Elucidating raw material variability--importance of surface properties and functionality in pharmaceutical powders

Functional in situ formed deep eutectic solvents improving mechanical properties of powders by enhancing interfacial interactions

As novel green solvents, deep eutectic solvent (DES) with distinct liquid properties has gained increasing interest in pharmaceutical fields. In this study, DES was firstly utilized for improving powder mechanical properties and tabletability of drugs, and the interfacial interaction mechanism was explored. Honokiol (HON), a natural bioactive compound, was used as model drug, and two novel HON-based DESs were synthesized with choline chloride (ChCl) and l-menthol (Men), respectively. The extensive non-covalent interactions were account for DES formation according to FTIR, ¹H NMR and DFT calculation. PLM, DSC and solid-liquid phase diagram revealed that DES successfully in situ formed in HON powders, and the introduction of trace amount DES (99:1 w/w for HON-ChCl, 98:2 w/w for HON-Men) significantly improve mechanical properties of HON. Surface energy analysis and molecular simulation revealed that the introduced DES promoted the formation of solid-liquid interfaces and generation of polar interactions, which increase interparticulate interactions, thus better tabletability. Compared to nonionic HON-Men DES, ionic HON-ChCl DES exhibited better improvement effect, since their more hydrogen-bonding interactions and higher viscosity promote stronger interfacial interactions and adhesion effect. The current study provides a brand-new green strategy for improving powder mechanical properties and fills in the blank of DES application in pharmaceutical industry.

Evaluation of alternative methods to derive particle density from compression data

The determination of particle density is a critical part of material characterization regarding compression analyses. Helium pycnometry as the most commonly used method is criticized for different aspects. Most prominent is the susceptibility to errors when measuring water-containing powders. Alternative methods for determining particle density using compression data have already been described. However, a systematic investigation and evaluation is still missing. In this study, the methods by Sun and Krumme were investigated in detail regarding their robustness against variations in tableting settings. Twelve pharmaceutical excipients were tableted at five different settings to verify the applicability and sensitivity to changes in the experimental set-up. Both methods were found to be robust against influencing parameters from the experiments. A sufficiently high compression pressure to approach a constant density value of the corresponding material during tableting was considered to be an essential requirement for the performance of the methods. Brittle materials with high yield pressure were found to be unsuitable for the application of both methods. The method of Krumme gave small deviations to measurements of helium pycnometry for water-free materials. By using the tablet density after in-die elastic recovery, Krumme's method could be used for water-containing materials as well. The method of Sun was found to give significantly smaller values for particle density due to inclusion of slow elastic recovery.

A digital workflow from crystallographic structure to single crystal particle attributes for predicting the formulation properties of terbutaline sulfate

A detailed inter-molecular (synthonic) analysis of terbutaline sulfate, an ionic addition salt for inhalation drug formulation, is related to its crystal morphology, the surface chemistry of the habit faces and hence to its crystal surface energy.

Raw material variability of an active pharmaceutical ingredient and its relevance for processability in secondary continuous pharmaceutical manufacturing

Active Pharmaceutical Ingredients (API) raw material variability is not always thoroughly considered during pharmaceutical process development, mainly due to low quantities of drug substance available. However, synthesis, crystallization routes and production sites evolve during product development and product life cycle leading to changes in physical material attributes which can potentially affect their processability. Recent literature highlights the need for a global approach to understand the link between material synthesis, material variability, process and product quality. The study described in this article aims at explaining the raw material variability of an API using extensive material characterization on a restricted number of representative batches using multivariate data analysis. It is part of a larger investigation trying to link the API drug substance manufacturing process, the resulting physical API raw material attributes and the drug product continuous manufacturing process. Eight API batches produced using different synthetic routes, crystallization, drying, delumping processes and processing equipment were characterized, extensively. Seventeen properties from seven characterization techniques were retained for further analysis using Principal Component Analysis (PCA). Three principal components (PCs) were sufficient to explain 92.9% of the API raw material variability. The first PC was related to crystal length, agglomerate size and fraction, flowability and electrostatic charging. The second PC was driven by the span of the particle size distribution and the agglomerates strength. The third PC was related to surface energy. Additionally, the PCA allowed to summarize the API batch-to-batch variability in only three PCs which can be used in future drug product development studies to quantitatively evaluate the impact of the API raw material variability upon the drug product process. The approach described in this article could be applied to any other compound which is prone to batch-to-batch variability.

Effect of compression pressure on inhalation grade lactose as carrier for dry powder inhalations

Introduction:

This study focused on the potential effects of compression forces experienced during lactose (InhaLac 70, 120, and 230) storage and transport on the flowability and aerosol performance in dry powder inhaler formulation.

Materials and Methods:

Lactose was subjected to typical compression forces 4, 10, and 20 N/cm². Powder flowability and particle size distribution analysis of un-compressed and compressed lactose was evaluated by Carr's index, Hausner's ratio, the angle of repose and by laser diffraction method. Aerosol performance of un-compressed and compressed lactose was assessed in dispersion studies using glass twin-stage-liquid-impenger at flow rate 40-80 L/min.

Results:

At compression forces, the flowability of compressed lactose was observed same or slightly improved. Furthermore, compression of lactose caused a decrease in in vitro aerosol dispersion performance.

Conclusion:

The present study illustrates that, as carrier size increases, a concurrent decrease in drug aerosolization performance was observed. Thus, the compression of the lactose fines onto the surfaces of the larger lactose particles due to compression pressures was hypothesized to be the cause of these observed performance variations. The simulations of storage and transport in an industrial scale can induce significant variations in formulation performance, and it could be a source of batch-to-batch variations.

Application of Multivariate Strategies to the Classification of Pharmaceutical Excipient Manufacturers Based on Near-Infrared (NIR) Spectra

Using partial least square discriminate analysis (PLSDA), we studied the spectroscopic differences between the commonly used filler-binder microcrystalline cellulose (MCC) from five manufactures. These samples had subtle differences in the chemical and physical properties, which are often the cause of differences in excipient performance. Studying these differences allowed us to build and validate a model to classify five manufacturers of MCC using near-infrared (NIR) spectra. The sample training set includes 39 MCC samples collected from five manufactures with regions spanning the United States of America, Japan, Taiwan, Germany, and Brazil. The samples from individual manufacturers include diverse grades that differ in moisture content, particle size, and bulk density. Optimized pretreatment methods were identified as standard normal variate normalization, followed by Savitzky-Golay second derivative, mean centering, and orthogonal signal correction. The model was optimized with cross-validation and validated with an independent sample set comprising nine samples collected from those five manufacturers. The results showed that none of the samples in the independent validation set was misclassified. The score and loading plots revealed that the differences in content of oxidized cellulose group, water content and states, hydrogen bonding, and degree of polymerization of the MCC samples are responsible for the class differentiation. Permutation test demonstrated that the outcome of the PLSDA model was significantly different from that of the randomly generated model. The advantages and limitations of the method in this type of application were discussed.

Nanomechanical testing technique for millimeter-sized and smaller molecular crystals

Large crystals are used as a control for the development of a mounting and nanoindentation testing technique for millimeter-sized and smaller molecular crystals. Indentation techniques causing either only elastic or elastic-plastic deformation produce similar results in assessing elastic modulus, however, the elastic indents are susceptible to surface angle and roughness effects necessitating larger sample sizes for similar confidence bounds. Elastic-plastic indentations give the most accurate results and could be used to determine the different elastic constants for anisotropic materials by indenting different crystal faces, but not by rotating the indenter about its axis and indenting the same face in a different location. The hardness of small and large crystals is similar, suggesting that defect content probed in this study is similar, and that small crystals can be compared directly to larger ones. The Young's modulus and hardness of the model test material, griseofulvin, are given for the first time to be 11.5GPa and 0.4GPa respectively.

Water soluble polymer films for intravascular drug delivery of antithrombotic biomolecules

Over the past 10 years, the number of percutaneous coronary intervention (PCI) procedures performed in the United States has increased by 33%; however, restenosis, which inhibits complete functional recovery of the vessel wall, remains a complication of this procedure. To traverse the complications associated with PCI, the investigation of therapeutic delivery has become an integral topic in modern research. One such therapeutic, a mimic of the proteoglycan decorin, termed DS-SILY, can mask exposed collagen and thereby effectively decrease platelet activation, has recently been developed by our lab. Drawing inspiration from coating technologies developed by the pharmaceutical industry, a fast-dissolving polymer film has been developed to deliver active therapeutic agents from a balloon catheter during PCI. This research investigates the release of DS-SILY from fast-dissolving polymer films composed of poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG). Thin, uniform polymer films were produced via spin coating technique. The dissolution speed of the polymer films was found to be dependent on the concentration of polymer solution, where at least 65% of the films were shown to dissolve into nanometer sized polymer fragments within 2 min. DS-SILY, up to 6.26 μg/cm(2), was loaded into the films and functional release of the mimic was demonstrated by its successful binding to collagen upon release. Furthermore, DS-SILY released from films resulted in increased platelet inhibition. These results indicate that use of fast-dissolving polymer films allow for the successful release of biomolecules and further investigation of their use for localized drug delivery during PCI procedures is warranted.

Theophylline cocrystals prepared by spray drying: physicochemical properties and aerosolization performance

The purpose of this work was to characterize theophylline (THF) cocrystals prepared by spray drying in terms of the physicochemical properties and inhalation performance when aerosolized from a dry powder inhaler. Cocrystals of theophylline with urea (THF-URE), saccharin (THF-SAC) and nicotinamide (THF-NIC) were prepared by spray drying. Milled THF and THF-SAC cocrystals were also used for comparison. The physical purity, particle size, particle morphology and surface energy of the materials were determined. The in vitro aerosol performance of the spray-dried cocrystals, drug-alone and a drug-carrier aerosol, was assessed. The spray-dried particles had different size distributions, morphologies and surface energies. The milled samples had higher surface energy than those prepared by spray drying. Good agreement was observed between multi-stage liquid impinger and next-generation impactor in terms of assessing spray-dried THF particles. The fine particle fractions of both formulations were similar for THF, but drug-alone formulations outperformed drug-carrier formulations for the THF cocrystals. The aerosolization performance of different THF cocrystals was within the following rank order as obtained from both drug-alone and drug-carrier formulations: THF-NIC>THF-URE>THF-SAC. It was proposed that micromeritic properties dominate over particle surface energy in terms of determining the aerosol performance of THF cocrystals. Spray drying could be a potential technique for preparing cocrystals with modified physical properties.