Sample Size Requirements of a Pharmaceutical Material Library: A Case in Predicting Direct Compression Tablet Tensile Strength by Latent Variable Modeling

The material library is an emerging, new data-driven approach for developing pharmaceutical process models. How many materials or samples should be involved in a particular application scenario is unclear, and the impact of sample size on process modeling is worth discussing. In this work, the direct compression process was taken as the research object, and the effects of different sample sizes of material libraries on partial least squares (PLS) modeling in the prediction of tablet tensile strength were investigated. A primary material library comprising 45 materials was built. Then, material subsets containing 5 × i (i = 1, 2, 3, …, 8) materials were sampled from the primary material library. Each subset underwent sampling 1000 times to analyze variations in model fitting performance. Both hierarchical sampling and random sampling were employed and compared, with hierarchical sampling implemented with the help of the tabletability classification index d. For each subset, modeling data were organized, incorporating 18 physical properties and tableting pressure as the independent variables and tablet tensile strength as the dependent variable. A series of chemometric indicators was used to assess model performance and find important materials for model training. It was found that the minimum R2 and RMSE values reached their maximum, and the corresponding values were kept almost unchanged when the sample sizes varied from 20 to 45. When the sample size was smaller than 15, the hierarchical sampling method was more reliable in avoiding low-quality few-shot PLS models than the random sampling method. Two important materials were identified as useful for building an initial material library. Overall, this work demonstrated that as the number of materials increased, the model's reliability improved. It also highlighted the potential for effective few-shot modeling on a small material library by controlling its information richness.

Elucidating the Impact of Material Properties on Tablet Manufacturability for Binary Paracetamol Blends

PURPOSE

Although the mechanical properties of paracetamol and MCC are extensively described in literature, there still is a need for a better understanding of the material properties impacting them. Thus, this study systematically analyzed material properties of paracetamol-MCC blends to elucidate their influence on the mechanical tablet properties in roller compaction and direct compression with special focus on surface properties.

METHODS

Multiple material characteristics of binary mixtures of paracetamol and MCC with varying drug loads were analyzed, with particular emphasis on specific surface area and surface energy. Subsequently, mechanical tablet properties of the materials in direct compression and after roller compaction were examined.

RESULTS

It was demonstrated that the impact of the initial material properties on mechanical tablet properties prevailed over the impact of processing route for paracetamol-MCC blends, underlining the importance of material characterization for tabletability of oral solid dosage forms. By applying bivariate as well as multivariate analysis, key material properties influencing the tabletability of paracetamol, MCC and its mixtures such as surface area, surface energy, effective angle of internal friction and density descriptors were identified.

CONCLUSIONS

This study highlighted the importance of comprehensive assessment of different material characteristics leading to a deeper understanding of underlying factors impacting mechanical tablet properties in direct compression and after roller compaction by the example of paracetamol-MCC mixtures with varying drug loads. Furthermore, it was shown that multivariate analysis could be a valuable extension to common bivariate analysis to reveal underlying correlations of material properties.

Investigations on Compaction Behavior of Kollidon®SR-Based Multi-component Directly Compressed Tablets for Preparation of Controlled Release Diclofenac Sodium

The physics of tablets mixtures has gained much attention lately. The purpose of this work is to evaluate the compaction properties of Kollidon® SR (KSR) in the presence of different excipients such as Microcrystalline cellulose (MCC), Monohydrous lactose (MH Lactose), Poly (vinyl acetate) (PVA100), and a water-soluble drug Diclofenac sodium (DNa) to prepare once daily formulation. Tablets were prepared using direct compression and were compressed into flat-faced tablets using hydraulic press at various pressures. The combination of MCC and KSR in the tablets showed reduced porosity, and almost constant low Py values as KSR levels increased; also, KSR-DNa tablets had higher percentage porosity and crushing strength values than KSR-MH Lactose tablets. The crushing strengths of KSR-MCC tablets were larger than those of KSR-DNa tablets. Ternary mixture tablets comprised of KSR-MCC-DNa showed decreased porosities and low Py values as the percentage of KSR increased especially at high compression pressures but had higher crushing strengths compared to KSR-DNa or MCC-DNa binary tablets. KSR-MH Lactose-DNa ternary tablets experienced lower porosities and crushing strengths compared to KSR-MCC-DNa tablets. Quaternary tablets of KSR-PVA100-MCC-DNa showed lower porosity and Py values than quaternary tablets obtained using similar proportion of MH Lactose instead of MCC. In conclusion, optimum quaternary tablets were obtained with optimum crushing strengths, relatively low Py, and moderate percentage porosities among all prepared quaternary tablets. The drug release of the optimum quaternary tablets demonstrated similar in vitro release profile compared to that of the marketed product with a mechanism of release that follows Korsmeyer-Peppas model.

Comparative Evaluation of the Powder and Tableting Properties of Regular and Direct Compression Hypromellose from Different Vendors

Hypromellose, a widely used polymer in the pharmaceutical industry, is available in several grades, depending on the percentage of substitution of the methoxyl and hydroxypropyl groups and molecular weight, and in various functional forms (e.g., suitable for direct compression tableting). These differences can affect their physicomechanical properties, and so this study aims to characterise the particle size and mechanical properties of HPMC K100M polymer grades from four different vendors. Eight polymers (CR and DC grades) were analysed using scanning electron microscopy (SEM) and light microscopy automated image analysis particle characterisation to examine the powder's particle morphology and particle size distribution. Bulk density, tapped density, and true density of the materials were also analysed. Flow was determined using a shear cell tester. Flat-faced polymer compacts were made at five different compression forces and the mechanical properties of the compacts were evaluated to give an indication of the powder's capacity to form a tablet with desirable strength under specific pressures. The results indicated that the CR grades of the polymers displayed a smaller particle size and better mechanical properties compared to the DC grade HPMC K100M polymers. The DC grades, however, had better flow properties than their CR counterparts. The results also suggested some similarities and differences between some of the polymers from the different vendors despite the similarity in substitution level, reminding the user that care and consideration should be given when substitution is required.

High-Speed Tableting of High Drug-Loaded Tablets Prepared from Fluid-Bed Granulated Isoniazid

The aim of this feasibility study was to investigate the possibility of producing industrial-scale relevant, robust, high drug-loaded (90.9%, w/w) 100 mg dose immediate-release tablets of isoniazid and simultaneously meet the biowaiver requirements. With an understanding of the real-life constrictions on formulation scientists during product development for the generic industry, this study was done considering a common set of excipients and manufacturing operations, as well as paying special attention to the industrial-scale high-speed tableting process as one of the most critical manufacturing operations. The isoniazid substance was not applicable for the direct compression method. Thus, the selection of granulation method was logically justified, and it was fluid-bed granulated with an aqueous solution of Kollidon^® 25, mixed with excipients, and tableted with a rotary tablet press (Korsch XL 100) at 80 rpm (80% of the maximum speed) in the compaction pressure range 170-549 MPa monitoring of ejection/removal forces, tablet weight uniformity, thickness, and hardness. Adjusting the main compression force, the Heckel plot, manufacturability, tabletability, compactability, and compressibility profiles were analysed to choose the main compression force that resulted in the desirable tensile strength, friability, disintegration, and dissolution profile. The study showed that highly robust drug-loaded isoniazid tablets with biowaiver requirements compliance can be prepared with a common set of excipients and manufacturing equipment/operations incl. the industrial-scale high-speed tableting process.

API co-crystals - Trends in CMC-related aspects of pharmaceutical development beyond solubility

Whereas pharmaceutical co-crystals are widely described as tool to improve solubility and dissolution behavior of poorly soluble drugs, so far less focus has been on their potential role to facilitate pharmaceutical manufacturability. This review summarizes recent developments in co-crystal research regarding new trends in co-crystal preparation routes and control of solid-state material attributes. Also, recent literature was reviewed to assess risks for co-crystals in formulation processes. A growing number of publications suggest that co-crystals show potential to specifically improve mechanical properties such as tabletability and compressibility, which can often be linked to intrinsic features of crystal structure properties. However, such trends must be treated with care, as molecular structures in reported co-crystal studies are not representative in some structural parameters governing also solid-state behavior (smaller molecular weight, more balanced hydrogen bond donor versus acceptor counts) compared to recent market approved small molecule drugs.

Improving the Manufacturability of Cohesive and Poorly Compactable API for Direct Compression of Mini-tablets at High Drug Loading via Particle Engineering

PURPOSE

To utilize a particle engineering strategy to improve the manufacturability of a cohesive and poorly compactable API at high drug loading for direct compression of mini-tablets.

METHODS

A high-shear mixer was used for wet milling during the API manufacturing process to obtain target particle size distributions. The targeted particles were characterized and formulated into blends by mixing with excipients. The formulated blends were compressed directly into mini-tablets using a compaction simulator. The tablet hardness, weight variation, and friability of the mini-tablets were characterized and compared with mini-tablets prepared with hammer milled APIs.

RESULTS

Compared to the hammer milled APIs, the wet milled APIs, had smoother surface, narrower particle size distributions and demonstrated a better flow properties. Moreover, the mini-tablets produced with the wet milled APIs exhibited better weight uniformity, robust tablet mechanical strength and ultimately better friability. In addition, unlike the hammer milled process, the wet milling process is controllable and easy to scale up.

CONCLUSIONS

This study successfully implemented API particle engineering through a high shear wet milling process to produce particles suitable for robust drug product manufacturing.

Influence of Roll Speed during Roll Compaction and Its Effect on the Prediction of Ribbon Solid Fraction

Influence of the roll speed (RS) during roll compaction on ribbon, granule, tablet properties and its effect on the prediction of the ribbon solid fraction at-gap is often neglected or controversially discussed. The aim of this study was to investigate the effect of the RS systematically. Microcrystalline cellulose (MCC) and lactose were compressed at several maximum roll pressures (Pmax) and RS combinations using a gap-controlled roll compactor. The ribbon solid fraction after elastic recovery (SFribbon), granule size distribution and tabletability of the granules as well as the ribbon solid fraction at-gap (SFgap) were measured. The Midoux number (Mi), derived from the Johanson model, was used to predict the ribbon solid fraction at-gap (SFMi). The measured SFgap and the predicted SFMi lead to a prediction accuracy (PA) of the Midoux number. The results are highly dependent on the material used and the applied Pmax. Higher plasticity of the material leads to a reduction in SFribbon and granule size with increasing RS. However, this effect can be overcome or reduced by adjusting Pmax above the yield pressure of the used material. These results allow for higher roll speeds as a potential upscaling method in roll compaction. On the other side, the PA of the Midoux number was also reduced with increased RS for MCC and had no effect for lactose. Thus, RS seems to be an important factor in the prediction of roll compaction processes and prediction models should include RS as a parameter to improve their accuracy.

Understanding the Multidimensional Effects of Polymorphism, Particle Size and Processing for D-Mannitol Powders

The relevance of the polymorphic form, particle size, and processing of mannitol for the mechanical properties of solid oral dosage forms was examined. Thus, particle and powder properties of spray granulated β D-mannitol, β D-mannitol, and δ D-mannitol were assessed in this study with regards to their manufacturability. D-mannitol is a commonly used excipient in pharmaceutical formulations, especially in oral solid dosage forms, and can be crystallized as three polymorphic forms, of which β is the thermodynamically most stable form and δ is a kinetically stabilized polymorph. A systematic analysis of the powders as starting materials and their respective roller compacted granules is presented to elucidate the multidimensional effects of powder and granules characteristics such as polymorphic form, particle size, and preprocessing on the resulting tablets’ mechanical properties. In direct compression and after roller compaction, δ polymorph displayed superior tableting properties over β mannitol, but was outperformed by spray granulated β mannitol. This could be primarily correlated to the higher specific surface area, leading to higher bonding area and more interparticle bonds within the tablet. Hence, it was shown that surface characteristics and preprocessing can prevail over the impact of polymorphism on manufacturability for oral solid dosage forms.

A novel soluble lornoxicam-sodium chelate monohydrate with improved plasticity and tabletability

Lornoxicam (LOR), a BCS Ⅱ nonsteroidal anti-inflammatory drug, has been clinically utilized for moderate to severe acute pain management. However, it has poor water solubility and insufficient tabletability, leading to erratic absorption and challenge in tablet processability. This study reported a novel solid state of LOR (i.e., LOR sodium chelate monohydrate, LOR-Na·H₂O) with significantly improved solubility, dissolution rate and tabletability. The prepared chelate (CCDC No.: 2125157) contains LOR^-, Na⁺, and H₂O in a molar ratio of 1:1:1, where Na⁺ ions bridged with O(5) of amide group, and N(2) of pyridine group on LOR^-, as well as O(4) on H₂O through coordination bonds. LOR-Na·H₂O displayed a superior dissolution rate (5∼465 folds) than commercial LOR due to its increased wettability (contact angle: 74.5° vs 85.6°) and lower solvation free energy (∼2-fold). In addition, the significant improvement in tabletability was caused by high plasticity and deformability, which was attributed to its special interlayer gliding with weak bonding interactions across layers but strong coordination bonding interactions within layers. The novel LOR-Na·H₂O with significantly enhanced pharmaceutical performance offers a promising strategy for further product development.

An extended macroindentation method for determining the hardness of poorly compressible materials

Indentation hardness, H, is an important mechanical property that quantifies the resistance to deformation by a material. For pharmaceutical powders, H can be determined using a macroindentation method, provided they can form intact tablets suitable for testing. This work demonstrates a method for determining the hardness of problematic materials that cannot form suitable tablets for macroindentation. The method entails predicting the hardness of a given powder at zero porosity (H₀) from those of microcrystalline cellulose and its binary mixture with the test compound using a power law mixing rule based on weight fraction. This method was found suitable for 13 binary mixtures. In addition, the H₀ values derived by this method could capture changes due to different particle sizes of sucrose and sodium chloride. Furthermore, the derived H₀ reasonably agreed with the single crystal indentation hardness of a set of 16 crystals when accounting for the effect of indentation condition and structural anisotropy. The mixture method thus extends the use of macroindentation for predicting indentation hardness of powders that cannot form intact tablets and, hence, their plasticity.

Improvements on multiple direct compaction properties of three powders prepared from Puerariae Lobatae Radix using surface and texture modification: comparison of microcrystalline cellulose and two nano-silicas

It has been reported that hydrophilic nano-silica (N) markedly improved direct compaction (DC) properties of Zingiberis Rhizoma alcoholic extract. This study aims to examine the broader scope and generality of the previous work by investigating (i) three powders, i.e., the directly pulverized product, ethanol extract, and water extract prepared from the same medicinal herb-Puerariae Lobatae Radix (named DP, EE, and WE) and (ii) the effects on their DC properties of co-processing with N, hydrophobic nano-silica (BN), or microcrystalline cellulose (C). Unexpectedly, C provided the best improvement on tabletability for WE, while N for both DP and EE. More importantly, only N could move all parent powders to a regime suitable for DC, and BN rather than C enabled parent WE to be directly compressed. Typically, 6/9 N-modified powders simultaneously met the requirements of DC on bulk density, flowability, and tablet tensile strength (σ_t). Principal component analysis indicated that DC properties were mainly governed by flowability and texture properties. The partial least-squares regression model revealed that flowability, texture parameters, and deformation behavior of powders were dominating factors impacting tablet σ_t and solid fraction. Overall, the findings are promising for the manufacture of high drug loading tablets of herbs by DC.

The Effect of Process Variables and Binder Concentration on Tabletability of Metformin Hydrochloride and Acetaminophen Granules Produced by Twin Screw Melt Granulation with Different Polymeric Binders

In twin screw melt granulation, granules are produced by passing mixtures of drug substances and polymeric binders through twin screw extruder such that temperatures are maintained below melting point of drugs but above glass transition of polymers used, whereby the polymers coat surfaces of drug particles and cause their agglomeration into granules. Since various formulation factors, such as binder type and concentration, and processing variables like extrusion temperature, screw configuration, and screw speed, can influence the granulation process, the present investigation was undertaken to study their effects on tabletability of granules produced. Three different types of polymeric binders, Klucel® EXF (hydroxypropyl cellulose), Eudragit® EPO (polyacrylate binder), and Soluplus® (polyvinyl caprolactam-co-vinyl acetate-ethylene glycol graft polymer), were used at 2, 5, and 10% concentrations. Metformin hydrochloride (HCl) (mp: 222°C) and acetaminophen (mp: 169°C) were used as model drugs, and drug-polymer mixtures with metformin HCl were extruded at 180, 160, and 130°C, while those with acetaminophen were extruded at 130 and 110°C. Other process variables included screw configurations: low, medium, and high shear for metformin HCl, and low and medium shear for acetaminophen; feed rates: 20 and 60 g/min; and screw speed of 100 and 300 RPM. Formulation and process variables had significant impact on tabletability. The target tensile strength of ≥2 MPa could be obtained with all polymers and at all processing temperatures when metformin HCl was granulated at 180°C and acetaminophen at 130°C. At other temperatures, the target tensile strength could be achieved at certain specific sets of processing conditions.

Amelioration of physicochemical, pharmaceutical, and pharmacokinetic properties of lornoxicam by cocrystallization with a novel coformer

OBJECTIVE

The present study was aimed to prepare and characterize new cocrystals of lornoxicam (LORX), a BCS class II drug employing 1,3-dimethyl urea (DMU) as a coformer to improve physicochemical, pharmaceutical, and pharmacokinetic performance.

METHODS

A screening study was conducted by employing three techniques viz. neat grinding, liquid-assisted grinding (LAG), and solvent evaporation (SE) using different drug-coformer molar ratios (1:1, 1:2, and 1:3). Samples were characterized by DSC, PXRD, ATR-FTIR, SEM, intrinsic dissolution rate (IDR) studies, compressional studies, and pharmacokinetic studies. In vitro dissolution and stability studies (25 °C/60%RH and 40 °C/75%RH for three months) were carried out for cocrystal tablets.

RESULTS

LAG and SE were found successful in ratio 1:3 and IDR showed approximately 28- and 19-fold increase, respectively in 0.1 N HCl (pH 1.2) and buffer (pH 7.4) as compared to pure LORX. The cocrystal exhibited good tabletability and was ∼2.5 times that of LORX at 6000 Psi. Dissolution profiles of tablets of cocrystal increased (56% and 100% at pH 1.2 and 7.4, respectively in contrast to those of physical mixture (PhyMix) (∼35% and ∼10%) and pure LORX (∼17% and ∼7%) within 60 min. The C_max and AUC_0-∞ for the selected cocrystal were significantly increased (p < 0.05) which was 2.4 and 2.5 times, respectively, that of LORX in a single dose oral pharmacokinetic study executed in rabbits. Tablets of cocrystal were found stable at both conditions.

CONCLUSION

The study indicates that cocrystallization with DMU can concomitantly improve tabletability, dissolution rate, and in vivo performance of dissolution limited drug LORX.

Evaluation of Binders in Twin-Screw Wet Granulation

The binders povidone (Kollidon 30), copovidone (Kollidon VA64), hypromellose (Pharmacoat 606), and three types of hyprolose (HPC SSL‑SFP, HPC SSL, and HPC SL‑FP) were evaluated regarding their suitability in twin-screw wet granulation. Six mixtures of lactose and binder as well as lactose without binder were twin-screw granulated with demineralized water at different barrel fill levels and subsequently tableted. A screening run with HPC SSL determined the amount of water as an influential parameter for oversized agglomerates. Subsequent examination of different binders, especially Kollidon 30 and Kollidon VA64 resulted in large granules. All binders, except Pharmacoat 606, led to a reduction of fines compared to granulation without a binder. The molecular weight of applied hyproloses did not appear as influential. Tableting required an upstream sieving step to remove overlarge granules. Tableting was possible for all formulations at sufficient compression pressure. Most binders resulted in comparable tensile strengths, while Pharmacoat 606 led to lower and lactose without a binder to the lowest tensile strength. Tablets without a binder disintegrated easily, whereas binder containing tablets of sufficient tensile strength often nearly failed or failed the disintegration test. Especially tablets containing Pharmacoat 606 and HPC SL‑FP disintegrated too slowly.

It is Possible to Achieve Tablets With Good Tabletability From Solid Dispersions - The Case of the High Dose Drug Gemfibrozil

BACKGROUND

Solid Dispersions (SDs) have been extensively used to increase the dissolution of poorly water-soluble drugs. However, there are few studies exploring SDs properties that must be considered during tablet development, like tabletability. Poorly water-soluble drugs with poor compression properties and high therapeutic doses, like gemfibrozil, are an additional challenge in the production of SDs-based tablets.

OBJECTIVE

This study evaluates the applicability of SDs to improve both tabletability and dissolution rate of gemfibrozil. A SD-based tablet formulation was also proposed.

METHODS

SDs were prepared by ball milling, using hydroxypropyl methylcellulose (HPMC) as a carrier, according to a 2³ factorial design. The formulation variables were gemfibrozil:HPMC ratio, milling speed, and milling time. The response in the factorial analysis was the tensile strength of the compacted SDs. Dissolution rate and solid-state characterization of SDs were also performed.

RESULTS

SDs showed simultaneous drug dissolution enhancement and improved tabletability when compared to corresponding physical mixtures and gemfibrozil. The main variable influencing drug dissolution and tabletability was the gemfibrozil:HPMC ratio. Tablets containing gemfibrozil- HPMC-SD (1:0.250 w/w) and croscarmellose sodium showed fast and complete drug release, while those containing the same SD and sodium starch glycolate exhibited poor drug release due to their prolonged disintegration time.

CONCLUSION

SDs proved to be effective for simultaneously improving tabletability and dissolution profile of gemfibrozil. Tablets containing gemfibrozil-HPMC-SD and croscarmellose sodium as disintegrating agent showed improved drug release and good mechanical strength, demonstrating the potential of HPMC-based SDs to simultaneously overcome the poor dissolution and tabletability properties of this drug.

Employing Multivariate Statistics and Latent Variable Models to Identify and Quantify Complex Relationships in Typical Compression Studies

The effect of storage condition (% RH) on flufenamic acid:nicotinamide (FFA:NIC) cocrystal compressibility, compactibility, and tabletability profiles was not observed after visual evaluation or linear regression analysis. However, multivariate statistical analysis showed that storage condition had a significant effect on each compressional profile. Shapiro and Heckel equations were used to determine the compression parameters: porosity, Shapiro's compression parameter (f), densification factor (Da), plastic yield pressure (YPpl), and elastic yield pressure (YPel). Latent variable models such as exploratory factor analysis, principal component analysis, and principal component regression were employed to decode complex hidden main, interaction, and quadratic effects of % RH and the compression parameters on FFA:NIC tablet mechanical strength (TMS). Statistically significant correlations between f and Da, f and YPpl, and Da and YPel supported the idea that both rearrangement and fragmentation, and plastic deformation are important to FFA:NIC TMS. To the authors knowledge, this is the first time that simultaneously operating dual mechanisms of fragmentation and plastic deformation in low and midrange compression, and midrange plastic deformation have been identified and reported. A quantitative PCR model showed that f, Da, and YPel had statistically significant main effects along with a significant antagonist storage condition-porosity "conditional interaction effect". f exhibited a 2.35 times greater impact on TMS compared to Da. The model root-mean-square error at calibration and prediction stages were 0.04 MPa and 0.08 MPa, respectively. The R² values at the calibration stage and at the prediction stage were 0.9005 and 0.7539, respectively. This research demonstrated the need for caution when interpreting the results of bivariate compression data because complex latent inter-relationships may be hidden from visual assessment and linear regression analysis, and result in false data interpretation as illustrated in this report.

The Role of Cocrystallization-Mediated Altered Crystallographic Properties on the Tabletability of Rivaroxaban and Malonic Acid

The present work aims to understand the crystallographic basis of the mechanical behavior of rivaroxaban-malonic acid cocrystal (RIV-MAL Co) in comparison to its parent constituents, i.e., rivaroxaban (RIV) and malonic acid (MAL). The mechanical behavior was evaluated at the bulk level by performing “out of die” bulk compaction and at the particle level by nanoindentation. The tabletability order for the three solids was MAL < RIV < RIV-MAL Co. MAL demonstrated “lower” tabletability because of its lower plasticity, despite it having reasonably good bonding strength (BS). The absence of a slip plane and “intermediate” BS contributed to this behavior. The “intermediate” tabletability of RIV was primarily attributed to the differential surface topologies of the slip planes. The presence of a primary slip plane (0 1 1) with flat-layered topology can favor the plastic deformation of RIV, whereas the corrugated topology of secondary slip planes (1 0 2) could adversely affect the plasticity. In addition, the higher elastic recovery of RIV crystal also contributed to its tabletability. The significantly “higher” tabletability of RIV-MAL Co among the three molecular solids was the result of its higher plasticity and BS. Flat-layered topology slip across the (0 0 1) plane, the higher degree of intermolecular interactions, and the larger separation between adjacent crystallographic layers contributed to improved mechanical behavior of RIV-MAL Co. Interestingly, a particle level deformation parameter H/E (i.e., ratio of mechanical hardness H to elastic modulus E) was found to inversely correlate with a bulk level deformation parameter σ₀ (i.e., tensile strength at zero porosity). The present study highlighted the role of cocrystal crystallographic properties in improving the tabletability of materials.

Molecular Interpretation of the Compaction Performance and Mechanical Properties of Caffeine Cocrystals: A Polymorphic Study

The 1:1 caffeine (CAF) and 3-nitrobenzoic acid (NBA) cocrystal (CAF:NBA) displays polymorphism. Each polymorph shares the same docking synthon that connects individual CAF and NBA molecules within the asymmetric unit; however, the extended intermolecular interactions are significantly different between the two polymorphic modifications. These alternative interaction topologies translate to distinct structural motifs, mechanical properties, and compaction performance. To assist our molecular interpretation of the structure-mechanics-performance relationships for these cocrystal polymorphs, we combine powder Brillouin light scattering (p-BLS) to determine the mechanical properties with energy frameworks calculations to identify potentially available slip systems that may facilitate plastic deformation. The previously reported Form 1 for CAF:NBA adopts a 2D-layered crystal structure with a conventional 3.4 Å layer-to-layer separation distance. For Form 2, a columnar structure of 1D-tapes is displayed with CAF:NBA dimers running parallel to the (110) crystallographic direction. Consistent with the layered crystal structure, the shear modulus for Form 1 is significantly reduced relative to Form 2, and moreover, our p-BLS spectra for Form 1 clearly display the presence of low-velocity shear modes, which support the expectation of a low-energy slip system available for facile plastic deformation. Our energy frameworks calculations confirm that Form 1 displays a favorable slip system for plastic deformation. Combining our experimental and computational data indicates that the structural organization in Form 1 of CAF:NBA improves the compressibility and plasticity of the material, and from our tabletability studies, each of these contributions confers superior tableting performance to that of Form 1. Overall, mechanical and energy framework data permit a clear interpretation of the functional performance of polymorphic solids. This could serve as a robust screening approach for early pharmaceutical solid form selection and development.

Polymer Nanocoating of Amorphous Drugs for Improving Stability, Dissolution, Powder Flow, and Tabletability: The Case of Chitosan-Coated Indomethacin

As a result of its higher molecular mobility, the surface of an amorphous drug can grow crystals much more rapidly than the bulk, causing poor stability and slow dissolution of drug products. We show that a nanocoating of chitosan (a pharmaceutically acceptable polymer) can be deposited on the surface of amorphous indomethacin by electrostatic deposition, leading to significant improvement of physical stability, wetting by aqueous media, dissolution rate, powder flow, and tabletability. The coating condition was chosen so that the positively charged polymer deposits on the negatively charged drug. Chitosan coating is superior to gelatin coating with respect to stability against crystallization and agglomeration of coated particles.

Aggregate Elasticity and Tabletability of Molecular Solids: a Validation and Application of Powder Brillouin Light Scattering

Describing the elastic deformation of single-crystal molecular solids under stress requires a comprehensive determination of the fourth-rank stiffness tensor (C_ijkl). Single crystals are, however, rarely utilized in industrial applications, and thus averaging techniques (e.g., the Voigt or Reuss approach) are employed to reduce the C_ijkl (or its inverse S_ijkl) to polycrystalline aggregate mechanical moduli. With increasing elastic anisotropy, the Voigt and Reuss-averaged aggregate moduli can diverge dramatically and, provided that drug molecules almost exclusively crystallize into low-symmetry space groups, warrants a significant need for accurate aggregate mechanical moduli. This elasticity data, which currently is largely absent for pharmaceutical materials, is expected to aid understanding how materials respond to direct compression and tablet formation. Powder Brillouin light scattering (p-BLS) has recently demonstrated facile access to porosity-independent, aggregate mechanical moduli. In this study, we extend our previous p-BLS model for obtaining mechanical properties and validate our approach against a broad library of molecular solids with diverse intermolecular interaction topologies and with previously determined C_ijkl which permits benchmarking our results. Our Young's and shear moduli determined with p-BLS strongly correlate, with limited bias (i.e., a near 1:1 relation), with the Voigt-averaged Young's and shear moduli determined using the C_ijkl. Through follow-on tabletability studies, we introduce initial classifications of tabletability behavior based on the results of our p-BLS studies and the apparent elastic anisotropy. With further development, this approach represents a robust and novel method to potentially identify materials for optimum tabletability at early developmental stages.

High-shear granulation of high-molecular weight hypromellose: effects of scale-up and process parameters on flow and compaction properties

CONTEXT

Knowledge of the effects of high-shear granulation process parameters and scale-up on the properties of the produced granules is essential for formulators who face challenges regarding poor flow and compaction during development of modified release tablets based on high-molecular weight hypromellose (hydroxypropylmethylcellulose (HPMC)) polymers. Almost none of the existing studies deal with realistic industrial formulation.

OBJECTIVE

The aim was to investigate the effects of scale-up and critical process parameters (CPPs) of high-shear granulation on the quality attributes of the granules, particularly in terms of the flow and compaction, using a realistic industrial formulation based on HPMC K100M polymer.

METHODS

The flow properties were determined using flow time, Carr index, tablet mass, and crushing strength variations. The compaction properties were quantified using the 'out-of-die' Heckel and modified Walker models, as well as the tensile strength profile and elastic recovery. High-shear granulation was performed at different scales: 4 L, 300 L, and 600 L.

RESULTS AND CONCLUSION

The scale itself had larger effects on the granule properties than the CPPs, which demonstrated high robustness of formulation on the individual scale level. Nevertheless, to achieve the desired flow and compaction, the values of the CPPs need to be precisely selected to fine-tune the process conditions. The best flow was achieved at high volumes of water addition, where larger and more spherical granules were obtained. The CPPs showed negligible influence on the compaction with no practical implications, however, the volume of water addition volume was identified as having the largest effects on compaction.

Development of paracetamol-caffeine co-crystals to improve compressional, formulation and in vivo performance

Paracetamol, a frequently used antipyretic and analgesic drug, has poor compression moldability owing to its low plasticity. In this study, new co-crystals of paracetamol (PCM) with caffeine (as a co-former) were prepared and delineated. Co-crystals exhibited improved compaction and mechanical behavior. A screening study was performed by utilizing a number of methods namely dry grinding, liquid assisted grinding (LAG), solvent evaporation (SE), and anti-solvent addition using various weight ratios of starting materials. LAG and SE were found successful in the screening study. Powders at 1:1 and 2:1 weight ratio of PCM/CAF by LAG and SE, respectively, resulted in the formation of co-crystals. Samples were characterized by PXRD, DSC, and ATR-FTIR techniques. Compressional properties of PCM and developed co-crystals were analyzed by in-die heckle model. Mean yield pressure (Py), an inverse measure of plasticity, obtained from the heckle plots decreased significantly (p < .05) for co-crystals than pure drug. Intrinsic dissolution profile of co-crystals showed up to 2.84-fold faster dissolution than PCM and physical mixtures in phosphate buffer pH 6.8 at 37 °C. In addition, co-crystals formulated into tablets by direct compression method showed better mechanical properties like hardness and tensile strength. In vitro dissolution studies on tablets also showed enhanced dissolution profiles (∼90-97%) in comparison to the tablets of PCM prepared by direct compression (∼55%) and wet granulation (∼85%) methods. In a single dose sheep model study, co-crystals showed up to twofold increase in AUC and C_max. A significant (p < .05) decrease in clearance as compared to pure drug was also recorded. In conclusion, new co-crystals of PCM were successfully prepared with improved tabletability in vitro and in vivo profile. Enhancement in AUC and C_max of PCM by co-crystallization might suggest the dose reduction and avoidance of side effects.

Evaluation of disintegrants functionality for orodispersible mini tablets

OBJECTIVE

This work evaluates the functionalities of different superdisintegrants (SD) for manufacturing orodispersible mini tablets (ODMT) by direct compression.

METHODS

Twenty-three formulations varying in SD type, concentration, and lubricant were used to manufacture ODMT. The ODMT were then characterized for the following properties: friability, porosity, tensile strength, in vivo and in vitro disintegration time (DT).

RESULTS

The results show that the presence, type, and concentration of SD did not influence friability, porosity, or tablet tensile strength. With regards to in vivo DT, only cross-linked poly (vinyl pyrrolidone) improved DT in all the tested formulations. Results also showed that when using microcrystalline cellulose (MCC) above 20% in the formulation, DT is longer. Cross-linked carboxymethyl cellulose accelerates DT when the MCC content is less than 20%. As for cross-linked carboxymethyl starch and calcium alginate showed no improvement on DT. Results for in vitro DT were all shorter than in vivo results and there was no correlation with the in vivo evaluation.

CONCLUSIONS

This study shows that there is a need to develop better in vitro testing that precisely simulates in vivo conditions and that are adapted to ODMT. This standardization of the test methods for ODMTs must be accompanied by an improvement in the comprehension of SD mechanisms.

Aggregate Elasticity, Crystal Structure, and Tableting Performance for p-Aminobenzoic Acid and a Series of Its Benzoate Esters

The tableting performance for p-aminobenzoic acid (PABA) and a series of its benzoate esters with increasing alkyl chain length (methyl-, ethyl-, and n-butyl) was determined over a broad range of compaction pressures. The crystalline structure of methyl benzoate (Me-PABA) exhibits no slip systems and does not form viable compacts under any compaction pressure. The ethyl (Et-PABA) and n-butyl (Bu-PABA) esters each have a similar, corrugated-layer structure that displays a prominent slip plane and improves material plasticity at low compaction pressure. The compact tensile strength for Et-PABA is superior to that for Bu-PABA; however, neither material achieved a tensile strength greater than 2 MPa over the compression range studied. Complementary studies with powder Brillouin light scattering (BLS) show the maxima of the shear wave, acoustic frequency distribution red shift in an order consistent with both the observed tabletability and attachment energy calculations. Moreover, zero-porosity aggregate elastic moduli are determined for each material using the average acoustic frequency obtained from specific characteristics of the powder BLS spectra. The Young's moduli for Et- and Bu-PABA is significantly reduced relative to PABA and Me-PABA, and this reduction is further evident in tablet compressibility plots. PABA, however, is distinct with high elastic isotropy as interpreted from the narrow and well-defined powder BLS frequency distributions for both the shear and compressional acoustic modes. The acoustic isotropy is consistent with the quasi-isotropic distribution of hydrogen bonding for PABA. At low compaction pressure, PABA tablets display the lowest tensile strength of the series; however, above a compaction pressure of ca. 70 MPa PABA tablet tensile strength continues to increase while that for Et- and Bu-PABA plateaus. PABA displays lower plasticity relative to either ester, and this is consistent with its crystalline structure and high yield pressure determined from in-die Heckel analysis. Overall the complementary approach of using both structural and the acoustic inputs uniquely provided from powder BLS is anticipated to expand our comprehension of the structure-mechanics relationship and its role in tableting performance.

Development of Solid SEDDS, IV: Effect of Adsorbed Lipid and Surfactant on Tableting Properties and Surface Structures of Different Silicates

PURPOSE

To compare six commonly available silicates for their suitability to develop tablets by adsorbing components of liquid lipid-based drug delivery systems.

METHODS

The tabletability of Aerosil® 200, Sipernat® 22, Sylysia® 350, Zeopharm® 600, Neusilin® US2 and Neusilin® UFL2 were studied by compressing each silicate into tablets in the presence of 20% microcrystalline cellulose and measuring the tensile strength of tablets produced. Three components of lipid based formulations, namely, Capmul® MCM EP (glycerol monocaprylocaprate), Captex® 355 EP/NF (caprylic/capric triglycerides) and Cremophor® EL (PEG-35 castor oil), were adsorbed individually onto the silicates at 1:1 w/w, and the mixtures were then compressed into tablets. The SEM photomicrographs of neat silicates and their 1:1 w/w mixtures (also 1:2 and 1:3 for Neusilin® US2 and Neusilin® UFL2) with one of the liquids (Cremophor® EL) were recorded.

RESULTS

Neat Aerosil® 200, Sipernat® 22 and Sylysia® 350 were non-tabletable to the minimum acceptable tensile strength of 1 MPa, and they were also non-tabletable in presence of liquid. While Zeopharm® 600, Neusilin® US2 and Neusilin® UFL2 were tabletable without the addition of liquids, only Neusilin® US2 retained acceptable tabletability with 1:1 liquid. The SEM images of silicate-liquid mixtures indicated that, except for Neusilin® US2, much of the adsorbed liquid distributed primarily at the surface of particles rather than inside pores, which hindered their compaction into tablets.

CONCLUSION

Among the six silicates studied, Neusilin® US2 was the only silicate able to produce tablets with acceptable tensile strength in presence of a lipid component at 1:1 w/w ratio due to the fact that the liquid was mostly adsorbed into the pores of the silicate rather than at the surface.