Physical stability and dissolution behaviors of amorphous pharmaceutical solids: Role of surface and interface effects

Co-amorphous systems of sulfasalazine with matrine-type alkaloids: Enhanced solubility behaviors and synergistic therapeutic potential

Sulfasalazine (SULF), a sulfonamide antibiotic, has been utilized in the treatment of rheumatoid arthritis (RA) and inflammatory bowel disease (IBD) since its discovery. However, its poor water solubility causes the high daily doses (1---3 g) for patients, which may lead to the intolerable toxic and side effects for their lifelong treatment for RA and IBD. In this work, two water-soluble natural anti-inflammatory alkaloids, matrine (MAR) and sophoridine (SPD), were employed to construct the co-amorphous systems of SULF for addressing its solubility issue. These newly obtained co-amorphous forms of SULF were comprehensively characterized by powder X-ray diffraction (PXRD), temperature-modulated differential scanning calorimetry (mDSC), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). We also investigated their dissolution behavior, including powder dissolution, in vitro release, and intrinsic dissolution rate. Both co-amorphous systems exhibited superior dissolution performance compared to crystalline SULF. The underlying mechanism responsible for the enhanced dissolution behaviors in co-amorphous systems were also elucidated. These mechanisms include the inhibition of nucleation, complexation, increased hydrophilicity, and robust intermolecular interactions in aqueous solutions. Importantly, these co-amorphous systems demonstrated satisfactory physical stability under various storage conditions. Network pharmacological analysis was utilized to investigate the potential therapeutic targets of both co-amorphous systems against RA, revealing similar yet distinct multi-target synergistic therapeutic mechanisms in the treatment of this condition. Our study suggests these drug-drug co-amorphous systems hold promise for optimizing SULF dosage in the future and providing a potential drug combination strategy.

Analysis of the Dissolution Behavior of Theophylline and Its Cocrystal Using ATR-FTIR Spectroscopic Imaging

Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic imaging is a powerful tool to visualize the distribution of components, and it has been used to analyze drug release from tablets. In this work, ATR-FTIR spectroscopic imaging was applied for observing the dissolution of molecular crystals from tablet compacts. The IR spectra provided chemically specific information about the transformation of crystal structures during the dissolution experiments. Theophylline (TPL) anhydrate and its cocrystals were used as model systems of molecular crystals. The IR spectra during the dissolution of TPL revealed information about the crystal structure of TPL, which transformed from anhydrate to monohydrate in water. During a dissolution test of a model cocrystal system, it was suggested that an active pharmaceutical ingredient (API) and a coformer were dissolved in water simultaneously. The IR spectra that were acquired during the dissolution of a cocrystal tablet showed new spectral bands attributed to the API after 5 min. This suggested that the precipitation of API was observed during the dissolution experiment. Measurements from ATR-FTIR spectroscopic imaging can visualize the drug release from the tablet and determine the transformation of molecular crystals during their dissolution. These results will have an impact on clarifying the dissolution mechanism of molecular crystals.

Implications of Low-concentration Polymer on the Physical Stability of Glassy Griseofulvin: Role of the Segmental Mobility

Crystallization of amorphous pharmaceutical solids are widely reported to be affected by the addition of polymer, while the underlying mechanism require deep study. Herein, crystal growth behaviors of glassy griseofulvin (GSF) doped with various 1% w/w polymer were systematically studied. From the molecular structure, GSF cannot form the hydrogen bonding interactions with the selected polymer poly(vinyl acetate), polyvinyl pyrrolidone (PVP), 60:40 vinyl pyrrolidone-vinyl acetate copolymer (PVP/VA 64), and poly(ethylene oxide) (PEO). 1% w/w polymer exhibited weak or no detectable effects on the glass transition temperature (Tg) of GSF. However, crystal growth rates of GSF was altered from 4.27-fold increase to 2.57-fold decrease at 8 ℃ below Tg of GSF. Interestingly, the ability to accelerate and inhibit the growth rates of GSF crystals correlated well with Tg of polymer, indicating the controlling role of segmental mobility of polymer. Moreover, ring-banded growth of GSF was observed in the polymer-doped systems. Normal compact bulk and ring-banded crystals of GSF were both characterized as the thermodynamically stable form I. More importantly, formation of ring-banded crystals of GSF can significantly weaken the inhibitory effects of polymer on the crystallization of glassy GSF.

Fused Deposition Modelling 3D printing and solubility improvement of BCS II and IV active ingredients - A narrative review

In the field of pharmaceutical research and development, Fused Deposition Modelling (FDM) 3D printing (3DP) has aroused growing interest within the last ten years. The use of thermoplastic polymers, combined with the melting process of the raw materials, offers the possibility of manufacturing amorphous solid dispersions (ASDs). In the pharmaceutical industry, the formulation of an ASD is a widely used strategy to improve the solubility of poorly soluble drugs (classified by the Biopharmaceutical Classification System (BCS) as class II and IV). In this review, an analysis of studies that have developed a FDM printed form containing a BCS class II or IV active substance was performed. The focus has been placed on the evaluation of the solid state of the active molecules (crystalline or amorphous) and on the study of their dissolution profile. Thus, the aim of this work is to highlight the interest of FDM 3DP to induce the amorphisation phenomenon of Class II and IV active substances by forming an ASD, and as result improving their solubility.

Mesoporous Drug Delivery System: From Physical Properties of Drug in Solid State to Controlled Release

Mesoporous materials, which exhibit great potential in the control of polymorphs and delivery of poorly water-soluble drugs, have obtained considerable attention in the field of pharmaceutical science. The physical properties and release behaviors of amorphous or crystalline drugs may be affected by formulating them into mesoporous drug delivery systems. In the past few decades, an increasing amount of papers have been written about mesoporous drug delivery systems, which play a crucial role in improving the properties of drugs. Herein, mesoporous drug delivery systems are comprehensively reviewed in terms of their physicochemical characteristics, control of polymorphic forms, physical stability, in vitro performance, and in vivo performance. Moreover, the challenges and strategies of developing robust mesoporous drug delivery systems are also discussed.

Polymorphism of Pradofloxacin: Crystal Structure Analysis, Stability Study, and Phase Transformation Behavior

PURPOSE

Pradofloxacin is an important antibiotic with poor physical stability. At present, there is no systematic study on its polymorphic form. The purpose of this study is to develop new crystal forms to improve the stability of Pradofloxacin and systematically study the crystal transformation relationships to guide industrial production.

METHOD

In this work, three solvent-free forms (Form A, Form B and Form C), a new dimethyl sulfoxide solvate (Form PL-DMSO) and a new hydrate (Form PL-H) were successfully obtained and the single crystal data of Form A, Form B and Form PL-DMSO were solved for the first time. Various solid state analysis techniques and slurry experiments have been used to evaluate the stability and determine phase transformation relationships of five crystal forms, the analysis of crystal structure provided theoretical support for the results.

RESULT

The water vapor adsorption and desorption experiences of Forms A, B, C and Form PL-H were studied, and the results show that the new hydrate has good hygroscopic stability and certain development potential. The thermal stability of different forms was determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and the crystal structure shows that there are more hydrogen bonds and C - H···π interactions in form B, which is the reason why Form B is more stable than form A. Finally, the phase transformation relationships of the five crystal forms were systematically studied and discussed.

CONCLUSION

These results are helpful to provide guiding methods in the production and storage of pradofloxacin.

Crystallization of Amorphous Nimesulide: The Relationship between Crystal Growth Kinetics and Liquid Dynamics

Understanding crystallization and its correlations with liquid dynamics is relevant for developing robust amorphous pharmaceutical solids. Herein, nimesulide, a classical anti-inflammatory agent, was used as a model system for studying the correlations between crystallization kinetics and molecular dynamics. Kinetic parts of crystal growth (u_kin) of nimesulide exhibited a power law dependence upon the liquid viscosity (η) as u_kin~η^-0.61. Bulk molecular diffusivities (D_Bulk) of nimesulide were predicted by a force-level statistical-mechanical model from the α-relaxation times, which revealed the relationship as u_kin~D_bulk^0.65. Bulk crystal growth kinetics of nimesulide in deeply supercooled liquid exhibited a fragility-dependent decoupling from τ_α. The correlations between growth kinetics and α-relaxation times predicted by the Adam-Gibbs-Vogel equation in a glassy state were also explored, for both the freshly made and fully equilibrated glass. These findings are relevant for the in-depth understanding and prediction of the physical stability of amorphous pharmaceutical solids.

Impact of Aluminum Oxide Nanocoating on Drug Release from Amorphous Solid Dispersion Particles

Atomic layer coating (ALC) is emerging as a particle engineering strategy to inhibit surface crystallization of amorphous solid dispersions (ASDs). In this study, we turn our attention to evaluating drug release behavior from ALC-coated ASDs, and begin to develop a mechanistic framework. Posaconazole/hydroxypropyl methylcellulose acetate succinate was used as a model system at both 25% and 50% drug loadings. ALC-coatings of aluminum oxide up to 40 nm were evaluated for water sorption kinetics and dissolution performance under a range of pH conditions. Scanning electron microscopy with energy dispersive X-ray analysis was used to investigate the microstructure of partially released ASD particles. Coating thickness and defect density (inferred from deposition rates) were found to impact water sorption kinetics. Despite reduced water sorption kinetics, the presence of a coating was not found to impact dissolution rates under conditions where rapid drug release was observed. Under slower releasing conditions, underlying matrix crystallization was reduced by the coating, enabling greater levels of drug release. These results demonstrate that water was able to penetrate through the ALC coating, hydrating the amorphous solid, which can initiate dissolution of drug and/or polymer (depending on pH conditions). Swelling of the ASD substrate subsequently occurs, disrupting and cracking the coating, which serves to facilitate rapid drug release. Water sorption kinetics are highlighted as a potential predictive tool to investigate the coating quality and its potential impact on dissolution performance. This study has implications for formulation design and evaluation of ALC-coated ASD particles.