Combining experimental design and orthogonal projections to latent structures to study the influence of microcrystalline cellulose properties on roll compaction

Implementation of mechanistic modeling and global sensitivity analysis (GSA) for design, optimization, and scale-up of a roller compaction process

The pharmaceutical industry has been shifting towards the application of mechanistic modeling to improve process robustness, enable scale-up, and reduce time to market. Modeling approaches have been well-developed for processes such as roller compaction, a continuous dry granulation process. Several mechanistic models/approaches have been documented with limited application to high drug-loaded formulations. In this study, the Johanson model was employed to optimize roller compaction processing and guide its scale-up for a high drug loaded formulation. The model was calibrated using a pilot-scale Minipactor and was validated for a commercial-scale Macropactor. Global sensitivity analysis (GSA) was implemented to determine the impact of process parameter variations (roll force, gap, speed) on a quality attribute [solid fraction (SF)]. The throughput method, which estimates SF values of ribbons using granule production rate, was also studied. The model predicted SF values for all 14 Macropactor batches within ± 0.04 SF. The throughput method estimated SF with ± 0.06 SF for 7 out of 11 batches. GSA confirmed that roll force had the largest impact on SF. This case study represents a process modeling approach to build quality into the products/processes and expands the use of mechanistic modeling during drug product development.

Influence of Roll Speed during Roll Compaction and Its Effect on the Prediction of Ribbon Solid Fraction

Influence of the roll speed (RS) during roll compaction on ribbon, granule, tablet properties and its effect on the prediction of the ribbon solid fraction at-gap is often neglected or controversially discussed. The aim of this study was to investigate the effect of the RS systematically. Microcrystalline cellulose (MCC) and lactose were compressed at several maximum roll pressures (Pmax) and RS combinations using a gap-controlled roll compactor. The ribbon solid fraction after elastic recovery (SFribbon), granule size distribution and tabletability of the granules as well as the ribbon solid fraction at-gap (SFgap) were measured. The Midoux number (Mi), derived from the Johanson model, was used to predict the ribbon solid fraction at-gap (SFMi). The measured SFgap and the predicted SFMi lead to a prediction accuracy (PA) of the Midoux number. The results are highly dependent on the material used and the applied Pmax. Higher plasticity of the material leads to a reduction in SFribbon and granule size with increasing RS. However, this effect can be overcome or reduced by adjusting Pmax above the yield pressure of the used material. These results allow for higher roll speeds as a potential upscaling method in roll compaction. On the other side, the PA of the Midoux number was also reduced with increased RS for MCC and had no effect for lactose. Thus, RS seems to be an important factor in the prediction of roll compaction processes and prediction models should include RS as a parameter to improve their accuracy.

Retrofitting Strategies Based on Orthogonal Array Testing to Develop Nearly Zero Energy Buildings

Retrofitting existing buildings to be a nearly zero energy building (nZEB) is an effective solution for greenhouse gas emissions and primary energy consumption reduction. A hybrid approach that integrates the building energy simulation method and orthogonal array testing (OAT) to renovate buildings to nZEB is proposed in this paper. Within a residential building in Changchun, Jilin of China, the total energy consumption index (TECI) and CO2 emission factor for heating are used as evaluation criteria. The reliability of the building energy model is validated and adopted to forecast the energy performance of different building renovation strategies. According to OAT, four passive measures can be ranked by their influence on TECI in descending order as follows: external wall heat transfer coefficient, airtightness, window heat transfer coefficient, and roof heat transfer coefficient. The optimal renovation solution of the studied building can reduce the TECI by 43.18% by only reducing the external wall heat transfer coefficient from 0.5 to 0.2 W/m2·K and the infiltration N50 from 3.6 to 0.4 ac/h. Besides, combined heat and power (CHP) utilities emit less CO2 than heat pumps in providing heating under the current CO2 emission factor of the power grid in China, making it impossible to give up district heating systems until carbon emissions of electricity generation have declined significantly. The results can provide a reference for the application of the nZEB standard in actual retrofitting projects.

Powder flow from an intermediate bulk container - Discharge predictions and experimental evaluation

Powders are usually dispensed, blended, and transferred between different manufacturing steps in so-called Intermediate Bulk Containers (IBCs), and discharge from an IBC plays a critical role in the ability to manufacture high-quality tablets. To better understand IBC discharge, the flow behavior of selected excipients was comprehensively characterized using a number of techniques including the Hausner ratio/Carr's index, Erweka flow test, FlowPro flow test, shear test and wall friction test as well as FT4 powder rheometer experiments. Jenike's hopper design methodology was then used to predict the minimum non-arching outlet diameter and the mode of flow. Furthermore, the discharge rate from an IBC was predicted using a simple model that takes into account gravity and aerodynamic drag. The predictions were experimentally verified by measuring the discharge rate from a 20 L IBC using five commonly-used excipients. The small-scale Erweka flow test provided the best prediction of the full-scale IBC discharge experiment. Furthermore, a simple model that relied only on the particle size of the material and the diameter of the discharge opening was found to predict the IBC discharge rate remarkably well.

Pharmaceutical application of multivariate modelling techniques: a review on the manufacturing of tablets

The tablet manufacturing process is a complex system, especially in continuous manufacturing (CM). It includes multiple unit operations, such as mixing, granulation, and tableting. In tablet manufacturing, critical quality attributes are influenced by multiple factorial relationships between material properties, process variables, and interactions. Moreover, the variation in raw material attributes and manufacturing processes is an inherent characteristic and seriously affects the quality of pharmaceutical products. To deepen our understanding of the tablet manufacturing process, multivariable modeling techniques can replace univariate analysis to investigate tablet manufacturing. In this review, the roles of the most prominent multivariate modeling techniques in the tablet manufacturing process are discussed. The review mainly focuses on applying multivariate modeling techniques to process understanding, optimization, process monitoring, and process control within multiple unit operations. To minimize the errors in the process of modeling, good modeling practice (GMoP) was introduced into the pharmaceutical process. Furthermore, current progress in the continuous manufacturing of tablets and the role of multivariate modeling techniques in continuous manufacturing are introduced. In this review, information is provided to both researchers and manufacturers to improve tablet quality.

Using a Material Library to Understand the Impacts of Raw Material Properties on Ribbon Quality in Roll Compaction

The purpose of this study is to use a material library to investigate the effect of raw material properties on ribbon tensile strength (TS) and solid fraction (SF) in the roll compaction (RC) process. A total of 81 pharmaceutical materials, including 53 excipients and 28 natural product powders (NPPs), were characterized by 22 material descriptors and were compacted under five different hydraulic pressures. The transversal and longitudinal splitting behaviors of the ribbons were summarized. The TS-porosity and TS-pressure relationships were used to explain the roll compaction behavior of powdered materials. Through defining the target ribbon quality (i.e., 0.6 ≤ SF ≤ 0.8 and TS ≥ 1 MPa), the roll compaction behavior classification system (RCBCS) was built and 81 materials were classified into three categories. A total of 24 excipients and five NPPs were classified as Category I materials, which fulfilled the target ribbon quality and had less occurrence of transversal splitting. Moreover, the multivariate relationships between raw material descriptors, the hydraulic pressure and ribbon quality attributes were obtained by PLS regression. Four density-related material descriptors and the cohesion index were identified as critical material attributes (CMAs). The multi-objective design space summarizing the feasible material properties and operational region for the RC process were visualized. The RCBCS presented in this paper enables a formulator to perform the initial risk assessment of any new materials, and the data modeling method helps to predict the impact of formulation ingredients on strength and porosity of compacts.

Model-based approach to the design of pharmaceutical roller-compaction processes

This work presents a new model based approach to process design and scale-up within the same equipment of a roller compaction process. The prediction of the operating space is not performed fully in-silico, but uses low-throughput experiments as input. This low-throughput data is utilized in an iterative calibration routine to describe the behavior of the powder in the roller compactor and improves the predictive quality of the mechanistic models at low and high-throughput. The model has been validated with an experimental design of experiments of two ibuprofen formulations. The predicted sweet spots in the operating space are in good agreement with the experimental results.

Optimization of the process variables of roller compaction, on the basis of granules characteristics (flow, mechanical strength, and disintegration behavior): an application of SeDeM-ODT expert system

The objective of the study was application of SeDeM-ODT expert system for optimization of process variables for roller compaction and for the preparation of granules with better flow, compressibility, and disintegration behavior. In the present study, granules were prepared at pre-determined (on the basis of factorial design) process variables and characterized using SeDeM-ODT expert system. Compatibility of ribavirin with excipients (microcrystalline cellulose, tablettose-80, cross carmellose sodium, and magnesium stearate) was evaluated by binary mixture approach, using FTIR. According to the SeDeM-ODT expert system, granules were characterized for various parameters related to flow, compressibility and disintegration behavior and Index of Good Compressibility and Buccodispersibility (IGCB) was calculated. The process variables resulting in highest IGCB value were considered as optimum. Ribavirin was found compatible with all the excipients used in the study and characteristics peaks were present in FTIR spectra after subjecting to stress conditions (75% relative humidity at 45 ± 5 °C) for 30 days. Both Ribavirin powder and Ribavirin containing powder blend had poor flow and compressibility while disintegration behavior was good due to higher water solubility. Screw speed of 35 rpm and roller speed at 12 rpm resulted in granules with acceptable characteristics. The IGCB value (5.63) of the granules was highest of all, indicating its better characteristics. SeDeM-ODT expert system presents a more practical picture of the granules and also predicts the mechanical strength and disintegration behavior of the tablets prepared from the granules. By proper optimization of screw and roller speed, efficiency of the process can be improved.

On Identification of Critical Material Attributes for Compression Behaviour of Pharmaceutical Diluent Powders

As one of the commonly-used solid dosage forms, pharmaceutical tablets have been widely used to deliver active drugs into the human body, satisfying patient's therapeutic requirements. To manufacture tablets of good quality, diluent powders are generally used in formulation development to increase the bulk of formulations and to bind other inactive ingredients with the active pharmaceutical ingredients (APIs). For formulations of a low API dose, the drug products generally consist of a large fraction of diluent powders. Hence, the attributes of diluents become extremely important and can significantly influence the final product property. Therefore, it is essential to accurately characterise the mechanical properties of the diluents and to thoroughly understand how their mechanical properties affect the manufacturing performance and properties of the final products, which will build a sound scientific basis for formulation design and product development. In this study, a comprehensive evaluation of the mechanical properties of the widely-used pharmaceutical diluent powders, including microcrystalline cellulose (MCC) powders with different grades (i.e., Avicel PH 101, Avicel PH 102, and DG), mannitol SD 100, lactose monohydrate, and dibasic calcium phosphate, were performed. The powder compressibility was assessed with Heckel and Kawakita analyses. The material elastic recovery during decompression and in storage was investigated through monitoring the change in the dimensions of the compressed tablets over time. The powder hygroscopicity was also evaluated to examine the water absorption ability of powders from the surroundings. It was shown that the MCC tablets exhibited continuous volume expansion after ejection, which is believed to be induced by (1) water absorption from the surrounding, and (2) elastic recovery. However, mannitol tablets showed volume expansion immediately after ejection, followed by the material shrinkage in storage. It is anticipated that the expansion was induced by elastic recovery to a limited extent, while the shrinkage was primarily due to the solidification during storage. It was also found that, for all powders considered, the powder compressibility and the elastic recovery depended significantly on the particle breakage tendency: a decrease in the particle breakage tendency led to a slight decrease in the powder compressibility and a significant drop in immediate elastic recovery. This implies that the particle breakage tendency is a critical material attribute in controlling the compression behaviour of pharmaceutical powders.

Statistical modeling methods to analyze the impacts of multiunit process variability on critical quality attributes of Chinese herbal medicine tablets

The quality of Chinese herbal medicine tablets suffers from batch-to-batch variability due to a lack of manufacturing process understanding. In this paper, the Panax notoginseng saponins (PNS) immediate release tablet was taken as the research subject. By defining the dissolution of five active pharmaceutical ingredients and the tablet tensile strength as critical quality attributes (CQAs), influences of both the manipulated process parameters introduced by an orthogonal experiment design and the intermediate granules’ properties on the CQAs were fully investigated by different chemometric methods, such as the partial least squares, the orthogonal projection to latent structures, and the multiblock partial least squares (MBPLS). By analyzing the loadings plots and variable importance in the projection indexes, the granule particle sizes and the minimal punch tip separation distance in tableting were identified as critical process parameters. Additionally, the MBPLS model suggested that the lubrication time in the final blending was also important in predicting tablet quality attributes. From the calculated block importance in the projection indexes, the tableting unit was confirmed to be the critical process unit of the manufacturing line. The results demonstrated that the combinatorial use of different multivariate modeling methods could help in understanding the complex process relationships as a whole. The output of this study can then be used to define a control strategy to improve the quality of the PNS immediate release tablet.

The influence of API concentration on the roller compaction process: modeling and prediction of the post compacted ribbon, granule and tablet properties using multivariate data analysis

OBJECTIVE

While previous research has demonstrated roller compaction operating parameters strongly influence the properties of the final product, a greater emphasis might be placed on the raw material attributes of the formulation. There were two main objectives to this study. First, to assess the effects of different process variables on the properties of the obtained ribbons and downstream granules produced from the rolled compacted ribbons. Second, was to establish if models obtained with formulations of one active pharmaceutical ingredient (API) could predict the properties of similar formulations in terms of the excipients used, but with a different API.

MATERIALS AND METHODS

Tolmetin and acetaminophen, chosen for their different compaction properties, were roller compacted on Fitzpatrick roller compactor using the same formulation. Models created using tolmetin and tested using acetaminophen. The physical properties of the blends, ribbon, granule and tablet were characterized. Multivariate analysis using partial least squares was used to analyze all data.

RESULTS

Multivariate models showed that the operating parameters and raw material attributes were essential in the prediction of ribbon porosity and post-milled particle size. The post compacted ribbon and granule attributes also significantly contributed to the prediction of the tablet tensile strength.

CONCLUSIONS

Models derived using tolmetin could reasonably predict the ribbon porosity of a second API. After further processing, the post-milled ribbon and granules properties, rather than the physical attributes of the formulation were needed to predict downstream tablet properties. An understanding of the percolation threshold of the formulation significantly improved the predictive ability of the models.

A study on the impact of hydroxypropyl methylcellulose on the viscosity of PEG melt suspensions using surface plots and principal component analysis

An understanding of the rheological behaviour of polymer melt suspensions is crucial in pharmaceutical manufacturing, especially when processed by spray congealing or melt extruding. However, a detailed comparison of the viscosities at each and every temperature and concentration between the various grades of adjuvants in the formulation will be tedious and time-consuming. Therefore, the statistical method, principal component analysis (PCA), was explored in this study. The composite formulations comprising polyethylene glycol (PEG) 3350 and hydroxypropyl methylcellulose (HPMC) of ten different grades (K100 LV, K4M, K15M, K100M, E15 LV, E50 LV, E4M, F50 LV, F4M and Methocel VLV) at various concentrations were prepared and their viscosities at different temperatures determined. Surface plots showed that concentration of HPMC had a greater effect on the viscosity compared to temperature. Particle size and size distribution of HPMC played an important role in the viscosity of melt suspensions. Smaller particles led to a greater viscosity than larger particles. PCA was used to evaluate formulations of different viscosities. The complex viscosity profiles of the various formulations containing HPMC were successfully classified into three clusters of low, moderate and high viscosity. Formulations within each group showed similar viscosities despite differences in grade or concentration of HPMC. Formulations in the low viscosity cluster were found to be sprayable. PCA was able to differentiate the complex viscosity profiles of different formulations containing HPMC in an efficient and time-saving manner and provided an excellent visualisation of the data.

Impact of microcrystalline cellulose material attributes: a case study on continuous twin screw granulation

The International Conference on Harmonisation (ICH) states in its Q8 'Pharmaceutical Development' guideline that the manufacturer of pharmaceuticals should have an enhanced knowledge of the product performance over a range of material attributes, manufacturing process options and process parameters. The present case study evaluates the effect of unspecified variability of raw material properties upon the quality attributes of granules; produced using a continuous from-powder-to-tablet wet granulation line (ConsiGma™ 25). The impact of different material attributes of six samples of microcrystalline cellulose (MCC) was investigated. During a blind study the different samples of MCC were used separately and the resulting granules were evaluated in order to identify the differences between the six samples. Variation in size distribution due to varying water binding capacity of the MCC samples was observed. The cause of this different water binding capacity was investigated and was caused by a different degree of crystallinity. Afterwards, an experimental design was conducted in order to evaluate the effect of both product and process variability upon the granule size distribution. This model was used in order to calculate the required process parameters to obtain a preset granule size distribution regardless of the type of MCC used. The difference in water binding capacity and its effect on granular properties was still present when combining the MCC grades with different binders.