Co amorphous systems: A product development perspective

Effect of PVP and HPMC on production of indomethacin amorphous nanoparticles: experiments and molecular dynamics simulations

OBJECTIVE

This study investigated the effect of molecular interactions between drug and polymers on preparation of nanoamorphous indomethacin (IND) through milling of solid dispersions (SDs).

SIGNIFICANCE

The polymer selection (molecular interaction) emerged as a critical factor in the dynamic milling process for achieving nanoamorphous drug.

METHODS

Polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) were selected as models. Amorphous dispersions were used to prepare nanoamorphous drugs by applying wet milling. Molecular simulations were employed to elucidate the molecular mechanisms of drug-polymer miscibility, interaction energy, and molecular migration.

RESULTS

Both PVP and HPMC related SDs could be nanosized after milling. The rate of size reduction might be related to the solid state of the dispersions. The combination of amorphous PVP SDs with reduced particle size significantly improved the dissolution rate of IND. However, HPMC-based samples exhibited recrystallization during milling. Molecular simulation indicated that PVP formed strong molecular interaction with the drug to maintain the amorphous form, which contributed to avoid recrystallization induced by the external milling forces. The radial distribution function of hydrated IND/HPMC amorphous cells demonstrated the absence of hydrogen bonding interactions between IND and HPMC.

CONCLUSION

PVP contributed to maintain the amorphous state during the milling process, which resulted from the higher molecular binding energy compared to HPMC. Controlled milling of amorphous SD with optimized polymer selection could simultaneously achieve nanoamorphous particle and enhanced dissolution rate.

Molar Ratio-Dependent Crystallization in Coamorphous Celecoxib-Carbamazepine Systems: The Interplay of Thermodynamics and Kinetics

Coamorphous drug delivery systems have emerged as a promising formulation strategy to enhance the solubility, oral bioavailability, and physical stability of poorly water-soluble drugs. The molar ratio of components in coamorphous systems plays a critical role in determining their physical stability. In this study, we investigated the crystallization behavior of coamorphous celecoxib-carbamazepine (CEL-CBZ) systems at different molar ratios. The growth rates of CEL crystals, CBZ crystals, and CEL-CBZ cocrystals were observed to exhibit distinct dependencies on the molar ratio of coamorphous systems, primarily due to their unique thermodynamic driving forces, despite sharing the same kinetic factor. The influence of the molar ratio on the crystallization of coamorphous systems arises from the interplay between its effects on molecular mobility and thermodynamic driving forces, leading to either cooperative or competing effects. Both the crystal growth and crystallization tendency results reveal that thermodynamics plays a more dominant role than kinetics in the crystallization of coamorphous CEL-CBZ systems across various molar ratios. This study provides fundamental insights into the mechanism by which the molar ratio influences the crystallization of coamorphous systems, highlighting the complex crystallization behavior of multicomponent amorphous systems as an interplay between kinetics and thermodynamics.

Multi-method coamorphous systems of lumefantrine with alpha ketoglutaric acid: Comprehensive characterization, biological evaluation and stability analysis

The coamorphous systems (CAM) of lumefantrine (LMF) and alpha-ketoglutaric acid (KGA) were developed using three different methods to address the solubility and bioavailability limitations of LMF. Powder X-ray diffraction spectroscopy (PXRD) and the differential scanning calorimetry (DSC) confirmed the complete amorphization of the three CAM by the halo pattern and glass transition temperature (Tg), respectively. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and nuclear magnetic resonance spectroscopy (NMR) results indicated that intermolecular interactions existed in the three CAM. Solid-state molecular dynamics simulations revealed the different intermolecular disordered environments present in all three CAM. Solubility analysis showed 14.73×, 12.8× and 9.81× improvement in the liquid-assisted grinding-based coamorphous system (CAM LAG), solvent evaporation-based coamorphous system (CAM SE) and quench-cool-based coamorphous system (CAM QC), respectively, compared to LMF crystalline (LMF CRY). In the in-vitro dissolution experiment 2.63-, 2.16- and 2.17-times increments were observed in CAM LAG, CAM SE and CAM QC compared to LMF CRY, respectively. In-vivo pharmacokinetics study revealed 10.86-, 9.24- and 8.46- folds increments in Cmax of CAM LAG, CAM SE and CAM QC, respectively, compared to LMF CRY. All three CAM illustrated anti-cancer activity in the A549 lung cancer cell line. Molecular dynamics simulation of LMF and KGA with Epidermal growth factor receptor (EGFR), a target for lung cancer treatment, revealed good binding affinity and stability. Stability studies performed under accelerated storage (40°C/75% RH) and extreme environmental conditions indicated that all three CAM have good stability. Different methods based prepared CAM have shown different physicochemical properties, bioavailability and stability profiles. These findings suggest that LMF-KGA CAM effectively addresses the solubility and bioavailability challenges of LMF, potentially leading to better therapeutic outcomes in lung cancer treatment.

Stability of Ternary Drug-Drug-Drug Coamorphous Systems Obtained Through Mechanochemistry

Background/Objectives: This study investigates the preparation of coamorphous systems composed entirely of active pharmaceutical ingredients (APIs), namely praziquantel, niclosamide, and mebendazole. The objective was to formulate and characterize binary and ternary coamorphous systems to evaluate their structural, thermal, and stability properties. Methods: Ten different mixtures (binary and ternary) were designed through a mixture design approach and prepared using a sustainable, one-step neat grinding process in a lab-scale vibrational mill. The systems were prepared reproducibly within 4 h across the entire experimental domain. Structural characterization was performed using PXRD and FTIR to confirm the absence of crystalline domains and the presence of molecular interactions. The glass transition temperature (Tg) was theoretically calculated using the Gordon-Taylor equation for three-component systems and determined experimentally via DSC. Stability studies were conducted on seven systems under different storage conditions (-30 °C, 5 °C, 25 °C, and 40 °C) for six months. Results: PXRD analysis confirmed the formation of coamorphous systems with no crystalline phases. DSC revealed a single Tg for most systems, indicating homogeneity. Stability studies demonstrated that five out of seven systems adhered to the "Tg-50 °C" stability rule, remaining physically stable over six months. Recrystallization studies indicated diverse pathways: some systems reverted to their original crystalline phases, while others formed new entities such as cocrystals. Conclusions: This study highlights the feasibility of coamorphous systems composed of multiple APIs using a simple, solvent-free grinding approach. The findings underscore the importance of molecular interactions in determining stability and recrystallization behavior, offering insights for designing robust coamorphous formulations.

Physical Properties for Novel Cilostazol Co-amorphous; Effect of Preparation Method and Molar Ratio on the Co-amorphous

Co-amorphous materials have gained special attention in the pharmaceutical field due to their high potential to enhance the oral bioavailability of poorly aqueous soluble drugs. In co-amorphous studies, few reports have examined the physical properties and molecular states of different active pharmaceutical ingredients (APIs) : co-amorphous former (CF) molar ratios and preparation methods. Therefore, we investigated the effect of molar ratio and preparation method on the physical properties of a novel co-amorphous system consisting of cilostazol and l-tryptophan, which we identified through screening. Co-amorphous consisting of molar ratios of 1 : 1 (co-milling (CM) 1 : 1), 1 : 1.5 (CM 1 : 1.5), and 1 : 2 (CM 1 : 2) were prepared by the CM method, while samples with a molar ratio of 1 : 1 (spray drying (SD) 1 : 1) were prepared by the spray drying method. CM 1 : 1.5 and CM 1 : 2 showed the highest solubility. Storage stability was excellent for CM 1:1.5, CM 1 : 2, and SD 1 : 1, whereas physical properties were improved by co-amorphization. To investigate the factors responsible for the improved physical properties, the molecular state of the co-amorphous system was evaluated, and it was inferred that hydrogen bonds were formed between cilostazol and l-tryptophan. Solid-state 13C-NMR showed several new peaks specific to the solid state in the co-milled sample compared to SD 1 : 1 and cilostazol amorphous, suggesting that the molecular state may differ depending on the preparation method. As described above, different physical properties and molecular states were observed in the novel co-amorphous system consisting of cilostazol and l-tryptophan when the molar ratio of APIs and CF, and the preparation method differed.

Development of a Novel Co-Amorphous Curcumin and L-Arginine (1:2): Structural Characterization, Biological Activity and Pharmacokinetics

Background: Curcumin appears to be well tolerated and effective for managing chronic inflammatory pain, but its poor oral bioavailability has been a hurdle in its use as a therapeutic agent. The current study was performed to characterize a novel co-amorphous compound based on curcumin/L-arginine 1:2 (CAC12). Methods: Stability, solubility and structural characterization of the CAC12 were carried out by spectrometry techniques and in vitro assays, whereas the antinociceptive and anti-inflammatory effects were evaluated by CFA or carrageenan models. The mechanism of action was determined by cytokine quantification, and pharmacokinetic parameters were obtained through UPLC-MS/MS. The co-amorphous compound was prepared by fast solvent evaporation. Powder XRD, 13C-NMR, ATR-FTIR and TGA/DSC thermal analysis showed a 1:2 stoichiometry for the CAC12. Results: CAC12 was 1000 times more soluble than curcumin, and it was stable for 1 month at 40 °C and 75% relative humidity or for 60 min in physiological medium at pH 4.5-6.8. Co-amorphous curcumin/L-arginine, but not curcumin + L-arginine, decreased carrageenan- or CFA-induced inflammation and nociception by decreasing IL-1α, IL-1β, IL-6, TNF-α, MCP-1 and CXCL1 cytokines. The bioavailability of free plasmatic curcumin increased about 22.4 times when it was given as CAC12 relative to a phytosome formulation at the equivalent dose. Conclusions: Results suggest the possible use of CAC12 to treat inflammatory pain disorders in human beings.

Evaluation of aspartame as a co-former in the preparation of co-amorphous formulations of dipyridamole using spray drying

Co-amorphous systems (CAMs) have shown promise in addressing the challenges associated with poorly water-soluble drugs. However, the limited selection of co-formers and the use of lab-scale techniques for their preparation present challenges in fully utilizing the advantages of CAMs. In this study, we used aspartame (a methyl ester of the aspartic acid/phenylalanine) as a model dipeptide with the BCS class II drug dipyridamole, to prepare co-amorphous systems using spray drying. The feed solutions were prepared by dissolving the drug and co-former into methanol-water mixtures. The spray drying process was evaluated and solid-state properties were compared with those of the individual amino acids, amino acid mixtures and aspartame as co-formers. Co-amorphous systems prepared with aspartame (AspPhe) exhibited better solid-state properties, including a higher glass transition temperature (Tg), compared to the individual amino acids and the mixture of amino acids. Additionally, this formulation showed improved physical stability when stored at 25 °C/60 % RH conditions. Hirshfeld Surface (HS) analysis was employed to visualize and analyse the molecular interaction sites within the crystal structures of dipyridamole and aspartame. The observed interactions were then correlated with the molecular interactions identified through FT-IR spectroscopic analysis within the CAMs. The spectroscopic analysis revealed molecular interactions between the sites found at the shortest distances in the HS analysis. The dominant hydrogen bond interactions identified in the co-amorphous DPM-AspPhe system was found to contribute significantly to its improve stability. X-ray powder diffraction in non-ambient mode reveals that both temperature and humidity play a role in the crystallization of the co-amorphous DPM-AspPhe. Crystallization rates increased notably at high temperature and humidity. To predict stability under accelerated conditions, the crystallization rates from DPM-AspPhe were fitted to a modified Arrhenius equation. However, the predictive accuracy of the resulting model was limited to a specific range of conditions.

Excipient effects on supersaturation, particle size dynamics, and thermodynamic activity of multidrug amorphous formulations

Multidrug formulations enhance patient compliance and extend the life cycle of pharmaceutical products. To overcome solubility challenges for multidrug combinations, amorphous formulations are commonly used. However, the excipients for creating amorphous formulations are often selected without an understanding of their effects on the bioavailability of the drugs. In this context, we investigated the impact of three types of excipients (polymers, surfactants and amino acids) on the supersaturation and thermodynamic activity of multidrug amorphous formulations. Additionally, we studied the particle size dynamics of the colloidal phase formed as a result of liquid-liquid phase separation. The amorphous solubility of two drugs, atazanavir and ritonavir, was determined in solutions containing predissolved excipients and the particle size dynamics of the colloidal particles was measured by dynamic light scattering. Dissolution experiments of atazanavir and ritonavir were conducted in predissolved sodium dodecyl sulfate (SDS), an anionic surfactant, and alanine solutions under non-sink conditions. Membrane transport of the drugs was evaluated using a MicroFLUX setup. The polymers had only minor effects on the amorphous solubility, but SDS significantly increased the solubilities of both drugs. In contrast, the other non-ionic surfactants and amino acids reduced the solubility of atazanavir but had no negative effect on ritonavir. Polymers were effective in maintaining supersaturation and preventing the coarsening of the colloidal particles. Conversely, alanine was neither able to inhibit the solution crystallization nor increase the flux of either drug. Despite the increase in the amorphous solubility of both drugs in SDS, flux was reduced. These results highlight the importance of properly selecting excipients for supersaturating amorphous formulations. The choice of excipient impacts the thermodynamic activity, the phase behaviour of the drugs and hence, the resulting absorption after oral intake.

Evaluating experimental, knowledge-based and computational cocrystal screening methods to advance drug-drug cocrystal fixed-dose combination development

Fixed-dose combinations (FDCs) offer significant advantages to patients and the pharmaceutical industry alike through improved dissolution profiles, synergistic effects and extended patent lifetimes. Identifying whether two active pharmaceutical ingredients have the potential to form a drug-drug cocrystal (DDC) or interact is an essential step in determining the most suitable type of FDC to formulate. The lack of coherent strategies to determine if two active pharmaceutical ingredients that can be co-administered can form a cocrystal, has significantly impacted DDC commercialisation. This review aims to accelerate the development of FDCs and DDCs by evaluating existing experimental, knowledge-based and computational cocrystal screening methods; the background of their development, their application in screening for cocrystals and DDCs, and their limitations are discussed. The evaluation provided in this review will act as a guide for selecting suitable screening methods to accelerate FDC development.

Self-micellizing solid dispersion of thymoquinone with enhanced biopharmaceutical and nephroprotective effects

The present study was designed to develop a self-micellizing solid dispersion (SMSD) containing Thymoquinone (TQM), a phytonutrient obtained from Nigella sativa seeds, aiming to improve its biopharmaceutical and nephroprotective functions. The apparent solubility of TQM in polymer solutions was used to choose an appropriate amphiphilic polymer that could be used to make an SMSD system. Based on the apparent solubility, Soluplus® was selected as an appropriate carrier, and mixing with TQM, SMSD-TQM with different loadings of TQM (5-15%) was made by solvent evaporation and freeze-drying techniques, respectively, and the formulations were optimized. The optimized SMSD-TQM was evaluated in terms of particle size distribution, morphology, release characteristics, pharmacokinetic behavior, and nephroprotective effects in a rat model of acute kidney injury. SMSD-TQM significantly improved the dissolution characteristics (97.8%) of TQM in water within 60 min. Oral administration of SMSD-TQM in rats exhibited a 4.9-fold higher systemic exposure than crystalline TQM. In a cisplatin-induced (6 mg/kg, i.p.) acute kidney-damaged rat model, oral SMSD-TQM (10 mg/kg) improved the nephroprotective effects of TQM based on the results of kidney biomarkers and histological abnormalities. These findings suggest that SMSD-TQM might be efficacious in enhancing the nephroprotective effect of TQM by overcoming biopharmaceutical limitations.

Amorphous solid dispersion to facilitate the delivery of poorly water-soluble drugs: recent advances on novel preparation processes and technology coupling

INTRODUCTION

Amorphous solid dispersion (ASD) technique has recently been used as an effective formulation strategy to significantly improve the bioavailability of insoluble drugs. The main industrialized preparation methods for ASDs are mainly hot melt extrusion and spray drying techniques; however, they face the limitations of being unsuitable for heat-sensitive materials and organic reagent residues, respectively, and therefore novel preparation processes and technology coupling for developing ASDs have received increasing attention.

AREAS COVERED

This paper reviews recent advances in ASD and provides an overview of novel preparation methods, mechanisms for improving drug bioavailability, and especially technology coupling.

EXPERT COVERED

As a mature pharmaceutical technology, ASD has broad application prospects and values. During the period from 2012 to 2024, the FDA has approved 49 formulation products containing ASDs. However, with the diversification of drug types and clinical needs, the traditional formulation technology of ASDs is gradually no longer sufficient to meet the needs of clinical medication. Therefore, this review summarizes the studies on both novel preparation processes and technology combinations; and provides a comprehensive overview of the mechanisms of ASD to improve drug bioavailability, in order to better select appropriate preparation methods for the development of ASD formulations.

Specific intermolecular interaction with sodium glycocholate generates the co-amorphous system showing higher physical stability and aqueous solubility of Y5 receptor antagonist of neuropeptide Y, a brick dust molecule

Drugs with poor water and lipid solubility are termed "brick dust." We previously successfully developed a co-amorphous system of a novel neuropeptide Y5 receptor antagonist (AntiY5R), a brick dust molecule, using sodium taurocholate (NaTC) as a co-former. However, the maximum improvement in AntiY5R dissolution by the co-amorphous system was only approximately 10 times greater than that of the crystals. Therefore, in the current study, other bile salts, including sodium cholate (NaC), sodium chenodeoxycholate (NaCC), and sodium glycocholate (NaGC), were examined as co-formers to further improve AntiY5R dissolution. NaC, NaCC, and NaGC have glass transition temperatures above 150°C. All three co-amorphous systems prepared successfully retained the amorphous form of AntiY5R for 3 months at 40°C, but the co-amorphous system with NaGC (AntiY5R-NaGC; 1:9 molar ratio) provided the highest improvement in AntiY5R dissolution, which was approximately 50 times greater than that of the crystals. Possible intermolecular interactions via the glycine moiety of NaGC more than the other bile salts would contribute to the highest dissolution enhancement with AntiY5R-NaGC. Thus, NaGC would be a promising co-former for formulating stable co-amorphous systems to enhance the dissolution behavior of brick dust molecules.

Impact of Methods of Preparation on Mechanical Properties, Dissolution Behavior, and Tableting Characteristics of Ibuprofen-Loaded Amorphous Solid Dispersions

This study aims to improve the biopharmaceutical, mechanical, and tableting properties of a poorly soluble drug, ibuprofen (IBP), by preparing amorphous solid dispersion (ASD) followed by a sustained-release tablet formulation. A suitable polymer to develop an ASD system was chosen by utilizing the apparent solubility of IBP in various polymer solutions. ASDs containing various ratios of IBP and selected polymer were prepared by the melt fusion (MF) method. ASD containing optimized drug-polymer ratio prepared by freeze-drying (FD) method was characterized and compared physicochemically. The solubility of IBP in water increased 28-fold and 35-fold when formulated as ASD by MF and FD, respectively. Precise formulations showed amorphization of IBP and increased surface area, improving solubility. The dissolution pattern of optimized ASD-IBP in pH 6.8 phosphate buffer after 60 min in MF and FD was enhanced 3-fold. In addition, direct compression tablets comprising optimized ASD granules from MF and FD were made and assessed using compendial and noncompendial methods. ASD-IBP/MF and ASD-IBP/FD formulations showed a similar drug release profile. In addition, 12 h of sustained IBP release from the ASD-IBP-containing tablets was obtained in a phosphate buffer with a pH of 6.8. From the dissolution kinetics analysis, the Weibull model fitted well. The drug release pattern indicated minimal variations between tablets formed using ASD-IBP prepared by both procedures; however, pre- and postcompression assessment parameters differed. From these findings, the application of ASD and sustained-release polymers in matrix formation might be beneficial in improving the solubility and absorption of poorly soluble drugs such as IBP.

Preparation of tofacitinib sustained-release tablets using hot melt extrusion technology

This study aimed to develop a tablet that shows a drug release profile similar to the tofacitinib sustained-release tablet (Xeljanz XR®; OROS™) using hot melt extrusion technology. Tofacitinib citrate was selected as the drug. HPMCAS, HPMCP, and Kollidon VA64 were used as thermoplastic polymers to prepare a hot-melt extrudate. The extrudate was obtained from a twin screw extruder and pelletizer. The granules were compressed using a single punch press machine and then coated. TGA, DSC, XRD, FT-IR, and SEM were performed on the hot melt extrudate to understand its physicochemical properties. Dissolution tests were performed using the paddle method (USP Apparatus II). The results showed that the crystallinity state of tofacitinib changed to amorphous after the hot melt extrusion process; however, no chemical change was observed. The drug release profile was similar to that of Xeljanz XR®, which has an initial lag time owing to its OROS™ formulation; a coating process was performed to obtain a similar drug release profile. The lag time was controlled by adjusting the thickness of the coating layer. Moreover, the extrudate size and compression force during tableting did not significantly affect drug release. In conclusion, the new tofacitinib sustained-release tablet prepared using hot melt extrusion showed a drug release behavior similar to that of Xeljanz XR®.

Rapid screening of ternary amorphous formulations by a spray drying robot

Spray drying is commonly used for producing amorphous solid dispersions to improve drug solubility. The development of such formulations typically relies on comprehensive excipient and composition screening, which requires the preparation of many spray-dried powder samples. This is both labour-intensive and time-consuming when carried out manually. In the present work, the formulation screening task was automated by coupling a laboratory spray dryer operated in a semi-continuous mode with custom-made add-ons, allowing for rapid, computer-controlled production of formulation samples with systematically varying composition. The practical use of the spray drying robot in formulation development was demonstrated on a case study of poorly water-soluble model drugs simvastatin and ezetimibe. Six different polymers and several drug:polymer ratios were screened for the enhancement of dissolution properties. From a pool of 28 spray-dried samples, ternary compositions containing Eudragit L100-55 were identified as the most suitable ones for further processing and characterisation. The ability to populate the formulation design space rapidly and automatically made it possible to construct maps of physico-chemical properties such as glass transition temperature or dissolution rate. The spray drying robot thus enables the acceleration of early formulation development and a deeper understanding of composition-property relationships for multi-component spray dried powders.

Recent advances in dual-drug co-amorphous systems

Poor solubility of drugs and therapeutic candidates poses a significant challenge in drug research and development. Biopharmaceutical class II drugs exhibit limited absorption because of their weak solubility and high permeability. Co-amorphous systems (CAMs) have been studied widely as a way to improve the solubility of drugs. This review summarizes recent advancements in dual-drug CAMs, including improvements in formulation, manufacturing, and solid-state characterization, and highlights the importance of enhancing solubility and stability. It emphasizes the potential synergistic effects of two drugs in CAMs and explores formulation strategies and challenges related to maintaining the amorphous state. Case studies demonstrate the successful application of CAMs in combination therapies that offer improved therapeutic efficacy.

Drug-drug co-amorphous systems: An emerging formulation strategy for poorly water-soluble drugs

Overcoming the poor water solubility of small-molecule drugs is a major challenge in the development of clinical pharmaceuticals. Amorphization of crystalline drugs is a highly effective strategy to improve their aqueous solubility. However, amorphous drugs are thermodynamically unstable and likely to crystallize during manufacturing and storage. Recently, drug-drug co-amorphous systems have emerged as a novel strategy to not only enable enhanced dissolution and physical stability of the individual drugs within the system but also to provide a strategy for combination therapy of the same or different clinical indications. This review serves to highlight advances in the methods used to manufacture and characterize drug-drug co-amorphous systems, summarize drug-drug co-amorphous applications reported in recent decades, and provide an outlook on future possibilities and perspectives.

Molecular complexes of drug combinations: A review of cocrystals, salts, coamorphous systems and amorphous solid dispersions

As the advancements in the medical technology and healthcare develop through the years, combinational therapy has evolved to be an important treatment modality in many disease settings, including cancer, cardiovascular disease and infectious diseases. In an effort to alleviate "pill burden" and improve patient compliance, fixed dose combinations (FDCs) have been developed to be used as effective therapeutics. Among all FDCs, the category of drug-drug molecular complexes has been proven an efficient methodology in designing and treating diseases, with many drugs being approved. Among all drug-drug molecular complexes, drug-drug cocrystals, salts, coamorphous systems and solid dispersions have been successfully developed and many have been approved by the FDA. In this review, we dwell deeply into the molecular mechanisms behind the different types of drug-drug molecular complexes, including the key functional groups involved in the intermolecular interactions, the applications of each category of molecular complexes, as well as the advantages and challenges thereof. This comprehensive review provides useful insights into the practical design and manufacture of drug-drug molecular complexes and points out the future direction for the development of new advantageous combinational therapies that benefit more patients.

Amorphization of Low Soluble Drug with Amino Acids to Improve Its Therapeutic Efficacy: a State-of-Art-Review

Low aqueous solubility of drug candidates is an ongoing challenge and pharmaceutical manufacturers pay close attention to amorphization (AMORP) technology to improve the solubility of drugs that dissolve poorly. Amorphous drug typically exhibits much higher apparent solubility than their crystalline form due to high energy state that enable them to produce a supersaturated state in the gastrointestinal tract and thereby improve bioavailability. The stability and augmented solubility in co-amorphous (COA) formulations is influenced by molecular interactions. COA are excellent carriers-based drug delivery systems for biopharmaceutical classification system (BCS) class II and class IV drugs. The three important critical quality attributes, such as co-formability, physical stability, and dissolution performance, are necessary to illustrate the COA systems. New amorphous-stabilized carriers-based fabrication techniques that improve drug loading and degree of AMORP have been the focus of emerging AMORP technology. Numerous low-molecular-weight compounds, particularly amino acids such as glutamic acid, arginine, isoleucine, leucine, valine, alanine, glycine, etc., have been employed as potential co-formers. The review focus on the prevailing drug AMORP strategies used in pharmaceutical research, including in situ AMORP, COA systems, and mesoporous particle-based methods. Moreover, brief characterization techniques and the application of the different amino acids in stabilization and solubility improvements have been related.

Coformer-Dependent Physical Stability in a Series of Naringenin-Based Coamorphous Materials with Caffeine, Theophylline, and Theobromine

PURPOSE

To investigate the production and physical stability of coamorphous materials (CAM) of naringenin (NAR) and coformers-caffeine, theophylline or theobromine (CAF/THY/THE, respectively). We independently assessed the impact of moisture and temperature on the physical stability of CAMs, and transformation products after destabilization were examined.

METHODS

Neat grinding, liquid assisted grinding and water slurry were selected to prepare multi-component materials with NAR and CAF, THY or THE. The physical stability of CAMs was investigated at 65°C/<10%RH, 21°C/85% RH and 21°C/<10% RH. Differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) were employed to monitor for recrystallization during the stability studies. Glass forming ability of amorphous NAR was assessed to understand CAM formation and physical stability.

RESULTS

NAR:THY and NAR:THE CAMs showed physical stability for approximately nine months, under 21°C/<10% RH while NAR:CAF CAMs destabilized in 2.5 weeks. All CAMs recrystallized within a week at 65°C/<10%RH, and the physical stability at 21°C/85% RH was in the order of - NAR:THY > NAR:THE > NAR:CAF. NAR:THY produced 1:1 cocrystal under all storage conditions, while NAR:CAF destabilized to a 1:1 cocrystal at high RH but a physical mixture at high temperature. NAR:THE was found to recrystallize as a physical mixture in all conditions. NAR was found to be strong glass, with moderate kinetic fragility and good glass forming ability.

CONCLUSION

Five naringenin-based multi-component solids were generated in this study: 3 new CAMs, 1 new cocrystal, and 1 previously reported cocrystal. Destabilization of CAMs was found to be exposure specific and coformer dependent.

Amorphous solid dispersions: Stability mechanism, design strategy and key production technique of hot melt extrusion

Solid dispersion (SD) system has been used as an effective formulation strategy to increase in vitro and in vivo performances of poorly water-soluble drugs, such as solubility/dissolution, stability and bioavailability. This review provides a comprehensive SD classification and identifies the most popular amorphous solid dispersions (ASDs). Meanwhile, this review further puts forward the systematic design strategy of satisfactory ASDs in terms of drug properties, carrier selection, preparation methods and stabilization mechanisms. In addition, hot melt extrusion (HME) as the continuous manufacturing technique is described including the principle and structure of HME instrument, key process parameters and production application, in order to guide the scale-up of ASDs and develop more ASD products to the market in pharmaceutical industry.

Solubility and Physical Stability Enhancement of Loratadine by Preparation of Co-Amorphous Solid Dispersion with Chlorpheniramine and Polyvinylpyrrolidone

Loratadine (LRD), a non-sedating and slow-acting antihistamine, is often given in combination with short-onset chlorpheniramine maleate (CPM) to increase efficacy. However, LRD has poor water solubility resulting in low bioavailability. The aim of this study was to improve LRD solubility by preparing co-amorphous LRD-CPM. However, the obtained co-amorphous LRD-CPM recrystallized rapidly, and the solubility of LRD returned to a poor state again. Therefore, co-amorphous LRD-CPM solid dispersions using polyvinylpyrrolidone (PVP) as a carrier were prepared. The obtained solid dispersions were characterized using X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR). The solubility, dissolution, and mechanism of drug release from the LRD-CPM/PVP co-amorphous solid dispersions were studied and compared with those of intact LRD, LRD/PVP solid dispersions, and co-amorphous LRD-CPM mixtures. The results from XRPD and DSC confirmed the amorphous form of LRD in the co-amorphous solid dispersions. The FTIR results indicated that there was no intermolecular interaction between LRD, CPM, and PVP. In conclusion, the obtained LRD-CPM/PVP co-amorphous solid dispersions can successfully increase the water solubility and dissolution of LRD and extend the amorphous state of LRD without recrystallization.

Effect of Basic Amino Acids on Folic Acid Solubility

To prevent neural tube defects and other cardiovascular diseases in newborns, folic acid (FA) is recommended in pregnant women. A daily dose of 600 µg FA consumption is widely prescribed for women during pregnancy and 400 µg for women with childbearing potential. FA is a class IV compound according to the Biopharmaceutics Classification System (BCS) due to its low permeability (1.7 × 10-6 cm/s) and low solubility (1.6 mg/L); therefore, it must be administered via a formulation that enhances its solubility. Studies reported in the literature have proved that co-amorphization and salt formation of a poorly soluble drug with amino acids (AA) can significantly increase its solubility. Although arginine has been used with FA as a supplement, there is no information on the effect of basic AA (arginine and lysine) on the physical and chemical properties of FA-AA binary formulations. The present study implemented a conductimetric titration methodology to find the effective molar ratio to maximize FA solubility. The results showed that a 1:2.5 FA:AA molar ratio maximized solubility for arginine and lysine. Binary formulations were prepared using different methods, which led to an amorphous system confirmed by the presence of a glass transition, broad FTIR bands, and the absence of an X-ray diffraction pattern. Results of FA:AA (1:2.5) solubility increased in the range of 5500-6000 times compared with pure FA. In addition to solubility enhancement, the binary systems presented morphological properties that depend on the preparation method and whose consideration could be strategic for scaling purposes.

Non-salt based co-amorphous formulation produced by freeze-drying

Amino acids-based co-amorphous system (CAM) has shown to be a promising approach to overcome the dissolution challenge of biopharmaceutics classification system class II drugs. To date, most CAM formulations are based on salt formation at a 1:1 M ratio and are prepared by mechanical activation. However, its use in medicinal products is still limited due to the lack of in-depth understanding of non-ionic based molecular interactions. There are also limited studies on the effect of drug-to-co-former ratio, the development of more scalable, less aggressive, manufacturing processes such as freeze drying and its dissolution benefits. This work aims to investigate the effect of the ratio of tryptophan (a model non-ionic amino acid) to indomethacin (a model drug) on a non-salt-based CAM prepared via freeze-drying with the tert-butyl alcohol-water cosolvent system. The CAM material was systemically characterized at various stages of the freeze-drying process using DSC, UV-Vis, FT-IR, NMR, TGA and XRPD. Dissolution performance and physical stability upon storage were also investigated. Freeze-drying using the cosolvent system has been successfully shown to produce CAMs. The molecular interactions involving H-bonding, H/π and π-π between compounds have been confirmed by FT-IR and NMR. The drug release rate for formulations with a 1.5:1 drug: amino acid molar ratio (or 1:0.42 wt ratio) or below is found to be significantly improved compared to the pure crystalline drug. Furthermore, formulation with a 2.3:1 drug:amino acid molar ratio (or 1:0.25 wt ratio) or below have shown to be physically stable for at least 9 months when stored at dry condition (5% relative humidity, 25 °C) compared to the pure amorphous indomethacin. We have demonstrated the potential of freeze-drying using tert-butyl alcohol-water cosolvent system to produce an optimal non-salt-based class II drug-amino acid CAM.

Wet granulation of co-amorphous indomethacin systems

The feasibility of co-amorphous systems to be wet granulated together with microcrystalline cellulose (MCC) was investigated. Solid state and molecular interactions were analysed for various co-amorphous drug-amino acid formulations of indomethacin with tryptophan and arginine, respectively, via XRPD, DSC and FTIR. The co-amorphous binary systems were produced by ball-milling for 90 min at different molar ratios followed by wet granulation with MCC and water in a miniaturised scale. Tryptophan containing systems showed crystalline reflections in their XRPD diffractograms and endothermal events in their DSC analyses, and were therefore excluded from upscaling attempts. The systems containing arginine were found to be remain amorphous for at least ten months and were upscaled for production in a high-shear blender under application of two different parameter settings. Under the harsher instrument settings, a composition with a low MCC ratio experienced recrystallisation during wet granulation, while all other compositions could be successfully processed via wet granulation and stayed stable for a storage period of at least twelve weeks, indicating that wet granulation of co-amorphous systems can be feasible.

A computational-based approach to fabricate Ceritinib co-amorphous system using a novel co-former Rutin for bioavailability enhancement

In this study, we used molecular simulations to design Ceritinib (CRT) co-amorphous materials (CAMs) with concurrent improvement in solubility and bioavailability. Computational modeling enabled us to select the co-former by estimating the binding energy and intermolecular interactions. Rutin (RTH) was selected as a co-former for CRT CAMs using the solvent evaporation method to anticipate simultaneous improvement of solubility and bioavailability. The solid state characterization using DSC, XRPD, FT-IR, and a significant shift in Gordon Taylor experimental Tg values of co-amorphous materials revealed single amorphous phase formation and intermolecular interactions between CRT and RTH. The co-amorphous materials exhibited physical stability for up to 4 months under dry conditions (40 °C). Further, co-amorphous materials maintained the supersaturation for 24 hrs and improved solubility as well as dissolution of CRT. CRT:RTH 1:1 CAMs improved the permeability of CRT by 2 fold, estimated by employing the everted gut sac method. The solubility advantage of CAMs was also reflected in pharmacokinetic parameters, with a 3.1-fold and 2-fold improvement of CRT:RTH 2:1 in CRT exposure (AUC 0-t) and plasma concentration (Cmax) compared to the physical mixture, respectively.

Diversity of Solid Forms Promoted by Ball Milling: Characterization and Intrinsic Dissolution Studies of Pioglitazone Hydrochloride and Fluvastatin Sodium Drug-Drug Systems

Coamorphous salt in a 1:1 ratio prepared by ball milling from Fluvastatin sodium (FLV) and Pioglitazone hydrochloride (PGZ·HCl) can be selectively formed by neat grinding (NG). Furthermore, the salt-cocrystal continuum was preferably formed by employing liquid-assisted grinding (LAG) using ethanol (EtOH). Attempts to prepare the coamorphous salt starting from the salt-cocrystal continuum by NG were unsuccessful. Interestingly, through ball milling by NG or LAG, a great diversity of solid forms (PGZ·HCl-FLV 1:1) could be accessed: NG and hexane (coamorphous); ethyl acetate (physical mixture); EtOH (salt-cocrystal continuum); and water (which presents two T_g, indicating immiscibility of the components). An exploration was performed at different drug-to-drug ratios by NG. By differential scanning calorimetry (DSC), the presence of two endothermic events was observed in this screening: incongruous melting point (solidus) and excess of one of the components (liquidus), except in the 1:1 solid form. From these results, eutectic behavior was observed. Through the construction of a binary phase diagram, it was determined that the 1:1 molar ratio gives rise to the formation of the most stable coamorphous composition. Dissolution profile studies of these solid forms were carried out, specifically on pure FLV and the solid forms of PGZ⋅HCl-FLV (1:2; 1:4; and 1:6), together with the coamorphous 1:1 salt. By itself, pure FLV presented the highest K_int (13.6270 ± 0.8127 mg/cm²⋅min). On the other hand, the coamorphous 1:1 showed a very low K_int (0.0220 ± 0.0014 mg/cm²·min), indicating very fast recrystallization by the FLV, which avoids observing a sudden release of this drug in the solution. This same behavior was observed in the eutectic composition 1:2. In the other solid forms, the value of K_int increases along with the %w of FLV. From the mechanochemical point of view, ball milling by NG or LAG became an important synthetic tool since it allows obtaining a great variety of solid forms to explore the solid-state reactivity of the drug-drug solid-form PGZ HCl-FLV.

Kinetic Stability and Glass-Forming Ability of Thermally Labile Quinolone Antibiotics

The application of drugs in the amorphous state is one way to improve their bioavailability. As such, the determination of the optimal conditions for production and the assessment of the stability of the amorphous system are actively researched topics of present-day pharmaceutical science. In the present work, we have studied the kinetic stability and glass-forming ability of the thermally labile quinolone antibiotics using fast scanning calorimetry. The critical cooling rates for avoiding crystallization of the melts of oxolinic and pipemidic acids and sparfloxacin were determined to be 10 000, 40, and 80 K·s^-1, respectively. The studied antibiotics were found to be "strong" glass formers. Based on a combination of nonisothermal and isothermal kinetic approaches, the Nakamura model was suitable for describing the crystallization process of the amorphous forms of the quinolone antibiotics.

Amorphization of Ethenzamide and Ethenzamide Cocrystals-A Case Study of Single and Binary Systems Forming Low-Melting Eutectic Phases Loaded on/in Silica Gel

The applicability of different solvent-free approaches leading to the amorphization of active pharmaceutical ingredients (APIs) was tested. Ethenzamide (ET), an analgesic and anti-inflammatory drug, and two ethenzamide cocrystals with glutaric acid (GLU) and ethyl malonic acid (EMA) as coformers were used as pharmaceutical models. Calcinated and thermally untreated silica gel was applied as an amorphous reagent. Three methods were used to prepare the samples: manual physical mixing, melting, and grinding in a ball mill. The ET:GLU and ET:EMA cocrystals forming low-melting eutectic phases were selected as the best candidates for testing amorphization by thermal treatment. The progress and degree of amorphousness were determined using instrumental techniques: solid-state NMR spectroscopy, powder X-ray diffraction, and differential scanning calorimetry. In each case, the API amorphization was complete and the process was irreversible. A comparative analysis of the dissolution profiles showed that the dissolution kinetics for each sample are significantly different. The nature and mechanism of this distinction are discussed.

Introduction to Pharmaceutical Co-amorphous Systems Using a Green Co-milling Technique

The concept of co-amorphous systems is introduced in an integrated laboratory experiment, designed for advanced chemistry students, using solvent-free, environmentally friendly mechanochemistry. The dual-drug naproxen-cimetidine co-amorphous system (NPX-CIM) is investigated as an example of the emergent field of medicinal mechanochemistry. Students are trained in solid-state characterization techniques including X-ray powder diffraction, Fourier-transform infrared spectroscopy, and thermal analysis by differential scanning calorimetry. This lab experiment also provides an opportunity to discuss the relevance of different solid forms of pharmaceutics, emphasizing particular properties of disordered materials. This experiment can easily fit the curriculum of any Chemistry or Pharmacy master level degree in courses dealing with instrumental analysis, solid state chemistry, or green chemistry, for classes of 6 to 18 students, in a 5-h lab session. Suggestions to adapt it to the use of a single characterization technique are provided.

In silico and in vitro investigation of bile salts as coformers for edaravone coamorphous dispersion- Part I

In the present study, we aimed to design the spray-dried coamorphous dispersion (COAM) of a neuroprotective agent-edaravone (EDR) with bile salts to improve oral bioavailability. After the initial screening of different bile salts, EDR-sodium taurocholate (NaTC) COAM showed 4-fold solubility than a pure drug in 1-7pH range. In silico studies to select coformer for COAM revealed a narrow energy gap, easy charge transfer and high chemical reactivity between EDR and NaTC. The optimized EDR-NaTC COAM in a 1:1 molar ratio was characterized for solid state characterizations and in vitro release study. Hydrogen bond formation between the pyrazolone ring of EDR and the -OH group of the phenanthrene ring of NaTC was observed in the ATR-FTIR spectra of COAM. The DSC and XRPD data indicated the formation of an amorphous halo, whereas SEM photographs demonstrated porous, spherical particles of COAM. The pH-independent in vitro drug release of COAM was observed in 0.1N HCl, pH 4.5 and 6.8 buffers which was 3-fold higher than EDR. The COAM was stable for 6 months at accelerated condition without showing a change in drug content or devitrification (Initial: 98.002±0.942%; Accelerated condition: 97.016±1.110%). Although coamorphous form and hydrogen bonding between EDR-NaTC dispersion were primarily responsible for improved dissolution, NaTC, an exceptional surfactant, has also contributed to it. Moreover, its exclusive structural characteristics could prevent the recrystallization of the drug in supersaturated conditions of the GIT and also minimize the effect of food on oral absorption of EDR which will be studied in animals in the second part of this work.

Characterization of Co-amorphous Carvedilol-Maleic Acid System Prepared by Solvent Evaporation

The aim of this study was to enhance the solubility and stability of the water-insoluble drug carvedilol (CAR) with maleic acid (MLE) to create a co-amorphous system by a solvent evaporation method. Phase diagrams of co-amorphous CAR-MLE, constructed from peak height in the Fourier-transform infrared (FTIR) spectra and the glass transition temperature (Tg) from differential scanning calorimetry (DSC) measurements, revealed that the optimal molar ratio of CAR to MLE was 2:1. The FTIR spectra indicated that the secondary amine-derived peak of CAR and the carboxy group-derived peak of MLE disappeared in the CAR:MLE (2:1) co-amorphous system. DSC measurements showed that the endothermic peaks associated with the melting of CAR and MLE disappeared and a Tg at 43 °C was apparent. Furthermore, the solubility of CAR tested using the shaking flask method for 24 h at 37 °C was 1.2 μg/mL, whereas that of the co-amorphous system was approximately three times higher, at 3.5 μg/mL. Finally, the stability was evaluated by powder- X-ray diffraction at 40 °C; no clear diffraction peaks originating from crystals were observed in the amorphous state until after approximately 3 months of storage. These results indicate that co-amorphization of CAR with MLE improved the solubility of CAR while maintaining its stability in an amorphous form.

Solid–Liquid Equilibrium in Co-Amorphous Systems: Experiment and Prediction

In this work, the solid–liquid equilibrium (SLE) of four binary systems combining two active pharmaceutical ingredients (APIs) capable of forming co-amorphous systems (CAMs) was investigated. The binary systems studied were naproxen-indomethacin, naproxen-ibuprofen, naproxen-probucol, and indomethacin-paracetamol. The SLE was experimentally determined by differential scanning calorimetry. The thermograms obtained revealed that all binary mixtures investigated form eutectic systems. Melting of the initial binary crystalline mixtures and subsequent quenching lead to the formation of CAM for all binary systems and most of the compositions studied. The experimentally obtained liquidus and eutectic temperatures were compared to theoretical predictions using the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state and conductor-like screening model for real solvents (COSMO-RS), as implemented in the Amsterdam Modeling Suite (COSMO-RS-AMS). On the basis of the obtained results, the ability of these models to predict the phase diagrams for the investigated API–API binary systems was evaluated. Furthermore, the glass transition temperature (Tg) of naproxen (NAP), a compound with a high tendency to recrystallize, whose literature values are considerably scattered, was newly determined by measuring and modeling the Tg values of binary mixtures in which amorphous NAP was stabilized. Based on this analysis, erroneous literature values were identified.

Influence of Co-amorphization on the Physical Stability and Dissolution Performance of an Anthelmintic Drug Flubendazole

In this work, the co-amorphization approach was applied to flubendazole (FluBZ), resulting in the formation of two novel solid forms of FluBZ with l-phenylalanine (Phe) and l-tryptophan (Trp). A variety of physicochemical techniques have been used to describe new systems, including powder X-ray diffraction, thermal methods, infrared spectroscopy, and scanning electron microscopy. Co-amorphization has been shown to suppress crystallization tendency and considerably increase the shelf-life storage of amorphous flubendazole solid across a wide range of relative humidities. The dissolution behavior of the amorphous forms in biorelevant media at pH = 1.6, pH = 6.5, and 37 °C has been studied in terms of C_max (maximum FluBZ concentration), T_max (time to attain peak drug concentration), and AUC (concentration area under the curve during dissolution). At pH = 6.5, a continuous supersaturation and the highest AUC value of all examined systems were observed for the FluBZ-Phe (1:1) system. The phase solubility diagrams revealed that the reason for the better dissolution performance of FluBZ-Phe (1:1) at pH = 6.5 is a complexation between the components in a solution. This work highlights the applicability of co-amorphous systems in improving the physical stability and dissolution performance of drug compounds with poor biopharmaceutical characteristics.

Compaction Behavior of Co-Amorphous Systems

Co-amorphous systems have been shown to be a promising strategy to address the poor water solubility of many drug candidates. However, little is known about the effect of downstream processing-induced stress on these systems. The aim of this study is to investigate the compaction properties of co-amorphous materials and their solid-state stability upon compaction. Model systems of co-amorphous materials consisting of carvedilol and the two co-formers aspartic acid and tryptophan were produced via spray drying. The solid state of matter was characterized using XRPD, DSC, and SEM. Co-amorphous tablets were produced with a compaction simulator, using varying amounts of MCC in the range of 24 to 95.5% (w/w) as a filler, and showed high compressibility. Higher contents of co-amorphous material led to an increase in the disintegration time; however, the tensile strength remained rather constant at around 3.8 MPa. No indication of recrystallization of the co-amorphous systems was observed. This study found that co-amorphous systems are able to deform plastically under pressure and form mechanically stable tablets.

Ball-Milling Preparation of the Drug-Drug Solid Form of Pioglitazone-Rosuvastatin at Different Molar Ratios: Characterization and Intrinsic Dissolution Rates Evaluation

Ball-milling using neat grinding (NG) or liquid-assisted grinding (LAG) by varying the polarity of the solvents allowed access to various drug-drug solid forms of pioglitazone hydrochloride (PGZ·HCl) and rosuvastatin calcium (RSV). Using NG, the coamorphous form was formed from the reaction of pioglitazone hydrochloride (PGZ·HCl) and rosuvastatin calcium (RSV) in a 2:1 molar ratio. The formation of the expected coamorphous salt could not be corroborated by FT-IR, but DSC data showed that it was indeed a single-phase amorphous mixture. By varying the molar ratios of the reactants, either keeping PGZ·HCl constant and varying RSV or vice versa, another coamorphous form was obtained when a 1:1 molar ratio was employed. In the case of the other outcomes, it was observed that they were a mixture of solid forms coexisting simultaneously with the coamorphous forms (1:1 or 2:1) together with the drug that was in excess. When RSV was in excess, it was in an amorphous form. In the case of PGZ·HCl, it was found in a semicrystalline form. The intrinsic dissolution rates (IDRs) of the solid forms of PGZ·HCl-RSV in stoichiometric ratios (1:1, 2:1, 1:4, 6:1, and 1:10) were evaluated. Interestingly, a synchronized release of both drugs in the dissolution medium was observed. In the case of the release of RSV, there were no improvements in the dissolution profiles, because the acidic media caused the formation of degradation products, limiting any probable modification in the dissolution processes. However, the coamorphous 2:1 form exhibited an improvement of 1.03 times with respect to pure PGZ·HCl. It is proposed that the modification of the dissolution process of the coamorphous 2:1 form was limited by changes in the pH of the media as RSV consumes protons from the media due to degradation processes.

Current Techniques of Water Solubility Improvement for Antioxidant Compounds and Their Correlation with Its Activity: Molecular Pharmaceutics

The aqueous solubility of a drug is important in the oral formulation because the drug can be absorbed from intestinal sites after being dissolved in the gastrointestinal fluid, leading to its bioavailability. Almost 80% of active pharmaceutical ingredients are poorly water-soluble, including antioxidant compounds. This makes antioxidant activity inefficient in preventing disease, particularly for orally administered formulations. Although several investigations have been carried out to improve the solubility of antioxidant compounds, there is still limited research fully discussing the subject. Therefore, this study aimed to provide an overview and discussion of the issues related to the methods that have been used to improve the solubility and activity of antioxidant compounds. Articles were found using the keywords "antioxidant" and "water solubility improvement" in the Scopus, PubMed, and Google Scholar databases. The selected articles were published within the last five years to ensure all information was up-to-date with the same objectives. The most popular methods of the strategies employed were solid dispersion, co-amorphous, and nanoparticle drug delivery systems, which were used to enhance the solubility of antioxidant compounds. These investigations produced impressive results, with a detailed discussion of the mechanism of improvement in the solubility and antioxidant activity of the compounds developed. This review shows that the strategies used to increase the solubility of antioxidant compounds successfully improved their antioxidant activity with enhanced free radical scavenging abilities.

Physicochemical Properties and Transdermal Absorption of a Flurbiprofen and Lidocaine Complex in the Non-Crystalline Form

Amorphous drug formulations exploiting drug-drug interactions have been extensively studied. This study aims to develop a transdermal system containing an amorphous complex of the nonsteroidal anti-inflammatory drug (NSAID) flurbiprofen (FLU) and lidocaine (LDC) for alleviating chronic pain. The high-viscosity complex between FLU and LDC (Complex) was obtained by heating in ethanol. For the complex, attenuated total reflection-Fourier transform infrared spectroscopy showed a shift in the carboxy-group-derived peak of FLU, and differential scanning calorimetry indicated the endothermic peaks associated with the melting of FLU and LDC disappeared. ¹³C dipolar decoupling and ¹⁵N cross-polarization magic-angle spinning nuclear magnetic resonance measurement suggested the interaction between the carboxyl group of FLU and the secondary amine of LDC. The interaction between the aromatic rings of FLU and LDC contributed to the molecular complex formation. The solubility of FLU from the complex was about 100 times greater than FLU alone. The skin permeation flux of FLU from the complex through the hairless mouse skin was 3.8 times higher than FLU alone in hypromellose gel. Thus, adding LDC to the formulation can be an effective method for enhancing the skin permeation of NSAIDs, which can prove useful for treating chronic pain and inflammatory diseases.

Gelation Elimination and Crystallization Inhibition by Co-Amorphous Strategy for Amorphous Curcumin

In the previous study, the development of amorphous curcumin (CUR) aimed to enhance the solubility/dissolution of CUR by disrupting its crystal lattice, but it unexpectedly showed a decreased dissolution than its crystalline counterpart on account of gel formation in its dissolution process. Whether such gelation could be eliminated by co-amorphous strategy was answered in this study. Herein, CUR by co-amorphization with chlorogenic acid (CHA) was successfully prepared using quench cooling. The formed co-amorphous material (namely CUR-CHA CM) eliminated the gelation and hence performed superior dissolution performance than crystalline/amorphous CUR. Meanwhile, it exhibited higher physical stability than amorphous CUR during dissolution as well as under long-term/accelerated conditions. To further study the such enhancement mechanism, the internal molecular interactions were investigated for CUR-CHA CM in the solid state as well as in aqueous solution. FTIR and solid-state ¹³C NMR spectra confirmed that intermolecular hydrogen bonds formed between CUR and CHA after co-amorphization. Furthermore, the nucleation of CUR was significantly inhibited by CHA in an aqueous solution, thus maintaining the supersaturated dissolution for a long time. The present study offers a feasible strategy to eliminate gelation and enhance stability of amorphous solids by co-amorphization and crystallization inhibition.

Sulfonic Acid Derivatives in the Production of Stable Co-Amorphous Systems for Solubility Enhancement

Co-amorphization is a promising approach to stabilize drugs in the amorphous form. Olanzapine, a poorly water-soluble drug was used in this study. Sulfonic acids (saccharin, cyclamic acid and acesulfame), free and in salt forms, were used as co-formers and compared with carboxylic acids commonly used in the preparation of co-amorphous systems. Several manufacturing techniques were tested, and the co-amorphous systems characterized by differential scanning calorimetry, X-ray powder diffraction, thermogravimetry and Fourier-transform infrared spectroscopy. Free sulfonic acids produced co-amorphous systems with the drug, unlike their salts. Spectroscopy data suggests the formation of salts between olanzapine and the sulfonic acids, used as co-formers. The co-amorphous system produced with saccharin by solvent evaporation, showed the most notable solubility enhancement (145 times). The stability of amorphous and co-amorphous olanzapine systems was assessed upon exposure to stress conditions during storage. Amorphized olanzapine readily reconverted back to the crystalline form while sulfonic acids:olanzapine co-amorphous were stable for up to 24 weeks in low/medium humidity conditions (11-75% RH). Results highlight the potential advantages offered by sulfonic acids as co-formers to produce stable and more soluble co-amorphous olanzapine.

Solventless amorphization and pelletization using a high shear granulator. Part II; Preparation of co-amorphous mixture-layered pellets using indomethacin and arginine

The aim of this study was to investigate the preparation of co-amorphous mixture-layered pellets using solventless pelletization and amorphization using a high shear granulator (as suggested in the first part of this study) by high shear mixing of drug crystals and a crystalline co-former with inactive spheres. Mixtures of crystalline indomethacin and arginine at various molar ratios were mixed with microcrystalline cellulose spheres at a weight ratio of 1:10 using the granulator and the resulting particles were characterized using solid-state and particle analytical techniques as well as dissolution testing and physical stability. At jacket temperatures of 20 °C or more of the granulator, co-processing of indomethacin and arginine enhanced amorphization of indomethacin and provided a co-amorphous mixture due to homogenous mixing of indomethacin and arginine amorphous phases. The co-amorphous mixture was deposited on the surface of the spheres, yielding co-amorphous mixture-layered pellets. The co-amorphous mixtures at molar ratios of indomethacin to arginine of 2:1 and 1:1, deposited on the pellets, did not recrystallize for at least 4 weeks. The pellets exhibited higher dissolution characteristics as additional hypromellose could prevent precipitation. These findings demonstrate the potential of this technique as a solventless approach to prepare co-amorphous mixture-layered pellets through a one-step process.

In Situ Co-Amorphization of Olanzapine in the Matrix and on the Coat of Pellets

In situ amorphization is a promising approach, considered in the present work, to enhance the solubility and dissolution rate of olanzapine, while minimizing the exposure of the amorphous material to the stress conditions applied during conventional processing. The production of pellets by extrusion/spheronization and the coating of inert beads were investigated as novel methods to promote the co-amorphization of olanzapine, a poorly water-soluble drug, and saccharin. Samples were characterized using differential scanning calorimetry, X-ray powder diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy, and dissolution and stability testing. The co-amorphous produced were compared with crystalline olanzapine, or physical mixture of olanzapine and saccharin. Results suggested that the addition of water to mixtures containing olanzapine and saccharin during the production of pellets, and the coating of inert beads, induced the in situ co-amorphization of these substances. The coating of inert beads enhanced the solubility and dissolution rate of olanzapine, especially when compared to pellets coated with the crystalline drug, but also with pellets containing the co-amorphous entity in the matrix of beads. Nine months stability tests (23 °C/60% RH) confirmed the preservation of the solid-state properties of the co-amorphous form on/in pellets. Overall, results highlighted the feasibility and benefits of in situ co-amorphization, either when the drug was entrapped in the pellets matrix, or preferentially applied directly on the surface of pellets.

Solid state of inhalable high dose powders

High dose inhaled powders have received increased attention for treating lung infections. These powders can be prepared using techniques such as spray drying, spray-freeze drying, crystallization, and milling. The selected preparation technique is known to influence the solid state of the powders, which in turn can potentially modulate aerosolization and aerosolization stability. This review focuses on how and to what extent the change in solid state of high dose powders can influence aerosolization. It also discusses the commonly used solid state characterization techniques and the application of potential strategies to improve the physical and chemical stability of the amorphous powders for high dose delivery.

Mechanical Activation by Ball Milling as a Strategy to Prepare Highly Soluble Pharmaceutical Formulations in the Form of Co-Amorphous, Co-Crystals, or Polymorphs

Almost half of orally administered active pharmaceutical ingredients (APIs) have low solubility, which affects their bioavailability. In the last two decades, several alternatives have been proposed to modify the crystalline structure of APIs to improve their solubility; these strategies consist of inducing supramolecular structural changes in the active pharmaceutical ingredients, such as the amorphization and preparation of co-crystals or polymorphs. Since many APIs are thermosensitive, non-thermal emerging alternative techniques, such as mechanical activation by milling, have become increasingly common as a preparation method for drug formulations. This review summarizes the recent research in preparing pharmaceutical formulations (co-amorphous, co-crystals, and polymorphs) through ball milling to enhance the physicochemical properties of active pharmaceutical ingredients. This report includes detailed experimental milling conditions (instrumentation, temperature, time, solvent, etc.), as well as solubility, bioavailability, structural, and thermal stability data. The results and description of characterization techniques to determine the structural modifications resulting from transforming a pure crystalline API into a co-crystal, polymorph, or co-amorphous system are presented. Additionally, the characterization methodologies and results of intermolecular interactions induced by mechanical activation are discussed to explain the properties of the pharmaceutical formulations obtained after the ball milling process.

Platensimycin-berberine chloride co-amorphous drug system: Sustained release and prolonged half-life

Co-amorphous technology is an emerging approach for pharmaceutical engineering of drugs and drug leads with improved physicochemical properties and bioavailability. Platensimycin (PTM) is a promising natural antibiotic lead that acts on bacterial fatty acid synthase and exhibits excellent antibacterial activity. Despite great strides to improve its poor pharmacokinetics by medicinal chemistry and nanotechnology, there are no convenient oral delivery systems developed. Here, a co-amorphous system of PTM and berberine chloride (BCL) was developed for oral delivery of PTM. Co-amorphous PTM-BCL was prepared by rotary vacuum evaporation method, and systematically characterized by powder X-ray diffraction, temperature modulated differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Compared with PTM or BCL alone, the equilibrium solubility and dissolution rate of both of them in the co-amorphous systems decreased significantly, showing the characteristics of sustained release. The molecular interactions between PTM and BCL were mediated by strong charged-mediated hydrogen bonds, based on FTIR, XPS, and NMR-based techniques. The co-amorphous PTM-BCL system showed excellent physiochemical stability at room and elevated (40 °C) temperature under dry conditions. The combination of PTM and BCL showed increased killing of a clinical isolated methicillin-resistant Staphylococcus aureus strain in killing checkerboard assays. Finally, co-amorphous PTM-BCL exhibited 2- or 3-fold longer half-life in rats than that of crystalline and amorphous PTM upon oral administration, respectively. Our study suggests a rational approach to realize the full potential of potent antibiotic PTM, which may be conveniently adapted for engineering of other important pharmaceutics.

Downstream Processing of Amorphous and Co-Amorphous Olanzapine Powder Blends

The work evaluates the stability of amorphous and co-amorphous olanzapine (OLZ) in tablets manufactured by direct compression. The flowability and the compressibility of amorphous and co-amorphous OLZ with saccharin (SAC) and the properties of the tablets obtained were measured and compared to those of tablets made with crystalline OLZ. The flowability of the amorphous and mostly of the co-amorphous OLZ powders decreased in comparison with the crystalline OLZ due to the higher cohesiveness of the former materials. The stability of the amorphous and co-amorphous OLZ prior to and after tableting was monitored by XRPD, FTIR, and NIR spectroscopies. Tablets presented long-lasting amorphous OLZ with enhanced water solubility, but the release rate of the drug decreased in comparison with tablets containing crystalline OLZ. In physical mixtures made of crystalline OLZ and SAC, an extent of amorphization of approximately 20% was accomplished through the application of compaction pressures and dwell times of 155 MPa and 5 min, respectively. The work highlighted the stability of amorphous and co-amorphous OLZ during tableting and the positive effect of compaction pressure on the formation of co-amorphous OLZ, providing an expedited amorphization technique, given that the process development-associated hurdles were overcome.

Prediction and Preparation of Coamorphous Phases of a Bislactam

The effectiveness of a partial least squares-discriminant analysis coamorphous prediction model was tested using coamorphous screening data for a promising coamorphous former, the dimer of N-vinyl(caprolactam) (bisVCap) with a range of active pharmaceutical ingredients. The prediction model predicted 71% of the systems correctly. An experimental coamorphous screen was performed with this coformer with 13 different active pharmaceutical ingredients, and the results were compared to the predictions from the model. A total of 85% of the systems were correctly predicted. Stability assessments of three coamorphous systems showed that the prediction model score did not strongly correlate with the stability of the coamorphous material. The model performed well with small-molecule coformers, such as bisVCap, despite the difference in structure and properties compared to the amino-acid-based model training set.

Amorphization of Drugs for Transdermal Delivery-a Recent Update

Amorphous solid dispersion is a popular formulation approach for orally administered poorly water-soluble drugs, especially for BCS class II. But oral delivery could not be an automatic choice for some drugs with high first-pass metabolism susceptibility. In such cases, transdermal delivery is considered an alternative if the drug is potent and the dose is less than 10 mg. Amorphization of drugs causes supersaturation and enhances the thermodynamic activity of the drugs. Hence, drug transport through the skin could be improved. The stabilization of amorphous system is a persistent challenge that restricts its application. A polymeric system, where amorphous drug is dispersed in a polymeric carrier, helps its stability. However, high excipient load often becomes problematic for the polymeric amorphous system. Coamorphous formulation is another approach, where one drug is mixed with another drug or low molecular weight compound, which stabilizes each other, restricts crystallization, and maintains a single-phase homogenous amorphous system. Prevention of recrystallization along with enhanced skin permeation has been observed by the transdermal coamorphous system. But scalable manufacturing methods, extensive stability study and in-depth in vivo evaluation are lacking. This review has critically studied the mechanistic aspects of amorphization and transdermal permeation by analyzing recent researches in this field to propose a future direction.