Method for the Tensile Strength Prediction of Tablets with Differing Powder Plasticities

Tablets are the most commonly used dosage form in the pharmaceutical industry, and their properties such as disintegration, dissolution, and portability are influenced by their strength. However, in industry, the mixing fraction of powders to obtain a tablet compact with sufficient strength is determined based on empirical rules. Therefore, a method for predicting tablet strength based on the properties of a single material is required. The objective of this study was to quantitatively evaluate the relationship between the compression properties and tablet strength of powder mixtures. The compression properties of the powder mixtures with different plasticities were evaluated based on the force-displacement curves obtained from the powder compression tests. Heckel and compression energy analyses were performed to evaluate compression properties. During the compression energy analysis, the ratio of plastic deformation energy to elastic deformation energy (Ep/Ee) was assumed to be the plastic deformability of the powder. The quantitative relationship between the compression properties and tensile strength of the tablets was investigated. Based on the obtained relationship and the compression properties of a single material, a prediction equation was put forward for the compression properties of the powder mixture. Subsequently, a correlation equation for tablet strength was proposed by combining the values of K and Ep/Ee obtained from the Heckel and compression energy analyses, respectively. Finally, by substituting the compression properties of the single material and the mass fraction of the plastic material into the proposed equation, the tablet strength of the powder mixture with different plastic deformabilities was predicted.

Finite Element Analysis and Modeling in Pharmaceutical Tableting

Finite element analysis (FEA) is a computational method providing numerical solutions and mathematical modeling of complex physical phenomena that evolve during compression tableting of pharmaceutical powders. Since the early 2000s, FEA has been utilized together with various constitutive material models in a quest for a deeper understanding and unraveling of the complex mechanisms that govern powder compression. The objective of the present review paper is to highlight the potential and feasibility of FEA for implementation in pharmaceutical tableting in order to elucidate important aspects of the process, namely: stress and density distributions, temperature evolution, effect of punch shape on tablet formation, effect of friction, and failure of the tablet under stress. The constitutive models and theoretical background governing the above aspects of tablet compression and tablet fracture under diametral loading are also presented. In the last sections, applications of FEA in pharmaceutical tableting are demonstrated by many examples that prove its utilization and point out further potential applications.

Design and Optimization of Scored Tablets with Concave Surface and Application of Bayesian Estimation for Solving Scaleup Problem

From the viewpoint of self-medication, it is valuable to develop patient-friendly scored tablets that possess dividing uniformity. In this context, we attempted to optimize the preparation conditions for a tablet with a unique shape, such as a concavely curved scored tablet (CCST). Employing a design of experiment and a response surface method incorporating a thin-plate spline interpolation, and a bootstrap resampling technique, the optimal preparation conditions for CCST were successfully developed. To make it possible to scaleup the optimal solution estimated on a trial-scale, a Bayesian estimation was applied. Credible ranges of critical responses in large-scale manufacturing were estimated as a posterior probability from the trial-scale experiment as a prior probability. In terms of the large-scale manufacturing, the possibility of solving the scaleup problem was suggested using Bayesian estimation. Furthermore, a simulation study using a finite element method revealed that strong tensile stresses generated along the tip of the score line in CCST when an outer force was applied to the back surface of CCST. An advantage in dividing uniformity is indicated by the unique shape of CCST.

Determination of Density Distribution of Tablets Using Synchrotron X-ray Computed Tomography

The purpose of this study was to determine the density distribution of scored and round-faced tablets using synchrotron X-ray computed tomography. The tablets were made by direct compression of standard formulations. The density distribution of scored flat-faced tablets was uniform in the whole cross-sectional image. However, the tablet formulated using microcrystalline cellulose (MCC) was very dense at the tip of the score only. It is caused by the poor fluidity of MCC particles. In the case of round-faced tablets, the density in the central section of the tablet was relatively low, compared with those of peripheral areas. These observations correlated well with the results obtained by the finite element method simulation using appropriate material models.