Cocrystalization and Simultaneous Agglomeration Using Hot Melt Extrusion

Comparison of mechanochemical methods in the synthesis of binaphthol-benzoquinone based cocrystals

Mechanochemical methods either under neat or liquid assisted conditions have proven to be successful in making cocrystals. In this paper we compare the outcome of cocrystallization using two different mechanochemical methods, ball milling (BM) and resonant acoustic mixing (RAM), with solution crystallization. Racemic binaphthol and benzoquinone based binary and ternary cocrystals were investigated by BM and RAM. Both mechanochemical methods were successful in making the binary and ternary cocrystals that have been observed in solid state and solution. It is shown that the type of mechanochemical force imparted to the sample is very different between BM and RAM and this in turn leads to different cocrystallization outcomes. Thus, different mechanochemical methods should not be treated as the same and care must be taken when choosing a mechanochemical method for a particular application.

Scalability of Pharmaceutical Co-Crystal Formation by Mechanochemistry in Batch

The development of mechanochemistry is considerably growing. Benign by design, this technology complies with several principles of green chemistry, contributing to the achievement of the United Nations Sustainable Development Goals (UN SDGs) and the European Green Deal objectives. Herein, we report the use of mechanochemical processes in batch to prepare kilogram-scale of the Active Pharmaceutical Ingredient (API): Ibuprofen-Nicotinamide (rac-IBP:NCT) co-crystal in an industrial eccentric vibration mill. This scenario shows a sustainable approach to the industrial up-scaling of pharmaceutical co-crystals by a solvent-free mechanochemical process in batch. The quantitative assessment of the greenness of the mechanochemical process against the Twelve Principles of Green Chemistry was performed using the DOZN 2.0 Green Chemistry Evaluator.

Melt Crystallization of Celecoxib-Carbamazepine Cocrystals with the Synchronized Release of Drugs

PURPOSE

The fixed-dose combination drug products have been increasingly used to treat some complex diseases. A cocrystal containing two therapeutic components, named as a drug-drug cocrystal, is an ideal solid form to formulate as a fixed-dose combination product. The aim of the study is to prepare celecoxib-carbamazepine (CEL-CBZ) cocrystals by melt crystallization to achieve the synchronized release of drugs.

METHOD

The crystal structure of the CEL-CBZ cocrystal was determined from the cocrystals harvested from melt by single crystal X-ray diffraction. The binary phase diagram and crystal growth kinetics of the CEL-CBZ cocrystal from melt were studied to optimize the process parameters of hot-melt extrusion for manufacturing large-scale cocrystals. The intrinsic dissolution rate studies were conducted to compare the dissolution profiles of drugs in the cocrystal and their individual forms.

RESULT

The CEL-CBZ cocrystal crystallized in the triclinic space group with one CEL and one CBZ molecule in the asymmetric unit. The crystallization of CEL-CBZ cocrystals were observed both in the supercooled liquid and glassy state. The formation of drug-drug cocrystals significantly alter the intrinsic dissolution rates of the parent drugs to favor the synchronized release.

CONCLUSION

Melt crystallization is an alternative, efficient and eco-friendly approach for preparing drug-drug cocrystals on a large scale. The synchronized drug release by drug-drug cocrystals can be used to modulate the release profiles of parent drugs in the fixed-dose combination products.

Application of resonant acoustic mixing in the synthesis of vitamin C-nicotinamide variable stoichiometry cocrystals

The use of resonant acoustic mixing (RAM) to synthesize variable stoichiometry cocrystals of nicotinamide and vitamin C was investigated. Liquid assisted RAM (LA-RAM) was used to generate two polymorphs, Form I and II, of the 1 : 1 cocrystal of nicotinamide and vitamin C at a 700 mg scale using ethanol and methanol respectively as the liquid additives. LA-RAM was used to scale up polymorphs I and II of the 1 : 1 cocrystal to 20 grams. Finally, LA-RAM used was to produce a high purity 3 : 1 cocrystal of nicotinamide and vitamin C when either methanol or ethanol was used as the liquid additive. LA-RAM is demonstrated to be a scalable, environmentally friendly, ball-free method to make variable stoichiometry cocrystals.

Co-crystal nanoarchitectonics as an emerging strategy in attenuating cancer: Fundamentals and applications

Cancer ranks as the second foremost cause of death in various corners of the globe. The clinical uses of assorted anticancer therapeutics have been limited owing to the poor physicochemical attributes, pharmacokinetic performance, and lethal toxicities. Various sorts of co-crystals or nano co-crystals or co-crystals-laden nanocarriers have presented great promise in targeting cancer via improved physicochemical attributes, pharmacokinetic performance, and reduced toxicities. These systems have also demonstrated the controlled cargo release and passive targeting via enhanced permeation and retention (EPR) effect. In addition, regional delivery of co-crystals via inhalation and transdermal route displayed remarkable potential in targeting lung and skin cancer effectively. However, more research is required on the use of co-crystals in cancer and their commercialization. The present review mainly emphasizes co-crystals as emerging avenues in the treatment of various cancers by modulating the physicochemical and pharmacokinetic attributes of approved anticancer therapeutics. The worth of co-crystals in cancer treatment, computational paths in the co-crystals screening, diverse experimental techniques of co-crystals fabrication, and sorts of co-crystals and their noteworthy applications in targeting cancer are also discussed. Besides, the game changer approaches like nano co-crystals and co-crystals-laden nanocarriers, and co-crystals in regional delivery in cancer are also explained with reported case studies. Furthermore, regulatory directives for pharmaceutical co-crystals and their scale-up, and challenges are also highlighted with concluding remarks and future initiatives. In essence, co-crystals and nano co-crystals emerge to be a promising strategy in overwhelming cancers through improving anticancer efficacy, safety, patient compliance, and reducing the cost.

Processing Poly (ethylene terephthalate) Waste into Functional Carbon Materials by Mechanochemical Extrusion

With the plastic pollution becoming worse, the upcycling of plastic waste into functional materials is a great challenge. Herein, a mechanochemical extrusion approach was developed for processing poly(ethylene terephthalate) (PET) waste into porous carbon materials. The essence of the cyclic extrusion approach lies in the solvent-free mixing of thermoplastic PET with pore-directing additive (e. g., silica or zinc chloride) at the molecular level. PET waste could be upcycled into functional carbon with high surface area (up to 1001 m²  g^-1 ), specific shapes, and preferred mechanical strength, after cyclic extrusion and carbonization. Moreover, metal species could be well dispersed onto porous carbons through solvent-free extrusion, different from traditional loading methods (impregnation method, deposition-precipitation method). In this manner, mechanochemical extrusion provides an alternative for upcycling plastic waste into value-added materials.

Crystal Engineering of Pharmaceutical Cocrystals in the Discovery and Development of Improved Drugs

The subject of crystal engineering started in the 1970s with the study of topochemical reactions in the solid state. A broad chemical definition of crystal engineering was published in 1989, and the supramolecular synthon concept was proposed in 1995 followed by heterosynthons and their potential applications for the design of pharmaceutical cocrystals in 2004. This review traces the development of supramolecular synthons as robust and recurring hydrogen bond patterns for the design and construction of supramolecular architectures, notably, pharmaceutical cocrystals beginning in the early 2000s to the present time. The ability of a cocrystal between an active pharmaceutical ingredient (API) and a pharmaceutically acceptable coformer to systematically tune the physicochemical properties of a drug (i.e., solubility, permeability, hydration, color, compaction, tableting, bioavailability) without changing its molecular structure is the hallmark of the pharmaceutical cocrystals platform, as a bridge between drug discovery and pharmaceutical development. With the design of cocrystals via heterosynthons and prototype case studies to improve drug solubility in place (2000-2015), the period between 2015 to the present time has witnessed the launch of several salt-cocrystal drugs with improved efficacy and high bioavailability. This review on the design, synthesis, and applications of pharmaceutical cocrystals to afford improved drug products and drug substances will interest researchers in crystal engineering, supramolecular chemistry, medicinal chemistry, process development, and pharmaceutical and materials sciences. The scale-up of drug cocrystals and salts using continuous manufacturing technologies provides high-value pharmaceuticals with economic and environmental benefits.

A molecularly enhanced proof of concept for targeting cocrystals at molecular scale in continuous pharmaceuticals cocrystallization

It is impossible to optimize a process for a target drug product with the desired profile without a proper understanding of the interplay among the material attributes, the process parameters, and the attributes of the drug product. There is a particular need to bridge the micro- and mesoscale events that occur during this process. Here, we propose а molecular engineering methodology for the continuous cocrystallization process, based on Raman spectra measured experimentally with a probe and from quantum mechanical calculations. Using molecular dynamics simulations, the theoretical Raman spectra were calculated from first principles for local mixture structures under an external shear force at various temperatures. A proof of concept is developed to build the process design space from the computed data. We show that the determined process design space provides valuable insight for optimizing the cocrystallization process at the nanoscale, where experimental measurements are difficult and/or inapplicable. The results suggest that our method may be used to target cocrystallization processes at the molecular scale for improved pharmaceutical synthesis.

Combination of co-crystal and nanocrystal techniques to improve the solubility and dissolution rate of poorly soluble drugs

Purpose

Solubility and dissolution rate are essential for the oral absorption and bioavailability of poorly soluble drugs. The aim of this study was to prepare nano-co-crystals by combination of nanocrystal and co-crystal technologies, and investigate its effect, in situ, on increased kinetic solubility and dissolution rate.

Methods

Co-crystals of itraconazole-fumaric acid, itraconazole-succinic acid, indomethacin-saccharin and indomethacin-nicotinamide were prepared and nano-sized by wet milling. The particle size and solid state of the co-crystals were characterized by optical microscope, LD, PCS, DSC and XRPD before and after milling.

Results

300-450 nm sized nano-co-crystals with a stable physical solid state were successfully prepared. Nano-co-crystals exhibited a lower crystallinity reduction than nanocrystals after wet milling. The particle size effect on the kinetic solubility of co-crystals was analysed for macro-, micro- and nano-co-crystals with in situ kinetic solubility studies. The maximum kinetic solubility of nano-co-crystals increased with excess conditions until a plateau. The highest increase was obtained with itraconazole-succinic acid nano-co-crystals with a kinetic solubility of 263.5 ± 3.9 μg/mL which was 51.5 and 6.6 times higher than the solubility of raw itraconazole and itraconazole-succinic acid co-crystal.

Conclusions

The synergistic effect of nanocrystals and co-crystals with regard to increased kinetic solubility and dissolution rate was proven. The combination of the advantages of nanocrystals and co-crystals is a promising formulation strategy to increase both the solubility and dissolution rate of poorly soluble drugs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-022-03243-9.

Creation of Hydrochlorothiazide Pharmaceutical Cocrystals Via Hot-Melt Extrusion for Enhanced Solubility and Permeability

Crystal engineering is an emerging tool for altering the physicochemical properties of drug candidates. The objective of the current investigation was to develop cocrystals of hydrochlorothiazide (HCT) with coformers such as nicotinamide (NIC), resorcinol (RSL), and catechol (CAT) using hot-melt extrusion (HME) technology. The liquid-assisted grinding (LAG) method was used to prepare cocrystals by grinding the drug and coformer in a definite molar ratio as a reference and to check the feasibility of cocrystal formation. Cocrystals were prepared using HME and evaluated with differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffractometry, and scanning electron microscopy and compared with LAG cocrystals. Barrel temperature was the critical process parameter for producing high-quality cocrystals in HME. All cocrystals exhibited improved solubility compared to the native drug, and HCT-NIC cocrystals showed a two-fold increase in solubility. Similarly, HCT-RSL and HCT-CAT showed higher solubility profiles and improved diffusion/permeability characteristics compared to that of the pure HCT due to the drug-coformer interactions in the cocrystals. In this study, the solubility of the coformer was the key factor determining cocrystal solubilization. However, hot-melt extrusion is an alternative technology for creating pharmaceutical cocrystals and has potential for industrial scale-up.

Two Novel Palbociclib-Resorcinol and Palbociclib-Orcinol Cocrystals with Enhanced Solubility and Dissolution Rate

Palbociclib (PAL) is an effective anti-breast cancer drug, but its use has been partly restricted due to poor bioavailability (resulting from extremely low water solubility) and serious adverse reactions. In this study, two cocrystals of PAL with resorcinol (RES) or orcinol (ORC) were prepared by evaporation crystallization to enhance their solubility. The cocrystals were characterized by single crystal X-ray diffraction, Hirshfeld surface analysis, powder X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared and scanning electron microscopy. The intrinsic dissolution rates of the PAL cocrystals were determined in three different dissolution media (pH 1.0, pH 4.5 and pH 6.8), and both cocrystals showed improved dissolution rates at pH 1.0 and pH 6.8 in comparison to the parent drug. In addition, the cocrystals increased the solubility of PAL at pH 6.8 by 2-3 times and showed good stabilities in both the accelerated stability testing and stress testing. The PAL-RES cocrystal also exhibited an improved relative bioavailability (1.24 times) than PAL in vivo pharmacokinetics in rats. Moreover, the in vitro cytotoxicity assay of PAL-RES showed an increased IC50 value for normal cells, suggesting a better biosafety profile than PAL. Co-crystallization may represent a promising strategy for improving the physicochemical properties of PAL with better pharmacokinetics.

Recent Advances in Pharmaceutical Cocrystals: From Bench to Market

The pharmacokinetics profile of active pharmaceutical ingredients (APIs) in the solid pharmaceutical dosage forms is largely dependent on the solid-state characteristics of the chemicals to understand the physicochemical properties by particle size, size distribution, surface area, solubility, stability, porosity, thermal properties, etc. The formation of salts, solvates, and polymorphs are the conventional strategies for altering the solid characteristics of pharmaceutical compounds, but they have their own limitations. Cocrystallization approach was established as an alternative method for tuning the solubility, permeability, and processability of APIs by introducing another compatible molecule/s into the crystal structure without affecting its therapeutic efficacy to successfully develop the formulation with the desired pharmacokinetic profile. In the present review, we have grossly focused on cocrystallization, particularly at different stages of development, from design to production. Furthermore, we have also discussed regulatory guidelines for pharmaceutical industries and challenges associated with the design, development and production of pharmaceutical cocrystals with commercially available cocrystal-based products.

Dry Powder Mixing Is Feasible in Continuous Twin Screw Extruder: Towards Lean Extrusion Process for Oral Solid Dosage Manufacturing

Using discrete element method (DEM) modeling and near-infrared (NIR) spectroscopy, the feasibility of powder mixing in the initial pre-melting zones of a twin screw extruder using two independent feeders was studied. Previous work in the pharmaceutical and food industry has focused on mixing when materials are melted or on material homogeneity at the extruder's output. Depending on the formulation, ensuring a fully blended formulation prior to melting may be desired. Experiments were conducted using a Coperion ZSK-18 extruder to evaluate if blend uniformity can be achieved by exploring screw configuration, screw speed, and powder feed rate. As powder exited the extruder and deposited on a conveyor belt, an in-line NIR spectrophotometer measured spectra of material. Chemometric-based models predicted unknown concentrations to evaluate if blend uniformity was achieved. Using the EDEM software, Hertz-Mindlin contact model, and dimensions of the extruder, DEM simulations complemented the experimental work. The DEM computational models provided understanding of mixing patterns inside the extruder at particle scale and helped select the screw configuration before doing experimentation. The simulations showed good axial mixing for all the screw configurations studied, while good cross (radial) mixing was only observed for the screw configuration with 90-degree kneading elements. Therefore, the screw configuration with two 90-degree kneading elements was chosen for the experimental study. The RTD profiles when using a screw configuration with only conveying screw elements are comparable to a plug flow reactor (PFR), while the profiles when using kneading elements are more comparable to an ideal continuous stirred tank reactor (CSTR). For the screw configuration with 90 degrees kneading elements, the mean residence time (MRT) decreases with an increase in the screw speed. Experimental NIR spectra showed that concentrations can be predicted with an error of 2%. It was demonstrated that the twin screw extruder can provide proper dry powder mixing of two powder feed streams based on a unit dose scale, enabling continuous powder mixing prior to the melting zone in the extruder for the formulation studied with a cohesive API. This setup may also work for other types of formulations. These studies can help in developing lean hot melt as well as wet extrusion/granulation processes using twin screw extruders for the continuous manufacturing of oral solid dosage products.

Improving chemical stability of resveratrol in hot melt extrusion based on formation of eutectic with nicotinamide

Hot melt extrusion (HME) is a technique applied in the preparation of pharmaceutical amorphous solid dispersions (ASD). Notably it is important to prevent thermal degradation of heat-sensitive drugs during HME. In this study, we present a new strategy to improve chemical stability of pharmaceutical compounds during HME through the formation of eutectics with small molecules. Resveratrol (RES) was selected as the model compound because it is a heat-liable natural product with a very high melting point of 267 °C. When heated at its melting point for 3 min, it degrades by 40%. RES can co-crystallize with nicotinamide (NIC) in solution, however, it can only form a eutectic with NIC during heating. HPMCAS was selected as the polymer matrix and the drug loading of RES was fixed as 20% (weight ratio). The lowest extrusion temperature that can result to RES-HPMCAS ASD is 215 °C. At this temperature, RES shows 7.36% degradation during extrusion. Replacement of 21.4% HPMCAS with NIC decreased the melting temperature of NIC and thus lowered the minimal extrusion temperature to 155 °C. This effectively prevented thermal degradation of RES without negatively affecting non-sink dissolution. The only extra cost for this method is stricter storage conditions (low temperature and low humidity) due to the low glass transition temperature of NIC. Similar strategy may be applied to other heat-liable drugs in similar ways. This study demonstrates the use of eutectic formation for preventing thermal degradation of drug during extrusion of ASD.

Multicomponent crystalline solid forms of aripiprazole produced via hot melt extrusion techniques: An exploratory study

Multicomponent crystalline solid forms (salts, cocrystals and eutectics) are a promising means of enhancing the dissolution behavior of poorly soluble drugs. The present study demonstrates the development of multicomponent solid forms of aripiprazole (ARP) prepared with succinic acid (SA) and nicotinamide (NA) as coformers using the hot melt extrusion (HME) technique. The HME-processed samples were characterized and analyzed using differential scanning calorimetry (DSC), hot stage microscopy (HSM), Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). The DSC and HSM analyses revealed a characteristic single melting temperature in the solid forms, which differed from the melting points of the individual components. The discernible changes in the FTIR (amide C=O stretching) and PXRD results for ARP-SA confirm the formation of new crystalline solid forms. In the case of ARP-NA, these changes were less prominent, without the appearance or disappearance of peaks, suggesting no change in the crystal lattice. The SEM images demonstrated morphological differences between the HME-processed samples and the individual parent components. The in vitro dissolution and microenvironment pH measurement studies revealed that ARP-SA showed a higher dissolution rate, which could be due to the acidic microenvironment pH imparted by the coformer. The observations of the present study demonstrate the applicability of the HME technique for the development of ARP multicomponent solid forms.

In-line Raman spectroscopy and chemometrics for monitoring cocrystallisation using hot melt extrusion

The application of in-line Raman spectroscopy to monitor the formation of a 1:1 cocrystal of ibuprofen (IBU) as a BCS class II drug and nicotinamide as coformer using hot-melt extrusion (HME) was investigated. The process was monitored over different experimental conditions inserting the Raman probe before the extruder die. Partial least square (PLS) was applied as a robust chemometric technique to build predictive models at different levels of chemometric by dividing the experimental data set into calibration and validation subsets. Powder X-Ray diffraction (PXRD) spectra of a set of standard samples were used as calibration to calculate the cocrystal yield from HME experiments regressed by the PLS models. Examination of the full spectra with standard normal variate (SNV) scatter correction with first derivative provided the best fitting goodness and reliability for prediction. Differential scanning calorimetry (DSC) was used as a complementary technique to confirm the composition of the extrudates. Tracking the cocrystal formation throughout the barrel by inserting two Raman probes simultaneously in two different heating zones revealed highly valuable information for understanding the mechanism of cocrystal formation during the HME process.

Molecular engineering of cocrystallization process in holt melt extrusion based on kinetics of elementary molecular processes

Continuous co-crystallization in a twin-screw granulator is a promising technology. In order to fundamentally optimize the process flow, it is necessary to investigate the kinetics of molecular interactions within the mixture and the effect of these interactions on co-crystal formation. In this study, the processes governing the co-crystallization of ibuprofen and nicotinamide were considered. Density functional theory calculations employing the Hirshfeld partitioning scheme were used to identify donor-acceptor sites on each molecule. A total of twenty-one different molecular interactions was identified (nine of ibuprofen and nicotinamide (resembling co-crystals), three of ibuprofen and itself (resembling the ibuprofen dimer), and nine of nicotinamide and itself (resembling the nicotinamide dimer)). Each interaction was defined as an artificial reversible reaction and the kinetics were calculated using the transition state theory of chemical reactions, where linear and quadratic synchronous transition methods were utilized to identify transition-state structures; the minimum energy path was determined using the nudged elastic band method. A kinetic Monte Carlo framework was used to study the collective/coupled effect of reactions on the progress of the co-crystallization process. it was found that operating at low temperatures (especially lower or very close to the melting temperature of ibuprofen) for longer residency times creates a safe route for maximizing the presence of ibuprofen and nicotinamide co-crystals. If the proposed route is applied, the purity and properties of the produced co-crystal would be significant, especially its desirable availability within the body.

Continuous Manufacture and Scale-Up of Theophylline-Nicotinamide Cocrystals

The aim of the study was the manufacturing and scale-up of theophylline-nicotinamide (THL-NIC) pharmaceutical cocrystals processed by hot-melt extrusion (HME). The barrel temperature profile, feed rate and screw speed were found to be the critical processing parameters with a residence time of approximately 47 s for the scaled-up batches. Physicochemical characterization using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction of bulk and extruded materials revealed the formation of high purity cocrystals (98.6%). The quality of THL-NIC remained unchanged under accelerated stability conditions.

Hot melt extrusion: An emerging manufacturing method for slow and sustained protein delivery

With the rapid development of the biopharmaceutical industry, an increasing number of new therapeutic protein products (TPPs) have been approved by the FDA and many others are under pre-clinical and clinical evaluation. A major limitation of biopharmaceuticals is their limited half-life when administered systemically. A one-time, implantable, sustained protein delivery device would be advantageous in order to improve the quality of life of patients. Hot melt extrusion (HME) is a mature technology that has been extensively used for a broad spectrum of applications in the polymer and pharmaceutical industry and has achieved success as evidenced by a variety of FDA-approved commercial products. These commercial products are mostly for sustained delivery of small molecule therapeutics, leaving a significant gap for HME formulation of therapeutic proteins. With the increasing need of sustained TPP delivery, HME shows promise as a downstream processing method due to its high efficiency and economic value. Several challenges remain for the application of HME in protein delivery. Progress of HME for protein delivery, challenges encountered, and potential solutions will be detailed in this review article. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Development and characterization of ibuprofen co-crystals granules prepared via fluidized bed granulation in a one-step process - a design of experiment approach

OBJECTIVE

The focus of this study was to investigate the possibility of producing ibuprofen-nicotinamide (IBU-NIC) and ibuprofen-isonicotinamide (IBU-INA) cocrystal-containing granules, using a one-step fluidized bed dryer granulation manufacturing process, and evaluate their mechanical properties.

SIGNIFICANCE

Pharmaceutical cocrystals represent a suitable strategy to improve properties of active pharmaceutical ingredients (APIs), such as solubility and processability. Ibuprofen (IBU) is a small molecule API which can form cocrystals with different coformers, including NIC and INA. An improvement in mechanical properties for IBU-NIC cocrystals relative to IBU was previously reported but, to date, the formulation of IBU cocrystals in a solid dosage form has not been investigated.

METHODS

In situ cocrystallization and granulation were achieved concurrently by processing in a lab-scale fluidized bed granulator following a design of experiment (DoE) approach using a two-level factorial design with both process and formulation variables. Solid-state, micrometric, dissolution, and mechanical (tabletability) characteristics of granules were assessed post-processing.

RESULTS

Granules containing cocrystals were successfully prepared for 11 of 16 DoE runs. Parameters with a significant effect on granule drug loading, flow function, porosity, and size could be identified from the DoE model. Process yield was increased by using a high inlet temperature at high solution feed rate. To avoid the formation of sticky particles, caking and over-wetting of the powder during the process, the utilization of high inlet temperature, low API + coformer:filler ratio, low API concentration in solution and low solution feed rate were suggested by the model.

CONCLUSION

The multivariable model developed enables accurate optimization of the granulation process for IBU cocrystals.

Pharmaceutical Co-Crystals, Salts, and Co-Amorphous Systems: A Novel Opportunity of Hot Melt Extrusion

Enhancing the solubility of active drug ingredients is a major challenge faced by scientists and researchers. Different approaches have been explored for the enhancement of solubility and physicochemical properties of drugs, without affecting their stability or pharmacological activity. Among the various strategies available, pharmaceutical co-crystals, co-amorphous systems, and pharmaceutical salts as multicomponent systems (MCS) have gained interest to improve physicochemical properties of drugs. Development of MCS by conventional methods involves the utilization of excess amount of solvents, thus, making the product prone to instability, and may also cause harmful side effects in patients. Scale up is critical and involves the investment of huge capital and time. Lately, hot-melt extrusion has been utilized in the development of MCS to enhance solubility, bioavailability, stability, and physicochemical properties of the drugs. In this review, the authors discussed the development of different MCS produced via hot-melt extrusion technology. Specifically, approaches for screening of co-formers and co-crystals, selection of excipients for co-amorphous systems, pharmaceutical salts, and significance of MCS and process parameters affecting product quality are discussed.

Fabrication and structural properties of water-dispersible phytosterol using hot melt extrusion

Hot-melt extrusion (HME) technology was employed to improve water dispersibility of phytosterol (P) using glycerol (G), lecithin (L), and gum arabic (A) as emulsifiers and stabilizers. The structural properties and water dispersibility of HME products were investigated. In contrast to physical mixtures, better water dispersibility and storage stability were observed for HME products, especially P:L:G:A extrudate. These improvements may be mainly associated with decreased crystallinity of phytosterol due to the occurrence of co-crystallization of phytosterol with glycerol during HME process, as confirmed by DSC and XRD data. In addition, HME-induced lecithin-arabic gum reaction products effectively stabilize phytosterol microparticle in aqueous dispersion by providing a steric hindrance. These results suggest that HME could be an effectively and potentially solvent-free technique to produce water-dispersible phytosterol on a large scale.

Engineering cocrystals of Paliperidone with enhanced solubility and dissolution characteristics

In the present study, co-crystals (CCs) of Paliperidone (PPD) with coformers like benzoic acid (BA) and P-amino benzoic acid (PABA) were synthesized and characterized to improve the physicochemical properties and dissolution rate. CCs were prepared by the solvent evaporation (SE) technique and were compared with the products formed by neat grinding (NG) and liquid assisted grinding (LAG) in their enhancement of solubility. The formation of CCs was confirmed by the IR spectroscopy, powder X-ray diffraction and thermal analysis methods. The saturation solubility studies indicate that the aqueous solubility of PPD-BA and PPD-PABA CCs was significantly improved to 1.343±0.162mg/ml and 1.964±0.452mg/ml, respectively, in comparison with the PPD solubility of 0.473mg/ml. This increase in solubility is 2.83-and 3.09-fold, respectively. PPD exhibited a poor dissolution of 37.8% in 60min, while the dissolution of the CCs improved tremendously to 96.07% and 89.65% in 60min. CCs of PPD with BA and PABA present a novel approach to overcome the solubility challenges of poorly water-soluble drug PPD.

Innovations in Thermal Processing: Hot-Melt Extrusion and KinetiSol® Dispersing

Thermal processing has gained much interest in the pharmaceutical industry, particularly for the enhancement of solubility, bioavailability, and dissolution of active pharmaceutical ingredients (APIs) with poor aqueous solubility. Formulation scientists have developed various techniques which may include physical and chemical modifications to achieve solubility enhancement. One of the most commonly used methods for solubility enhancement is through the use of amorphous solid dispersions (ASDs). Examples of commercialized ASDs include Kaletra®, Kalydeco®, and Onmel®. Various technologies produce ASDs; some of the approaches, such as spray-drying, solvent evaporation, and lyophilization, involve the use of solvents, whereas thermal approaches often do not require solvents. Processes that do not require solvents are usually preferred, as some solvents may induce toxicity due to residual solvents and are often considered to be damaging to the environment. The purpose of this review is to provide an update on recent innovations reported for using hot-melt extrusion and KinetiSol® Dispersing technologies to formulate poorly water-soluble APIs in amorphous solid dispersions. We will address development challenges for poorly water-soluble APIs and how these two processes meet these challenges.

Pharmaceutical cocrystal: a game changing approach for the administration of old drugs in new crystalline form

Pharmaceutical cocrystals are still gaining the interest of the researchers due to their potential to alter physicochemical, mechanical, and pharmacokinetic properties of active pharmaceutical ingredients without negotiating therapeutic action. The diverse new applications of cocrystals, like taste masking, reduced toxicity, patenting opportunities, commercial potential, etc. act as driving force to the rising interest of the pharmaceutical industries. Initially, cocrystals from the view of regulatory authorities, design strategies, cocrystal preparation in brief with special emphasis on scalable and solvent-free hot melt extrusion method, and practical guide to characterization have been provided. The special focus has been given to the biopharmaceutical attributes of the cocrystal. Finally, challenges before and after cocrystal preparation are presented in this review along with some commercial examples of the cocrystals.

Cocrystallization: Cutting Edge Tool for Physicochemical Modulation of Active Pharmaceutical Ingredients

Cocrystallization is a widely accepted and clinically relevant technique that has prospered very well over the past decades to potentially modify the physicochemical properties of existing active pharmaceutic ingredients (APIs) without compromising their therapeutic benefits. Over time, it has become an integral part of the pre-formulation stage of drug development because of its ability to yield cocrystals with improved properties in a way that other traditional methods cannot easily achieve. Cocrystals are solid crystalline materials composed of two or more than two molecules which are non-covalently bonded in the same crystal lattice. Due to the continuous efforts of pharmaceutical scientists and crystal engineers, today cocrystals have emerged as a cutting edge tool to modulate poor physicochemical properties of APIs such as solubility, permeability, bioavailability, improving poor mechanical properties and taste masking. The success of cocrystals can be traced back by looking at the number of products that are getting regulatory approval. At present, many cocrystals have obtained regulatory approval and they successfully made into the market place followed by a fair number of cocrystals that are currently in the clinical phases. Considering all these facts about cocrystals, the formulation scientists have been inspired to undertake more relevant research to extract out maximum benefits. Here in this review cocrystallization technique will be discussed in detail with respect to its background, different synthesis approaches, synthesis mechanism, application and improvements in drug delivery systems and its regulatory perspective.

Polymer-Assisted Aripiprazole-Adipic Acid Cocrystals Produced by Hot Melt Extrusion Techniques

Pharmaceutical cocrystals are a promising strategy to increase the solubility and dissolution rate of poorly soluble drugs. However, their manufacturing process requires a large quantity of solvents. The present study aimed to produce cocrystals by a solvent-free hot melt extrusion (HME) method to improve their solubility and dissolution rate. Aripiprazole (ARP) and adipic acid (ADP) were used as a weakly basic drug and acidic coformer, respectively. The processability of a plain ARP-ADP physical mixture (PM) compared with a PM with 5% Soluplus® (SOL) was investigated. Incorporating 5% SOL into the ARP-ADP blend reduced the processing torque and improved processability. The effects of temperature and screw speed on the formation of cocrystals were studied, and cocrystals were characterized by differential scanning calorimetry (DSC), fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy, and hot-stage microscopy. FTIR spectra revealed noncovalent interaction between ARP and ADP, which was confirmed by NMR spectra. Similarly, PXRD data exhibited characteristic peaks confirming the formation of new crystalline material. Further, the results indicated that cocrystals demonstrated higher dissolution rates and improved compressibility, as well as enhanced flow characteristics compared with pure ARP, suggesting its suitability in the development of solid dosage forms.

Polymorphism and stability of ibuprofen/nicotinamide cocrystal: The effect of the crystalline synthesis method

The development over the past decade of design strategies for cocrystal preparation have led to numerous methods for the synthesis of cocrystal without take care of their influence on the precise structure and stability of cocrystalline states. On the other hand the mechanism of cocrystal formation remains widely unclear, especially the identification of the type of interactions mostly responsible for the cocrystalline stability. The present study focuses on the influence of the crystalline synthesis method on the polymorphism of cocrystals was analyzed from the preparation of S-ibuprofen/nicotinamide and RS-ibuprofen/nicotinamide cocrystals by co-milling, slow solvent evaporation and crystallization from the melt. X-ray diffraction and Raman spectroscopy experiments have shown that the polymorphic form of the cocrystals obtained by recrystallization from the melt (Form A) is different from that prepared by milling and by slow evaporation in solution (Form B). It was shown that both isothermal and non-isothermal recrystallizations from the melt blending are observed via a transient metastable micro/nano structure of form A. Additionally, it was observed that form A transforms into Form B upon heating via very weak changes in the hydrogen bond network. The crystallization in form A from the melt, instead of form B by other methods, was explained by the difficulty to form a supramolecular organization too far energetically from that existing in the melt. This study shows the crucial role of supramolecular H-bonding on the formation mechanism of cocrystals and how does the synthesis method of cocrystals change the supramolecular organization and the related structure of cocrystals.

Green Method for the Synthetic Ugi Reaction by Twin Screw Extrusion without a Solvent and Catalyst

This study describes the solvent and catalyst-free Ugi reaction by way of twin screw extrusion (TSE). Multicomponent chemical synthesis can be converted into a single process without repeated use of solvents through TSE. High synthetic yields are achieved in short reaction times and produced in solvent-free conditions, which lead to a more environmentally friendly process.

Mechanochemical synthesis and X-ray structural characterization of three 3-nitrophenol cocrystals with three aminal cage azaadamantanes: the role of the stereoelectronic effect on intermolecular hydrogen-bonding patterns

The structures of the cocrystalline adducts of 3-nitrophenol (3-NP) with 1,3,5,7-tetraazatricyclo[3.3.1.1^3,7]decane [HMTA, (1)] as the 2:1:1 hydrate, 2C₆H₅NO₃·C₆H₁₂N₄·H₂O, (1a), with 1,3,6,8-tetraazatricyclo[4.3.1.1^3,8]undecane [TATU (2)] as the 2:1 cocrystal, 2C₆H₅NO₃·C₇H₁₄N₄, (2a), and with 1,3,6,8-tetraazatricyclo[4.4.1.1^3,8]dodecane [TATD, (3)] as the 2:1 cocrystal, 2C₆H₅NO₃·C₈H₁₆N₄, (3a), are reported. In the binary crystals (2a) and (3a), the 3-nitrophenol molecules are linked via O-H...N hydrogen bonds into aminal cage azaadamantanes. In (1a), the structure is stabilized by O-H...N and O-H...O hydrogen bonds, and generates ternary cocrystals. There are C-H...O hydrogen bonds present in all three cocrystals, and in (1a), there are also C-H...O and C-H...π interactions present. The presence of an ethylene bridge in the structures of (2) and (3) defines the formation of a hydrogen-bonded motif in the supramolecular architectures of (2a) and (3a). The differences in the C-N bond lengths of the aminal cage structures, as a result of hyperconjugative interactions and electron delocalization, were analysed. These three cocrystals were obtained by the solvent-free assisted grinding method. Crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation from a mixture of hexanes.

MCR-ALS analysis of IR spectroscopy and XRD for the investigation of ibuprofen - nicotinamide cocrystal formation

To improve aqueous solubility, a poorly water-soluble active ingredient is classically combined with a conformer to form cocrystals. Hot melt extrusion is one preparation method for the formation of cocrystal solids. The aim of our study was to determine the optimal temperature conditions for the formation of ibuprofen and nicotinamide cocrystals using real-time infrared (IR) and X-ray diffraction (XRD) measurements. IR spectra and XRD patterns were subjected to multivariate curve resolution alternating least squares (MCR-ALS) analysis and decomposed into several components. Each component was descriptive of a specific step in the formation of the cocrystal. Cocrystal formation was followed by a separation phase between amorphous ibuprofen and crystalline nicotinamide. Our results suggest that, when using the hot melt exclusion method, careful consideration should be made towards optimizing processing temperatures in order to prevent amorphization and promote control over the process of cocrystal formation.

Impact of polymeric excipient on cocrystal formation via hot-melt extrusion and subsequent downstream processing

Pharmaceutical cocrystals have gained increasing interest due to their potential to modify the physicochemical properties of drugs. Herein, a 1:1 cocrystal of ibuprofen (IBU) as a BCS class II active pharmaceutical ingredient (API) and nicotinamide as coformer was produced using a hot-melt extrusion (HME) process. The effect of process parameters such as barrel temperature and screw speed were studied. It was shown that the addition of polymeric excipient such as soluplus (Sol) decreases the cocrystallization temperature by enhancing the interaction between API and coformer. In order to study the effect of cocrystallization on the tableting properties of IBU-NIC cocrystal, 5 different formulations of pure IBU, IBU-NIC cocrystal, IBU-NIC physical mixture, IBU-NIC-Sol physical mixture and IBU-NIC-Sol cocrystal were tableted by a compaction simulator. Tabletability, compactibility and compressibility were investigated. The sample with IBU-NIC-Sol cocrystal formulation outperformed all the other formulations in terms of tabletability, compactibility and compressibility. Interestingly, this sample was even superior to the IBU-NIC cocrystal sample which verified the advantageous effect of the presence of an excipient. Moreover, dissolution test confirmed a noticeable increase in the dissolution of not only the cocrystal samples but even the physical mixtures of IBU and NIC compared with pure IBU.

Continuous manufacturing of co-crystals: challenges and prospects

The last decade has witnessed extensive growth in the field of co-crystallization for mitigating the solubility and dissolution-related issues of poorly soluble drugs. This is largely because co-crystals can modify the physicochemical properties of drugs without any covalent modification in the drug molecules. The US Food and Drug Administration (FDA) now considers drug products that are designed to contain a new co-crystal, analogous to new polymorph of the active pharmaceutical ingredient (API). This positive change in regulatory perspective coupled with successful commercialization of valsartan-sacubitril co-crystal (Entresto, Novartis) has now brought co-crystals into focus, in both industries as well as academia. Co-crystal prediction, screening, and synthesis have been reported in literature; however, co-crystal production at a larger scale needs further investigations. With this aim, the article describes various continuous methods for co-crystal production, along with in-line monitoring during co-crystal production, emphasizing on process analytical technology (PAT). In addition, the scale-up issues of continuous and batch co-crystallization and other suitable techniques for pharmaceutical scale up are detailed. Quality control aspects and regulatory viewpoint crucial for commercial success are elaborated in the future perspective.

An update on the contribution of hot-melt extrusion technology to novel drug delivery in the twenty-first century: part II

INTRODUCTION

Interest in hot-melt extrusion (HME) technology for novel applications is growing day by day, which is evident from several hundred publications within the last 5 years. HME is a cost-effective, solvent free, 'green' technology utilized for various formulations with low investment costs compared to conventional technologies. HME has also earned the attention of the pharmaceutical industry by the transformation of this technology for application in continuous manufacturing.

AREAS COVERED

Part II of the review focuses on various novel opportunities or innovations of HME such as multiple component systems (co-crystals, co-amorphous systems and salts), twin-screw granulation, semi-solids, co-extrusion, abuse deterrent formulations, solid self-emulsifying drug delivery systems, chronotherapeutic drug delivery systems, and miscellaneous applications.

EXPERT OPINION

HME is being investigated as an alternative technology for preparation of multicomponent systems such as co-crystals and co-amorphous techniques. Twin-screw granulation has gained increased interest in preparation of granules via twin-screw melt granulation or twin-screw dry granulation. This novel application of the HME process provides a promising alternate approach in the formulation of granules and solid dosage forms. However, this technology may need to be further investigated for scalability aspects of these novel applications for industrial production.

The development of an inline Raman spectroscopic analysis method as a quality control tool for hot melt extruded ramipril fixed-dose combination products

Currently in the pharmaceutical industry, continuous manufacturing is an area of significant interest. In particular, hot-melt extrusion (HME) offers many advantages and has been shown to significantly reduce the number of processing steps relative to a conventional product manufacturing line. To control product quality during HME without process interruption, integration of inline analytical technology is critical. Vibrational spectroscopy (Raman, NIR and FT-IR) is often employed and used for real-time measurements because of the non-destructive and rapid nature of these analytical techniques. However, the establishment of reliable Process Analytical Technology (PAT) tools for HME of thermolabile drugs is challenging. Indeed, the Raman effect is inherently weak and might be subject to interference. Moreover, during HME, heating and photodecomposition can occur and disrupt spectra acquisition. The aim of this research article was to explore the use of inline Raman spectroscopy to characterise a thermolabile drug, ramipril (RMP), during continuous HME processing. Offline measurements by HPLC, LC-MS and Raman spectroscopy were used to characterise RMP and its main degradation product, ramipril-diketopiperazine (RMP-DKP, impurity K). A set of HME experiments together with inline Raman spectroscopic analyses were performed. The feasibility of implementing inline Raman spectroscopic analysis to quantify the level of RMP and RMP-DKP in the extrudate was addressed. Two regions in the Raman spectrum were selected to differentiate RMP and RMP-DKP. When regions were combined, a principle component analysis (PCA) model defined by these two main components (PC 1 = 50.1% and PC 2 = 45%) was established. Using HPLC analyses, we were able to confirm that the PC 1 score was attributed to the level of RMP-DKP, and the PC 2 score was related to the RMP drug content. Investigation of the PCA scatterplot indicated that HME processing temperature was not the only factor causing RMP degradation. Additionally, the plasticiser content, feeding speed and screw rotating speed contributed to RMP degradation during HME processing.

Insights into mechanochemical reactions at the molecular level: simulated indentations of aspirin and meloxicam crystals

Although solvent-free mechanochemical synthesis continues to gain ever greater importance, the molecular scale processes that occur during such reactions remain largely uncharacterised. Here, we apply computational modelling to indentations between particles of crystals of aspirin and meloxicam under a variety of conditions to mimic the early stages of their mechanochemical cocrystallisation reaction. The study also extends to the effects of the presence of small amounts of solvent. It is found that, despite the solid crystalline nature of the reactants and the presence of little or no solvent, mixing occurs readily at the molecular level even during relatively low-energy collisions. When indented crystals are subsequently drawn apart, a connective neck formed by a mixture of the reactant molecules is observed, suggesting plastic-like behaviour of the reacting materials. Overall the work reveals some striking new insights including (i) relatively facile mixing of crystals under solvent-free conditions, (ii) no appreciable local temperature increases, (iii) localised amorphisation at the contact region and neck of the reacting crystals, and (iv) small amounts of solvent have relatively little effect during this early stage of the reaction, suggesting that their accelerating effect on the reaction may be exerted at later stages.