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

Self-nanomicellizing solid dispersion: A promising platform for oral drug delivery

Amorphous solid dispersion (ASD) has been widely used to enhance the oral bioavailability of water-insoluble drugs for oral delivery because of its advantages of enhancing solubility and dissolution rate. However, the problems related to drug recrystallization after drug dissolution in media or body fluid have constrained its application. Recently, a self-nanomicellizing solid dispersion (SNMSD) has been developed by incorporating self-micellizing polymers as carriers to settle the problems, markedly improving the ability of supersaturation maintenance and enhancing the oral bioavailability of drug. Spontaneous formation and stability of the self-nanomicelle (SNM) have been proved to be the key to supersaturation maintenance of SNMSD system. This offers a novel research direction for maintaining supersaturation and enhancing the bioavailability of ASDs. To delve into the advantages of SNMSDs, we provide a concise review introducing the formation mechanism, characterization methods and stability of SNMs, emphasizing the advantages of SNMSDs for oral drug delivery facilitated by SNM formation, and discussing relevant research prospects.

The Continuous and Reversible Transformation of the Polymorphs of an MGAT2 Inhibitor (S-309309) from the Anhydrate to the Hydrate in Response to Relative Humidity

Polymorphic control is vital for the quality control of pharmaceutical crystals. Here, we investigated the relationship between the hydrate and anhydrate polymorphs of a monoacylglycerol acyltransferase 2 inhibitor (S-309309). Solvent evaporation and slurry conversion revealed two polymorphs, the hydrate and the solvate. The solvate was transformed into the hydrate by heating. X-ray powder diffraction demonstrated that the hydrate was transformed into an anhydrate via an intermediate state when heated. These crystal forms were confirmed under controlled humidity conditions; the presence of the anhydrate, the intermediate hydrate, or the hydrate depended on the relative humidity at 25 °C. The stoichiometry of S-309309 in water in the hydrate form was 4:1. The hydrates and anhydrates exhibited similar crystal structures and stability. The water of hydration in the intermediate hydrate was 0.1-0.15 mol according to the dynamic vapor sorption profile. The stability and dissolution profile of the anhydrate and hydrate showed no significant change due to similar crystal lattices and quick rehydration of the anhydrate. A mechanism for the reversible crystal transformation between the anhydrate and pseudo-polymorphs of the hydrate was discovered. We concluded that S-309309 causes a pseudo-polymorphic transformation; however, this is not a critical issue for pharmaceutical use.

Preparation and Evaluation of Berberine-Excipient Complexes in Enhancing the Dissolution Rate of Berberine Incorporated into Pellet Formulations

Berberine is used in the treatment of metabolic syndrome and its low solubility and very poor oral bioavailability of berberine was one of the primary hurdles for its market approval. This study aimed to improve the solubility and bioavailability of berberine by preparing pellet formulations containing drug-excipient complex (obtained by solid dispersion). Berberine-excipient solid dispersion complexes were obtained with different ratios by the solvent evaporation method. The maximum saturation solubility test was performed as a key factor for choosing the optimal complex for the drug-excipient. The properties of these complexes were investigated by FTIR, DSC, XRD and dissolution tests. The obtained pellets were evaluated and compared in terms of pelletization efficiency, particle size, mechanical strength, sphericity and drug release profile in simulated media of gastric and intestine. Solid-state analysis showed complex formation between the drug and excipients used in solid dispersion. The optimal berberine-phospholipid complex showed a 2-fold increase and the optimal berberine-gelucire and berberine-citric acid complexes showed more than a 3-fold increase in the solubility of berberine compared to pure berberine powder. The evaluation of pellets from each of the optimal complexes showed that the rate and amount of drug released from all pellet formulations in the simulated gastric medium were significantly lower than in the intestine medium. The results of this study showed that the use of berberine-citric acid or berberine-gelucire complex could be considered a promising technique to increase the saturation solubility and improve the release characteristics of berberine from the pellet formulation.

The baicalein amorphous solid dispersion to enhance the dissolution and bioavailability and effects on growth performance, meat quality, antioxidant capacity and intestinal flora in Taihang chickens

Baicalein (BAI) is a natural flavonoid with antioxidant, antitumor and antibacterial properties. However, the bioavailability of BAI was limited due to low solubility. This study aims to improve the solubility of BAI through the amorphous solid dispersion (ASD) and evaluate changes in its pharmacokinetics and pharmacodynamics in Taihang chickens. Polyethylene caprolactam-polyvinyl acetate-polyethylene glycol grafted copolymer (Soluplus) was chosen as the carrier, and ASD was prepared by rotary evaporation and was characterized by powder X-ray diffractions (PXRD), differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FT-IR). In vitro dissolution assays were used to screen the optimal ratio of drug to carrier, in vivo pharmacokinetic assays were conducted to investigate the promoting effect on the absorption. In addition, the effects of ASD on the growth performance, meat quality, antioxidant capacity and intestinal flora were investigated. ASD (1:9 and 2:8) did not exhibit crystal diffraction peaks of BAI in PXRD or endothermic peaks in DSC, indicating the successful preparation of ASD. The results of in vitro dissolution assay showed that the cumulative dissolution rate of ASD (2:8) within 600 min was 52.67%, which was 7.84-fold higher than BAI. The pharmacokinetic results showed that the peak concentration (Cmax) and the area under the drug-time curve (AUC0∼24) of ASD (2:8) was (5.20 ± 0.82) μg/mL and (17.03 ± 0.67) μg·h/mL, which was 1.91 and 2.64-fold higher than BAI, respectively. Dietary supplementation of BAI and ASD could increase average daily gain (ADG), while decrease feed conversion ratio (FCR), but there was no significant difference (P > 0.05). The drip loss of BAIASD group was lower than BAI group (P < 0.05). In addition, the antioxidant capacity of Taihang chickens were enhanced, the diversity and the abundance of beneficial bacteria was improved. Results of BAI upon the dietary supplementation tested in Taihang chickens, after preparation of ASD, indicating a superior enhancement effect in growth performance, meat quality, antioxidant capacity and intestinal flora due to an improved solubility and optimized bioavailability.

Data-Driven Modeling of the Spray Drying Process. Process Monitoring and Prediction of the Particle Size in Pharmaceutical Production

Spray drying is used in the pharmaceutical industry for particle engineering of amorphous solid dispersions (ASDs). The particle size of the spray-dried (SD) powders is one of their key attributes due to its impact on the downstream processes and the drug product's functional properties. Offline and inline laser diffraction methods can be used to estimate the product's particle size; however, the final release of these ASDs is based on offline instruments. This paper presents a novel data-driven modeling approach for predicting the particle size of SD products. The model-based characterization of the process and the product's particle size, as a critical quality attribute, follows the quality by design principles. The resulting model can be used for online process monitoring, reducing the risks of out-of-specifications products and supporting their real-time release. A Tucker3 model is trained to capture and factorize the deterministic variability of the process. Subsequently, a partial least-squares regression model is calibrated to model the impact that variability in the input material properties, the process parameters, and the spray nozzle have on the products' particle size. This strategy has been calibrated and validated using large scale production data for two intermediate drug products under high sparsity of particle size data. Despite the challenges, high accuracy was obtained in predicting the median particle size (dv50) for release. The 99% confidence interval results in an error of maximum 2.5 μm, which is less than 10% of the allowed range of variation.

Amorphous solid dispersion of a binary formulation with felodipine and HPMC for 3D printed floating tablets

This study focuses on the combination of three-dimensional printing (3DP) and amorphous solid dispersion (ASD) technologies for the manufacturing of gastroretentive floating tablets. Employing hot melt extrusion (HME) and fused deposition modeling (FDM), the study investigates the development of drug-loaded filaments and 3D printed (3DP) tablets containing felodipine as model drug and hydroxypropyl methylcellulose (HPMC) as the polymeric carrier. Prior to fabrication, solubility parameter estimation and molecular dynamics simulations were applied to predict drug-polymer interactions, which are crucial for ASD formation. Physical bulk and surface characterization complemented the quality control of both drug-loaded filaments and 3DP tablets. The analysis confirmed a successful amorphous dispersion of felodipine within the polymeric matrix. Furthermore, the low infill percentage and enclosed design of the 3DP tablet allowed for obtaining low-density systems. This structure resulted in buoyancy during the entire drug release process until a complete dissolution of the 3DP tablets (more than 8 h) was attained. The particular design made it possible for a single polymer to achieve a zero-order controlled release of the drug, which is considered the ideal kinetics for a gastroretentive system. Accordingly, this study can be seen as an advancement in ASD formulation for 3DP technology within pharmaceutics.

The challenge of downstream processing of spray dried amorphous solid dispersions into minitablets designed for the paediatric population - A sustainable product development approach

Poorly water-soluble drugs present a significant challenge in the development of oral solid dosage forms (OSDs). In formulation development the appropriate use of excipients to adjust solubility, and the choice of manufacturing method and pharmaceutical processes to obtain a dosage form to meet the needs of the patient group, is crucial. Preparing an amorphous solid dispersion (ASD) is a well-established method for solubility enhancement, and spray drying (SD) a common manufacturing method. However, the poor flowability of spray dried materials poses a significant challenge for downstream processing. Promoting sustainability in OSD development involves embracing a versatile formulation design, which enables a broader spectrum of patients to use the product, as opposed to altering existing dosage forms retrospectively. The objective of the current study was to develop a formulation of spray dried indomethacin ASD suited to the production, by direct compression, of instant release paediatric minitablets. Excipients evaluated were PVP or HPMCAS in solid dispersions at the preformulation phase, and MCC and lactose as a filler in direct compression. From the studied formulations, a 3:1 ratio blend of Vivapur 200/Pharmatose 200 M (MCC/lactose) with 0.5% (w/w) magnesium stearate was found to be the most promising in tableting, and minitablets containing a 6.22% content of spray-dried ASD of indomethacin/PVP K 29-32 could be obtained with desired tablet hardness and pharmaceutical quality, complying with tests of weight variation and fast disintegration in an aqueous environment. As a case example, this study provides a good foundation for further studies in harnessing a sustainable approach to the development of pharmaceutical formulations that can appropriately serve different patient sub-populations.

Hydrolysis of Cellulose Acetate Phthalate and Hydroxypropyl Methylcellulose Phthalate in Amorphous Solid Dispersions

The preparation of amorphous solid dispersions (ASDs) represents a promising strategy for addressing the solubility limitations of poorly soluble drugs, facilitating enhanced oral absorption. Acidic polymers such as cellulose acetate phthalate (CAP) and hydroxypropyl methylcellulose phthalate (HPMCP) have emerged as effective carriers for ASDs. Although the hydrolytic degradation of these polymers has been documented, its impact on the stability of ASDs has not been systematically investigated. This research aimed to explore the potential hydrolysis of CAP and HPMCP and how it influences the stability of ASDs containing ketoconazole (KTZ), at drug loadings of 10 % and 50 %. Our study utilized thermal analysis, infrared spectroscopy, and evaluations of physical and chemical stability. The results revealed that although KTZ remained physically stable in all ASDs over 60 days under various stability conditions, the emergence of crystalline phthalic acid (PA), a byproduct of polymer hydrolysis, was observed at elevated temperatures and relative humidity levels. The acidic microenvironment fostered by the release of PA further catalyzed drug chemical degradation. This study underscores the susceptibility of CAP and HPMCP to hydrolytic degradation, highlighting the inherent risk of PA-induced drug degradation, particularly for acid-labile compounds. These insights into the understanding of polymer hydrolysis in ASDs pave the way for the development of targeted approaches to safeguard drug stability and optimize pharmaceutical formulations for enhanced bioavailability, efficacy, and safety.

Early evaluation of opportunities in oral delivery of PROTACs to overcome their molecular challenges

PROteolysis TArgeting Chimeras (PROTACs) offer new opportunities in modern medicine by targeting proteins that are intractable to classic inhibitors. Heterobifunctional in nature, PROTACs are small molecules that offer a unique mechanism of protein degradation by hijacking the ubiquitin-mediated protein degradation pathway, known as the ubiquitin-proteasome system. Herein, we present an analysis on the structural characteristics of this novel chemical modality. Furthermore, we review and discuss the formulation opportunities to overcome the oral delivery challenges of PROTACs in drug discovery.

Drug-drug co-amorphous systems: An emerging formulation strategy for poorly water-soluble drugs

Overcoming the poor water solubility of small-molecule drugs is a major challenge in the development of clinical pharmaceuticals. Amorphization of crystalline drugs is a highly effective strategy to improve their aqueous solubility. However, amorphous drugs are thermodynamically unstable and likely to crystallize during manufacturing and storage. Recently, drug-drug co-amorphous systems have emerged as a novel strategy to not only enable enhanced dissolution and physical stability of the individual drugs within the system but also to provide a strategy for combination therapy of the same or different clinical indications. This review serves to highlight advances in the methods used to manufacture and characterize drug-drug co-amorphous systems, summarize drug-drug co-amorphous applications reported in recent decades, and provide an outlook on future possibilities and perspectives.

In Vitro and Biological Evaluation of Oral Fast-Disintegrating Films Containing Ranitidine HCl and Syloid® 244FP-Based Ternary Solid Dispersion of Flurbiprofen

Flurbiprofen (FBP), a nonsteroidal anti-inflammatory drug (NSAID), is commonly used to treat the pain of rheumatoid arthritis, but in prolonged use it causes gastric irritation and ulcer. To avoid these adverse events of NSAIDs, the simultaneous administration of H2 receptor antagonists such as ranitidine hydrochloride (RHCl) is obligatory. Here, we developed composite oral fast-disintegrating films (ODFs) containing FBP along with RHCl to provide a gastroprotective effect as well as to enhance the solubility and bioavailability of FBP. The ternary solid dispersion (TSD) of FBP was fabricated with Syloid® 244FP and poloxamer® 188 using the solvent evaporation technique. The synthesized FBP-TSD (coded as TSD) was loaded alone (S1) and in combination with plain RHCl (S2) in the composite ODFs based on hydroxypropyl methyl cellulose E5 (HPMC E5). The synthesized composite ODFs were evaluated by in vitro (thickness, folding endurance, tensile strength, disintegration, SEM, FTIR, XRD and release study) and in vivo (analgesic, anti-inflammatory activity, pro-inflammatory cytokines and gastroprotective assay) studies. The in vitro characterization revealed that TSD preserved its integrity and was effectively loaded in S1 and S2 with optimal compatibility. The films were durable and flexible with a disintegration time ≈15 s. The release profile at pH 6.8 showed that the solid dispersion of FBP improved the drug solubility and release when compared with pure FBP. After in vitro studies, it was observed that the analgesic and anti-inflammatory activity of S2 was higher than that of pure FBP and other synthesized formulations (TSD and S1). Similarly, the level of cytokines (TNF-α and IL-6) was also markedly reduced by S2. Furthermore, a gastroprotective assay confirmed that S2 has a higher safety profile in comparison to pure FBP and other synthesized formulations (TSD and S1). Thus, composite ODF (S2) can effectively enhance the FBP solubility and its therapeutic efficacy, along with its gastroprotective effect.

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

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

Formulation strategies for the development of high drug-loaded amorphous solid dispersions

Amorphous solid dispersions (ASD) have gained tremendous attention over the past two decades as one of the most promising techniques for enhancing the solubility of poorly water-soluble drugs. However, low drug loading is one of the major challenges of ASD technology that limits its commercialization to only a few drug candidates. Increasing the drug loading increases the risk of recrystallization during storage (solid state) and/or during dissolution (solution state). Various formulation and process-related strategies have been explored that open the possibility of formulating high drug-loaded ASDs without the risk of recrystallization. Here, we review various formulation approaches, such as the use of surfactants, mesoporous silicas, polymer combinations, in situ thermal crosslinking, structural modification of polymeric carriers, and surface nanocoating using minerals. We also discuss the mechanisms by which these approaches inhibit solid state and/or solution state recrystallization.

Probing Molecular Packing of Amorphous Pharmaceutical Solids Using X-ray Atomic Pair Distribution Function and Solid-State NMR

The structural investigation of amorphous pharmaceuticals is of paramount importance in comprehending their physicochemical stability. However, it has remained a relatively underexplored realm primarily due to the limited availability of high-resolution analytical tools. In this study, we utilized the combined power of X-ray pair distribution functions (PDFs) and solid-state nuclear magnetic resonance (ssNMR) techniques to probe the molecular packing of amorphous posaconazole and its amorphous solid dispersion at the molecular level. Leveraging synchrotron X-ray PDF data and employing the empirical potential structure refinement (EPSR) methodology, we unraveled the existence of a rigid conformation and discerned short-range intermolecular C-F contacts within amorphous posaconazole. Encouragingly, our ssNMR 19F-13C distance measurements offered corroborative evidence supporting these findings. Furthermore, employing principal component analysis on the X-ray PDF and ssNMR data sets enabled us to gain invaluable insights into the chemical nature of the intermolecular interactions governing the drug-polymer interplay. These outcomes not only furnish crucial structural insights facilitating the comprehension of the underlying mechanisms governing the physicochemical stability but also underscore the efficacy of synergistically harnessing X-ray PDF and ssNMR techniques, complemented by robust modeling strategies, to achieve a high-resolution exploration of amorphous structures.

Sugars and Polyols of Natural Origin as Carriers for Solubility and Dissolution Enhancement

Crystalline carriers such as dextrose, sucrose, galactose, mannitol, sorbitol, and isomalt have been reported to increase the solubility, and dissolution rates of poorly soluble drugs when employed as carriers in solid dispersions (SDs). However, synthetic polymers dominate the preparation of drugs: excipient SDs have been created in recent years, but these polymer-based SDs exhibit the major drawback of recrystallisation upon storage. Also, the use of high-molecular-weight polymers with increased chain lengths brings forth problems such as increased viscosity and unnecessary bulkiness in the resulting dosage form. An ideal SD carrier should be hydrophilic, non-hygroscopic, have high hydrogen-bonding propensity, have a high glass transition temperature (Tg), and be safe to use. This review discusses sugars and polyols as suitable carriers for SDs, as they possess several ideal characteristics. Recently, the use of low-molecular-weight excipients has gained much interest in developing SDs. However, there are limited options available for safe, low molecular excipients, which opens the door again for sugars and polyols. The major points of this review focus on the successes and failures of employing sugars and polyols in the preparation of SDs in the past, recent advances, and potential future applications for the solubility enhancement of poorly water-soluble drugs.

HPMCAS-Based Amorphous Solid Dispersions in Clinic: A Review on Manufacturing Techniques (Hot Melt Extrusion and Spray Drying), Marketed Products and Patents

Today, therapeutic candidates with low solubility have become increasingly common in pharmaceutical research pipelines. Several techniques such as hot melt extrusion, spray drying, supercritical fluid technology, electrospinning, KinetiSol, etc., have been devised to improve either or both the solubility and dissolution to enhance the bioavailability of these active substances belonging to BCS Class II and IV. The principle involved in all these preparation techniques is similar, where the crystal lattice of the drug is disrupted by either the application of heat or dissolving it in a solvent and the movement of the fine drug particles is arrested with the help of a polymer by either cooling or drying to remove the solvent. The dispersed drug particles in the polymer matrix have higher entropy and enthalpy and, thereby, higher free energy in comparison to the crystalline drug. Povidone, polymethaacrylate derivatives, hydroxypropyl methyl cellulose (HPMC) and hydroxypropyl methylcellulose acetate succinate derivatives are commonly used as polymers in the preparation of ASDs. Specifically, hydroxypropylmethylcellulose acetate succinate (HPMCAS)-based ASDs have become well established in commercially available products and are widely explored to improve the solubility of poorly soluble drugs. This article provides an analysis of two widely used manufacturing techniques for HPMCAS ASDs, namely, hot melt extrusion and spray drying. Additionally, details of HPMCAS-based ASD marketed products and patents have been discussed to emphasize the commercial aspect.

A Comparative Assessment of Cocrystal and Amorphous Solid Dispersion Printlets Developed by Hot Melt Extrusion Paired Fused Deposition Modeling for Dissolution Enhancement and Stability of Ibuprofen

The primary focus of the research is to study the role of cocrystal and amorphous solid dispersion approaches for enhancing solubility and preserving the stability of a poorly soluble drug, i.e., ibuprofen (IBP). First, the solvent-assisted grinding approach determined the optimum molar ratio of the drug and the coformer (nicotinamide (NIC)). Later, the polymeric filaments of cocrystals and amorphous solid dispersions were developed using the hot melt extrusion (HME) process, and the printlets were fabricated using the fused deposition modeling (FDM) additive manufacturing process. In addition, the obtained filaments were also milled and compressed into tablets as reference samples. The formation of cocrystals and amorphous solid dispersions was evaluated and confirmed using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and powder X-ray diffraction (PXRD) analysis. The drug release profiles of 3D printlets with 50% infill were found to be faster and are in line with the release profiles of compressed tablets. In addition, the 3D-printed cocrystal formulation was stable for 6 months at accelerated conditions. However, the 3D printlets of amorphous solid dispersions and compressed tablets failed to retain stability attributed to the recrystallization of the drug and loss in tablet mechanical properties. This shows the suitability of a cocrystal platform as a novel approach for developing stable formulations of poorly soluble drug substances over amorphous solid dispersions.

In Silico Modeling Approaches Coupled with In Vitro Characterization in Predicting In Vivo Performance of Drug Delivery System Formulations

Optimization of the in vivo performance of dosage forms in humans is essential in developing not only conventional formulations but also drug delivery system (DDS) formulations. Although animal experiments are still useful for these formulations, in silico approaches have become increasingly important for DDS formulations with regard to species-specific differences in physiology that can affect the in vivo performance of dosage forms between animals and humans. Furthermore, it is also important to couple in vitro characterizations with in silico models to predict in vivo performance in humans precisely. In this review article, I summarized in vitro-in silico approaches to predicting the in vivo performance of oral DDS formulations (amorphous solid dispersions, lipid-based formulations, nanosized formulations, cyclodextrins-based formulations, sustained release products, enteric coat products, and orally disintegrating tablets) and parenteral DDS formulations (cyclodextrins-based formulations, liposomes, and inhaled formulations).

Development and evaluation of febuxostat solid dispersion through screening method

Febuxostat (Febux) is a BCS II drug and has a very low solubility. In order to overcome this shortcoming, the purpose of study is to increase the in vitro dissolution (%) and drug release (%) of Febux by using a screening method. The Febux-SD formulation was prepared by screening solubilizers, pH agents, and carriers using with a solvent evaporation method. The novel Febux SD formulation was successfully developed. The dissolution (%) of Febux of optimal formulation (SD3) was higher than that of Feburic® tab in pH 1.2, distilled water (DW), and pH 6.8 buffer by 6.3-, 2.6-, and 1.1-fold, respectively, at 60 min. The in vitro drug release (%) and permeability (μg/cm2) of SD3 formulation were improved compared to those of Feburic® tab in the pH shifting method and PBS (7.4), respectively. The SD3 formulation was well maintained the stability for 6 months, and that of physicochemical properties were altered. In conclusion, the Febux solubilization study with meglumine was first attempted and successfully performed. Through the improved dissolution (%) of Febux, high bioavailability of SD3 formulation is expected in animal and human studies.

Review of industrially recognized polymers and manufacturing processes for amorphous solid dispersion based formulations

Evolving therapeutic landscape through combinatorial chemistry and high throughput screening have resulted in an increased number of poorly soluble drugs. Drug delivery strategies quickly adapted to convert these drugs into successful therapies. Amorphous solid dispersion (ASD) technology is widely employed as a drug delivery strategy by pharmaceutical industries to overcome the challenges associated with these poorly soluble drugs. The development of ASD formulation requires an understanding of polymers and manufacturing techniques. A review of US FDA-approved ASD-based products revealed that only a limited number of polymers and manufacturing technologies are employed by pharmaceutical industries. This review provides a comprehensive guide for the selection and overview of polymers and manufacturing technologies adopted by pharmaceutical industries for ASD formulation. The various employed polymers with their underlying mechanisms for solution-state and solid-state stability are discussed. ASD manufacturing techniques, primarily implemented by pharmaceutical industries for commercialization, are presented in Quality by Design (QbD) format. An overview of novel excipients and progress in manufacturing technologies are also discussed. This review provides insights to the researchers on the industrially accepted polymers and manufacturing technology for ASD formulation that has translated these challenging drugs into successful therapies.

Molecular Dynamics Simulations of Selected Amorphous Stilbenoids and Their Amorphous Solid Dispersions with Poly(Vinylpyrrolidone)

Amorphous solid dispersions (ASDs) are one of the promising strategies to improve the solubility and dissolution rate of poorly soluble compounds. In this study, Molecular Dynamics simulations were used to investigate the interactions between three selected stilbenoids with important biological activity (resveratrol, pinostilbene and pterostilbene) and poly(vinylpyrrolidone). The analysis of the pair distribution functions and hydrogen bond distributions reveals a significant weakening of the hydrogen bond network of the stilbenoids in ASDs compared to the pure (no polymer) amorphous systems. This is accompanied by an increase in the mobility of the stilbenoid molecules in the ASDs, both in the translational dynamics determined from the molecular mean square displacements, and in the molecular reorientations followed by analysing several torsional distributions.

Veering to a Continuous Platform of Fused Deposition Modeling Based 3D Printing for Pharmaceutical Dosage Forms: Understanding the Effect of Layer Orientation on Formulation Performance

Three-dimensional (3D) printing of pharmaceuticals has been centered around the idea of personalized patient-based 'on-demand' medication. Fused deposition modeling (FDM)-based 3D printing processes provide the capability to create complex geometrical dosage forms. However, the current FDM-based processes are associated with printing lag time and manual interventions. The current study tried to resolve this issue by utilizing the dynamic z-axis to continuously print drug-loaded printlets. Fenofibrate (FNB) was formulated with hydroxypropyl methylcellulose (HPMC AS LG) into an amorphous solid dispersion using the hot-melt extrusion (HME) process. Thermal and solid-state analyses were used to confirm the amorphous state of the drug in both polymeric filaments and printlets. Printlets with a 25, 50, and 75% infill density were printed using the two printing systems, i.e., continuous, and conventional batch FDM printing methods. Differences between the two methods were observed in the breaking force required to break the printlets, and these differences reduced as the infill density went up. The effect on in vitro release was significant at lower infill densities but reduced at higher infill densities. The results obtained from this study can be used to understand the formulation and process control strategies when switching from conventional FDM to the continuous printing of 3D-printed dosage forms.

Amorphization of Ethenzamide and Ethenzamide Cocrystals-A Case Study of Single and Binary Systems Forming Low-Melting Eutectic Phases Loaded on/in Silica Gel

The applicability of different solvent-free approaches leading to the amorphization of active pharmaceutical ingredients (APIs) was tested. Ethenzamide (ET), an analgesic and anti-inflammatory drug, and two ethenzamide cocrystals with glutaric acid (GLU) and ethyl malonic acid (EMA) as coformers were used as pharmaceutical models. Calcinated and thermally untreated silica gel was applied as an amorphous reagent. Three methods were used to prepare the samples: manual physical mixing, melting, and grinding in a ball mill. The ET:GLU and ET:EMA cocrystals forming low-melting eutectic phases were selected as the best candidates for testing amorphization by thermal treatment. The progress and degree of amorphousness were determined using instrumental techniques: solid-state NMR spectroscopy, powder X-ray diffraction, and differential scanning calorimetry. In each case, the API amorphization was complete and the process was irreversible. A comparative analysis of the dissolution profiles showed that the dissolution kinetics for each sample are significantly different. The nature and mechanism of this distinction are discussed.

Real-time in situ X-ray micro-computed tomography study of the effect of impurities on the crystallization of amorphous nifedipine

Controlling the physical stability of noncrystalline active pharmaceutical ingredients remains a major challenge in the development of amorphous formulations such as amorphous solid-dispersion (ASD) formulations. To establish new evaluation and formulation strategies, the spatial distribution of the crystal phase in bulk amorphous nifedipine (NFD) was investigated as a model. The crystallization of amorphous NFD and the effect of a deliberately added impurity were investigated using powder X-ray diffraction (PXRD), differential scanning calorimetry and real-time in situ X-ray micro-computed tomography (X-ray CT). The stability data of amorphous samples, i.e., NFD and a mixture of NFD with an oxidative degradation product of NFD, impurity A (Imp A), at a weight ratio of 90:10, presented as percent amorphous remaining, suggests that Imp A accelerates the bulk crystal growth of NFD. Real-time in situ X-ray CT results showed surface-enhanced crystal growth and cavity formation in solid NFD samples. Moreover, the crystals were heterogeneous in density. These results suggest that Imp A affects the physical stability of the amorphous NFD. X-ray CT equipped with a heating unit can aid in-situ evaluation and assessment of physicochemical properties and physical stability of amorphous samples and formulations.

Effect of Different Seed Crystals on the Supersaturation State of Ritonavir Tablets Prepared by Hot-Melt Extrusion

Hot-melt extrusion (HME) is a technology increasingly common for the commercial production of pharmaceutical amorphous solid dispersions (ASDs), especially for poorly water-soluble active pharmaceutical ingredients (APIs). However, recrystallization of the APIs during dissolution must be prevented to maintain the supersaturation state enabled by ASD. Unfortunately, the amorphous formulation may be contaminated by seed crystals during the HME manufacturing process, which could lead to undesirable crystal growth during the dissolution process. In this study, the dissolution behavior of ritonavir ASD tablets prepared using both Form I and Form II polymorphs was examined, and the effects of different seed crystals on crystal growth rates were investigated. The aim was to understand how the presence of seed crystals can impact the dissolution of ritonavir, and to determine the optimal polymorph and seeding conditions for the production of ASDs. The results showed that both Form I and Form II ritonavir tablets had similar dissolution profiles, which were also similar to the reference listed drug (RLD). However, it was observed that the presence of seed crystals, particularly the metastable Form I seed, led to more precipitation compared to the stable Form II seed in all formulations. The Form I crystals that precipitated from the supersaturated solution were easily dispersed in the solution and could serve as seeds to facilitate crystal growth. On the other hand, Form II crystals tended to grow more slowly and presented as aggregates. The addition of both Form I and Form II seeds could affect their precipitation behaviors, and the amount and form of the seeds had significant effects on the precipitation process of the RLD tablets, as are the tablets prepared with different polymorphs. In conclusion, the study highlights the importance of minimizing the contamination risk of seed crystals during the manufacturing process and selecting the appropriate polymorph for the production of ASDs.

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.

Twin Screw Melt Granulation: Alternative Approach for Improving Solubility and Permeability of a Non-steroidal Anti-inflammatory Drug Ibuprofen

The current research is focused on investigating the suitability of the twin screw melt granulation (TSMG) approach for improving the solubility of a non-steroidal anti-inflammatory (NSAIDs) drug (ibuprofen), by developing granules using lipid surfactants. The solubility of the drug within the solid lipid excipients (Gelucire® 48/16 and Gelucire® 50/13) was determined by differential scanning calorimetry (DSC). The formulations were developed for drug and lipid ratios of 1:1.5, 1:3, and 1:4.5 using Neusilin® US2 as a solid adsorbent carrier. The solid-state properties of the drug investigated using differential scanning calorimetry (DSC) have revealed the conversion of the drug to an amorphous form for 1:3 and 1:4.5 ratios of formulations confirmed by powder x-ray diffraction analysis (PXRD). Drug-excipient compatibility and formation of no interactions were characterized using Fourier transform infrared spectroscopy (FTIR). The granules with a 1:3 and 1:4.5 ratios of drug and lipid have improved drug dissolution and permeation, attributing to the formation of micellar emulsions. The stability of formulation with a 1:3 ratio of drug and lipid surfactant was preserved when stored in accelerated conditions. However, the formulation with a 1:4.5 ratio of drug and lipid failed to retain the amorphous state evidenced by the recrystallization of the drug. This shows the suitability of TSMG as a single-step continuous manufacturing process for developing melt granules to improve the solubility of poorly water-soluble drug substances.