Influence of Solvent Composition on the Performance of Spray-Dried Co-Amorphous Formulations

Co-Amorphization of Acemetacin with Basic Amino Acids as Co-Formers for Solubility Improvement and Gastric Ulcer Mitigation

Acemetacin (ACM) is a new non-steroidal anti-inflammatory drug with anti-inflammatory, analgesic, and antipyretic effects. However, the poor water solubility and gastrointestinal side effects limit its use. Recently, the co-amorphous (CAM) strategy has attracted great interest to improve solubility for poorly water-soluble drugs, and basic amino acids have the potential to protect the gastrointestinal tract. In order to develop a highly efficient and low-toxic ACM formulation, we prepared ACM CAM systems, with basic amino acids (lysine, arginine, and histidine) as co-formers, using a cryo-milling method. The solid-state behaviors of the ACM CAM systems were characterized by polarizing light microscopy, differential scanning calorimetry, and powder X-ray diffraction. Fourier transform infrared spectroscopy and molecular docking were carried out to understand the formation mechanism. Moreover, the gastro-protective effects of ACM CAM systems were evaluated in a rat gastric ulcer model. The results demonstrated that the CAM systems improved the dissolution rates of ACM compared with the neat amorphous counterpart. Furthermore, ACM CAM systems are significantly effective in mitigating the ACM-induced gastric ulcer in rats, and the ulcer inhibition rates were almost 90%. More importantly, this study provided a useful method for mitigating drug-induced gastrointestinal damage and broadened the applications of drug-amino acid CAM systems.

Genistein Co-Amorphous Systems with Amino Acids: An Investigation into Enhanced Solubility and Biological Activity

Genistein, an isoflavone known for its antioxidant and antidiabetic effects, suffers from the drawback of low solubility. To overcome this limitation, co-amorphous systems were synthesized by incorporating amino acids that were chosen through computational methods. The confirmation of the amorphous state of lysine and arginine-containing systems was ascertained by X-ray powder diffraction. Subsequently, the characterization of these systems was extended by employing thermo-gravimetry, differential scanning calorimetry, Fourier-transform infrared spectroscopy, and scanning electron microscopy. The investigation also included an assessment of the physical stability of the samples during storage. The apparent solubility of the systems was studied in an aqueous medium. To evaluate the in vitro permeability through the gastrointestinal tract, the parallel artificial membrane permeability assay was employed. The biological properties of the systems were assessed with regard to their antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl and cupric ion-reducing antioxidant capacity assays, as well as their ability to inhibit α-glucosidase. The systems' glass transition temperatures were determined, and their homogeneity confirmed via differential scanning calorimetry analysis, while Fourier-transform infrared spectroscopy analysis provided data on molecular interactions. Stability was maintained for the entire 6-month storage duration. The co-amorphous system containing lysine displayed the most pronounced apparent solubility improvement, as well as a significant enhancement in antioxidant activity. Notably, both systems demonstrated superior α-glucosidase inhibition relative to acarbose, a standard drug for managing type 2 diabetes. The results indicate that co-amorphous systems with lysine and arginine have the potential to significantly enhance the solubility and biological activity of genistein.

Co-Amorphous Versus Deep Eutectic Solvents Formulations for Transdermal Administration

Transdermal administration can be considered as an interesting route to overcome the side-effects inherent to oral intake. Designing topical formulations with maximum drug efficiency requires the optimization of the permeation and the stability of the drug. The present study focuses on the physical stability of amorphous drugs within the formulation. Ibuprofen is commonly used in topical formulations and then was selected as a model drug. Additionally, its low Tg allows easy, unexpected recrystallization at room temperature with negative consequence on skin penetration. In this study, the physical stability of amorphous ibuprofen was investigated in two types of formulations: (i) in terpenes-based deep eutectic solvents (DES) and (ii) in arginine-based co-amorphous blends. The phase diagram of ibuprofen:L-menthol was mainly analyzed by low-frequency Raman spectroscopy, leading to the evidence of ibuprofen recrystallization in a wide range of ibuprofen concentration. By contrast, it was shown that amorphous ibuprofen is stabilized when dissolved in thymol:menthol DES. Forming co-amorphous arginine-ibuprofen blends by melting is another route for stabilizing amorphous ibuprofen, while recrystallization was detected in the same co-amorphous mixtures obtained by cryo-milling. The mechanism of stabilization is discussed from determining T_g and analyzing H-bonding interactions by Raman investigations in the C=O and O-H stretching regions. It was found that recrystallization of ibuprofen was inhibited by the inability to form dimers inherent to the preferential formation of heteromolecular H-bonding, regardless of the glass transition temperatures of the various mixtures. This result should be important for predicting ibuprofen stability within other types of topical formulations.

Sinapic Acid Co-Amorphous Systems with Amino Acids for Improved Solubility and Antioxidant Activity

The objective of this study was to obtain co-amorphous systems of poorly soluble sinapic acid using amino acids as co-formers. In order to assess the probability of the interaction of amino acids, namely, arginine, histidine, lysine, tryptophan, and proline, selected as co-formers in the amorphization of sinapic acid, in silico studies were carried out. Sinapic acid systems with amino acids in a molar ratio of 1:1 and 1:2 were obtained using ball milling, solvent evaporation, and freeze drying techniques. X-ray powder diffraction results confirmed the loss of crystallinity of sinapic acid and lysine, regardless of the amorphization technique used, while remaining co-formers produced mixed results. Fourier-transform infrared spectroscopy analyses revealed that the co-amorphous sinapic acid systems were stabilized through the creation of intermolecular interactions, particularly hydrogen bonds, and the potential formation of salt. Lysine was selected as the most appropriate co-former to obtain co-amorphous systems of sinapic acid, which inhibited the recrystallization of sinapic acid for a period of six weeks in 30 °C and 50 °C. Obtained co-amorphous systems demonstrated an enhancement in dissolution rate over pure sinapic acid. A solubility study revealed a 12.9-fold improvement in sinapic acid solubility after introducing it into the co-amorphous systems. Moreover, a 2.2-fold and 1.3-fold improvement in antioxidant activity of sinapic acid was observed with respect to the ability to neutralize the 2,2-diphenyl-1-picrylhydrazyl radical and to reduce copper ions, respectively.

Poly (amino acid)s as new co-formers in amorphous solid dispersion

The drug-amino acid co-amorphous systems and amorphous solid dispersions (ASDs) are promising methods to address the poor water solubility of poorly water-soluble drugs. However, some amino acids might not be perfect co-formers for co-amorphous systems, and the relatively low drug-loading of many ASDs is one of the main disadvantages of ASDs. Thus, poly-l-lysine and polyglutamic acid were selected as the co-formers, ball milled with basic mebendazole, neutral tadalafil and acidic valsartan at different weight ratios (from 3:1 to 1:3) to prepare poly (amino acid)-based ASDs, aiming to combine the advantages of co-amorphous systems (high drug-loading) and ASDs (relatively high T_g and high physical stability). All the mixtures were converted into amorphous after milling. The powder dissolution studies showed that drug-poly (amino acid) ASDs improved the dissolution rate of the drug in different ways and to different degrees. Moreover, the two poly (amino acid)s enhanced the physical stability of amorphous drugs. It is worthy to mention that the salt formation between the drug and the poly (amino acid) does not necessarily mean better performance compared to non-salt forming systems, and salt formation is also not a prerequisite for the formation of promising drug-poly (amino acid) ASDs.

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.

Potential application of low molecular weight excipients for amorphization and dissolution enhancement of carvedilol

In this study, four low molecular weight (LMW) excipients, tryptophan (TRY), phenylalanine (PHE), lysine (LYS) and saccharin (SAC) were evaluated as co-formers to generate co-amorphous systems (CAMS) by ball milling with carvedilol (CRV). Mixtures of CRV and LMW excipient in 1:0.5, 1:1 and 1:2 drug:excipient molar ratios were ball milled and analysed by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), Fourier transform (FT-IR) infrared spectroscopy and dissolution testing. CAMS were formed by milling of a mixture of CRV with TRY in 1:2 M ratio and SAC in 1:1 M ratio, while amorphization of only CRV was achieved in other mixtures with SAC. In other samples containing TRY and PHE, milling resulted in partial amorphization, while LYS was the least suitable excipient for the amorphization of CRV. Unexpectedly, the highest supersaturation of CRV was achieved from samples containing CRV and LYS in 1:1 and 1:2 M ratios, despite the absence of a significant reduction in CRV crystallinity upon milling of these samples. Increase of hydrophobic surface area caused by milling of samples with TRY and PHE and agglomeration during dissolution testing of samples containing SAC are likely causes of poor dissolution performance of mixtures containing fully or partially amorphous CRV.

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.

A critical review of spray-dried amorphous pharmaceuticals: Synthesis, analysis and application

New drugs are frequently found with poor water-solubility in recent pharmaceutical projects, which brings difficulties of bioavailability for the clinical development of new drugs. When these drug compounds in a crystalline state are absorbed by gastrointestinal tract, their dissolution rates and absorption rates are very limited. Nowadays, various methods have been developed to improve the solubility, dissolution and bioavailability of drugs. According to the characteristics of drugs, this work suggests the use of spray drying technology to amorphize APIs (active pharmaceutical ingredients) to improve their bioavailability. This work reviews the properties of the spray-dried amorphous drugs, the progress made in drug synthesis and application, and the existing problems.

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 %.

Preparation of Co-Amorphous Systems by Freeze-Drying

Freeze-drying was evaluated as a production technique for co-amorphous systems of a poorly water-soluble drug. Naproxen was freeze-dried together with arginine and lysine as co-former. To increase the solubility of naproxen in the starting solution, the applicability of five surfactants was investigated, namely sodium dodecyl sulfate, pluronic F-127, polyoxyethylene (40) stearate, tween 20 and TPGS 1000. The influence of the surfactant type, surfactant concentration and total solid content to be freeze-dried on the solid state of the sample was investigated. X-ray powder diffraction and differential scanning calorimetry showed that the majority of systems formed co-amorphous one-phase systems. However, at higher surfactant concentrations, and depending on the surfactant type, surfactant reflections were observed in the XRPD analysis upon production. Crystallization of both naproxen and amino acid occurred from some combinations under storage. In conclusion, freeze-drying was shown to be a feasible technique for the production of a selection of co-amorphous drug–amino acid formulations.

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.

Whey proteins as stabilizers in amorphous solid dispersions

Whey proteins are extensively used as nutritional supplements but have so far not been investigated as co-formers for amorphous solid dispersions (ASD) to enhance the solubility and dissolution rate of poorly water soluble drugs. In this study, whey protein isolate (WPI) and whey protein hydrolysate (WPH) were each mixed with three poorly water soluble drugs (indomethacin: IND, carvedilol: CAR and furosemide: FUR) and prepared as ASDs at 50% (w/w) drug loading using vibrational ball milling. Subsequently, solid state characteristics, dissolution rate and physical stability of the obtained samples were analyzed. All ASDs showed a significant increase in their glass transition temperatures, as well as faster dissolution rates and higher apparent solubilities compared to both the respective pure crystalline and amorphous drugs. The saturation solubility of the drugs was increased in the presence of the whey proteins, and the investigated ASDs showed supersaturation by attaining higher drug concentrations compared to the respective saturation solubilities. Upon storage, ASDs containing IND were found to be physically stable for at least 27 months, whereas, ASDs containing CAR or FUR were stable for about 8 months and 17 months, respectively. This was a tremendous increase in physical stability compared to the pure amorphous drugs which recrystallized within less than one week. Overall, WPI and WPH proved to be promising co-formers and amorphous stabilizers in ASD formulations.

Influence of preparation technique on co-amorphization of carvedilol with acidic amino acids

Basic amino acids (AAs) have successfully been used as co-formers with acidic drugs for the preparation of co-amorphous formulations using ball-milling (BM) and spray-drying (SD). In contrast, acidic AAs have been reported as poor co-formers for co-amorphous formulations, even for basic drugs, when using BM as a preparation technique. In this study the basic drug carvedilol (CAR) and the two acidic AAs, glutamic acid and aspartic acid, were used to explore the possibilities of producing co-amorphous formulations using BM, SD and liquid assisted grinding (LAG). X-ray powder diffraction, thermal analysis and Fourier-transform infrared spectroscopy were used to determine the solid state form of the various CAR-AA mixtures prepared. BM the CAR-AA mixtures for 60 min did not result in co-amorphization as XRPD revealed remaining crystallinity of both CAR and the AA. On the other hand, successful co-amorphous salt formation was obtained for all SD samples. Differential scanning calorimetry showed that all the SD CAR-AA mixtures had a single glass transition temperature of approximately 80 °C. The CAR-AA mixtures prepared by LAG showed some polymorphic conversion of CAR. Intrinsic dissolution testing showed the highest dissolution rate for all SD mixtures due to co-amorphous salt formation. Hence it was observed that of the three preparation techniques used, successful co-amorphous formulations of a basic drug with an acidic AA could only be prepared by SD.

Fast Dissolving of Ferulic Acid via Electrospun Ternary Amorphous Composites Produced by a Coaxial Process

Enhancing the dissolution of insoluble active ingredients comprises one of the most important issues in the pharmaceutical and biomaterial fields. Here, a third generation solid dispersion (3rd SD) of ferulic acid was designed and fabricated by a modified coaxial electrospinning process. A traditional second generation SD (2nd SD) was also prepared by common one-fluid blending electrospinning and was used as a control. With poly(vinyl alcohol) as the fiber matrix and polyvinylpyrrolidone K10 as an additive in the 3rd SDs, the two electrospinning processes were investigated. The prepared 2nd and 3rd SDs were subjected to a series of characterizations, including X-ray diffraction (XRD), scanning electron microscope (SEM), hydrophilicity and in vitro drug dissolving experiments. The results demonstrate that both SDs were monolithic nanocomposites and that the drugs were amorphously distributed within the matrix. However, the 3rd SDs had better morphology with smaller size, narrower size distribution, and smaller water contact angles than the 2nd SDs. Dissolution tests verified that the 3rd SDs could release their loaded cargoes within 60 s, which was over three times faster than the 2nd SDs. Therefore, a combined strategy based on the modified coaxial electrospinning and the logical selections of drug carriers is demonstrated for creating advanced biomaterials.