Pharmaceutical amorphous solid dispersion: A review of manufacturing strategies

Current Trends on Solid Dispersions: Past, Present, and Future

Solid dispersions have achieved significant interest as an effective means of enhancing the dissolution rate and thus the bioavailability of a range of weakly water-soluble drugs. Solid dispersions of weakly water-soluble drugs with water-soluble carriers have lowered the frequency of these problems and improved dissolution. Solid dispersion is a solubilization technology emphasizing mainly on, drug-polymer two-component systems in which drug dispersion and its stabilization is the key to formulation development. Therefore, this technology is recognized as an exceptionally useful means of improving the dissolution properties of poorly water-soluble drugs and in the latest years, a big deal of understanding has been accumulated about solid dispersion, however, their commercial application is limited. In this review article, emphasis is placed on solubility, BCS classification, and carriers. Moreover, this article presents the diverse preparation techniques for solid dispersion and gathers some of the recent technological transfers. The different types of solid dispersions based on the carrier used and molecular arrangement were underlined. Additionally, it summarizes the mechanisms, the methods of preparing solid dispersions, and the marketed drugs that are available using solid dispersion approaches.

Recent Advances in Amorphous Solid Dispersions: Preformulation, Formulation Strategies, Technological Advancements and Characterization

Amorphous solid dispersions (ASDs) are among the most popular and widely studied solubility enhancement techniques. Since their inception in the early 1960s, the formulation development of ASDs has undergone tremendous progress. For instance, the method of preparing ASDs evolved from solvent-based approaches to solvent-free methods such as hot melt extrusion and Kinetisol^®. The formulation approaches have advanced from employing a single polymeric carrier to multiple carriers with plasticizers to improve the stability and performance of ASDs. Major excipient manufacturers recognized the potential of ASDs and began introducing specialty excipients ideal for formulating ASDs. In addition to traditional techniques such as differential scanning calorimeter (DSC) and X-ray crystallography, recent innovations such as nano-tomography, transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray microscopy support a better understanding of the microstructure of ASDs. The purpose of this review is to highlight the recent advancements in the field of ASDs with respect to formulation approaches, methods of preparation, and advanced characterization techniques.

Nano-Dry-Melting: A Novel Technology for Manufacturing of Pharmaceutical Amorphous Solid Dispersions

Amorphous solid dispersions (ASD) are one of the most prominent formulation approaches to overcome bioavailability issues that are often presented by new poorly soluble drug candidates. State-of-the art manufacturing techniques include hot melt extrusion and solvent-based methods like spray drying. The high thermal and mechanical shear stress during hot melt extrusion, or the use of an organic solvent during solvent-based methods, are examples of clear drawbacks for those methods, limiting their applicability for certain systems. In this work a novel process technology is introduced, called Nano-Dry-Melting (NDM), which can provide an alternative option for ASD manufacturing. NDM consists of a comminution step in which the drug is ground to nanosize and a drying step provides a complete amorphization of the system at temperatures below the melting point. Two drug–polymer systems were prepared using NDM with a wet media mill and a spray dryer and analyzed regarding their degree of crystallinity using XRD analysis. Feasibility studies were performed with indomethacin and PVP. Furthermore, a “proof-of-concept” study was conducted with niclosamide. The experiments successfully led to amorphous samples at temperatures of about 50 K below the melting point within seconds of heat exposition. With this novel, solvent-free and therefore “green” production technology it is feasible to manufacture ASDs even with those drug candidates that cannot be processed by conventional process technologies.

Scientific and regulatory activities initiated by the U.S. food and drug administration to foster approvals of generic dry powder inhalers: Quality perspective

Regulatory science for generic dry powder inhalation products worldwide has evolved over the last decade. The revised draft guidance Metered Dose Inhaler (MDI) and Dry Powder Inhaler (DPI) Products - Quality Considerations [1] (Revision 1, April 2018) that FDA issued summarizes product considerations and potential critical quality attributes (CQAs). This guidance emphasizes the need to apply the principles of quality by design (QbD) and elements of pharmaceutical development discussed in the International Conference for Harmonisation of (ICH) guidelines. Research studies related to quality were used to support guidance recommendations, which preceded the first approval of a generic DPI product in the U.S. This review outlines scientific and regulatory hurdles that need to be surmounted to successfully bring a generic DPI to the market. The goal of this review focuses on relevant issues and various challenges pertaining to CMC topics of the generic DPI quality attributes. Furthermore, this review provides recommendations to abbreviated new drug application (ANDA) applicants to expedite generic approvals.

Development of a multiparticulate drug delivery system for in situ amorphisation

In the current study, the concept of multiparticulate drug delivery systems (MDDS) was applied to tablets intended for the amorphisation of supersaturated granular ASDs in situ, i.e. amorphisation by microwave irradiation within the final dosage form. The MDDS concept was hypothesised to ensure geometric and structural stability of the dosage form and to improve the in vitro disintegration and dissolution characteristics. Granules were prepared in two sizes (small and large) containing the crystalline drug celecoxib (CCX) and polyvinylpyrrolidone/vinyl acetate copolymer (PVP/VA) at a 50 % w/w drug load as well as sodium dihydrogen phosphate monohydrate as the microwave absorbing excipient. The granules were subsequently embedded in an extra-granular tablet phase composed of either the filler microcrystalline cellulose (MCC) or mannitol (MAN), as well as the disintegrant crospovidone and the lubricant magnesium stearate. The tensile strength and disintegration time were investigated prior to and after 10 min of microwave irradiation (800 and 1000 W) and the formed ASDs were characterised by X-ray powder diffraction and modulated differential scanning calorimetry. Additionally, the internal structure was elucidated by X-ray micro-Computed Tomography (XµCT) and, finally, the dissolution performance of selected tablets was investigated. The MDDS tablets displayed no geometrical changes after microwave irradiation, however, the tensile strength and disintegration time increased. Complete amorphisation of CCX was achieved only for the MCC-based tablets at a power input of 1000 W, while MAN-based tablets displayed partial amorphisation independent of power input. The complete amorphisation of CCX was associated with the fusion of individual ASD granules within the tablets, which impacted the subsequent disintegration and dissolution performance. For these tablets, supersaturation was only observed after 60 min. On the other hand, the partially amorphised MDDS tablets displayed complete disintegration during the dissolution experiments, resulting in a fast onset of supersaturation within 5 min and an approx. 3.5-fold degree of supersaturation within the experimental timeframe (3 h). Overall, the MDDS concept was shown to potentially be a feasible dosage form for in situ amorphisation, however, there is still room for improvement to obtain a fully amorphous and disintegrating system.

High Bulk-Density Amorphous Dispersions to Enable Direct Compression of Reduced Tablet Size Amorphous Dosage Units

Amorphous solid dispersions (ASDs) are an attractive option to improve the bioavailability of poorly water-soluble compounds. However, the material attributes of ASDs can present formulation and processability challenges, which are often mitigated by the addition of excipients albeit at the expense of tablet size. In this work, an ASD manufacturing train combining co-precipitation and thin film evaporation (TFE) was used to generate high bulk-density co-precipitated amorphous dispersion (cPAD). The cPAD/TFE material was directly compressed into tablets at amorphous solid dispersion loadings up to 89 wt%, representing a greater than 60% reduction in tablet size relative to formulated tablets containing spray dried intermediate (SDI). This high ASD loading was possible due to densification of the amorphous dispersion during drying by TFE. Pharmacokinetic performance of the TFE-isolated, co-precipitated dispersion was shown to be equivalent to an SDI formulation. These data highlight the downstream advantages of this novel ASD manufacturing pathway to facilitate reduced tablet size via high ASD loading in directly compressed tablets.

Preparation of a camptothecin analog FLQY2 self-micelle solid dispersion with improved solubility and bioavailability

BACKGROUND

7-p-trifluoromethylphenyl-FL118 (FLQY2) is a camptothecin analog with excellent antitumor efficacy against various solid tumors. However, its poor solubility and low bioavailability limited the development of the drug. Polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus^®), an emerging carrier for preparing solid dispersion (SD), encapsulated FLQY2 to circumvent the above limitations.

RESULTS

In this project, FLQY2-SD was prepared by solvent evaporation method and self-assembled into micelles in aqueous solutions owing to the amphiphilic nature of Soluplus^®. The physicochemical characterizations demonstrated that FLQY2 existed in a homogeneous amorphous form in SD and was rapidly dissolved. The micelles did not affect cytotoxicity or cellular uptake of FLQY2 in vitro, and the oral bioavailability was increased by 12.3-fold compared to the FLQY2 cyclodextrin suspension. The pharmacokinetics of FLQY2-SD showed rapid absorption, accumulation in the intestine, and slow elimination via fecal. Metabolite identification studies showed 14 novel metabolites were identified, including 12 phase I metabolites (M1-M12) and 2 phase II metabolites (M13-M14), of which M2 (oxidation after decarboxylation) and M7 (dioxolane ring cleavage) were the primary metabolites in the positive mode and negative mode, respectively. The tumor growth inhibition rate (TGI, 81.1%) of FLQY2-SD (1.5 mpk, p.o./QW) in tumor-bearing mice after oral administration was higher than that of albumin-bound Paclitaxel (15 mpk, i.v./Q4D) and Irinotecan hydrochloride (100 mpk, i.p./QW).

CONCLUSIONS

The successful preparation, pharmacokinetics, and pharmacodynamics studies of FLQY2-SD showed that the solubility and bioavailability of FLQY2 were improved, which facilitated the further druggability development of FLQY2.

Supercritical CO2 Assisted Electrospray to Produce Poly(lactic-co-glycolic Acid) Nanoparticles

This work proposes an improvement of the traditional electrospraying process, in which supercritical carbon dioxide (SC-CO2) is used to produce poly(lactic-co-glycolic acid) (PLGA) nanoparticles. The experiments were performed at different PLGA concentrations (1, 3 and 5% w/w), applied voltages (10 and 30 kV) and operating pressures (80, 120 and 140 bar). It was found that working at 140 bar and 30 kV, spherical nanoparticles, with mean diameters of 101 ± 13 nm and 151 ± 45 nm, were obtained, when solutions at 1% w/w and 3% w/w PLGA were electrosprayed, respectively. Increasing PLGA concentration up to 5% w/w, a mixture of fibers and particles was observed, indicating the transition to the electrospinning regime.

Fast-Fed Variability: Insights into Drug Delivery, Molecular Manifestations, and Regulatory Aspects

Among various drug administration routes, oral drug delivery is preferred and is considered patient-friendly; hence, most of the marketed drugs are available as conventional tablets or capsules. In such cases, the administration of drugs with or without food has tremendous importance on the bioavailability of the drugs. The presence of food may increase (positive effect) or decrease (negative effect) the bioavailability of the drug. Such a positive or negative effect is undesirable since it makes dosage estimation difficult in several diseases. This may lead to an increased propensity for adverse effects of drugs when a positive food effect is perceived. However, a negative food effect may lead to therapeutic insufficiency for patients suffering from life-threatening disorders. This review emphasizes the causes of food effects, formulation strategies to overcome the fast-fed variability, and the regulatory aspects of drugs with food effects, which may open new avenues for researchers to design products that may help to eliminate fast-fed variability.

Melt Fusion Techniques for Solubility Enhancement: A Comparison of Hot Melt Extrusion and KinetiSol® Technologies

A successful candidate for oral drug delivery needs to possess adequate solubility and dissolution rate to elicit its therapeutic action. Extensive research is being carried out to enhance the solubility of poorly soluble drugs through a number of techniques involving polymeric and non-polymeric approaches. Non-polymeric approaches such as micronization and nanocrystals are successful in improving the apparent solubility of drugs, but the sustenance of solubility is not always possible. Amorphous solid dispersions (ASDs) lead to solubility enhancement as well as the maintenance of solubility with the assistance of polymers, thereby improving bioavailability. Spray drying, hot melt extrusion (HME), and KinetiSol® technologies are some of the techniques capable of manufacturing ASDs. Each of these techniques has its own advantages and disadvantages in terms of processing challenges and applicability in preparing ASDs. The latter two technologies are similar in being fusion and non-solvent techniques to improve solubility. This review compares both HME and KinetiSol® techniques regarding mechanism, equipment design, formulation, and process parameters involved and scalability.

Amorphous Solid Dispersions: Role of the Polymer and Its Importance in Physical Stability and In Vitro Performance

Amorphous solid dispersions stabilized by one or more polymer(s) have been widely used for delivering amorphous drugs with poor water solubilities, and they have gained great market success. Polymer selection is important for preparing robust amorphous solid dispersions, and considerations should be given as to how the critical attributes of a polymer can enhance the physical stability, and the in vitro and in vivo performances of a drug. This article provides a comprehensive overview for recent developments in the understanding the role of polymers in amorphous solid dispersions from the aspects of nucleation, crystal growth, overall crystallization, miscibility, phase separation, dissolution, and supersaturation. The critical properties of polymers affecting the physical stability and the in vitro performance of amorphous solid dispersions are also highlighted. Moreover, a perspective regarding the current research gaps and novel research directions for better understanding the role of the polymer is provided. This review will provide guidance for the rational design of polymer-based amorphous pharmaceutical solids with desired physicochemical properties from the perspective of physical stability and in vitro performance.

Supersaturated amorphous solid dispersions of celecoxib prepared by in situ microwave irradiation

This study investigated the ability of in situ amorphization using microwave irradiation in order to prepare highly supersaturated ASDs, i.e. ASDs with drug loads higher than the saturation solubility in the polymer at ambient temperature. For this purpose, compacts containing the crystalline drug celecoxib (CCX) and polyvinylpyrrolidone (PVP), polyvinylpyrrolidone-vinyl acetate copolymer (PVP/VA), or polyvinyl acetate (PVAc), were prepared at drug loads between 30-90 % w/w. Sodium dihydrogen phosphate (NaH₂PO₄) monohydrate was included in all compacts, as a source of water, to facilitate the dielectric heating of the compacts upon dehydration during microwave irradiation. After processing, the samples were analysed towards their solid state using X-ray powder diffraction (XRPD) and modulated differential scanning calorimetry (mDSC). Complete amorphisation of CCX was achieved across all the investigated polymers and with a maximal drug load of 90, 80, and 50 % w/w in PVP, PVP/VA, and PVAc, respectively. These drug loads corresponded to a 2.3-, 2.4-, and 10.0-fold supersaturation in the investigated polymers at ambient temperature. However, dissolution experiments with the in situ prepared ASDs in fasted state simulated intestinal fluid (FaSSIF), showed a lower initial drug release (0-2 hours) compared to equivalent physical mixtures of crystalline CCX and polymers or crystalline CCX alone. The lower drug release rate was explained by the fusion of individual drug and polymer particles during microwave irradiation and, subsequently, a lack of disintegration of the monolithic ASDs. Nevertheless, supersaturation of CCX in FaSSIF was achieved with the in situ amorphised ASDs with PVP and PVP/VA, albeit only after 3-24 h. Overall, the present study confirmed that it is feasible to prepare supersaturated ASDs in situ. However, in the current experimental setup, the monolithic nature of the resulting ASDs is considered a limiting factor in the practical applicability of this preparation method, due to limited disintegration and the associated negative effect on the drug release.

The Effect of Various Poly (N-vinylpyrrolidone) (PVP) Polymers on the Crystallization of Flutamide

In this study, several experimental techniques were applied to probe thermal properties, molecular dynamics, crystallization kinetics and intermolecular interactions in binary mixtures (BMs) composed of flutamide (FL) and various poly(N-vinylpyrrolidone) (PVP) polymers, including a commercial product and, importantly, samples obtained from high-pressure syntheses, which differ in microstructure (defined by the tacticity of the macromolecule) from the commercial PVP. Differential Scanning Calorimetry (DSC) studies revealed a particularly large difference between the glass transition temperature (Tg) of FL+PVPsynth. mixtures with 10 and 30 wt% of the excipient. In the case of the FL+PVPcomm. system, this effect was significantly lower. Such unexpected findings for the former mixtures were strictly connected to the variation of the microstructure of the polymer. Moreover, combined DSC and dielectric measurements showed that the onset of FL crystallization is significantly suppressed in the BM composed of the synthesized polymers. Further non-isothermal DSC investigations carried out on various FL+10 wt% PVP mixtures revealed a slowing down of FL crystallization in all FL-based systems (the best inhibitor of this process was PVP Mn = 190 kg/mol). Our research indicated a significant contribution of the microstructure of the polymer on the physical stability of the pharmaceutical-an issue completely overlooked in the literature.

19F Solid-state NMR characterization of pharmaceutical solids

Solid-state NMR has been increasingly recognized as a high-resolution and versatile spectroscopic tool to characterize drug substances and products. However, the analysis of pharmaceutical materials is often carried out at natural isotopic abundance and a relatively low drug loading in multi-component systems and therefore suffers from challenges of low sensitivity. The fact that fluorinated therapeutics are well represented in pipeline drugs and commercial products offers an excellent opportunity to utilize fluorine as a molecular probe for pharmaceutical analysis. We aim to review recent advancements of ¹⁹F magic angle spinning NMR methods in modern drug research and development. Applications to polymorph screening at the micromolar level, structural elucidation, and investigation of molecular interactions at the Ångström to submicron resolution in drug delivery, stability, and quality will be discussed.

The antisolvent coprecipitation method for enhanced bioavailability of poorly water-soluble drugs

In recent years, poorly water-soluble drug candidates in the drug development pipeline have been a challenging issue for the pharmaceutical industry. Many delivery systems such as nanocrystals, cocrystals, nanoparticles, and amorphous solid dispersions (ASDs) have been developed to overcome these problems. A large number of methods are utilized to realize the above delivery systems. Among all the preparation methods, the antisolvent coprecipitation method is a relatively simple, cost-effective method, offering many advantages over conventional methods. An overview of recent developments for each solubility enhancement approach using the antisolvent coprecipitation method is presented. This current review details a comprehensive overview of the antisolvent coprecipitation process and its properties, as well as the fundamentals for enhancing the solubility and bioavailability of poorly water-soluble drugs by nanotization, polymorph control with polymers and/or surfactants. Furthermore, this review also presents insights into the factors affecting the antisolvent coprecipitation process.

Design of Ternary Amorphous Solid Dispersions for Enhanced Dissolution of Drug Combinations

Using sulfamethoxazole (SMZ) and trimethoprim (TMP) as model drugs, we designed amorphous solid dispersions (ASDs) for the simultaneous solubility enhancement of two active pharmaceutical ingredients (APIs) by exploiting the drug-drug and drug-polymer interactions. In order to make this approach broadly applicable and over a wide dose range, a mixture of SMZ and TMP at weight ratios of 5:1 and 1:5 (w/w) were formulated into ternary ASDs. Depending on the dose ratio of the two drugs, the polymer used was either an aminoalkyl methacrylate copolymer (Eudragit, EDE) or polyacrylic acid. The drug-drug and drug-polymer interactions were characterized to be ionic by infrared and solid-state nuclear magnetic resonance spectroscopy. The interactions resulted in a substantial reduction in molecular mobility, evident from the increase in the structural relaxation time determined by dielectric spectroscopy. The drug-drug interaction resulted in ∼3 orders of magnitude reduction in molecular mobility. The addition of a polymer led to a further decrease in molecular mobility of up to 4 orders of magnitude. The strength of intermolecular interactions was also estimated from the glass transition temperatures of the ASDs obtained by differential scanning calorimetry. The strong intermolecular interactions yielded highly stable ASDs with no evidence of crystallization, both at elevated temperatures and under accelerated storage conditions (40 °C/75% relative humidity; 6 weeks). The dissolution performances of the ASDs were evaluated using the area under the curve (AUC) obtained from the concentration-time profiles under the non-sink condition. SMZ and TMP in their ternary ASDs, when compared with their crystalline counterparts, exhibited up to 6.4- and 4.6-fold increases in AUC, respectively. Importantly, the synchronized release of the two drugs was observed, a desirable attribute in synergistic formulations. A single-phase ternary ASD, stabilized by drug-drug and drug-polymer interactions, is likely responsible for the unique release profile.

Downstream Processing of Itraconazole:HPMCAS Amorphous Solid Dispersion: From Hot-Melt Extrudate to Tablet Using a Quality by Design Approach

The downstream processing of hot-melt extruded amorphous solid dispersions (ASDs) into tablets is challenging due to the low tabletability of milled ASDs. Typically, the extrudate strand is sized before milling, as the strand cannot be fed directly into the milling system. At the lab scale, the strand can be sized by hand-cutting before milling. For scaling up, pelletizers or chill roll and flaker systems can be used to break strands. Due to the different techniques used, differences in milling and tablet compaction are to be expected. We present a systematic study of the milling and tableting of an extruded ASD of itraconazole with hypromellose acetate succinate (HPMCAS) as a carrier polymer. The strand was sized using different techniques at the end of the extruder barrel (hand-cutting, pelletizer, or chill roll and flaker) before being milled at varying milling speeds with varying screen sizes. The effects of these variables (sizing technology, milling speed, and screen size) on the critical quality attributes (CQAs) of the milled ASD, such as yield, mean particle size (D50), tablet compaction characteristics, and tablet dissolution, were established using response surface methodology. It was found that the CQAs varied according to sizing technology, with chill roll flakes showing the highest percentage yield, the lowest D50, and the highest tabletability and dissolution rate for itraconazole. Pearson correlation coefficient tests indicated D50 as the most important CQA related to tabletability and dissolution. For certain milling conditions, the milling of hand-cut filaments results in similar particle size distributions (PSDs) to the milling of pellets or chill roll flakes.

ASD Formation Prior to Material Characterization as Key Parameter for Accurate Measurements and Subsequent Process Simulation for Hot-Melt Extrusion

Process simulation facilitates scale-up of hot-melt extrusion (HME) and enhances proper understanding of the underlying critical process parameters. However, performing numeric simulations requires profound knowledge of the employed materials' properties. For example, an accurate description of the compounds' melt rheology is paramount for proper simulations. Hence, sample preparation needs to be optimized to yield results as predictive as possible. To identify the optimal preparation method for small amplitude oscillatory shear (SAOS) rheological measurements, binary mixtures of hydroxypropylmethylcellulose acetate succinate or methacrylic acid ethyl acrylate copolymer (Eudragit L100-55) together with the model drugs celecoxib and ketoconazole were prepared. The physical powder mixtures were introduced into the SAOS as a compressed tablet or a disk prepared via vacuum compression molding (VCM). Simulations with the derived parameters were conducted and compared to lab-scale extrusion trials. VCM was identified as the ideal preparation method resulting in the highest similarity between simulated and experimental values, while simulation based on conventional powder-based methods insufficiently described the HME process.

Solid dispersion technology as a formulation strategy for the fabrication of modified release dosage forms: A comprehensive review

Solubility limited bioavailability is one of the crucial parameters that affect the formulation development of the new chemical entities. Thus the major constraint in the pharmaceutical product development is the suitable solubility enhancement technique for Active Pharmaceutical Ingredient. Solid dispersion (SD) is an established and preferred method for improving the solubility which ultimately may be helpful to enhance bioavailability. For long period of time Amorphous solid dispersion (ASD) have been preferred for improving solubility, but since last two decades, ASD approach have been combined with different modified release approaches to improvise the stability and site specificity of SD to grasp a hold over the specific advantages associated with such dosage forms. It is an established fact now that the SD technique not only improves solubility limited bioavailability, but it may be combined with other approaches to modify the drug release profile from the formulation as per the requirement based on the apt selection of SD carriers and suitable technology. This review covers the comprehensive overview of all such formulations where SD technology is used to serve dual purpose rather than only the sole purpose of solubility enhancement. The SD approach has been successfully implemented for some of the poorly soluble herbal drugs and still there is a vast scope of advancement in that area. The current review will provide a broad outcome in the area of SD technology for modified release formulations along with the description of current status and future prospective of SD. The SD formed by dispersing drug within the conventional carrier to form ASD increases solubility, dissolution rate and bioavailability; whereas fourth generation hydrophobic carriers provide added advantage of controlled release (CR) or sustained release (SR) profile along with enhanced stability of SD. On the other frontier, pH dependant carriers enable the SD to achieve site specificity or delayed release (DR) profile.

API solubility in semi-crystalline polymer: Kinetic and thermodynamic phase behavior of PVA-based solid dispersions

The formulation of amorphous solid dispersions (ASDs) represents a promising strategy for improving the poor bioavailability of many active pharmaceutical ingredients (APIs). The objective of this study was to investigate and compare the long-term physical stability (LTPS) of polyvinyl alcohol (PVA)-based solid dispersions formulated via hot-melt extrusion (HME) with their respective API-PVA temperature-composition (T-C) phase diagram. Furthermore, the impact of API glass-forming ability (GFA) on the LTPS was evaluated through the selection of two APIs with contrasting GFA (i.e., indomethacin (IND; good GFA) and naproxen (NAP; poor GFA)). Even though the predicted solubility of both APIs in PVA was less than 1 wt% at T = 25 °C, IND remained fully amorphous in HME-formulated IND-PVA extrudates with initial API loadings of 50, 40, and 30 wt% after a 24-month storage period. Meanwhile, NAP recrystallized to a considerable degree in each analogous sample with an amorphous NAP content of 22.5-23.5 wt% remaining after a 12-month storage period. While the constructed T-C phase diagrams were still in agreement with their respective LTPS study, they did not account for the impact of water uptake as well as potential HME-induced effects on the extrudate glass-transition temperature. This work may serve as a useful reference point for researchers who are interested in determining the solubility of an API in a semi-crystalline polymer and the challenges therein.

Ammonio Methacrylate Copolymer (Type B)-Diltiazem Interactions in Solid Dispersions and Microsponge Drug-Delivery Systems

This paper presents a complex analytical study on the distribution, solubility, amorphization, and compatibility of diltiazem within the composition of Eudragit RS 100-based particles of microspongeous type. For this purpose, a methodology combining attenuated total reflectance Fourier transform infrared (ATR-FTIR) absorption spectroscopy, differential scanning calorimetry (DSC), scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDX), and in vitro dissolution study is proposed. The correct interpretation of the FTIR and drug-dissolution results was guaranteed by the implementation of two contrasting reference models: physical drug–polymer mixtures and casting-obtained, molecularly dispersed drug–polymer composites (solid dispersions). The spectral behavior of the drug–polymer composites in the carbonyl frequency (νCO) region was used as a quality marker for the degree of their interaction/mutual solubility. A spectral-pattern similarity between the microsponge particles and the solid dispersions indicated the molecular-type dispersion of the former. The comparative drug-desorption study and the qualitative observations over the DSC and SEM-EDX results confirmed the successful synthesis of a homogeneous coamorphous microsponge-type formulation with excellent drug-loading capacity and “controlled” dissolution profile. Among them, the drug-delivery particles with 25% diltiazem content (M-25) were recognized as the most promising, with the highest population of drug molecules in the polymer bulk and the most suitable desorption profile. Furthermore, an economical and effective analytical algorithm was developed for the comprehensive physicochemical characterization of complex delivery systems of this kind.

Preparation of DNC Solid Dispersion by a Mechanochemical Method with Glycyrrhizic Acid and Polyvinylpyrrolidone to Enhance Bioavailability and Activity

To exploit aqueous-soluble formulation and improve the anticoccidial activity of 4,4'-dinitrocarbanilide (DNC, active component of nicarbazin), this paper prepared DNC/GA/PVP K30 solid dispersion (SD) with glycyrrhizic acid (GA) and polyvinylpyrrolidone (PVP) K30 by a mechanical ball milling method without using any organic solvent. Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy were used for the solid state characterization. High performance liquid chromatography, critical micelle concentration, particle characterization, and transmission electron microscopy were used to evaluate the behavior in aqueous solution. In addition, the oral bioavailability, tissue distribution, and anticoccidial activity of DNC/GA/PVP K30 SD were investigated as well. Compared with free drug, the novel formulation not only improved the solubility and dissolution rate of DNC, but also inhibited the fecal output of oocysts and enhanced the therapeutic effect of coccidiosis. According to the experiment results, the DNC/GA/PVP K30 SD increased 4.64-fold in oral bioavailability and dramatically enhanced the concentration in liver which provided a basis for further research in schistosomiasis. In summary, our findings suggested that DNC/GA/PVP K30 SD may have promising applications in the treatment of coccidiosis.

A Hot-Melt Extrusion Risk Assessment Classification System for Amorphous Solid Dispersion Formulation Development

Several literature publications have described the potential application of active pharmaceutical ingredient (API)–polymer phase diagrams to identify appropriate temperature ranges for processing amorphous solid dispersion (ASD) formulations via the hot-melt extrusion (HME) technique. However, systematic investigations and reliable applications of the phase diagram as a risk assessment tool for HME are non-existent. Accordingly, within AbbVie, an HME risk classification system (HCS) based on API–polymer phase diagrams has been developed as a material-sparing tool for the early risk assessment of especially high melting temperature APIs, which are typically considered unsuitable for HME. The essence of the HCS is to provide an API risk categorization framework for the development of ASDs via the HME process. The proposed classification system is based on the recognition that the manufacture of crystal-free ASD using the HME process fundamentally depends on the ability of the melt temperature to reach the API’s thermodynamic solubility temperature or above. Furthermore, we explored the API–polymer phase diagram as a simple tool for process design space selection pertaining to API or polymer thermal degradation regions and glass transition temperature-related dissolution kinetics limitations. Application of the HCS was demonstrated via HME experiments with two high melting temperature APIs, sulfamerazine and telmisartan, with the polymers Copovidone and Soluplus. Analysis of the resulting ASDs in terms of the residual crystallinity and degradation showed excellent agreement with the preassigned HCS class. Within AbbVie, the HCS concept has been successfully applied to more than 60 different APIs over the last 8 years as a robust validated risk assessment and quality-by-design (QbD) tool for the development of HME ASDs.

Benchmarking the Solubility Enhancement and Storage Stability of Amorphous Drug–Polyelectrolyte Nanoplex against Co-Amorphous Formulation of the Same Drug

Amorphization, typically in the form of amorphous solid dispersion (ASD), represents a well-established solubility enhancement strategy for poorly soluble drugs. Recently, two amorphous drug formulations, i.e., the amorphous drug–polyelectrolyte nanoparticle complex (nanoplex) and co-amorphous system, have emerged as promising alternatives to circumvent the issues faced by ASD (i.e., large dosage requirement, high hygroscopicity). In the present work, the nanoplex was benchmarked against the co-amorphous system in terms of the preparation efficiency, drug payload, thermal stability, dissolution rate, supersaturation generation, and accelerated storage stability. Weakly acidic curcumin (CUR) and weakly basic ciprofloxacin (CIP) were used as the model poorly soluble drugs. The CUR and CIP nanoplexes were prepared using chitosan and sodium dextran sulfate as the polyelectrolytes, respectively. The co-amorphous CUR and CIP were prepared using tannic acid and tryptophan as the co-formers, respectively. The benchmarking results showed that the amorphous drug nanoplex performed as well as, if not better than, the co-amorphous system depending on the drug in question and the aspects being compared. The present work successfully established the nanoplex as an equally viable amorphous drug formulation as the more widely studied co-amorphous system to potentially serve as an alternative to ASD.

Compression Modulus and Apparent Density of Polymeric Excipients during Compression-Impact on Tabletability

The present study focuses on the compaction behavior of polymeric excipients during compression in comparison to nonpolymeric excipients and its consequences on commonly used Heckel analysis. Compression analysis at compaction pressures (CPs) from 50 to 500 MPa was performed using a compaction simulator. This study demonstrates that the particle density, measured via helium pycnometer (ρpar), of polymeric excipients (Kollidon®VA64, Soluplus®, AQOAT®AS-MMP, Starch1500®, Avicel®PH101) was already exceeded at low CPs (<200 MPa), whereas the ρpar was either never reached for brittle fillers such as DI-CAFOS®A60 and tricalcium citrate or exceeded at CPs above 350 MPa (FlowLac®100, Pearlitol®100SD). We hypothesized that the threshold for exceeding ρpar is linked with predominantly elastic deformation. This was confirmed by the start of linear increase in elastic recovery in-die (ERin-die) with exceeding particle density, and in addition, by the applicability in calculating the elastic modulus via the equation of the linear increase in ERin-die. Last, the evaluation of “density under pressure” as an alternative to the ρpar for Heckel analysis showed comparable conclusions for compression behavior based on the calculated yield pressures. However, the applicability of Heckel analysis for polymeric excipients was questioned in principle. In conclusion, the knowledge of the threshold provides guidance for the selection of suitable excipients in the formulation development to mitigate the risk of tablet defects related to stored elastic energy, such as capping and lamination.

Bio-enabling strategies to mitigate the pharmaceutical food effect: a mini review

The concomitant administration of oral drugs with food can result in significant changes in bioavailability, leading to variable pharmacokinetics and considerable clinical implications, such as over- or under-dosing. Consequently, there is increasing demand for bio-enabling formulation strategies to reduce variability in exposure between the fasted and fed state and/or mitigate the pharmaceutical food effect. The current review critically evaluates technologies that have been implemented to overcome the positive food effects of pharmaceutical drugs, including, lipid-based formulations, nanosized drug preparations, cyclodextrins, amorphisation and solid dispersions, prodrugs and salts. Additionally, improved insight into preclinical models for predicting the food effect is provided. Despite the wealth of research, this review demonstrates that application of optimal formulation strategies to mitigate the positive food effects and the evaluation in preclinical models is not a universal approach, and improved standardisation of models to predict the food effects would be desirable. Ultimately, the successful reformulation of specific drugs to eliminate the food effect provides a panoply of advantages for patients with regard to clinical efficacy and compliance.

Activated charcoal dispersion of carbon monoxide prodrugs for oral delivery of CO in a pill

A novel orally bioavailable solid formulation to deliver a gaseous signaling molecule, carbon monoxide (CO), was developed by adsorbing oxalyl saccharin, a newly developed organic CO prodrug, in activated charcoal (AC). The resulting solid dispersion formulation addresses key developability issues of this CO prodrug. By taking advantage of the large surface area of AC, the paradoxical problem of low water solubility of the prodrug and the requirement of hydrolysis to release CO is resolved, and the need for an organic cosolvent is completely circumvented. The AC formulation also mitigates the adverse effect of low pH on the CO release yield, allowing steady CO release in simulated gastric and intestine fluids. This formulation allows encapsulation in normal and enteric-coated gel capsules, which enables controllable CO delivery to the upper or lower GI system. It also features an advantage of trapping CO prodrug and CO release product in the AC, therefore lowering systemic absorption of these chemicals. Through in-vivo pharmacokinetic studies in mice, the AC formulation showed better efficiency of delivering CO through oral administration compared to the prodrug dosed with an organic cosolvent. The AC formulation has also been applied to address similar developability issues of another cheletropic reaction-based CO prodrug. We envision the wide applicability of this formulation in facilitating the future development of CO-based therapeutics.

Recent advances in the surfactant and controlled release polymer-based solid dispersion

The oral route is the most preferred delivery route for drug administration due to its advantages such as lower cost, improved patient compliance, no need for trained personnel and the drug reactions are generally less severe. The major problem with new molecules in the drug discovery pipeline is poor solubility and dissolution rate that ultimately results in low oral bioavailability. Numerous techniques are available for solubility and bioavailability (BA) enhancement, but out of all, solid dispersion (SD) is proven to be the most feasible due to the least issues in manufacturing, processing, storage, and transportation. In the past few years, SD had been extensively applied to reinforce the common issues of insoluble drugs. Currently, many hydrophobic and hydrophilic polymers are used to prepare either immediate release or controlled release SDs. Therefore, the biological behavior of the SDs is contingent upon the use of appropriate polymeric carriers and methods of preparation. The exploration of novel carriers and methodologies in SD technology leads to improved BA and therapeutic effectiveness. Moreover, the clinical applicability of SD-based formulations has been increased with the discovery of novel polymeric carriers. In this review, emphasis is laid down on the present status of recent generations of SDs (i.e., surfactant and controlled release polymer-based SD) and their application in modifying the physical properties of the drug and modulation of pharmacological response in different ailments.

A Nanocrystal Platform Based on Metal-Phenolic Network Wrapping for Drug Solubilization

The preparation of drugs into nanocrystals represents a practical pharmaceutical technology to solubilize poorly water-soluble drugs and enhance bioavailability. However, commonly used stabilizers in nanocrystals like polymers and surfactants are frequently inefficient and cannot stabilize nanocrystals for an expected time. This study reports an exquisite platform for nanocrystal production based on a metal-phenolic network (MPN). MPN-wrapped nanocrystal particles (MPN-NPs) were fabricated through an anti-solvent precipitation method using tannic acid and Fe^III or Al^III as coupling agents and characterized by dynamic light scattering, transmission electron microscope, ultraviolet and visible spectrophotometry, fourier-transform infrared spectroscopy, and X-ray powder diffraction. In vitro release, cytotoxicity, and stability were mainly studied with MPN-NPs loading paclitaxel. The suitability of MPN as a nanocrystal stabilizer was also investigated for other classical hydrophobic drugs, including simvastatin, andrographolide, atorvastatin calcium, ferulic acid, and famotidine. The results showed that MPN could effectively wrap and stabilize various drug nanocrystals apart from famotidine. The maximum solubilization of MPN towards atorvastatin calcium was up to 1587 folds, and it also exhibited an excellent solubilizing effect on other hydrophobic drugs. We disclosed that the drug was entrapped in MPN in the nanocrystal form, and there were distinct physiochemical interactions between MPN and the payload. Our findings suggested that MPN may be a promising platform for nanocrystal production to address the challenge of low solubility associated with hydrophobic drugs. Graphical abstract.

Increasing Drug Loading of Weakly Acidic Telmisartan in Amorphous Solid Dispersions through pH Modification during Hot-Melt Extrusion

Oral drug therapy requiring large quantities of active pharmaceutical ingredients (APIs) can cause a substantial pill burden, which can increase nonadherence and worsen healthcare outcomes. Maximizing the drug loading of APIs in oral dosage forms is essential to reduce pill burden. This can be challenging for poorly water-soluble APIs without compromising performance. We show a promising strategy for maximizing the drug loading of pH-dependent APIs in amorphous solid dispersions (ASDs) produced by hot-melt extrusion (HME) without compromising their dissolution performance. We examine potential increases in the drug loading (w/w) of telmisartan in ASDs by incorporating bases to modify pH during HME. Telmisartan is a weakly acidic, poorly water-soluble API with pH-dependent solubility. It is practically insoluble at physiological pH, but its solubility increases exponentially at pH values above 10. Telmisartan was extruded with the polymer Soluplus and various bases. With no base, the maximum drug loading achieved by extrusion was only 5% before crystalline telmisartan was detected. Including a strong, water-soluble base (NaOH or KOH) increased the maximum amorphous drug loading to 50%. These results indicate that telmisartan has pH-dependent solubility in a molten polymer, similar to that in an aqueous solution. We also examine the stability of Soluplus when extruded with a strong base, using solid-state nuclear magnetic resonance (ssNMR) to determine that NaOH (but not KOH) causes degradation by hydrolysis. Supersaturation was maintained for at least 20 h during dissolution testing of a 50% telmisartan ASD in biorelevant media.

Liquisolid systems as a novel approach in formulation and manufacturing of solid dosage forms: Challenges and perspectives

Liquisolid systems are a novel, promising platform for the production of solid dosage forms with a high liquid content, i.e. dispersion of the drug in a suitable, hydrophilic, non-volatile liquid vehicle or liquid drug. This technology requires conventional, but highly porous excipients (carrier and coating material in the appropriate ratio) able to absorb/adsorb liquid medication, resulting in both good flowability and acceptable compression properties. This approach has shown great potential to improve the dissolution rate and bioavailability of poorly soluble drugs, and has been recognized as a good alternative to common, more complex and expensive techniques. A variety of applications of this simple technique have been investigated recently, including the preparation of: modified release tablets, orally disintegrating tablets, solid dosage forms with liquid herbal extracts, etc. This emerging technology has numerous advantages, and the most important are: simplicity, cost-effectiveness, applicability in large scale production and environmental friendliness. However, it is accompanied by certain challenges as well, such as limited applicability in the case of highly dosed drugs. This article aims to give a comprehensive overview of recent progress regarding the potential applications of this technology, as well as to give an insight into the new liquisolid-based techniques intending to further support its commercial applicability.

Development of starch/chitosan expandable films as a gastroretentive carrier for ginger extract-loaded solid dispersion

Gastroretentive expandable films were developed to provide controlled release of ginger extract (GE) for treatment of gastric diseases. The dosage form consisted of ginger extract solid dispersion (GE-SD) loaded in a starch/chitosan composite film, which was subsequently folded and inserted into a hard gelatin capsule. GE-SD was prepared by solvent evaporation using an optimum weight ratio of 1:1 for GE and PVP K30. Expandable films containing GE-SD were prepared by solvent casting combinations of chitosan and either rice-, glutinous rice - or pregelatinized maize starch with glycerin incorporated as a plasticizer. The optimized film formulation prepared from glutinous rice starch, exhibited tensile strength of 5.4 N/cm² and high expansion in simulated gastric fluid (SGF), resulting in a 2.8-fold increase in area. The films resulted in sustained release of up to 90% of the content of 6-gingerol during 8 h exposure to SGF. Furthermore, the 6-gingerol released from the film displayed dose-dependent cytotoxic activity against AGS human gastric adenocarcinoma cells and anti-inflammatory activity by inhibiting the production of nitric oxide (NO) in LPS-stimulated RAW264.7 cells.

Amorphous Solid Dispersions: Utilization and Challenges in Preclinical Drug Development within AstraZeneca

The poor aqueous solubility of many active pharmaceutical ingredients (APIs) dominates much of the early drug development portfolio and poses a major challenge in pharmaceutical development. Polymer-based amorphous solid dispersions (ASDs) are becoming increasingly common and offer a promising formulation strategy to tackle the solubility and oral absorption issues of these APIs. This review discusses the design, manufacture, and utilisation of ASD formulations in preclinical drug development, with a key focus on the pre-formulation assessments and workflows employed at AstraZeneca.

Computational Modeling of Fluidized Beds with a Focus on Pharmaceutical Applications: A Review

The fluidized bed is an essential and standard equipment in the field of process development. It has a wide application in various areas and has been extensively studied. This review paper aims to discuss computational modeling of a fluidized bed with a focus on pharmaceutical applications. Eulerian, Lagrangian, and combined Eulerian-Lagrangian models have been studied for fluid bed applications with the rise of modeling capabilities. Such models assist in optimizing the process parameters and expedite the process development cycle. This paper discusses the background of modeling and then summarizes research papers relevant to pharmaceutical unit operations.

Effect of Storage Humidity on Physical Stability of Spray-Dried Naproxen Amorphous Solid Dispersions with Polyvinylpyrrolidone: Two Fluid Nozzle vs. Three Fluid Nozzle

In a spray drying operation, a two-fluid nozzle (2FN) with a single channel is commonly used for atomizing the feed solution. However, the less commonly used three-fluid nozzle (3FN) has two separate channels, which allow spray drying of materials in two incompatible solution systems. Although amorphous solid dispersions (ASDs) prepared using a 3FN have been reported to deliver comparable drug dissolution performance relative to those prepared using a 2FN, few studies have systematically examined the effect of 3FN on the physical stability. Therefore, the goal of this work is to systematically study the physical stability of ASDs that are spray-dried using a 3FN compared to those prepared using the traditional 2FN. For the 2FN, a single solution of naproxen and polyvinylpyrrolidone (PVP) was prepared in a mixture of acetone and water at a 1:1 volume ratio because 2FN allows for only one solution inlet. For the 3FN, naproxen and PVP were dissolved individually in acetone and water, respectively, because 3FN allows simultaneous entry of two solutions. Upon storage of the formulated ASDs at different humidity levels (25%, 55% and 75% RH), naproxen crystallized more quickly from the 3FN ASDs as compared with the 2FN ASDs. 3FN ASDs crystallized after 5 days of storage at all conditions, whereas 2FN ASDs did not crystallize even at 55% RH for two months. This relatively higher crystallization tendency of 3FN ASDs was attributed to the inhomogeneity of drug and polymers as identified by the solid-state Nuclear Magnetic Resonance findings, specifically due to poor mixing of water- and acetone-based solutions at the 3FN nozzle. When only acetone was used as a solvent to prepare drug-polymer solutions for 3FN, the formulated ASD was found to be stable for >3 months of storage (at 75% RH), which suggests that instability of the 3FN ASD was due to the insufficient mixing of water and acetone solutions. This study provides insights into the effects of solvent and nozzle choices on the physical stability of spray-dried ASDs.