Characterization of wet massing behavior of silicified microcrystalline cellulose and alpha-lactose monohydrate using near-infrared spectroscopy

Using 3D Printing for Rapid Prototyping of Characterization Tools for Investigating Powder Blend Behavior

There is an increasing need to provide more detailed insight into the behavior of particulate systems. The current powder characterization tools are developed empirically and in many cases, modification of existing equipment is difficult. More flexible tools are needed to provide understanding of complex powder behavior, such as mixing process and segregation phenomenon. An approach based on the fast prototyping of new powder handling geometries and interfacing solutions for process analytical tools is reported. This study utilized 3D printing for rapid prototyping of customized geometries; overall goal was to assess mixing process of powder blends at small-scale with a combination of spectroscopic and mechanical monitoring. As part of the segregation evaluation studies, the flowability of three different paracetamol/filler-blends at different ratios was investigated, inter alia to define the percolation thresholds. Blends with a paracetamol wt% above the percolation threshold were subsequently investigated in relation to their segregation behavior. Rapid prototyping using 3D printing allowed designing two funnels with tailored flow behavior (funnel flow) of model formulations, which could be monitored with an in-line near-infrared (NIR) spectrometer. Calculating the root mean square (RMS) of the scores of the two first principal components of the NIR spectra visualized spectral variation as a function of process time. In a same setup, mechanical properties (basic flow energy) of the powder blend were monitored during blending. Rapid prototyping allowed for fast modification of powder testing geometries and easy interfacing with process analytical tools, opening new possibilities for more detailed powder characterization.

Application of near-infrared spectroscopy to optimize dissolution profiles of tablets according to the granulation mechanism

We developed a method for the optimization of dissolution properties of solid oral dosage forms manufacturing using high shear wet granulation (HSWG) by using near-infrared spectroscopy (NIRS) with chemometrics in small-scale experiments. The changes in rheology and NIR spectra of the granules were monitored to verify the granulation mechanism and determine the suitable water amount for model formulation during the HSWG. Tablets were manufactured by altering the added water amount to investigate the impact of the granulation mechanism on drug product qualities. Model formulation granules were prepared with 10-20% w/w water in a funicular state, corresponding to the plateau region in score plots obtained by principal component analysis (PCA). The dissolution rate of model formulation tablets manufactured with more than 20% w/w of water was significantly delayed while tablets manufactured with 15% w/w water showed 100% dissolution at 15 min. NIRS and PCA are applicable to the optimization of dissolution properties via the process understanding of HSWG at the early formulation development stage and could facilitate drug development.

Real-time release monitoring for water content and mean particle size of granules in lab-sized fluid-bed granulator by near-infrared spectroscopy

Simultaneous real-time monitoring of water content and mean particle size in the powder bed of a fluidized-bed granulator was performed by near-infrared (NIR) spectroscopy through a window, and the findings were used to evaluate the granular properties.

Near infrared spectroscopy in the development of solid dosage forms

The use of near infrared (NIR) spectroscopy has rapidly grown partly due to demands of process analytical applications in the pharmaceutical industry. Furthermore, newest regulatory guidelines have advanced the increase of the use of NIR technologies. The non-destructive and non-invasive nature of measurements makes NIR a powerful tool in characterization of pharmaceutical solids. These benefits among others often make NIR advantageous over traditional analytical methods. However, in addition to NIR, a wide variety of other tools are naturally also available for analysis in pharmaceutical development and manufacturing, and those can often be more suitable for a given application. The versatility and rapidness of NIR will ensure its contribution to increased process understanding, better process control and improved quality of drug products. This review concentrates on the use of NIR spectroscopy from a process research perspective and highlights recent applications in the field.

Real-Time Assessment of Granule and Tablet Properties Using In-line Data From a High-shear Granulation Process

A method for real-time assessment of granule and tablet properties was investigated. A mixture of microcrystalline cellulose:mannitol:povidone (78.5:18.5:3) was used in the study and granulated with five different water amounts and two impeller speeds. This represents a full-factorial design with two factors, thus giving a causal structure to the variation between the experiments. Process data (power consumption, temperature and in-line near-infrared spectra) were collected during the granulations. In addition to the in-line process data, critical granule and tablet quality properties (such as particle size, porosity and tablet hardness) were measured in order to achieve in-depth process understanding. Neither power consumption nor temperature gave information that could be directly attributable to tablet properties, and these techniques were also heavily dependent on the speed of the impeller. In contrast, when using the first NIR overtone band for water (1460 nm), in-line real-time assessment of dry granule and tablet properties could be achieved.

Starch–dextrin mixtures as base excipients for extrusion–spheronization pellets

Extrusion-spheronization pellets are generally produced with microcrystalline cellulose (MCC) as the principal excipient, giving rise to particles of very high quality. A number of alternative excipients have been proposed and evaluated, mostly other cellulose derivatives (e.g. different grades of Avicel), or mixtures of MCCs and other excipients. In the present study, we evaluated the possible use of starch+agglutinant mixtures as principal excipients for extrusion-spheronization pellets, with the aim of producing pellets with more suitable properties for certain types of release. We first characterized the different excipients in terms of morphometry and basic physical properties. Subsequently, torque-rheometry was used to characterize the rheology of wetted masses of the different excipients and excipient mixtures, with the aim of determining optimal amount of wetting agent (water). We also evaluated the water absorption and water retention capacities of each excipient. In view of the results obtained, we produced pellets with the different starch+agglutinant mixtures (but without drug), and used image analysis to characterize pellet morphology. Our results show that some of the mixtures-notably starch (corn starch or wheat starch)+20% white dextrin-gave high-quality pellets with good size and shape distributions. In addition, the properties of the different materials tested suggest that it may be possible to obtain pellets with very different properties.

Prediction of Drug Dissolution from Tablets Using Near‐Infrared Diffuse Reflectance Spectroscopy as a Nondestructive Method

The goal of this study is to use near-infrared (NIR) reflectance spectroscopy to measure the percentage drug dissolution from a series of tablets compacted at different compressional forces, calibrate NIR data vs. laboratory equipment data, develop a model equation, validate the model, and test the model predictive ability. Seven theophylline tablet formulations of the same composition but with different dissolution profiles were prepared. Laboratory dissolution profiles were compared with NIR diffuse reflectance data. Linear regression, quadratic, cubic, and partial least-square techniques were used to determine the relationship between dissolution profiles data and NIR spectra. The results demonstrated that a decrease in the amount of drug dissolution produced an increase in NIR absorbance. A series of model equations, depending on the mathematical technique used for regression, were developed from the calibration of the percentage of drug dissolution by using laboratory equipment vs. the NIR diffuse reflectance for each formulation. The results of NIR dissolution data were similar to laboratory tests. The NIR diffuse reflectance spectroscopy method is an alternative, nondestructive method for measurement of drug dissolution from tablets.

Comparison of torque measurements and near-infrared spectroscopy in characterization of a wet granulation process

The purpose of this study was to compare impeller torque measurements and near-infrared (NIR) spectroscopy in the characterization of the water addition phase of a wet granulation process. Additionally, the effect of hydrate formation during granulation on the impeller torque was investigated. Anhydrous theophylline, alpha-lactose monohydrate, and microcrystalline cellulose (MCC) were used as materials for the study. The materials and mixtures of them were granulated using purified water in a small-scale high-shear mixer. The impeller torque was registered and NIR spectra of wet samples were recorded at-line. The torque and the NIR baseline-corrected water absorbances increased with increasing water content. A plateau in the NIR baseline-corrected water absorbances was observed for wet masses containing MCC. This was at the region of optimal water amount for granulation according to the torque results. In the case of anhydrous theophylline, the slope of baseline-corrected water absorbance values increased at the same water amount as the impeller torque started to increase. The hydrate formation of theophylline during granulation was observed as a slight decrease in the impeller torque. In addition, the hydrate formation during granulation affected the granulation liquid requirement. The liquid requirement was different for monohydrate formed during granulation compared to one formed in high relative humidity before the granulation. The results suggest that NIR spectroscopy may be applicable to process monitoring of wet granulation, also in cases where monitoring of impeller torque is difficult to apply.

Effects of excipients on hydrate formation in wet masses containing theophylline

Transformations between solid phases in dosage forms can lead to instability in drug release. Thus, it is important to understand mechanisms and kinetics of phase transformations and factors that may influence them. During wet granulation theophylline shows pseudopolymorphic changes that may alter its dissolution rate. The aim of this study was to investigate whether excipients, such as alpha-lactose monohydrate or the highly water absorbing silicified microcrystalline cellulose (SMCC) can influence the hydrate formation of theophylline. In particular, the aim was to study if SMCC offers protection against the formation of theophylline monohydrate relative to alpha-lactose monohydrate in wet masses after an overnight equilibration and the stability of final granules during controlled storage. In addition, the aim was to study the use of spectroscopic methods to identify hydrate formation in the formulations containing excipients. Off-line evaluation of materials was performed using X-ray powder diffractometry, near infrared and Raman spectroscopy. alpha-Lactose monohydrate with minimal water absorbing potential was not able to prevent but enhanced hydrate formation of theophylline. Even though SMCC is able to take large amounts of water into its internal structure, it was able to inhibit the formation of theophylline monohydrate only at low moisture contents, not at the amounts of water needed to form granules. Both the spectroscopic methods used could identify the hydrate formation even though there were excipients in the formulation.

A novel method of producing a microcrystalline beta-sitosterol suspension in oil

This paper describes a novel method of producing a microcrystalline oral suspension containing beta-sitosterol in oil for the treatment of hypercholesterolaemia. beta-Sitosterol pseudopolymorphs with different water contents were crystallized from acetone and acetone-water solutions. Structural analyses of the crystals were performed by Karl-Fisher titration, thermogravimetric analyses, X-ray diffraction and near infrared spectroscopy. The suspensions studied were composed of different concentrations of beta-sitosterol, oil and water. Suspensions were prepared by crystallization of hot concentrated solution of beta-sitosterol in oil by cooling with simultaneous agitation and water addition. The structural analyses of the suspensions were performed by X-ray diffraction, near infrared spectroscopy and optical microscopy. The viscosity of the suspensions was analysed as a function of shear stress. beta-Sitosterol was observed to exist in three different forms: anhydrous, hemihydrated and monohydrated crystals. By changing both the beta-sitosterol and the water concentration of the suspension, the crystal size and shape could be controlled. Addition of water resulted in the formation of monohydrated needle-shaped crystals instead of platy-like anhydrous crystals. Needle-shaped particles formed structured suspensions with shear thinning behaviour. By increasing the volume fraction of solid particles in suspension by increasing the water and/or sterol concentration, the viscosity increased. A high sterol concentration resulted in high supersaturation and thus formation of small crystals.

Microcrystalline cellulose-water interaction--a novel approach using thermoporosimetry

PURPOSE

To study the physical state of water in microcrystalline cellulose (MCC) and in silicified microcrystalline cellulose wet masses and the effect of granulation on different water fractions.

METHODS

Thermoporosimetry, together with the solute exclusion technique, was used to measure different water fractions and pore size distributions of wet granules. To understand the effect of granulation on the physical state of water, both ungranulated and granulated wet masses were studied. In addition, dynamic and isothermal step melting procedures were compared.

RESULTS

Four distinct fractions of water (nonfreezing, freezing bound, free, and bulk water) could be detected in MCC wet masses. Granulation decreased the volume of bulk water and increased the volume of freezing bound and free water. Consequently, granulated wet masses were able to hold more water inside the particles compared to ungranulated wet masses. Thus, granulation had a similar effect on MCC as beating has on cellulose fibers in the papermaking proces

CONCLUSIONS

Thermoporosimetry and solute exclusion increased the understanding of MCC-water interaction and showed how the physical state of water in MCC wet masses changes during granulation.

Process analysis of fluidized bed granulation

This study assesses the fluidized bed granulation process for the optimization of a model formulation using in-line near-infrared (NIR) spectroscopy for moisture determination. The granulation process was analyzed using an automated granulator and optimization of the verapamil hydrochloride formulation was performed using a mixture design. The NIR setup with a fixed wavelength detector was applied for moisture measurement. Information from other process measurements, temperature difference between process inlet air and granules (T(diff)), and water content of process air (AH), was also analyzed. The application of in-line NIR provided information related to the amount of water throughout the whole granulation process. This information combined with trend charts of T(diff) and AH enabled the analysis of the different process phases. By this means, we can obtain in-line documentation from all the steps of the processing. The choice of the excipient affected the nature of the solid-water interactions; this resulted in varying process times. NIR moisture measurement combined with temperature and humidity measurements provides a tool for the control of water during fluid bed granulation.

Evaluation of the functional equivalence of crospovidone NF from different sources. II. Standard performance test

Current NF monographs do not provide tests that reflect on the functionality of Crospovidone NF from multiple sources. Physical characterization studies such as particle size and distribution, surface area, porosity, and surface morphology revealed major differences among the crospovidones from different sources (Shah, U.; Augsburger, L.L. J. Pharm. Dev. Technol. 2001, 6 (1), 39-51). Differences in disintegration and dissolution were also observed for a model drug in an insoluble filler system (see Shah and Augsburger, 2001). The objective of this study was to determine the relationship between physical differences observed and disintegrant functionality and to develop standard performance test. Tests performed included settling volume studies, measurement of initial rate as well as extent of liquid uptake of the loose disintegrant powder, and simultaneous measurement of the axial and radial disintegrating forces along with the rate and extent of liquid uptake of the pure disintegrant compacts. Significant differences among the crospovidones were observed for all tests performed. Settling volume, liquid uptake, and disintegration force are recommended as standard performance tests to determine differences among crospovidones from different sources.

Characterization of microcrystalline cellulose and silicified microcrystalline cellulose wet masses using a powder rheometer

A powder rheometer has been used to study the properties of wet powder masses and the results have been compared to the mixer torque rheometer (MTR). Two different microcrystalline cellulose (MCC) grades (Avicel and Emcocel) and silicified microcrystalline cellulose (SMCC, Prosolv) were used as model powders. The wet massing behaviour of one material (Prosolv) was studied by the powder rheometer using liquid addition experiments, while the rheological properties of wet granules were studied using both the powder rheometer and the MTR. In water addition measurements the torque behaved in a similar way to MTR measurements and the maximum value of ZTL (zero torque limit) was achieved at the capillary state of wet mass. The wet granules exhibited different behaviour in the powder rheometer and the MTR experiments, which indicates that these rheometers involve different shear forces or they measure different properties of the wet granules. Emcocel wet masses achieved the capillary state at lower liquid amount than Avicel and Prosolv masses, which indicates that Emcocel is not able to hold as much water in the internal structure as Avicel and Prosolv. The powder rheometer proved to be a sensitive piece of equipment, which can be used to study both dry and wet powder masses. It was able to distinguish wet granules from wet powder masses after liquid addition, whereas the MTR could not. However, before the powder rheometer can be properly utilised in wet powder mass studies, the problem of torque overload requires resolution.