Continuous powder feeding for pharmaceutical solid dosage form manufacture: a short review

Abstract

There has been a noticeable shift from pharmaceutical batch processing towards a more continuous mode of manufacture for solid oral dosage forms. Continuous solid oral dose processes would not be possible in the absence of a highly accurate feeding system. The performance of feeders defines the content of formulations and is therefore a critical operation in continuous manufacturing of solid dosage forms. It was the purpose of this review to review the role of the initial powder feeding step in a continuous manufacturing process. Different feeding mechanisms are discussed with a particular emphasis on screw controlled loss in weight (LIW) feeding. The importance of understanding the physical properties of the raw materials and its impact on the feeding process is reviewed. Prior knowledge of materials provides an initial indication of how the powders will behave through processing and facilitates in the selection of the most suitable (i) feeder (capacity), (ii) feeding mechanism, and (iii) in the case of screw feeder – screw type. The studies identified in this review focus on the impact of material on powder feeding performance.     

Continuous Twin Screw Wet Granulation and Drying—Control Strategy for Drug Product Manufacturing

The use of continuous manufacturing has been increasing within the pharmaceutical industry over the last few years. Continuous direct compression has been the focus of publications on the topic to date. The use of wet granulation can improve segregation resistance, uniformity, enhance density, and flow properties for improved tabletability, or improve stability of products that cannot be manufactured by using a direction compression process. This article focuses on development of appropriate control strategies for continuous wet granulation (especially twin screw wet granulation) through equipment design, material properties and manufacturing process along with areas where additional understanding is required. The article also discusses the use of process analytical technologies as part of the control and automation approach to ensure a higher assurance of product quality. Increased understanding of continuous wet granulation should result in increased utilization of the technique, thereby allowing for an increase in diversity of products manufactured by continuous manufacturing and the benefits that comes with a more complex process such as wet granulation compared with direct compression process.     

Crystal and Particle Engineering Strategies for Improving Powder Compression and Flow Properties to Enable Continuous Tablet Manufacturing by Direct Compression

Continuous manufacturing of tablets has many advantages, including batch size flexibility, demand-adaptive scale up or scale down, consistent product quality, small operational foot print, and increased manufacturing efficiency. Simplicity makes direct compression the most suitable process for continuous tablet manufacturing. However, deficiencies in powder flow and compression of active pharmaceutical ingredients (APIs) limit the range of drug loading that can routinely be considered for direct compression. For the widespread adoption of continuous direct compression, effective API engineering strategies to address power flow and compression problems are needed. Appropriate implementation of these strategies would facilitate the design of high-quality robust drug products, as stipulated by the Quality-by-Design framework. Here, several crystal and particle engineering strategies for improving powder flow and compression properties are summarized. The focus is on the underlying materials science, which is the foundation for effective API engineering to enable successful continuous manufacturing by the direct compression process.     

Modeling and simulation of continuous powder blending applied to a continuous direct compression process

Abstract

Continuous manufacturing techniques are increasingly being adopted in the pharmaceutical industry and powder blending is a key operation for solid-dosage tablets. A modeling methodology involving axial and radial tanks-in-series flowsheet models is developed to describe the residence time distribution (RTD) and blend uniformity of a commercial powder blending system. Process data for a six-component formulation processed in a continuous direct compression line (GEA Pharma Systems) is used to test the methodology. Impulse tests were used to generate experimental RTDs which are used along with parameter estimation to determine the number of axial tanks in the flowsheet. The weighted residual from the parameter estimation was less than the χ² value at a 95% confidence indicating a good fit between the model and measured data. In-silico impulse tests showed the tanks-in-series modeling methodology could successfully describe the RTD behavior of the blenders along with blend uniformity through the use of radial tanks. The simulation output for both impulse weight percentage and blend uniformity were within the experimentally observed variance.     

Using Residence Time Distributions (RTDs) to Address the Traceability of Raw Materials in Continuous Pharmaceutical Manufacturing

Continuous processing in pharmaceutical manufacturing is a relatively new approach that has generated significant attention. While it has been used for decades in other industries, showing significant advantages, the pharmaceutical industry has been slow in its adoption of continuous processing, primarily due to regulatory uncertainty. This paper aims to help address these concerns by introducing methods for batch definition, raw material traceability, and sensor frequency determination. All of the methods are based on established engineering and mathematical principles, especially the residence time distribution (RTD). This paper introduces a risk-based approach to address content uniformity challenges of continuous manufacturing. All of the detailed methods are discussed using a direct compaction manufacturing line as the main example, but the techniques can easily be applied to other continuous manufacturing methods such as wet and dry granulation, hot melt extrusion, capsule filling, etc.     

Continuous Mixing Technology: Characterization of a Vertical Mixer Using Residence Time Distribution

Continuous powder mixing technology (CMT) application during continuous direct compression has emerged as a leading technology used in the development and manufacture of solid oral dosage forms. The critical quality attributes of the final product are heavily dependent on the performance of the mixing step as the quality of mixing directly influences the drug product quality attributes. This study investigates the impact of blend material properties (bulk density, API particle size distribution) and process parameters (process throughput, hold up mass and impeller speed) on the mixing performance. Mixing of the blend was characterized using the Residence Time Distribution (RTD) of the process by trending the outlet stream of the mixer using a near-infrared (NIR) probe after the injection of a small mass of tracer at the inlet stream. The outcomes of this study show that the RTDs of the mixer with throughput ranging between 15 and 30 kg/h; impeller speed ranging between 400 and 600 rpm and hold up mass (HUM) ranging between 500 and 850 g can be described by a series of two ideal Continuous Stirred Tank Reactors (CSTRs) with different volumes, and correspondingly, different mean residence times. It is also observed that the mixing is mainly occurring in the lower chamber of the CMT and the normalized RTDs of the mixer are similar across the range of process conditions and material attributes studied. The results also showed that the formulation blend with different API particle sizes and bulk properties, like bulk density and flowability, provide insignificant impact on the mixing performance. The CMT allows independent selection of target set points for HUM, impeller rotational speed and line throughput and it shows great robustness and flexibility for continuous blending in solid oral dose manufacturing.     

Sensor Network Robustness Using Model-Based Data Reconciliation for Continuous Tablet Manufacturing

Advances in continuous manufacturing in the pharmaceutical industry necessitate reliable process monitoring systems that are capable of handling measurement errors inherent in all sensor technologies and detecting measurement outliers to ensure operational reliability. The purpose of this work was to demonstrate data reconciliation (DR) and gross error detection methods as real-time process management tools to accomplish robust process monitoring. DR mitigates the effects of random measurement errors, while gross error detection identifies nonrandom sensor malfunctions. DR is an established methodology in other industries (i.e., oil and gas) and was recently investigated for use in drug product continuous manufacturing. This work demonstrates the development and implementation of model-based steady-state data reconciliation on 2 different end-to-end continuous tableting lines: direct compression and dry granulation. These tableting lines involve different equipment and sensor configurations, with sensor network redundancy achieved using equipment-embedded sensors and in-line process analytical technology tools for the critical process parameters and critical quality attributes. The nonlinearity of the process poses additional challenges to solve the steady-state data reconciliation optimization problem in real time. At-line and off-line measurements were used to validate the framework results.     

A Training on: Continuous Manufacturing (Direct Compaction) of Solid Dose Pharmaceutical Products

As the pharmaceutical industry increasingly adopts continuous manufacturing technology, significant attention must be paid to process analytical technology (PAT), process integration, and process control. Published information is no substitute for hands-on comprehensive training, which is critical to implementing and operating continuous pharmaceutical manufacturing systems effectively and efficiently. In this article, an intensive hands-on training course has been developed and implemented at the Engineering Research Center for Structured Organic Particulate Systems (C-SOPS) based on 15 years of experience and several implemented systems. Here, we brought the details of the four integral components in a continuous direct compression manufacturing process: (1) unit operations, (2) PAT, (3) modeling and process controls, and (4) material characterization. Each section built-in classroom lectures with a brief overview on the theoretical aspects of each topic, followed by a hands-on session covering the classroom theory. The training program is described here in sufficient detail to enable creation of similar programs at other institutions.     

Rapid Prototyping of Miniaturized Powder Mixing Geometries

Continuous manufacturing is an important element of future manufacturing solutions enabling for both high product quality and streamlined development process. The increasing possibilities with computer simulations allow for innovating novel mixing principles applicable for continuous manufacturing. However, these innovative ideas based on simulations need experimental validation. The use of rapid prototyping based on additive manufacturing opens a possibility to evaluate these ideas at a low cost. In this study, a novel powder mixing geometry was prototyped using additive manufacturing and further, interfaced with an in-line near-IR spectrometer allowing for investigating the residence time distribution (RTD) in this geometry.     

Use of the crushing strength parameter for quality control of phenobarbital-microcrystalline cellulose tablets

Three variables of the tablet manufacturing process (duration of mixing with lubricant, maximum compression force and compression rate) were studied for their effects on various properties of direct compression phenobarbital-microcrystalline cellulose tablets. Mixing time and maximum compression force were found to have a marked influence on friability and dissolution rate; crushing strength was found to be a useful parameter for quality control.     

Nondestructive measurements of the compact strength and the particle-size distribution after milling of roller compacted powders by near-infrared spectroscopy

Compact strength and the particle-size distribution of milled roller compacted compacts were correlated to the slope of the best-fit line through near-infrared spectra for samples prepared under different roll speeds and feed rates. The above correlations were found to hold for compacts prepared from microcrystalline cellulose powder as well as from a typical direct compression pharmaceutical powder blend containing tolmetin sodium dihydrate, microcrystalline cellulose, and dicalcium phosphate dihydrate. Near-infrared spectra were also collected real time for the compacts prepared from the tolmetin powder blend. The real-time slope values for the spectra showed good agreement with the off-line data. The strength of compacts was determined using three-point beam bending method and the particle-size distribution of the milled compacts was determined using sieve analysis. The results suggest that the real-time values of the slope of the best-fit line through the near-infrared spectrum offers a robust, yet simple and fast quality control tool to monitor/control manufacturing and scale-up processes involving dry granulation by roller compaction.     

Degree of compression as a potential process control tool of tablet tensile strength

The current view on the development and manufacturing of pharmaceutical preparations points towards improved control tools that can be implemented in pharmaceutical manufacturing as a means to better control end product properties. The objective of this paper was to investigate the relationship between tablet tensile strength and the degree of bed compression in order to evaluate the suitability of assessing the straining of the powder bed during tableting as a process control tool of tablet tensile strength. Microcrystalline cellulose was used as powder raw material and subjected to wet granulation by different procedures to create agglomerates of different physical and compression properties. The produced agglomerates thus showed a large variation in compressibility and compactibility. However, in terms of the relationship between the degree of compression and the tablet tensile strength, all agglomerates gathered reasonably around a single general relationship. The degree of compression hence appears to be a potential valuable process control tool of the tablet tensile strength that may enable the use of an adaptive tableting process with improved product quality consistency.     

基于ICHQ13的碳酸钙原料药连续制造监管探析

目的：通过实际案例研究找寻ICH Q13指南背后的基本原理,促进连续制造技术在我国制药行业的应用。方法：以原料药碳酸钙生产为实例,分析其连续制造生产线中部分工序的连续生产设计与实现方式,并参照ICH Q13指南的要求,提出监管层面的考虑。结果与结论：类似于碳酸钙这种工艺简单的品种非常适合转化为先进的连续制造工艺,现有条件可实现部分工序连续生产,也非常有望实现真正的全过程连续制造,为药品连续制造在我国的顺利落地实施提供了实践参考。     

Determination of Residence Time Distribution in a Continuous Powder Mixing Process With Supervised and Unsupervised Modeling of In-line Near Infrared (NIR) Spectroscopic Data

Successful implementation of continuous manufacturing processes requires robust methods to assess and control product quality in a real-time mode. In this study, the residence time distribution of a continuous powder mixing process was investigated via pulse tracer experiments using near infrared spectroscopy for tracer detection in an in-line mode. The residence time distribution was modeled by applying the continuous stirred tank reactor in series model for achieving the tracer (paracetamol) concentration profiles. Partial least squares discriminant analysis and principal component analysis of the near infrared spectroscopy data were applied to investigate both supervised and unsupervised chemometric modeling approaches. Additionally, the mean residence time for three powder systems was measured with different process settings. It was found that a significant change in the mean residence time occurred when comparing powder systems with different flowability and mixing process settings. This study also confirmed that the partial least squares discriminant analysis applied as a supervised chemometric model enabled an efficient and fast estimate of the mean residence time based on pulse tracer experiments.     

Real-Time Monitoring of Powder Mass Flowrates for Plant-Wide Control of a Continuous Direct Compaction Tablet Manufacturing Process

While measurement and monitoring of powder/particulate mass flow rate are not essential to the execution of traditional batch pharmaceutical tablet manufacturing, in continuous operation, it is an important additional critical process parameter. It has a key role both in establishing that the process is in a state of control, and as a controlled variable in process control system design. In current continuous tableting line operations, the pharmaceutical community relies on loss-in-weight feeders to monitor and understand upstream powder flow dynamics. However, due to the absence of established sensing technologies for measuring particulate flow rates, the downstream flow of the feeders is monitored and controlled using various indirect strategies. For example, the hopper level of the tablet press is maintained as a controlled process output by adjusting the turret speed of the tablet press, which indirectly controlling the flow rate. This gap in monitoring and control of the critical process flow motivates our investigation of a novel PAT tool, a capacitance-based sensor (ECVT), and its effective integration into the plant-wide control of a direct compaction process. First, the results of stand-alone experimental studies are reported, which confirm that the ECVT sensor can provide real-time measurements of mass flow rate with measurement error within -1.8 ~ 3.3% and with RMSE of 0.1 kg/h over the range of flow rates from 2 to 10 kg/h. The key caveat is that the powder flowability has to be good enough to avoid powder fouling on the transfer line walls. Next, simulation case studies are carried out using a dynamic flowsheet model of a continuous direct compression line implemented in Matlab/Simulink to demonstrate the potential structural and performance advantages in plant-wide process control enabled by mass flow sensing. Finally, experimental studies are performed on a direct compaction pilot plant in which the ECVT sensor is located at the exit of the blender, to confirm that the powder flow can be monitored instantaneously and controlled effectively at the specified setpoint within a plant-wide feedback controller system.     

阿莫西林胶囊生产过程质量控制方案初探

摘要：目的 本文依据质量源于设计理念,对阿莫西林胶囊质量的过程控制进行了初探。方法与结果 通过对目标产品 全过程检验数据的分析,确定影响制剂成品的关键质量属性(CQAs)为阿莫西林闭环二聚体(最大单杂),并设定了其控制界限 (μ±3σ)范围;通过比较各生产环节中间体检测数据的差异性,确定阿莫西林胶囊生产过程中的关键工艺为干法制粒环节,其 过程失水量为关键工艺参数表征值(CPPs)。通过多元线性回归构建了原料单杂(CMAs)、CPPs和制剂CQAs增长量之间的量值关 系,即质控函数;并通过近红外光谱技术(NIRS)实现了对CPPs的实时监测和生产反馈,可基于质控函数提前预知制剂成品质量 是否在CQAs控制界限内。结论 上述阿莫西林胶囊质控方案,可实现对产品质量的风险控制由终端前移至生产过程,以逐步     

处方工艺对瑞舒伐他汀钙片混合均匀度及含量均匀度的影响

目的 研究处方中的辅料及工艺对瑞舒伐他汀钙片混合均匀度及含量均匀度的影响。方法 采用粉末直接压片工艺，通过单因素试验，考察处方中乳糖的型号、微晶纤维素的型号、乳糖与微晶纤维素的比例、钙盐的种类及交联聚维酮用量对混合均匀度及含量均匀度的影响；同时研究混合工艺对混合均匀度及压片工艺对含量均匀度的影响。结果 不同的乳糖型号（T80、PW80、315）、微晶纤维素型号（PH102、M102、102）、乳糖与微晶纤维素的比例（1:1、3:1、1:3）、钙盐的种类（磷酸钙（细颗粒）、无水磷酸氢钙（细颗粒、细粉）、碳酸钙（细粉））的处方混合均匀度及含量均匀度良好，磷酸钙（粗颗粒）的处方混合均匀度及含量均匀度较差。在混合容器中加入50%的乳糖，之后加入原料药、微晶纤维素、交联聚维酮和磷酸钙，以10 r·min-1混合20~25 min；再加入剩余的乳糖，以10 r·min-1混合15~25 min，物料混合均匀度良好。重力加料器及压片速度（10~20 r·min-1）的含量均匀度良好；强制加料器及压片速度（30 r·min-1）的含量均匀度较差。结论：通过研究筛选出了适合粉末直压工艺的乳糖型号、微晶纤维素型号、乳糖与微晶纤维素比例、钙盐种类及交联聚维酮用量。考察了混合工艺参数范围，优选了重力加料器及压片速度（10~20 r·min-1），获得了良好的混合均匀度和含量均匀度。     

Orodispersible films: Product transfer from lab-scale to continuous manufacturing

Orodispersible films have been described as new beneficial dosage forms for special patient populations. Due to various production settings, different requirements on film formulations are required for non- continuous and continuous manufacturing. In this study, a continuous coating machine was qualified in regards of the process conditions for film compositions and their effects on the formed films. To investigate differences between both manufacturing processes, various film formulations of hydrochlorothiazide and hydroxypropylcellulose (HPC) or hydroxypropylmethycellulose (HPMC) as film formers were produced and the resulting films were characterized.The qualification of the continuously operating coating machine reveals no uniform heat distribution during drying. Coating solutions for continuous manufacturing should provide at least a dynamic viscosity of 1?Pa*s (wet film thickness of 500?μm, velocity of 15.9?cm/min). HPC films contain higher residuals of ethanol or acetone in bench-scale than in continuous production mode. Continuous production lead to lower drug content of the films. All continuously produced films disintegrate within less than 30?s. There are observed significant effects of the production process on the film characteristics. When transferring film manufacturing from lab-scale to continuous mode, film compositions, processing conditions and suitable characterization methods have to be carefully selected and adopted.