Challenges encountered in the transfer of atorvastatin tablet manufacturing - commercial batch-based production as a basis for small-scale continuous tablet manufacturing tests

As is the case with batch-based tableting processes, continuous tablet manufacturing can be conducted by direct compression or with a granulation step such as dry or wet granulation included in the production procedure. In this work, continuous manufacturing tests were performed with a commercial tablet formulation, while maintaining its original material composition. Challenges were encountered with the feeding performance of the API during initial tests which required designing different powder pre-blend compositions. After the pre-blend optimization phase, granules were prepared with a roller compactor. Tableting was conducted with the granules and an additional brief continuous direct compression run was completed with some ungranulated mixture. The tablets were assessed with off-line tests, applying the quality requirements demanded for the batch-manufactured product. Chemical maps were obtained by Raman mapping and elemental maps by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Large variations in both tablet weights and breaking forces were observed in all tested samples, resulting in significant quality complications. It was suspected that the API tended to adhere to the process equipment, accounting for the low API content in the powder mixture and tablets. These results suggest that this API or the tablet composition was unsuitable for manufacturing in a continuous line; further testing could be continued with different materials and changes in the process.

Developing a Virtual Flowability Sensor for Monitoring a Pharmaceutical Dry Granulation Line

Current technologies to measure granule flowability involve at-line methods that can take hours to perform. This is problematic for a continuous dry granulation tableting line, where the quality assurance and control of the final tablet products depend on real-time monitoring and control of powder flowability. Hence, a real-time alternative is needed for measuring the flowability of the granular products coming out of the roller compactor, which is the unit operation immediately preceding the tablet press. Since particle analyzers have the potential to take inline measurements of the size and shape of granules, they can potentially serve as real-time flowability sensors, given that the size and shape measurements can be used to reliably predict flowability measurements. This paper reports on the use of Partial Least Squares (PLS) regression to utilize distributions of size and shape measurements in predicting the output of three different types of flowability measurements: rotary drum flow, orifice flow, and tapped density analysis. The prediction performance of PLS had a coefficient of determination ranging from 0.80 to 0.97, which is the best reported performance in the literature. This is attributed to the ability of PLS to handle high collinearity in the datasets and the inclusion of multiple shape characteristics-eccentricity, form factor, and elliptical form factor-into the model. The latter calls for a change in industry perspective, which normally dismisses the importance of shape in favor of size; and the former suggests the use of PLS as a better way to reduce the dimensionality of distribution datasets, instead of the widely used practice of pre-selecting distribution percentiles.

Using a Model-based Material Sparing Approach for Formulation and Process Development of a Roller Compacted Drug Product

The present work details a material sparing approach that combines material profiling with Instron uniaxial die-punch tester and use of a roller compaction mathematical model to guide both formulation and process development of a roller-compacted drug product. True density, compression profiling, and frictional properties of the pre-blend powders are used as inputs for the predictive roller compaction model, while flow properties, particle size distribution, and assay uniformity of roller compaction granules are used to select formulation composition and ribbon solid fraction. Using less than 10 g of a model drug compound for material profiling, roller compacted blend in capsule formulations with appropriate excipient ratios were developed at both 1.4% and 14.4% drug loadings. Subsequently, scale-up batches were successfully manufactured based on the roller compaction process parameters obtained from predictive modeling. The measured solid fractions of roller compaction ribbon samples from the scale-up batches were in good agreement with the target solid fraction of the modeling. This approach demonstrated considerable advantages through savings in both materials and number of batches in the development of a roller-compacted drug product, which is of particular value at early development stages when drug substance is often limited and timelines are aggressive.

Downstream processing of spray-dried ASD with hypromellose acetate succinate - Roller compaction and subsequent compression into high ASD load tablets

Despite wide commercial application of hypromellose acetate succinate (HPMCAS) in spray-dried amorphous solid dispersion (ASD) drug products, little information is available in the references on downstream processing of spray-dried dispersions with HPMCAS. Poor flow and high dilution factor are a challenge in formulating spray-dried ASDs into tablets, leaving little space for other excipients facilitating binding and disintegration. Direct compression is not possible due to the poor powder flow of spray-dried ASDs. Moisture has to be avoided due to the plasticizing properties of water on the ASD, resulting in reduced stability of the amorphous state. Thus, dry granulation by roller compaction and subsequent tablet compression is the preferred downstream process. We report the investigation of downstream processing by roller compaction and tablet compression of a high load formulation with 75% of spray-dried amorphous solid dispersion (Nifedipine:HPMCAS 1:2). A head to head comparison of microcrystalline cellulose/croscarmellose (MCC/cl-NaCMC) as binder/disintegrant vs. MCC and low-substituted hydroxypropyl cellulose (L-HPC) as excipient for binding and disintegration showed improved re-workability of the formulation with MCC/L-HPC after roller compaction. Upon transfer to the rotary press, a 45% higher tensile strength of tablets is observed after dry granulation with MCC/L-HPC.

The effects of screw-to-roll speed ratio on ribbon porosity during roll compaction

Dry granulation through roll compaction is a technology commonly used in the pharmaceutical industry for producing roll compacted ribbons. The significance of the feed screw speed and roll speed during ribbon production was highlighted in recent publications. However, previous studies focused primarily on the individual effects of either the feed screw speed or roll speed on ribbon porosity, and the synergetic effect of these parameters was rarely examined. The aim of this study therefore was to investigate the effects of the screw-to-roll speed ratio on the porosity of roll compacted ribbons, produced at different roll compaction conditions using the microcrystalline cellulose MCC, Avicel PH-102 feed material. It was observed that ribbon porosity decreased linearly with increasing screw-to-roll speed ratio. Furthermore, an increase in the speed ratio led to an increase in the roll gap and mass throughput while a decrease in the screw constant was observed. Thus, this study demonstrates that the screw-to-roll speed ratio can be treated as one of the critical process parameters for controlling ribbon porosity and can also be used to determine the optimum operating regimes during roll compaction.

Solventless granulation and spheronization of indomethacin crystals using a mechanical powder processor: Effects of mechanically induced amorphization on particle formation

Our aim was to reveal the effects of mechanically-induced amorphization on the solventless agglomeration and spheronization of drug crystals using a mechanical powder processor. This process can provide spherical particles comprising 100% drug. Indomethacin crystals were mechanically treated using various jacket temperatures and the resulting particles were characterized using particle and crystalline analyses. Also, the adhesive and mechanical properties of amorphous indomethacin were examined. At 20 °C, the indomethacin crystals fragmented and amorphized during processing, indicating that glassy-state indomethacin with no adhesiveness does not contribute to agglomeration or spheronization. At 40 °C, agglomeration occurred due to the transformation of mechanically-induced amorphous phases from non-adhesive glass to an adhesive supercooled liquid at around the glass transition temperature. However, at higher temperatures, the formation of agglomerates was suppressed by recrystallization of the amorphous surface. At 60 °C, the indomethacin crystals compacted and spheronized due to deformation of the particle surface, consistent with results showing that the stiffness of amorphous indomethacin decreased suddenly above 60 °C. The lifespan of the amorphous phase decreased due to enhanced recrystallization as the temperature increased, thereby reducing the degree of spheronization. In conclusion, agglomeration and spheronization are affected by the glass transition temperature and recrystallization of the mechanically-induced amorphous phase.

Elastic recovery in roll compaction simulation

Roll compaction/dry granulation is a widely used granulation method in the pharmaceutical industry. The simulation of the process is of great interest, especially in the early phase of formulation development of solid dosage forms. The hybrid modeling approach allows to predict the roll compaction process parameters to produce ribbons with a desired solid fraction. Based on the process parameters, compacts (ribblets) of the same solid fraction are produced on a single punch press. So far, the prediction accuracy for the solid fraction of the ribbons was not satisfactory. It was found that the lack in prediction accuracy was due to the elastic recovery, which was not considered in the model. In this study, the fast in-die and the slow out-of-die elastic recovery of different excipients with varying compaction properties were investigated. A method was established to compensate for the elastic recovery of compacts in roll compaction simulation and to improve the prediction accuracy of the solid fraction considerably. The results were successfully implemented into the model through an additional learning step. Moreover, the findings were transferred to the mimicking of an API containing formulation. By modeling, it was possible to accurately predict the process settings to obtain ribbons with the desired solid fraction using only a small amount of material.

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.

Use of roller compaction and fines recycling process in the preparation of erlotinib hydrochloride tablets

This study focuses on improving the manufacturing process for a generic immediate-release tablet containing erlotinib hydrochloride by adding a fines recycling process during roller compaction. Due to the large fraction of small-sized API particles, the starting powder mixture was inconsistently fed into the roller compactor. Consequently, poorly flowing granules with a high ratio of fines were produced. A fines recycling step was, therefore, added to the existing roller compaction process to minimize the risks caused by the poor granule flow. A laboratory scale roller compactor and a tablet simulator were used to prepare granules at various process conditions. The effect of dry granulation parameters on size distribution, API distribution, powder flow, compaction properties, and dissolution profile was evaluated. The granule batch after fines recycling had markedly improved size distribution and flowability while maintaining acceptable tablet tensile strength and rapid dissolution profile. The application of the fines recycling process at commercial scale resulted in reliable dissolution performance and batch-to-batch consistency, which were further confirmed by bioequivalence to the reference product. Understanding how granule properties are impacted by the fines recycling process may enable fine-tuning of the dry granulation process for optimal product quality.

Exploratory studies in heat-assisted continuous twin-screw dry granulation: A novel alternative technique to conventional dry granulation

Dry granulation is the preferred technique for solvent-sensitive products, especially drugs with stability problems such as hydrolysis. Twin-screw granulation is a continuous granulation technique, offering a potential alternative to conventional dry granulation techniques such as roller compaction. The major advantage of twin-screw granulation is the ability to adjust process parameters of dry granulation without compromising the compression properties. This study was aimed to perform exploratory studies of heat-assisted continuous twin-screw dry granulation process to formulate sustained release tablets for APIs with different melting points: theophylline, acetaminophen and lidocaine hydrochloride hydrate. Granulation feasibility was studied with different binders (e.g. Klucel™ EF, Kollidon® VA64), sustained release agents (e.g. Klucel™ MF, Eudragit® RSPO) and diluents at various drug loads. The processing conditions were below the melting point or glass transition temperature of the formulation ingredients. After successful granulation, DSC and XRD studies revealed the crystalline nature of the granules and FTIR studies showed no interaction of the API with the excipients. The granules were compressed into sustained release tablets without any compressibility issues. The tablets were stable after testing for 6 months at 25 °C/60% RH. This novel continuous dry granulation technique may offer an excellent alternative to conventional dry granulation techniques.

How relevant is ribbon homogeneity in roll compaction/dry granulation and can it be influenced?

A homogeneous distribution of solid fraction in ribbons is generally assumed to be beneficial during roll compaction/dry granulation. Numerous attempts have been made to increase this homogeneity by modification of the machine, i.e. the roll design and the design of the feeding unit. It has however not been critically tested how relevant this homogeneity really is during subsequent processing. This study investigated two resulting questions: How can process parameters used to increase homogeneity in ribbons and how relevant is this homogeneity for properties of resulting tablets? For that, a statistically designed experiment were performed and ribbon homogeneity analyzed using X-ray micro-computed tomography. Independent from the sealing system used during manufacturing, larger gap widths led to higher homogeneity. The effect of specific compaction force was strongly dependent on the sealing system. When using the cheek plate system, higher specific compaction forces decreased the ribbon homogeneity, while it had no influence when rim rolls were used. In a subsequent study, ribbons of different homogeneity were milled and the resulting granules compressed to tablets. Tablets from homogeneous and inhomogeneous ribbons showed comparable strength and tablet mass variability. Reduced tabletability from highly densified regions of inhomogeneous ribbons was compensated by higher amounts of fines which originate from the more porous regions of ribbons. It was concluded that the relevance of ribbon homogeneity in roll compaction might generally be overestimated.

Impact of non-binder ingredients and molecular weight of polymer binders on heat assisted twin screw dry granulation

Two grades of commercial AFFINISOL™ HPMC HME were used as polymer binders to explore the influence of polymer viscosity and concentration on a novel heat assisted dry granulation process with a twin screw extruder. Contributions of other non-binder ingredients in the formulations were also studied for lactose, microcrystalline cellulose and an active pharmaceutical ingredient of caffeine. As sensitive indicators of processing conditions that expose the drug to high internally generated heat, dehydration of α-lactose monohydrate and polymorphic transformation of caffeine were monitored by differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD). Additionally, any decomposition of caffeine was determined by high-performance liquid chromatography (HPLC). Granular samples were characterized by particle size, circularity, fracture strength and their temperature on the exit of extruder. Higher screw speed and lower feed rate were found to help particles agglomerate by allowing feed particles a greater opportunity to increase in temperature. Lower binder molecular weight and higher binder concentration enable granules to build stronger strength and thereby lead to higher particle size. This new twin screw dry granulation was demonstrated as offering advantages over conventional hot melt granulation by minimizing thermal degradation of the tested ingredients.

Understanding the Impact of Chemical Variability and Calibration Algorithms on Prediction of Solid Fraction of Roller Compacted Ribbons Using Near-Infrared (NIR) Spectroscopy

The study is aimed at developing a near-infrared (NIR) method for predicting solid fraction (SF) of dry granulated ribbons manufactured with formulation variability. The study investigated the impact of unmodeled chemical variability and regression approaches on method performance. The study utilized an excipient-only formulation system. Calibration compacts were created with chemical and processing variability; followed by collection of NIR spectra. Partial least squares (PLS) and spectral slope algorithms were utilized to model compact SF. Later, the models were deployed to predict SF of test ribbons and compacts containing an API at various concentrations. The risk associated with unmodeled chemical variation manifested itself through generation of new peaks and decreased baseline absorbance in the NIR spectra. The spectral slope was able to better manage this risk, as demonstrated by relatively higher robustness to the increasing load of the active pharmaceutical ingredient (API). The reduced robustness of the PLS approach was attributed to the impact of chemical variability on both spectral baseline and peak absorbance. A prediction error of approximately 5% was observed at 10% drug load using the spectral slope approach. An understanding of the risk associated with unmodeled variability will enable NIR method development as an API sparing technique for low-dose product development.

Implementation of quality by design approach in manufacturing process optimization of dry granulated, immediate release, coated tablets - a case study

The aim of this study was to optimize the process of tablets compression and identification of film-coating critical process parameters (CPPs) affecting critical quality attributes (CQAs) using quality by design (QbD) approach. Design of experiment (DOE) and regression methods were employed to investigate hardness, disintegration time, and thickness of uncoated tablets depending on slugging and tableting compression force (CPPs). Plackett-Burman experimental design was applied to identify critical coating process parameters among selected ones that is: drying and preheating time, atomization air pressure, spray rate, air volume, inlet air temperature, and drum pressure that may influence the hardness and disintegration time of coated tablets. As a result of the research, design space was established to facilitate an in-depth understanding of existing relationship between CPPs and CQAs of intermediate product (uncoated tablets). Screening revealed that spray rate and inlet air temperature are two most important factors that affect the hardness of coated tablets. Simultaneously, none of the tested coating factors have influence on disintegration time. The observation was confirmed by conducting film coating of pilot size batches.

A novel use of friability testing for characterising ribbon milling behaviour

Dry granulation using roll compaction (DGRC) has been increasingly adopted in the pharmaceutical industry due to its unique advantage of not requiring liquid binder and a subsequent drying process. However the DGRC process presents also some challenges, in particular, a high fine fraction generated during the milling stage significantly limits its application. Although the fines produced can be recycled in practice, it may lead to poor content uniformity of the final product. At present there is a lack of mechanistic understanding of milling of roll compacted ribbons. For instance, it is not clear how fines are generated, what are the dominant mechanisms and controlling attributes and whether any measurement technique can be used to characterise ribbon milling behaviour. Therefore, the aim of this paper was to assess whether ribbon milling behaviour can be assessed using some characterisation methods. For this purpose, friability was evaluated for ribbons made of microcrystalline cellulose (MCC) powders using a friability tester that was originally developed for characterising the tendency of pharmaceutical tablets to generate small pieces while being abraded. Granules were also produced by milling of the ribbons and their size distributions were measured. The correlation between the fine fraction of the granules with ribbon friability was then explored. It was found that there was a strong correlation between ribbon friability and the fine fraction of granules generated during milling. This implies that friability tests can be performed to characterise ribbon milling behaviour, and ribbon friability provides a good indication of the fraction of fines generated during ribbon milling.

Evaluation of roll compaction as a preparation method for hydroxypropyl cellulose-based matrix tablets

Roll compaction was applied for the preparation of hydroxypropyl cellulose (HPC)-based sustained-release matrix tablets. Matrix tablets made via roll compaction exhibited higher dosage uniformity and faster drug release than direct-compacted tablets. HPC viscosity grade, roll pressure, and milling speed affected tablet properties significantly. Roll compaction seems to be an adequate granulation method for the preparation of HPC-based matrix tablets due to the simplicity of the process, less handling difficulty from HPC tackiness as well as easier particle size targeting. Selecting the optimum ratio of plastic excipients and the particle size of starting materials can however be critical issues in this method.