Amorphous Active Pharmaceutical Ingredients Research Articles

Evaluation of Suitable Polymeric Matrix/Carriers during Loading of Poorly Water Soluble Drugs onto Mesoporous Silica: Physical Stability and In Vitro Supersaturation.

The application of mesoporous carriers in formulations of amorphous solid dispersions (ASDs) has been suggested to enhance the stability of amorphous drugs. However, mesoporous carriers do not demonstrate satisfactory inhibitory effects on the precipitation of active pharmaceutical ingredients (APIs), and the inclusion of an appropriate polymer within ASDs becomes imperative to maintaining drug supersaturation. The aim of this study was to evaluate ternary olanzapine (OLN) ASDs with Syloid 244FP and to find an appropriate polymeric carrier. The polymer's selection criteria were based on the physical stability of the ASDs and the release rate of the drug from the systems. The polymers investigated were hydroxypropylmethyl cellulose (HPMC) and copovidone (coPVP). The formation of ASDs was achievable in all investigated cases, as demonstrated by the complete lack of crystallinity confirmed through both powder X-ray diffraction (pXRD) analysis and differential scanning calorimetry (DSC) for all developed formulations. The solvent shift method was employed to evaluate the ability of the studied carriers to inhibit the precipitation of supersaturated OLN. coPVP emerged as a more suitable precipitation inhibitor compared with HPMC and Syloid 244 FP. Subsequently, in vitro dissolution studies under non-sink conditions revealed a higher degree of supersaturation in ternary systems where coPVP was used as a polymeric carrier, as these systems exhibited, under the examined conditions, up to a 2-fold increase in the released OLN compared with the pure crystalline drug. Moreover, stability studies conducted utilizing pXRD demonstrated that ternary formulations incorporating coPVP and Syloid 244 FP maintained stability for an extended period of 8 months. In contrast, binary systems exhibited a comparatively shorter stability duration, indicating the synergistic effect of coPVP and Syloid 244 FP on the physical stability of the amorphous API. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) studies showed that the development of stronger molecular interactions can be provided as an explanation for this synergistic effect, as the formation of robust H-bonds may be considered responsible for inhibiting the precipitation of the supersaturated API. Therefore, the incorporation of coPVP into OLN ASDs with Syloid 244 FP is considered a highly promising technique for increasing the degree of OLN supersaturation in in vitro dissolution studies and improving the stability of systems.

Towards rational design of API-poly(D, L-lactide-co-glycolide) based micro- and nanoparticles: The role of API-polymer compatibility prediction

Due to their unique properties, such as controlled drug release and improved bioavailability, polymeric microparticles and nanoparticles (MPs and NPs) have gained considerable interest in the pharmaceutical industry. Nevertheless, the high costs associated with biodegradable polymers and the active pharmaceutical ingredients (APIs) used for treating serious diseases, coupled with the vast number of API-polymer combinations, make the search for effective API-polymer MPs and NPs a costly and time-consuming process. In this work, the correlation between the compatibility of selected model APIs (i.e., ibuprofen, naproxen, paracetamol, and indomethacin) with poly(lactide-co-glycolide) (PLGA) derived from respective binary phase diagrams and characteristics of prepared MPs and NPs, such as the drug loading and solid-state properties, was investigated to probe the possibility of implementing the modeling of API-polymer thermodynamic and kinetic phase behavior as part of rational design of drug delivery systems based on MPs and NPs. API–PLGA-based MPs and NPs were formulated using an emulsion-solvent evaporation technique and were characterized for morphology, mean size, zeta potential, drug loading, and encapsulation efficiency. The solid-state properties of the encapsulated APIs were assessed using differential scanning calorimetry and X-ray powder diffraction. The evaluated compatibility was poor for all considered API–PLGA pairs, which is in alignment with the experimental results showing low drug loading in terms of amorphous API content. At the same time, drug loading of the studied APIs in terms of amorphous content was found to follow the same trend as their solubility in PLGA, indicating a clear correlation between API solubility in PLGA and achievable drug loading. These findings suggest that API-polymer phase behavior modeling and compatibility screening can be employed as an effective preformulation tool to estimate optimum initial API concentration for MP and NP preparation or, from a broader perspective, to tune or select polymeric carriers offering desired drug loading.

The shelf life of ASDs: 2. Predicting the shelf life at storage conditions

Amorphous solid dispersions (ASDs) are a widely used formulation technology for poorly water-soluble active pharmaceutical ingredients (API). Depending on the API-polymer combination and API load in the ASD, the amorphous API might be thermodynamically metastable and crystallize over time. The crystallization onset is one critical factor that can define the shelf life of the ASD. Thus, for ASD formulations, long-term stability against crystallization of the API is of particular interest. This work presents a method for predicting the long-term physical stability of ASDs (crystallization onset time). The new approach combines the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation with classical nucleation theory. The shelf life predicted using the new approach depends on supersaturation (determined with PC-SAFT), viscosity (determined with WLF equation or Arrhenius equation) and two specific model parameters k’ and B. The latter were fitted to a few fast crystallization-kinetics measurements above the glass transition of the ASD. An additional crystallization-kinetics measurement below the glass-transition temperature of the ASD was used to determine the Arrhenius parameters. Once all parameters are determined for a given API/polymer combination and manufacturing method, they are valid for any API load, temperature, and RH. The proposed approach allows predicting the shelf life (crystallization onset) of a potential ASD in early stage of development within a few days. It was successfully verified for ASDs stored at 25 °C and 10% RH or 60% RH.

Kinetic stability and glass-forming ability of phenacetin by fast scanning calorimetry

In the present work, an amorphous active pharmaceutical ingredient, phenacetin, was obtained by fast scanning calorimetry. The critical cooling rate and kinetic fragility of its supercooled melt were determined. The process of cold crystallization of phenacetin was studied by methods of isothermal and non-isothermal kinetics. It was found that the best correspondence between the two kinetic approaches is observed in the case of using the Nakamura crystallization model. The results obtained can find their application in the development of approaches to obtaining amorphous forms of drugs prone to crystallization.

Quantitative analysis of amorphous form in indomethacin binary polymorphic mixtures using infrared spectroscopy analytical techniques combined with chemometrics methods

Pharmaceutical corporations prefer amorphous active pharmaceutical ingredients (APIs) because of their high apparent solubility and bioavailability, which are caused by long-range disorder, large unit surface free energy, and easily wetted particle surfaces. APIs in amorphous form tend to recrystallize into crystalline form during production, transportation, and storage, leading to differences in safety and clinical efficacy, which has been a major obstacle to development of amorphous drugs. In this study, rapid and nondestructive methods for quantitative analysis of amorphous indomethacin (A-INDO) content in A-INDO and γ-indomethacin (γ-INDO) binary mixtures were established based on Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR-FTIR) and Near-Infrared spectroscopy (NIR) combined with chemometrics methods. Partial least squares regression (PLSR) was used to establish quantitative analysis models of A-INDO content ranging from 0.000 % to 10.000 % w/w %. A variety of spectral pretreatment methods were used to pretreat the spectral, reducing the influence of inconsistent particle size and uneven mixing, and highlighting the sample component information. The two analytical techniques’ best PLSR models were selected, and the performance of the best models was confirmed by the validation samples. The most effective PLSR model based on ATR-FTIR was Y = 0.99456 X + 0.21526, R2 = 0.99456, the limit of detection (LOD) was 0.714 % and the limit of quantification (LOQ) was 2.164 %. The optimal PLSR model based on NIR was Y = 0.99950 X + 0.07465, R2 = 0.99950, with LOD = 0.246 % and LOQ = 0.747 %. The results showed that the PLSR models established by ATR-FTIR and NIR solid-state analytical techniques combined with stoichiometric method could be used to detect the content of amorphous APIs and to control the production quality of APIs.

Hot Melt Extruded Posaconazole-Based Amorphous Solid Dispersions-The Effect of Different Types of Polymers.

Four model polymers, representing (i) amorphous homopolymers (Kollidon K30, K30), (ii) amorphous heteropolymers (Kollidon VA64, KVA), (iii) semi-crystalline homopolymers (Parteck MXP, PXP), and (iv) semi-crystalline heteropolymers (Kollicoat IR, KIR), were examined for their effectiveness in creating posaconazole-based amorphous solid dispersions (ASDs). Posaconazole (POS) is a triazole antifungal drug that has activity against Candida and Aspergillus species, belonging to class II of the biopharmaceutics classification system (BCS). This means that this active pharmaceutical ingredient (API) is characterized by solubility-limited bioavailability. Thus, one of the aims of its formulation as an ASD was to improve its aqueous solubility. Investigations were performed into how polymers affected the following characteristics: melting point depression of the API, miscibility and homogeneity with POS, improvement of the amorphous API's physical stability, melt viscosity (and associated with it, drug loading), extrudability, API content in the extrudate, long term physical stability of the amorphous POS in the binary drug-polymer system (in the form of the extrudate), solubility, and dissolution rate of hot melt extrusion (HME) systems. The obtained results led us to conclude that the physical stability of the POS-based system increases with the increasing amorphousness of the employed excipient. Copolymers, compared to homopolymers, display greater homogeneity of the investigated composition. However, the enhancement in aqueous solubility was significantly higher after utilizing the homopolymeric, compared to the copolymeric, excipients. Considering all of the investigated parameters, the most effective additive in the formation of a POS-based ASD is an amorphous homopolymer-K30.

Study of the Technological Methods Effect on Dissolution of the X-ray Amorphous Efavirenz-mesoporous Carrier System

Introduction. The low solubility of active pharmaceutical ingredients (APIs) in the physiological pH range of the intestinal tract can adversely affect their absorption and bioavailability. Various methods of increasing the solubility of APIs have been proposed in recent decades. Among them there are preparation of solid dispersions, micronization, solubilization and other methods, including ones based on the amorphization of the crystalline substances, such as, spray drying, hot melt extrusion, absorption on mesoporous carriers such as magnesium aluminosilicate, silica, etc.Aim. Study the technological methods effect on dissolution at physiological temperature and pH range of practically insoluble API efavirenz amorphized by absorption on mesoporous carriers.Materials and methods. Efavirenz form І (EFA) (LLC "AMEDART", Russia, batch 010520). Efavirenz reference standard (USP № R09740). Mesoporous carriers (MC): Silica – Syloid® 244FP (244), Syloid® XDP 3150 (3150) (W.R. Grace&Co.-Conn, USA); FujiSil™ (FSL) (Fuji Chemical Industries Co., Ltd., Japan); Aeroperl® 300 (APL) (Evonik, Germany); Parteck® SLC (SLC) (Merck Millipore, USA); Synthetic magnesium aluminometasilicate – Neusilin® US2 (US2), Neusilin® UFL (UFL) (Fuji Chemical Industry Co., Ltd., Japan). The API absorption on MC was performed via solvent wetting and hot melt extrusion methods.Results and discussion. The dissolution increases in the MC series as the following: SLC > FSL > UFL = US2 > 244 = 3150. The data are consistent with an increase in the surface area and a decrease in the pore size of MC. The crystalline state of the system API efavirenz-Aeroperl® is caused by the largest pore size. It is obvious according to the data that the solvent wetting method gives better results in comparison with the hot melt extrusion as the method of obtaining X-ray amorphous systems API efavirenz-MC.Conclusion. Solvent wetting technology is recommended for increasing the dissolution of practically insoluble APIs. The preferable mesoporous carriers are silica Parteck® SLC or synthetic magnesium aluminometasilicate Neusilin® US2.

New Development in Understanding Drug–Polymer Interactions in Pharmaceutical Amorphous Solid Dispersions from Solid-State Nuclear Magnetic Resonance

Pharmaceutical amorphous solid dispersions (ASDs) represent a widely used technology to increase the bioavailability of active pharmaceutical ingredients (APIs). ASDs are based on an amorphous API dispersed in a polymer, and their stability is driven by the presence of strong intermolecular interactions between these two species (e.g., hydrogen bond, electrostatic interactions, etc.). The understanding of these interactions at the atomic level is therefore crucial, and solid-state nuclear magnetic resonance (NMR) has demonstrated itself as a very powerful technique for probing API-polymer interactions. Other reviews have also reported exciting approaches to study the structures and dynamic properties of ASDs and largely focused on the study of API-polymer miscibility and on the identification of API-polymer interactions. Considering the increased use of NMR in the field, the aim of this Review is to specifically highlight recent experimental strategies used to identify API-polymer interactions and report promising recent examples using one-dimensional (1D) and two-dimensional (2D) experiments by exploiting the following emerging approaches of very-high magnetic field and ultrafast magic angle spinning (MAS). A range of different ASDs spanning APIs and polymers with varied structural motifs is targeted to illustrate new ways to understand the mechanism of stability of ASDs to enable the design of new dispersions.

Measuring and Modeling Water Sorption in Amorphous Indomethacin and Ritonavir

The amorphous state of an active pharmaceutical ingredient (API) enhances its water solubility compared to its crystalline state. However, it is well known that amorphous substances can absorb significant amounts of water therewith inducing API recrystallization. This work explores methods to obtain reliable information about water sorption in amorphous APIs and its modeling. Experimental water-sorption curves over a broad humidity range were obtained by measuring the mass increase of well-defined films of amorphous APIs. Water-sorption isotherms modeled using perturbed-chain statistical associating fluid theory (PC-SAFT) showed better accordance with the experimental data than those obtained using the Flory-Huggins model. Crank's diffusion equation was used to describe the water-sorption kinetics providing Fickian diffusion coefficients of water in indomethacin and in ritonavir. Stefan-Maxwell diffusion coefficients were obtained by converting Fickian diffusion coefficients using water activity coefficients obtained from PC-SAFT. Finally, the free-volume theory was applied to explain the persistent water concentration dependency of the Stefan-Maxwell diffusion coefficients.

Interpreting the Physicochemical Meaning of a Molecular Descriptor Which Is Predictive of Amorphous Solid Dispersion Formation in Polyvinylpyrrolidone Vinyl Acetate.

A molecular descriptor known as R3m (the R-GETAWAY third-order autocorrelation index weighted by the atomic mass) was previously identified as capable of grouping members of an 18-compound library of organic molecules that successfully formed amorphous solid dispersions (ASDs) when co-solidified with the co-polymer polyvinylpyrrolidone vinyl acetate (PVPva) at two concentrations using two preparation methods. To clarify the physical meaning of this descriptor, the R3m calculation is examined in the context of the physicochemical mechanisms of dispersion formation. The R3m equation explicitly captures information about molecular topology, atomic leverage, and molecular geometry, features which might be expected to affect the formation of stabilizing non-covalent interactions with a carrier polymer, as well as the molecular mobility of the active pharmaceutical ingredient (API) molecule. Molecules with larger R3m values tend to have more atoms, especially the heavier ones that form stronger non-covalent interactions, generally, more irregular shapes, and more complicated topology. Accordingly, these molecules are more likely to remain dispersed within PVPva. Furthermore, multiple linear regression modeling of R3m and more interpretable descriptors supported these conclusions. Finally, the utility of the R3m descriptor for predicting the formation of ASDs in PVPva was tested by analyzing the commercially available products that contain amorphous APIs dispersed in the same polymer. All of these analyses support the conclusion that the information about the API geometry, size, shape, and topological connectivity captured by R3m relates to the ability of a molecule to interact with and remain dispersed within an amorphous PVPva matrix.

High-Drug-Loading Amorphous Solid Dispersions via In Situ Thermal Cross-Linking: Unraveling the Mechanisms of Stabilization.

This article takes a step forward in understanding the mechanisms involved during the preparation and performance of cross-linked high-drug-loading (HDL) amorphous solid dispersions (ASDs). Specifically, ASDs, having 90 wt % poorly water-soluble drug indomethacin (IND), were prepared via in situ thermal cross-linking of poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) and thoroughly evaluated in terms of physical stability and in vitro supersaturation. Results showed that HDL ASDs having excellent active pharmaceutical ingredient (API) amorphous stability and prolonged in vitro supersaturation were prepared by fine tuning the cross-linking procedure. Unraveling of the processes involved during ASD's formation shed light on the significant role of the cross-linking conditions (i.e., temperature and time), the physicochemical properties of the API, and the hydrolysis level of the cross-linker as key factors in modulating ASD's stability. In-depth analysis of the prepared systems revealed the (1) reduction of API's molecular motions within the cross-linked polymeric networks (through API's strong spatial confinement), (2) the structural changes in the prepared cross-linked matrices (induced by the high API drug loading), and (3) the tuning of the cross-linking density via utilization of low-hydrolyzed PVA as the major mechanisms responsible for ASD's exceptional performance. Complementary analysis by means of molecular dynamics simulations also highlighted the vital role of strong drug-polymer intermolecular interactions evolving among the ASD components. Overall, the impression of the complexity of in situ cross-linked ASDs has been reinforced with the excessive variation of parameters investigated in the current study, offering thus insights up to the submolecular level to lay the groundwork and foundations for the comprehensive assessment of a new emerging class of HDL amorphous API formulations.

Ternary Eutectic Ezetimibe-Simvastatin-Fenofibrate System and the Physical Stability of Its Amorphous Form.

In this study, the phase diagram of the ternary system of ezetimibe–simvastatin–fenofibrate was established. It has been proven that the ternary composition recommended for the treatment of mixed hyperlipidemia forms a eutectic system. Since eutectic mixtures are characterized by greater solubility and dissolution rate, the obtained result can explain the marvelous medical effectiveness of combined therapy. Considering that another well-known method for improving the aqueous solubility is amorphization, the ternary system with eutectic concentration was converted into an amorphous form. Thermal properties, molecular dynamics, and physical stability of the obtained amorphous system were thoroughly investigated through various experimental techniques compared to both: neat amorphous active pharmaceutical ingredients (considered separately) and other representative concentrations of ternary mixture. The obtained results open up a new way of selecting the therapeutic concentrations for combined therapies, a path that considers one additional variable: eutecticity.

Anormal Thermal History Effect on the Structural Dynamics of Probucol Infiltrated into Porous Alumina

Herein, broadband dielectric (BDS) and Fourier transform infrared spectroscopy (FTIR), together with differential scanning calorimetry (DSC) and X-ray diffraction (XRD), were applied to study the molecular dynamics, molecular interactions as well as physical stability of an amorphous Active Pharmaceutical Ingredient (API)—probucol (PRO)—infiltrated into anodic aluminum oxide (AAO) membranes of pore size, d ∼ 10–160 nm. Interestingly, the behavior of examined substance strongly depends on the applied thermal protocol. Remarkably, for the first time, we observed that the structural dynamics of the slowly cooled PRO under confinement is significantly enhanced when compared to that of the quenched material. This unusual behavior was interpreted as a result of surface-induced effects (including the formation of well-resolved interfacial H-bonded layer and adsorption–desorption processes near the interface) that are magnified by the extremely high sensitivity to density fluctuation of studied PRO, reflected in the enormous pressure coefficient of the glass transition temperature dTg/dp = 427 K/GPa. In fact, FTIR investigations revealed that PRO tends to self-associate under confinement and forms a strongly bonded interfacial layer, which controls the variation in the structural dynamics of core molecules. Finally, we observed that the tendency to crystallize of confined API is reduced with respect to the bulk, even though the critical size of PRO nuclei (rc ∼ 3 nm) is significantly lower than the smallest examined pore size. Nevertheless, after few weeks of storage, the investigated substance crystallized in larger pores, while it remained stable in the nanochannels of d = 10 nm. A combination of XRD and DSC measurements indicated that the infiltrated PRO forms two polymorphs, the stable form I (dominating in bulk) and unstable form II (prevailing under confinement). That means that porous matrices might be used to obtain and maintain prolonged stability of unstable polymorphic forms of API.

Impact of the Chain Length and Topology of the Acetylated Oligosaccharide on the Crystallization Tendency of Naproxen from Amorphous Binary Mixtures.

The impact of the chain length or dispersity of polymers in controlling the crystallization of amorphous active pharmaceutical ingredients (APIs) has been discussed for a long time. However, because of the weak control of these parameters in the majority of macromolecules used in pharmaceutical formulations, the abovementioned topic is poorly understood. Herein, four acetylated oligosaccharides, maltose (acMAL), raffinose (acRAF), stachyose (acSTA), and α-cyclodextrin (ac-α-CD) of growing chain lengths and different topologies (linear vs cyclic), mimicking the growing backbone of the polymer, were selected to probe the influence of these structural factors on the crystallization of naproxen (NAP)—an API that does not vitrify regardless of the cooling rate applied in our experiment. It was found that in equimolar systems composed of NAP and linear acetylated oligosaccharides, the progress and activation barrier for crystallization are dependent on the molecular weight of the excipient despite the fact that results of Fourier transform infrared studies indicated that there is no difference in the interaction pattern between measured samples. On the other hand, complementary dielectric, calorimetric, and X-ray diffraction data clearly demonstrated that NAP mixed with ac-α-CD (cyclic saccharide) does not tend to crystallize even in the system with a much higher content of APIs. To explain this interesting finding, we have carried out further density functional theory computations, which revealed that incorporation of NAP into the cavity of ac-α-CD is hardly possible because this state is of much higher energy (up to 80 kJ/mol) with respect to the one where the API is located outside of the saccharide torus. Hence, although at the moment, it is very difficult to explain the much stronger impact of the cyclic saccharide on the suppression of crystallization and enhanced stability of NAP with respect to the linear carbohydrates, our studies clearly showed that the chain length and the topology of the excipient play a significant role in controlling the crystallization of this API.

Combining crystalline and polymeric excipients in API solid dispersions – Opportunity or risk?

Amorphous solid dispersions (ASDs) are often metastable against crystallization of the active pharmaceutical ingredient (API) and thus might undergo unwanted changes during storage. The crystallization tendency of ASDs is influenced by the API crystallization driving force (CDF) and the mobility of the molecules in the ASD. Low molecular weight-excipients are known to stabilize amorphous APIs in so-called co-amorphous formulations. Due to their success in stabilizing co-amorphous APIs, low-molecular weight excipients might also enhance the stability of polymeric ASDs. In this work, we investigated the potential of combined low-molecular weight excipient/polymer formulations with in-silico tools and validated the predictions with long-term stability tests of the most promising excipient/polymer combinations. The considered critical quality attributes for the ASDs were the occurrence of amorphous phase separation, API CDF, and molecular mobility in the ASD.As an example, carbamazepine/polyvinylpyrrolidone ASDs were investigated combined with the excipients fructose, lactose, sucrose, trehalose, saccharin, tryptophan, and urea. Although all excipients had a negative impact on the ASD stability, saccharin still turned out to be the most promising one. Long-term stability studies with ASDs containing either saccharin or tryptophan verified -in agreement to the predictions- that API crystallization occurred faster than in the reference ASDs without additional excipient.This work showed that the addition of crystalline excipients to polymeric ASDs might not only offer opportunities but might also bear risks for the long-term stability of the ASD, even though the crystalline excipient stabilizes the polymer-free API. Consequently, excipients should be evaluated based on the thermodynamic phase behavior of the individual mixture of API/polymer/excipient, rather than based on pure-component properties of the excipient only. In-silico predictions proposed in this work remarkably decrease the number of screening tests for identifying suitable formulation excipients.

X-ray Powder Diffraction Spectroscopy as a Robust Tool in Early Predicting Bioavailability of Pharmaceutical Formulation Containing Polymorphic Drug Substance

: X-ray powder diffraction (XRPD) is a unique, solid-state analytical tool used to study the 3D structure of small or macromolecules by their x-ray diffraction or scattering patterns. X-ray diffraction by a crystal reflects the periodicity of crystal architecture; any imperfections within the crystal architecture can be easily identified by its poor diffraction pattern. Recently, an open crystallography database reported that more than 85 % of drug compounds are crystalline and exist in different polymorphic states. Physicochemical properties of pharmaceutical drug products composed of active pharmaceutical ingredients (APIs) and excipients are interdependent on the physical state and forms in which APIs are distributed in excipients that determine the in-vivo and ex-vivo performance of the product. Amorphous APIs have relatively higher dissolution and bioavailability than crystalline form but with lower phase stability. During the formulation development and storage phase, the conversion is higher that largely impacts the bioavailability of the drug product. In this manuscript, we have presented the case study of itraconazole and apigenin; both are crystalline APIs, that, with the help of solid dispersion technology, are converted into amorphous drug products with enhanced oral bioavailability. The realtime monitoring of the physical form of API in the formulation was possible with the help of XRPD and other supporting data obtained from differential scanning calorimeter (DSC), which can be correlated with the dissolution and in-vivo performance of the formulation.

A Mechanistic Model for Predicting the Physical Stability of Amorphous Solid Dispersions.

In this paper, we establish a mechanistic model for the prediction of amorphous solid dispersion (ASD) stability. The novel approach incorporates fundamental physical parameters, principally supersaturation, diffusivity, and interfacial energy, to model crystallization in ASDs accounting for both kinetic and thermodynamic drivers. API dependent decoupling coefficients were also considered which allowed dynamic mechanical analysis to probe molecular mobility, with viscosity measurements, across an exceptionally broad range of temperatures to support ASD stability simulations. ASDs are multicomponent systems in which the amorphous form of active pharmaceutical ingredients (APIs) are molecularly dispersed within a carrier. This gives rise to a transiently supersaturated API solution upon dissolution which increases the driving force for oral absorption and results in increased bioavailability as compared to that of the crystalline API. A major shortcoming of ASDs, however, is that there is the potential for amorphous APIs to revert to their more stable crystalline form during storage, despite the use of polymer carriers to stabilize formulations and limit recrystallization. Hot melt extrusion (HME) has been employed as the preparation method for ASDs used in this study as it is well-suited for the formation of uniform dispersions. The ASDs were stored under controlled temperature conditions, in the absence of humidity, to determine recrystallization kinetics. Our mechanistic model, considering both crystal nucleation and growth processes, describes temporal ASD stability through a system of coupled differential equations that connect the physiochemical properties of the ASD system to drug recrystallization. The model and prolonged time scale of crystallization observed highlight the importance of considering both thermodynamic and kinetic factors in the preparation of stable ASDs. Experimental observations were found to be in good agreement with predictions of the model confirming its utility in predicting the temporal physical stability of amorphous solid dispersions through a mechanistic lens.

Effect of Polymers and Storage Relative Humidity on Amorphous Rebamipide and Its Solid Dispersion Transformation: Multiple Spectra Chemometrics of Powder X-Ray Diffraction and Near-Infrared Spectroscopy.

This study aimed to investigate the effect of polymers and storage relative humidity on amorphous rebamipide (RB) and its solid dispersion phase transformation using chemometrics based on multiple datasets. The amorphous RB was prepared using particle mixture and grinding methods with hydroxypropyl cellulose, polyvinylpyrrolidone, and sodium dodecyl sulfate. Prepared amorphous RB and solid dispersion samples were stored under a relative humidity of 30% and 75% for four weeks. Infrared spectra of the dispersion samples suggested that the hydrogen bond network was constructed among quinolinone, carbonyl acid, and amide of RB and other polymers. The dataset combining near-infrared (NIR) spectra and powder X-ray diffractograms were applied to principal component analysis (PCA). The relationship between diffractograms and NIR spectra was evaluated using loadings and the PCA score. The multiple spectra analysis is useful for evaluating model amorphous active pharmaceutical ingredients without a standard sample.

Amorphous solid dispersions: An update for preparation, characterization, mechanism on bioavailability, stability, regulatory considerations and marketed products.

Amorphous solid dispersions (ASDs) are being employed frequently to improve bioavailability of poorly soluble molecules by enhancing the rate and extant of dissolution in drug product development process. These systems comprise of an amorphous active pharmaceutical ingredient stabilized by a polymer matrix to provide enhanced stability. This review discussed the methodologies of preparation and characterization of ASDs with an emphasis on understanding and predicting stability. Rational selection of polymers, preparation techniques with its advantages and disadvantages and characterization of polymeric amorphous solid dispersions have discussed. Stability aspects have been described as per ICH guidelines which intend to depend on selection of polymers and preparation methods of ASD. The mechanism involved on improvement of bioavailability also considered. Regulatory importance of ASD and current evolving details of QBD approach were reviewed. Amorphous products and particularly ASDs are currently most emerging area in the pharmaceutical field. This strategic approach presents huge impact and advantageous features concerning the overall improvement of drug product performance in clinical settings which ultimately lead to drug product approval by leading regulatory agencies into the market.

Terahertz-spectroscopy for non-destructive determination of crystallinity of L-tartaric acid in smartFilms® and tablets made from paper

Newly developed active pharmaceutical ingredients (API) often experience low solubility in aqueous media and thus possess poor oral bioavailability. The SmartFilm®-technology is a novel approach to overcome poor solubility. The technique uses commercial paper in which API can be loaded in amorphous state, thus increasing dissolution rate dc/dt and solubility cs when compared to bulk material. However, the preservation of the amorphous state is a prerequisite for an efficient use of the smartFilm-technology and thus the crystalline state needs to be inspected during storage. Preferably, this should be done non-destructively. Traditional techniques, such as x-ray diffraction (XRD) or differential scanning calorimetry (DSC), do not allow for non-destructive crystallinity investigations, whereas Terahertz (THz) spectroscopy is a non-destructive technique, that is sensitive to the crystalline state of many molecular crystals. Therefore, the potential of THz-spectroscopy for crystallinity state inspection of API in smartFilms and tablets made from smartFilms was investigated in this study. The THz results obtained were compared to results obtained from XRD and DSC measurements. Whereas DSC measurements failed to reliably detect crystalline API in the smartFilms, XRD and THz-spectroscopy showed similar results and revealed that it was possible to prepare smartFilms loaded with >23% (w/w) amorphous API. Results indicate the great potential of THz spectroscopy for the non-destructive determination of the crystalline state of APIs in smartFilms and/or tablets made from paper.