Novel approach to evaluating granulation and segregation level considering the contribution of hydroxypropyl cellulose to the surface property change of granules.

The granulation process is critical to the uniformity of not only the active ingredient (API) but also other excipients in granules. Insufficient granulation results in unexpected product quality, e.g. delayed dissolution and lack of uniformity of API. Therefore, evaluating the granulation and segregation level of granules helps secure the uniformity of drug product quality. Here, we found that the polar surface free energy (SFE) of studied granules increased as granulation by a high shear granulator proceeded. Among the excipients formulated in the studied granules, only hydroxypropyl cellulose (HPC) showed a higher specific free energy of adsorption (ΔGsp) of chloroform, which is a parameter used to calculate polar SFE. This indicates that the ΔGsp of chloroform in granules helps detect the level of contribution of HPC to the granulation progress by inverse gas chromatography (IGC). We concluded that the ΔGsp of chloroform in a granulated sample is a novel critical material attribute (CMA) in relation to granulation level. In addition, we propose a novel approach to evaluating the quantitative granulation and segregation level based on the ΔGsp of chloroform in a granulated sample by focusing on the distribution of HPC in the granulated sample.

New approach to optimizing risk management of the sticking problem using scale-independent critical material attributes and the quantitative process parameter.

In pharmaceutical manufacturing of solid formulations, blending with a lubricant is a key process in preventing sticking during compression. Sticking not only results in tablets with a disfigured appearance but also brings about the interruption of continuous operations. The aim of our study was to identify blending scale-independent critical material attributes (CMAs) in relation to the sticking problem to appropriately define the end-point of the blending process with magnesium stearate as lubricant. Results showed that the dispersive surface free energy (SFE) and the specific free energy absorptions (ΔGsp) of ethanol decreased during blending with magnesium stearate. As the two parameters decreased, the sticking problem was improved. In conclusion, we propose that the dispersive SFE and ΔGsp of ethanol are scale-independent CMAs, and that the minimum blending time (BTmin), which can be calculated from the two CMAs, of the quantitative process parameter show the minimum blending time required to achieve higher risk assessment of the sticking problem.

A Scale-up Approach for Film Coating Process Based on Surface Roughness as the Critical Quality Attribute.

Scale-up approaches for film coating process have been established for each type of film coating equipment from thermodynamic and mechanical analyses for several decades. The objective of the present study was to establish a versatile scale-up approach for film coating process applicable to commercial production that is based on critical quality attribute (CQA) using the Quality by Design (QbD) approach and is independent of the equipment used. Experiments on a pilot scale using the Design of Experiment (DoE) approach were performed to find a suitable CQA from surface roughness, contact angle, color difference, and coating film properties by terahertz spectroscopy. Surface roughness was determined to be a suitable CQA from a quantitative appearance evaluation. When surface roughness was fixed as the CQA, the water content of the film-coated tablets was determined to be the critical material attribute (CMA), a parameter that does not depend on scale or equipment. Finally, to verify the scale-up approach determined from the pilot scale, experiments on a commercial scale were performed. The good correlation between the surface roughness (CQA) and the water content (CMA) identified at the pilot scale was also retained at the commercial scale, indicating that our proposed method should be useful as a scale-up approach for film coating process.

Application of Terahertz Attenuated Total Reflection Spectroscopy to Detect Changes in the Physical Properties of Lactose during the Lubrication Process Required for Drug Formulation.

Manufacturing the solid dosage form of an orally administered drug requires lubrication to enhance manufacturability, ensuring that critical quality attributes such as disintegration and dissolution of the drug product are maintained during manufacture. Here, to evaluate lubrication performance during manufacture, we used terahertz attenuated total reflection (THz-ATR) spectroscopy to detect differences in the physical characteristics of the lubricated powder. We applied a simple formulation prepared by blending granulated lactose as filler with magnesium stearate as lubricant. A flat tablet was prepared using the lubricated powder to acquire sharp THz-ATR absorption peaks of the samples. First, we investigated the effects of lubricant concentration and compression pressure on preparation of the tablet and then determined the effect of the pressure applied to samples in contact with the ATR prism on sample absorption amplitude. We focused on the differences in the magnitudes of spectra at the lactose-specific frequency. Second, we conducted the dynamic lubrication process using a 120-L mixer to investigate differences in the magnitudes of absorption corresponding to the lactose-specific frequency during lubrication. In both studies, enriching the lubricated powder with a higher concentration of magnesium stearate or prolonging blending time correlated with higher magnitudes of spectra at the lactose-specific frequency. Further, in the dynamic lubrication study, the wettability and disintegration time of the tablets were compared with the absorption spectra amplitudes at the lactose-specific frequency. We conclude that THz-ATR spectroscopy is useful for detecting differences in densities caused by a change in the physical properties of lactose during lubrication.

Application of terahertz pulse imaging as PAT tool for non-destructive evaluation of film-coated tablets under different manufacturing conditions.

Film-coated tablets (FCTs) are a popular solid dosage form in pharmaceutical industry. Manufacturing conditions during the film-coating process affect the properties of the film layer, which might result in critical quality problems. Here, we analyzed the properties of the film layer using a non-destructive approach with terahertz pulsed imaging (TPI). Hydrophilic tablets that become distended upon water absorption were used as core tablets and coated with film under different manufacturing conditions. TPI-derived parameters such as film thickness (FT), film surface reflectance (FSR), and interface density difference (IDD) between the film layer and core tablet were affected by manufacturing conditions and influenced critical quality attributes of FCTs. Relative standard deviation of FSR within tablets correlated well with surface roughness. Tensile strength could be predicted in a non-destructive manner using the multivariate regression equation to estimate the core tablet density by film layer density and IDD. The absolute value of IDD (Lateral) correlated with the risk of cracking on the lateral film layer when stored in a high-humidity environment. Further, in-process control was proposed for this value during the film-coating process, which will enable a feedback control system to be applied to process parameters and reduced risk of cracking without a stability test.

Influence of binder droplet dimension on granulation rate during fluidized bed granulation.

Here, we statistically identified the critical factor of the granulation rate during the fluidized bed granulation process. Lactose was selected as the excipient and was granulated with several binders, including hydroxypropyl cellulose, hydroxypropyl methyl cellulose, and polyvinylpyrrolidone. The viscosity, density, and surface tension of the binder solution, contact angle, and the work done during adhesion and cohesion between the binder and lactose, mist diameter, Stokes number, and the dimension of the droplet were considered. The Stokes number was defined as the ratio of the inertial force to the viscous-damping force of a particle. We confirmed that droplet diameter after adhesion had the highest correlation coefficient with the granulation rate constant in our investigated parameters. Partial least squares regression revealed two critical principal components of the granulation rate: one relating to the droplet dimension, which is composed of mist diameter and diameter and thickness of the droplet after adhesion of the binder to the lactose surface; and the other relating to wettability, which involves the work done during adhesion and cohesion, surface tension, and the thickness of the droplet after adhesion of the binder to the lactose surface.

Evaluation of models for predicting spray mist diameter for scaling-up of the fluidized bed granulation process.

We evaluated models for predicting spray mist diameter suitable for scaling-up the fluidized bed granulation process. By precise selection of experimental conditions, we were able to identify a suitable prediction model that considers changes in binder solution, nozzle dimension, and spray conditions. We used hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC), or polyvinylpyrrolidone (PVP) binder solutions, which are commonly employed by the pharmaceutical industry. Nozzle dimension and spray conditions for oral dosing were carefully selected to reflect manufacturing and small (1/10) scale process conditions. We were able to demonstrate that the prediction model proposed by Mulhem optimally estimated spray mist diameter when each coefficient was modified. Moreover, we developed a simple scale-up rule to produce the same spray mist diameter at different process scales. We confirmed that the Rosin-Rammler distribution could be applied to this process, and that its distribution coefficient was 1.43-1.72 regardless of binder solution, spray condition, or nozzle dimension.