A Strategy for Co-former Selection to Design Stable Co-amorphous Formations Based on Physicochemical Properties of Non-steroidal Inflammatory Drugs

Specific inter-molecular 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 M 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.

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.

Improvement in Inhalation Properties of Theophylline and Levofloxacin by Co-Amorphization and Enhancement in Its Stability by Addition of Amino Acid as a Third Component

Co-amorphous systems are amorphous formulations stabilized by the miscible dispersion of small molecules. This study aimed to design a stable co-amorphous system for the co-delivery of two drugs to the lungs as an inhaled formulation. Theophylline (THE) and levofloxacin (LEV) were used as model drugs for treating lung infection with inflammation. Leucine (LEU) or tryptophan (TRP) was employed as the third component to improve the inhalation properties. The co-amorphous system containing THE and LEV in an equal molar ratio was successfully prepared via spray drying where reduction of the particle size and change to the spherical morphology were observed. The addition of LEU or TRP at a one-tenth molar ratio to THE-LEV did not affect the formation of the co-amorphous system, but only TRP acted as an antiplasticizer. The Fourier transform infrared spectroscopy spectra revealed intermolecular interactions between THE and LEV in the co-amorphous system that were retained after the addition of LEU or TRP. The co-amorphous THE-LEV system exhibited better in vitro aerodynamic performance than a physical mixture of these compounds and permitted the simultaneous delivery of both drugs in various stages. The co-amorphous THE-LEV system crystallized at 40 °C, and this crystallization was not prevented by LEU. However, THE-LEV-TRP maintained its amorphous state for 1 month. Thus, TRP can act as a third component to improve the physical stability of the co-amorphous THE-LEV system, while maintaining the enhanced aerodynamic properties.

Application of Sucrose Acetate Isobutyrate in Development of Co-Amorphous Formulations of Tacrolimus for Bioavailability Enhancement

The focus of the present work was to develop co-amorphous dispersion (CAD) formulations of tacrolimus (TAC) using sucrose acetate isobutyrate as a carrier, evaluate by in vitro and in vivo methods and compare its performance with hydroxypropyl methylcellulose (HPMC) based amorphous solid dispersion (ASD) formulation. CAD and ASD formulations were prepared by solvent evaporation method followed by characterization by Fourier transformed infrared spectroscopy, X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), dissolution, stability, and pharmacokinetics. XRPD and DSC indicated amorphous phase transformation of the drug in the CAD and ASD formulations, and dissolved more than 85% of the drug in 90 min. No drug crystallization was observed in the thermogram and diffractogram of the formulations after storage at 25 °C/60% RH and 40 °C/75% RH. No significant change in the dissolution profile was observed after and before storage. SAIB-based CAD and HPMC-based ASD formulations were bioequivalent as they met 90% confidence of 90-11.1% for C_max and AUC. The CAD and ASD formulations exhibited C_max and AUC 1.7-1.8 and 1.5-1.8 folds of tablet formulations containing the drug's crystalline phase. In conclusion, the stability, dissolution, and pharmacokinetic performance of SAIB-based CAD and HPMC-based ASD formulations were similar, and thus clinical performance would be similar.

Data-Driven Prediction of the Formation of Co-Amorphous Systems

Co-amorphous systems (COAMS) have raised increasing interest in the pharmaceutical industry, since they combine the increased solubility and/or faster dissolution of amorphous forms with the stability of crystalline forms. However, the choice of the co-former is critical for the formation of a COAMS. While some models exist to predict the potential formation of COAMS, they often focus on a limited group of compounds. Here, four classes of combinations of an active pharmaceutical ingredient (API) with (1) another API, (2) an amino acid, (3) an organic acid, or (4) another substance were considered. A model using gradient boosting methods was developed to predict the successful formation of COAMS for all four classes. The model was tested on data not seen during training and predicted 15 out of 19 examples correctly. In addition, the model was used to screen for new COAMS in binary systems of two APIs for inhalation therapy, as diseases such as tuberculosis, asthma, and COPD usually require complex multidrug-therapy. Three of these new API-API combinations were selected for experimental testing and co-processed via milling. The experiments confirmed the predictions of the model in all three cases. This data-driven model will facilitate and expedite the screening phase for new binary COAMS.

Mechanism for Stabilizing an Amorphous Drug Using Amino Acids within Co-Amorphous Blends

Designing co-amorphous formulations is now recognized as a relevant strategy for improving the bioavailability of low-molecular-weight drugs. In order to determine the most suitable low-molecular-weight excipients for stabilizing the drug in the amorphous state, screening methods were developed mostly using amino acids as co-formers. The present study focused on the analysis of the thermal stability of co-amorphous blends prepared by cryo-milling indomethacin with several amino acids in order to understand the stabilization mechanism of the drug in the amorphous state. Combining low- and mid-frequency Raman investigations has provided information on the relation between the physical properties of the blends and those of the H-bond network of the amorphous drug. This study revealed the surprising capabilities of L-arginine to stiffen the H-bond network in amorphous indomethacin and to drastically improve the stability of its amorphous state. As a consequence, this study suggests that amino acids can be considered as stiffeners of the H-bond network of indomethacin, thereby improving the stability of the amorphous state.

Design of a Stable Coamorphous System Using Lactose as an Antiplasticizing Agent for Diphenhydramine Hydrochloride with a Low Glass Transition Temperature

Coamorphous systems comprising small molecules are emerging as counterparts to polymeric solid dispersions. However, the glass transition temperatures (T_gs) of coamorphous materials are relatively low because of the lack of polymeric carriers with higher T_gs. This study aimed to investigate the applicability of lactose (LAC) as an antiplasticizing coformer to a coamorphous system. Diphenhydramine hydrochloride (DPH) was selected as a model drug (T_g = 16 °C). Differential scanning calorimetry showed a comelting point in addition to a decrease in the neat melting points depending on the composition of the physical mixtures, suggesting that the mixture of DPH-LAC was eutectic. The melting point of the eutectic mixture was calculated according to the Schröder-van Laar equation. The heat of fusion of the eutectic mixture was maximized at a 70:30 molar ratio of DPH to LAC; at this point, the melting peaks of the pure components disappeared. The heat flow profiles following the melting and cooling of DPH-LAC physical mixtures at the ratios from 10:90 to 90:10 showed a single T_g, suggesting the formation of a coamorphous system. Lactose showed a T_g of over 100 °C, and the T_g of DPH increased with the molar ratio of LAC; it was 84 °C at a 10:90 molar ratio of DPH to LAC. The Raman image indicated the formation of a homogeneous dispersion of DPH and LAC in the coamorphous system. Peak shifts in the infrared spectra indicated the presence of intermolecular interactions between the amino group of DPH and the hydroxyl group of LAC. Principal component analysis of the infrared spectra revealed a significant change at the 70:30 molar ratio of DPH to LAC, which was in agreement with the results of the thermal analysis. A stability test at 40 °C revealed rapid crystallization of the supercooled liquid DPH. The coamorphous samples containing 10-50% of LAC remained in an amorphous state for 21 days, and no crystallization was observed for the samples containing >60% of LAC for 28 days. The relatively lower T_g (less than 40 °C) of the coamorphous system containing 10-50% of LAC might have caused crystallization during storage. These findings indicate that LAC, which is a safe and widely used pharmaceutical excipient, can be applied to coamorphous systems as an antiplasticizing coformer.

Amino acids and its pharmaceutical applications: A mini review

Amino acids are natural compounds that can be safely used in pharmaceutical applications. Considering the great interest in the amino acids used in the pharmaceutical industry, this article presents an overview of investigations reported in recent years. In this regard, the first sections begin with an introductory description of the properties, classification and safety of amino acids, while in the other sections the most common methods for the preparation of amino acids formulations and their application on solubilization, permeation and stabilization of several active pharmaceutical ingredients are described. Furthermore, available data about the multicomponent systems approach is included. Lastly, the impact of amino acids formulations on therapeutic efficacy is explored. The advantages illustrated suggest that amino acids are capable of improving the biopharmaceutical properties of drugs.

Understanding Hygroscopicity of Theophylline via a Novel Cocrystal Polymorph: A Charge Density Study

The charge density distribution in a novel cocrystal (1) complex of 1,3-dimethylxanthine (theophylline) and propanedioic acid (malonic acid) has been determined. The molecules crystallize in the triclinic, centrosymmetric space group P1̅, with four independent molecules (Z = 4) in the asymmetric unit (two molecules each of theophylline and malonic acid). Theophylline has a notably high hygroscopic nature, and numerous cocrystals have shown a significant improvement in stability to humidity. A charge density study of the novel polymorph has identified interesting theoretical results correlating the stability enhancement of theophylline via cocrystallization. Topological analysis of the electron density highlighted key differences (up to 17.8) in Laplacian (∇²ρ) between the experimental (EXP) and single-point (SP) models, mainly around intermolecular-bonded carbonyls. Further investigation via molecular electrostatic potential maps reaffirmed that the charge redistribution enhanced intramolecular hydrogen bonding, predominantly for N(2') and N(2) (61.2 and 61.8 kJ mol^-1, respectively). An overall weaker lattice energy of the triclinic form (-126.1 kJ mol^-1) compared to that of the monoclinic form (-133.8 kJ mol^-1) suggests a lower energy threshold to overcome to initiate dissociation. Future work via physical testing of the novel cocrystal in both dissolution and solubility will further solidify the correlation between theoretical and experimental results.

Crystallization kinetics and molecular dynamics of binary coamorphous systems of nimesulide and profen analogs

Coamorphous drug delivery systems have emerged as a promising formulation technique for improving the solubility and oral bioavailability of poorly soluble drugs. The selection of a suitable coformer is the key to obtaining a successful coamorphous formulation. This study aims to investigate the impacts of coformers with similar chemical structures but different physical properties on the crystallization behavior and molecular dynamics of binary amorphous systems. The addition of three profen analogs, ibuprofen (IBU), ketoprofen (KETO) and indoprofen (INDO) leads to significantly different effects on the crystallization kinetics of amorphous nimesulide (NIME). The crystal growth rates for amorphous NIME are substantially accelerated in the presence of IBU, but drastically reduced in the presence of INDO, while the incorporation of KETO results in a negligible effect. Broadband dielectric spectroscopy is employed to characterize the molecular dynamics of neat amorphous NIME and coamorphous systems. The addition of three structural analogs alters the molecular mobility of amorphous NIME in different ways, which is consistent with the trend observed for their impacts on the crystallization kinetics, suggesting that the relative mobility between the components of coamorphous mixtures governs the physical stability. In addition, it is found that the temperature dependence of the α-relaxation times for NIME with and without coformers is superimposed once the temperature is scaled by T_g/T, whereas the crystallization kinetics do not overlap on a T_g/T scale. This deviation can result from a complex interplay of thermodynamic and kinetic factors involved in multicomponent amorphous systems. This study provides insights into the crystallization kinetics and molecular dynamics of coamorphous systems containing drug analogs, which can potentially offer more flexibility for the control of physical stability without sacrificing therapeutic efficacy.

Recent Technologies for Amorphization of Poorly Water-Soluble Drugs

Amorphization technology has been the subject of continuous attention in the pharmaceutical industry, as a means to enhance the solubility of poorly water-soluble drugs. Being in a high energy state, amorphous formulations generally display significantly increased apparent solubility as compared to their crystalline counterparts, which may allow them to generate a supersaturated state in the gastrointestinal tract and in turn, improve the bioavailability. Conventionally, hydrophilic polymers have been used as carriers, in which the amorphous drugs were dispersed and stabilized to form polymeric amorphous solid dispersions. However, the technique had its limitations, some of which include the need for a large number of carriers, the tendency to recrystallize during storage, and the possibility of thermal decomposition of the drug during preparation. Therefore, emerging amorphization technologies have focused on the investigation of novel amorphous-stabilizing carriers and preparation methods that can improve the drug loading and the degree of amorphization. This review highlights the recent pharmaceutical approaches utilizing drug amorphization, such as co-amorphous systems, mesoporous particle-based techniques, and in situ amorphization. Recent updates on these technologies in the last five years are discussed with a focus on their characteristics and commercial potential.

Prediction of the Synergistic Glass Transition Temperature of Coamorphous Molecular Glasses Using Activity Coefficient Models

The glass transition temperature (T_g) of a binary miscible mixture of molecular glasses, termed a coamorphous glass, is often synergistically increased over that expected for an athermal mixture due to the strong interactions between the two components. This synergistic interaction is particularly important for the formulation of coamorphous pharmaceuticals since the molecular interactions and resulting T_g strongly impact stability against crystallization, dissolution kinetics, and bioavailability. Current models that describe the composition dependence of T_g for binary systems, including the Gordon-Taylor, Fox, Kwei, and Braun-Kovacs equations, fail to describe the behavior of coamorphous pharmaceuticals using parameters consistent with experimental ΔC_P and Δα. Here, we develop a robust thermodynamic approach extending the Couchman and Karasz method through the use of activity coefficient models, including the two-parameter Margules, non-random-two-liquid (NRTL), and three-suffix Redlich-Kister models. We find that the models, using experimental values of ΔC_P and fitting parameters related to the binary interactions, successfully describe observed synergistic elevations and inflections in the T_g versus composition response of coamorphous pharmaceuticals. Moreover, the predictions from the NRTL model are improved when the association-NRTL version of that model is used. Results are reported and discussed for four different coamorphous systems: indomethacin-glibenclamide, indomethacin-arginine, acetaminophen-indomethacin, and fenretinide-cholic acid.

Considerations for the selection of co-formers in the preparation of co-amorphous formulations

Co-amorphous drug delivery systems are evolving as a credible alternative to amorphous solid dispersions technology. In Co-amorphous systems (CAMs), a drug is stabilized in amorphous form using small molecular weight compounds called as co-formers. A wide variety of small molecular weight co-formers have been leveraged in the preparation of CAMs. The stability and supersaturation potential of prepared co-amorphous phases largely depend on the type of co-former employed in the CAMs. However, the rationality behind the co-former selection in co-amorphous systems is poorly understood and scarcely compiled in the literature. There are various facets to the rational selection of co-former for CAMs. In this context, the present review compiles various factors affecting the co-former selection. The factors have been broadly classified under Thermodynamic, Kinetic and Pharmacokinetic-Pharmacologically relevant parameters. In particular, the importance of Glass transition, Miscibility, Liquid-Liquid phase separation (LLPS), Crystallization inhibition has been deliberated in detail.

Co-Amorphous Drug Formulations in Numbers: Recent Advances in Co-Amorphous Drug Formulations with Focus on Co-Formability, Molar Ratio, Preparation Methods, Physical Stability, In Vitro and In Vivo Performance, and New Formulation Strategies

Co-amorphous drug delivery systems (CAMS) are characterized by the combination of two or more (initially crystalline) low molecular weight components that form a homogeneous single-phase amorphous system. Over the past decades, CAMS have been widely investigated as a promising approach to address the challenge of low water solubility of many active pharmaceutical ingredients. Most of the studies on CAMS were performed on a case-by-case basis, and only a few systematic studies are available. A quantitative analysis of the literature on CAMS under certain aspects highlights not only which aspects have been of great interest, but also which future developments are necessary to expand this research field. This review provides a comprehensive updated overview on the current published work on CAMS using a quantitative approach, focusing on three critical quality attributes of CAMS, i.e., co-formability, physical stability, and dissolution performance. Specifically, co-formability, molar ratio of drug and co-former, preparation methods, physical stability, and in vitro and in vivo performance were covered. For each aspect, a quantitative assessment on the current status was performed, allowing both recent advances and remaining research gaps to be identified. Furthermore, novel research aspects such as the design of ternary CAMS are discussed.

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.

Predictive identification of co-formers in co-amorphous systems

This work aims to understand the properties of co-formers that form co-amorphous pharmaceutical materials and to predict co-amorphous system formation. A partial least square - discriminant analysis (PLS-DA) was performed using known co-amorphous systems described by 36 variables based on the properties of the co-former and the binding energy of the system. The PLS-DA investigated the propensity to form co-amorphous material of the active pharmaceutical ingredients: mebendazole, carvedilol, indomethacin, simvastatin, carbamazepine and furosemide in combination with 20 amino acid co-formers. The variables that were found to favour the propensity to form co-amorphous systems appear to be a relatively large value for average molecular weight and the sum of the difference between hydrogen bond donors and hydrogen bond acceptors for both components, and a relatively small or negative value for excess enthalpy of mixing, excess enthalpy of hydrogen bonding and the difference in the Hansen parameter for hydrogen bonding of the coformer and the active pharmaceutical ingredient (API). To test the predictive power of this model, 29 potential co-formers were used to form either co-amorphous or crystalline two-component materials with mebendazole. Of these 29 two-component systems, the co-amorphous nature of a total of 26 materials was correctly predicted by the model, giving a predictive hit rate of 90 %.

Formulation of co-amorphous systems from naproxen and naproxen sodium and in situ monitoring of physicochemical state changes during dissolution testing by Raman spectroscopy

Co-amorphous systems comprising low-molecular weight drugs and co-formers constitute an interesting approach to optimize pharmaceutical performance of drugs with low aqueous solubility. Within the different types of co-amorphous systems, the combination of a drug with its own salt may be an attractive formulation option due the absence of any inactive co-formers. The aim of this study was to investigate the possibility of forming a co-amorphous system from naproxen (NAP) and its sodium salt (NAP(Na)). Ball milling of NAP and NAP(Na) at equal molar ratio resulted in the formation of a co-amorphous system whilst NAP and NAP(Na) alone were crystalline following both, ball milling and melt quenching. Infrared spectroscopy and physical stability testing revealed that intermolecular interactions were able to maintain the ball milled NAP-NAP(Na) system amorphous for 2 months at 40 °C. Surprisingly, the dissolution rate of co-amorphous NAP-NAP(Na) was only intermediate between those of crystalline NAP and crystalline NAP(Na). In situ Raman spectroscopic measurements indicated an initial phase separation of the co-amorphous form to NAP and NAP(Na) followed by dissociation of sodium from NAP(Na) and crystallization to NAP. These findings contribute to the design of co-amorphous formulations with the combination of a drug and its own salt.

Does the molecular mobility and flexibility of the saccharide ring affect the glass-forming ability of naproxen in binary mixtures?

In this paper, we studied the impact of saccharides having a similar backbone but differing in the degree of freedom, local molecular mobility, flexibility of the ring and intermolecular interactions on the glass-forming ability (GFA) of naproxen (NAP) in binary mixtures. For this purpose, a series of methyl and acetyl derivatives of glucose (GLS) and anhydroglucose (anhGLS), as well as neat anhGLS have been used to produce homogeneous solid dispersions (SDs) of varying molar concentration of examined active pharmaceutical ingredient (API). Systematic measurements with the use of Differential Scanning Calorimetry (DSC) and Broadband Dielectric Spectroscopy (BDS) enabled us to determine the phase transitions, homogeneity and molecular mobility of the investigated binary mixtures as well as the impact of excipient on the crystallization tendency of NAP. It turned out that acetylated glucose (acGLS), one of the most mobile and flexible saccharides of all examined herein materials, is the best excipient enhancing the GFA of studied API. Although, it should be noted that upon storage at room temperature, we observed the recrystallization of NAP from binary mixtures. Interestingly, API always crystallized to the initial polymorphic form, as shown by X-ray diffraction (XRD) investigations. Finally, since additional measurements with the use of Fourier Transform Infrared (FTIR) Spectroscopy clearly indicated that there are no significant differences in the intermolecular interactions in the systems composed of NAP and all examined saccharides, one can postulate that the mobility and ring flexibility of the matrix have, , the most important impact on the crystallization tendency of NAP upon cooling. Consequently, it seems that in some cases, more mobile/flexible matrices can be a much better choice to enhance the glass-forming ability of studied pharmaceutical.

Preparation of Amorphous Composite Particles of Drugs with Ursodeoxycholic Acid as Preclinical Formulations

We studied the possibility of using ursodeoxycholic acid (UDCA) as an excipient to create an amorphous composite that can be administered to animals in preclinical studies of experimental drugs. Three UDCA-based amorphous samples composed of nifedipine (NIF), indomethacin (IND), and naproxen (NAP) were found by screening. The UDCA-based formulations were adjudged amorphous by solid-state analysis using X-ray powder diffraction and differential scanning calorimetry. In addition, amorphous samples of NIF-UDCA, IND-UDCA, and NAP-UDCA did not crystallize while in 1% methyl cellulose (MC) solution for 120 min, although an amorphous solid dispersion of NIF-poly(vinylpyrrolidone) (PVP) crystallized rapidly. The low hygroscopicity of UDCA helps NIF maintain an amorphous state in 1% MC solution. The UDCA-based amorphous composites can be administered as suspended formulations to animals in preclinical studies.

Study the influence of formulation process parameters on solubility and dissolution enhancement of efavirenz solid solutions prepared by hot-melt extrusion: a QbD methodology

The current study investigates the dissolution rate performance of amorphous solid solutions of a poorly water-soluble drug, efavirenz (EFV), in amorphous Soluplus® (SOL) and Kollidon® VA 64 (KVA64) polymeric systems. For the purpose of the study, various formulations with varying drug loadings of 30, 50, and 70% w/w were developed via hot-melt extrusion processing and adopting a Box-Behnken design of experiment (DoE) approach. The polymers were selected based on the Hansen solubility parameter calculation and the prediction of the possible drug-polymer miscibility. In DoE experiments, a Box-Behnken factorial design was conducted to evaluate the effect of independent variables such as Soluplus® ratio (A₁), HME screw speed (A₂), and processing temperature (A₃), and Kollidon®VA64 ratio (B₁), screw speed (B₂), and processing temperature (B₃) on responses such as solubility (X₁ and Y₁) and dissolution rate (X₂ and Y₂) for both ASS [EFV:SOL] and BSS [EFV:KVA64] systems. DSC and XRD data confirmed that bulk crystalline EFV transformed to amorphous form during the HME processing. Advanced chemical analyses conducted via 2D COSY NMR, FTIR chemical imaging, AFM analysis, and FTIR showed that EFV was homogenously dispersed in the respective polymer matrices. The maximum solubility and dissolution rate was observed in formulations containing 30% EFV with both SOL and KVA64 alone. This could be attributed to the maximum drug-polymer miscibility in the optimized formulations. The actual and predicted values of both responses were found precise and close to each other.

Application of Co-Amorphous Technology for Improving the Physicochemical Properties of Amorphous Formulations

Co-amorphous technology was recently introduced to stabilize drugs in the amorphous state for drug development. We examined the predictability of the formation of co-amorphous systems and identified two reliable indicators of successful formation: (1) a negative Δ H_mix value and (2) small Δlog P between components. Moreover, we found that the stability of co-amorphous systems was improved when (1) Δ H_mix was negative and (2) amorphous forms of the constituent compounds were stable. Furthermore, we concluded that co-amorphous systems with small (negatively large) Δ H_mix values had lower hygroscopicity. Typically, amorphous solid dispersions exhibit hygroscopicity because polymers exhibit large hygroscopicity. We proved the superiority of co-amorphous technology over amorphous solid dispersion in this respect. Our results provide methods for (1) establishing a screening method and (2) improving hygroscopicity, which may make co-amorphous technology more useful than amorphous solid dispersion technology.

Advances in coamorphous drug delivery systems

In recent years, the coamorphous drug delivery system has been established as a promising formulation approach for delivering poorly water-soluble drugs. The coamorphous solid is a single-phase system containing an active pharmaceutical ingredient (API) and other low molecular weight molecules that might be pharmacologically relevant APIs or excipients. These formulations exhibit considerable advantages over neat crystalline or amorphous material, including improved physical stability, dissolution profiles, and potentially enhanced therapeutic efficacy. This review provides a comprehensive overview of coamorphous drug delivery systems from the perspectives of preparation, physicochemical characteristics, physical stability, in vitro and in vivo performance. Furthermore, the challenges and strategies in developing robust coamorphous drug products of high quality and performance are briefly discussed.

Co-amorphous palbociclib–organic acid systems with increased dissolution rate, enhanced physical stability and equivalent biosafety

The preparation of co-amorphous drug systems by adding a small molecular excipient is a promising formulation in the modern pharmaceutical industry to improve the solubility, dissolution rate, and bioavailability of poorly soluble drugs. In this study, palbociclib co-amorphous systems with organic acids (succinic, tartaric, citric, and malic acid) at molar ratios of 1 : 1 were prepared by co-milling and characterized by differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR) and solid-state nuclear magnetic resonance (SS-NMR). These solid-state investigations have confirmed the formation of co-amorphous salts between PAL and organic acids. The solubility, dissolution rate and stability of the four co-amorphous drug systems were significantly improved compared with these of crystalline and amorphous palbociclib. The biosafety of the co-amorphous drug systems was the same as that of palbociclib without affecting the efficacy of the drug and eliciting toxic side effects. These comprehensive approaches for the palbociclib–acid co-amorphous drug systems provided a theoretical basis for its clinical applications.

The study of co-amorphous systems presented a safe and effective formulation technology for the development of new palbociclib solid forms with great dissolution rates, good physical stability, and high bioavailability.

Role of hydrogen bonding in cocrystals and coamorphous solids: indapamide as a case study

Crystalline and amorphous stable binary compounds of indapamide for high solubility and permeability.

Co-Amorphous Solid Dispersions for Solubility and Absorption Improvement of Drugs: Composition, Preparation, Characterization and Formulations for Oral Delivery

The amorphous solid state offers an improved apparent solubility and dissolution rate. However, due to thermodynamic instability and recrystallization tendencies during processing, storage and dissolution, their potential application is limited. For this reason, the production of amorphous drugs with adequate stability remains a major challenge and formulation strategies based on solid molecular dispersions are being exploited. Co-amorphous systems are a new formulation approach where the amorphous drug is stabilized through strong intermolecular interactions by a low molecular co-former. This review covers several topics applicable to co-amorphous drug delivery systems. In particular, it describes recent advances in the co-amorphous composition, preparation and solid-state characterization, as well as improvements of dissolution performance and absorption are detailed. Examples of drug-drug, drug-carboxylic acid and drug-amino acid co-amorphous dispersions interacting via hydrogen bonding, π−π interactions and ionic forces, are presented together with corresponding final dosage forms.

Curcumin-Artemisinin Coamorphous Solid: Xenograft Model Preclinical Study

Curcumin is a natural compound present in Indian spice turmeric. It has diverse pharmacological action but low oral solubility and bioavailability continue to limit its use as a drug. With the aim of improving the bioavailability of Curcumin (CUR), we evaluated Curcumin-Pyrogallol (CUR-PYR) cocrystal and Curcumin-Artemisinin (CUR-ART) coamorphous solid. Both of these solid forms exhibited superior dissolution and pharmacokinetic behavior compared to pure CUR, which is practically insoluble in water. CUR-ART coamorphous solid showed two fold higher bioavailability than CUR-PYR cocrystal (at 200 mg/kg oral dose). Moreover, in simulated gastric and intestinal fluids (SGF and SIF), CUR-ART is stable up to 3 and 12 h, respectively. In addition, CUR-PYR and CUR-ART showed no adverse effects in toxicology studies (10 times higher dose at 2000 mg/kg). CUR-ART showed higher therapeutic effect and inhibited approximately 62% of tumor growth at 100 mg/kg oral dosage of CUR in xenograft models, which is equal to the positive control drug, doxorubicin (2 mg/kg) by i.v. administration.

Curcumin: pharmaceutical solids as a platform to improve solubility and bioavailability

The remarkable improvements in the pharmacokinetics and high bioavailability of curcumin polymorphs, amorphous, cocrystals, eutectics, and coamorphous solids are discussed. The importance of pharmaceutical solids in the advanced formulation development of herbal and bioactive molecule curcumin is presented.

Survival of the Fittest: Time-To-Event Modeling of Crystallization of Amorphous Poorly Soluble Drugs

The objective of this study was to gain a quantitative understanding of the link between physicochemical properties and long-term and time-censored amorphous stability of poorly water-soluble drugs using parametric time-to-event modeling. Previously published data on amorphous stability and physicochemical properties of 25 structurally diverse neutral, poorly soluble compounds were used. To describe the general shape of the survival curve (probability of event at time >t), Constant, Gompertz, and Weibull hazard functions and their linear combinations were tested. For a selected Weibull hazard base model, the effect of each physicochemical covariate was investigated, with combined influence of enthalpy of fusion (Hf) and molecular weight (Mr) showing the highest statistical significance. The covariate model was used to simulate survival curves and calculate the median survival time for different values of Hf and Mr. It was found that a decrease in Hf or an increase in Mr contribute to longer survival times. The derived model equation was validated against external data sets consisting of 11 compounds. It showed better predictive ability than a previously published multiple linear regression model incorporating Hf and Mr. The proposed Weibull covariate model may assist in faster and more cost-effective decision making in the pre-formulation phase of drug development, where compound properties and appropriate drug formulation strategies are investigated.

Coamorphous Active Pharmaceutical Ingredient-Small Molecule Mixtures: Considerations in the Choice of Coformers for Enhancing Dissolution and Oral Bioavailability

In the recent years, coamorphous systems, containing an active pharmaceutical ingredient (API) and a small molecule coformer have appeared as alternatives to the use of either amorphous solid dispersions containing polymer or cocrystals of API and small molecule coformers, to improve the dissolution and oral bioavailability of poorly soluble crystalline API. This Commentary article considers the relative properties of amorphous solid dispersions and coamorphous systems in terms of methods of preparation; miscibility; glass transition temperature; physical stability; hygroscopicity; and aqueous dissolution. It also considers important questions concerning the fundamental criteria to be used for the proper selection of a small molecule coformer regarding its ability to form either coamorphous or cocrystal systems. Finally, we consider various aspects of product development that are specifically associated with the formulation of commercial coamorphous systems as solid oral dosage forms. These include coformer selection; screening; methods of preparation; preformulation; physical stability; bioavailability; and final formulation. Through such an analysis of coamorphous API-small molecule coformer systems, against the more widely studied API-polymer dispersions and cocrystals, it is believed that the strengths and weaknesses of coamorphous systems can be better understood, leading to more efficient formulation and manufacture of such systems for enhancing oral bioavailability.

Reactive Melt Extrusion To Improve the Dissolution Performance and Physical Stability of Naproxen Amorphous Solid Dispersions

The purpose of this study was to investigate the reaction between naproxen (NPX) and meglumine (MEG) at elevated temperature and to study the effect of this reaction on the physical stabilities and in vitro drug-release properties of melt-extruded naproxen amorphous solid dispersions (ASDs). Differential scanning calorimetry, hot-stage polarized light microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses demonstrated that in situ salt formation with proton transfer between NPX and MEG occurred at elevated temperature during the melt extrusion process. The amorphous NPX-MEG salt was physically most stable when two components were present at a 1:1 molar ratio. Polymeric carriers, including povidone, copovidone, and SOLUPLUS, did not interfere with the reaction between NPX and MEG during melt extrusion. Compared to the traditional NPX ASDs consisting of NPX and polymer only, NPX-MEG ASDs were physically more stable and remained amorphous following four months storage at 40 °C and 75% RH (relative humidity). Based on nonsink dissolution testing and polarized light microscopy analyses, we concluded that the conventional NPX ASDs composed of NPX and polymers failed to improve the NPX dissolution rate due to the rapid recrystallization of NPX in contact with aqueous medium. The dissolution rate of NPX-MEG ASDs was two times greater than the corresponding physical mixtures and conventional NPX ASDs. This study demonstrated that the acid-base reaction between NPX and MEG during melt extrusion significantly improved the physical stability and the dissolution rate of NPX ASDs.

Co-amorphous Formation Induced by Combination of Tranilast and Diphenhydramine Hydrochloride

In this study, we investigated the formation of a co-amorphous system of tranilast (TRL) and diphenhydramine hydrochloride (DPH), which are drugs used for treating allergies and inflammation. The crystallization from undercooled melts of the drugs and drug mixtures was evaluated by thermal analysis. Both drugs in the amorphous state underwent crystallization on heating, although the mixture remained in the amorphous state, indicating the formation of a co-amorphous system. The physicochemical properties of co-amorphous TRL-DPH prepared by the melting-cooling process were studied. The glass transition temperature of co-amorphous TRL-DPH deviated from the theoretical value. The enthalpy relaxation rate of the amorphous drugs, which reflected the molecular mobility, was reduced by the formation of a co-amorphous system. The intermolecular interactions between TRL and DPH in the co-amorphous system were measured by the change in the IR spectra. These results were consistent with the high physical stability. The co-amorphous sample remained in the amorphous state for over 30 days at 40°C, whereas the amorphous drugs showed rapid crystallization. Our findings demonstrate that TRL and DPH form a co-amorphous system, which dramatically decreases their crystallization without an excipient.