Evaluation and modeling of the eutectic composition of various drug-polyethylene glycol solid dispersions

Utilizing the allyl-terminated copolymer methoxy(poly(ethylene glycol))-block-poly(jasmine lactone) in the development of amorphous solid dispersions: A comparative study of functionalized and non-functionalized polymer

Molecular interactions are crucial to stabilize amorphous drugs in amorphous solid dispersions (ASDs). Most polymers, however, have only a limited ability to form strong molecular interactions with drugs. Polymers tailored to fit the physicochemical properties of the drug molecule to be incorporated, for instance by allowing the incorporation of specific functional groups, would be highly sought-for in this regard. For this purpose, the novel allyl-terminated polymer methoxy(polyethylene glycol)-block-poly(jasmine lactone) (mPEG-b-PJL) has been synthesized and functionalized to potentially enhance specific drug-polymer interactions. This study investigated the use of mPEG-b-PJL in ASDs, using carvedilol (CAR), a weakly basic model drug. The findings revealed that the acidic functionalized form of the polymer (mPEG-b-PJL-COOH) indeed established stronger molecular interactions with CAR compared to its non-functionalized counterpart mPEG-b-PJL. Evaluations on polymer effectiveness in forming ASDs demonstrated that mPEG-b-PJL-COOH outperformed its non-functionalized counterpart in miscibility, drug loading ability, and stability, inferred from reduced molecular mobility. However, dissolution tests indicated that ASDs with mPEG-b-PJL-COOH did not significantly improve the dissolution behaviour compared to amorphous CAR alone, despite potential solubility enhancement through micelle formation. Overall, this study confirms the potential of functionalized polymers in ASD formulations, while the challenge of improving dissolution performance in these ASDs remains an area of further development.

Solubility and Physical Stability Enhancement of Loratadine by Preparation of Co-Amorphous Solid Dispersion with Chlorpheniramine and Polyvinylpyrrolidone

Loratadine (LRD), a non-sedating and slow-acting antihistamine, is often given in combination with short-onset chlorpheniramine maleate (CPM) to increase efficacy. However, LRD has poor water solubility resulting in low bioavailability. The aim of this study was to improve LRD solubility by preparing co-amorphous LRD-CPM. However, the obtained co-amorphous LRD-CPM recrystallized rapidly, and the solubility of LRD returned to a poor state again. Therefore, co-amorphous LRD-CPM solid dispersions using polyvinylpyrrolidone (PVP) as a carrier were prepared. The obtained solid dispersions were characterized using X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR). The solubility, dissolution, and mechanism of drug release from the LRD-CPM/PVP co-amorphous solid dispersions were studied and compared with those of intact LRD, LRD/PVP solid dispersions, and co-amorphous LRD-CPM mixtures. The results from XRPD and DSC confirmed the amorphous form of LRD in the co-amorphous solid dispersions. The FTIR results indicated that there was no intermolecular interaction between LRD, CPM, and PVP. In conclusion, the obtained LRD-CPM/PVP co-amorphous solid dispersions can successfully increase the water solubility and dissolution of LRD and extend the amorphous state of LRD without recrystallization.

Study on the regulation mechanism of effective glass transition temperature on the crystallization of crystalline solid dispersion

The focus of this investigation was to determine the mechanism of effective glass transition temperature (TgE) on the crystallization behavior and microstructure of drugs in crystalline solid dispersion (CSD). CSDs were prepared by rotary evaporation using ketoconazole (KET) as a model drug and the triblock copolymer poloxamer 188 as a carrier. The pharmaceutical properties of CSDs, such as crystallite size, crystallization kinetics, and dissolution behavior, were investigated to provide a foundation for studying the crystallization behavior and the microstructure of drugs in CSDs. According to classical nucleation theory, the relationship of treatment temperature-drug crystallite size-TgE of CSD was investigated. Voriconazole, a compound that is structurally similar to KET but with different physicochemical properties, was used to verify the conclusions. The dissolution behavior of KET was significantly enhanced compared to the raw drug due to smaller crystallite size. Crystallization kinetic studies revealed a two-step crystallization mechanism for KET-P188-CSD, in which P188 crystallized first and KET crystallized later. When the treatment temperature was near TgE, the drug crystallite size was smaller and more numerous, which suggests nucleation and slow growth. With the increase of temperature, the drug changed from nucleation to growth, and the number of crystallites decreased and the size of the drug increased. This result suggests it is possible to prepare CSDs with higher drug loading and smaller crystallite size by adjusting the treatment temperature and TgE, so as to maximize the drug dissolution rate. The VOR-P188-CSD maintained a relationship between treatment temperature, drug crystallite size, and TgE. The findings of our study demonstrate that TgE and the treatment temperature can be used to regulate the drug crystallite size and improve the drug solubility and dissolution rate.

Templated Reactive Crystallization of Active Pharmaceutical Ingredient in Hydrogel Microparticles Enabling Robust Drug Product Processing

Commercialization of most promising active pharmaceutical ingredients (APIs) is impeded either by poor bioavailability or challenging physical properties leading to costly manufacture. Bioavailability of ionizable hydrophobic APIs can be enhanced by its conversion to salt form. While salt form of the API presents higher solution concentration than the non-ionized form, poor physical properties resulting from particle anisotropy or non-ideal morphology (needles) and particle size distribution not meeting dissolution rate targets can still inhibit its commercial translation. In this regard, API physical properties can be improved through addition of non-active components (excipients or carriers) during API manufacture. In this work, a facile method to perform reactive crystallization of an API salt in presence of the microporous environment of a hydrogel microparticle is presented. Specifically, the reaction between acidic antiretroviral API, raltegravir and base potassium hydroxide is performed in the presence of polyethylene glycol diacrylamide hydrogel microparticles. In this bottom-up approach, the spherical template hydrogel microparticles for the reaction lead to monodisperse composites loaded with inherently micronized raltegravir-potassium crystals, thus improving API physical properties without hampering bioavailability. Overall, this technique provides a novel approach to reactive crystallization while maintaining the API polymorph and crystallinity.

Advances in the development of amorphous solid dispersions: The role of polymeric carriers

Amorphous solid dispersion (ASD) is one of the most effective approaches for delivering poorly soluble drugs. In ASDs, polymeric materials serve as the carriers in which the drugs are dispersed at the molecular level. To prepare the solid dispersions, there are many polymers with various physicochemical and thermochemical characteristics available for use in ASD formulations. Polymer selection is of great importance because it influences the stability, solubility and dissolution rates, manufacturing process, and bioavailability of the ASD. This review article provides a comprehensive overview of ASDs from the perspectives of physicochemical characteristics of polymers, formulation designs and preparation methods. Furthermore, considerations of safety and regulatory requirements along with the studies recommended for characterizing and evaluating polymeric carriers are briefly discussed.

Investigating the physicochemical properties of solid dispersions based on semicrystalline carriers: A case study with ketoprofen

Hydrophilic semicrystalline carriers represent an alternative to amorphous polymers due to their low melting temperature, useful for the production of solid dispersions (SDs) by melting-based technologies. This research aims to compare SDs of ketoprofen (KET) and three different semicrystalline carriers (PEG, Poloxamer and Gelucire) regarding miscibility, phase behavior, molecular interactions and stability. KET was chosen owing to its low solubility and high glass forming ability. Estimation of drug-excipient miscibility was performed by Flory-Huggins theory. Negative Gibbs free energy indicated a spontaneous mixing of KET with the three carriers and miscibility in the order PEG > Poloxamer > Gelucire. SDs up to 40 % w/w of drug were produced by melting process at a temperature below KET melting point. Characterization of SDs was performed by differential scanning calorimetry, polarized light microscopy and powder X-ray diffraction. In case of PEG and Poloxamer, the drug incorporation did not affect carrier crystallinity, while KET was in the amorphous state. Differently, KET retarded the crystallization of Gelucire and at high drug loadings the SDs were amorphous and semisolid. FT-IR analysis revealed a strong interaction between KET and the three carriers. Finally, PEG-based SDs above 20 % KET loading displayed drug crystallization after 6 months of storage; while Poloxamer and Gelucire-based SDs showed KET crystallization only at 40 % KET. Due to its less hydrophilic character and limited water uptake, Gelucire showed the best stability among the three excipients.

Microwave-Induced in Situ Drug Amorphization Using a Mixture of Polyethylene Glycol and Polyvinylpyrrolidone

The use of a mixture of polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) was investigated for microwave-induced in situ amorphization of celecoxib (CCX) inside compacts. Such amorphization requires the presence of a dipolar excipient in the formulation to ensure heating of the compact by absorption of the microwaves. Previously, the hygroscopic nature of PVP was exploited for this purpose. By exposing PVP-based compacts for set time intervals at defined relative humidity, controlled water sorption into the compacts was achieved. In the present study, PEG was proposed as the microwave absorbing excipient instead of water, to avoid the water sorption step. However, it was found that PEG alone melted upon exposure to microwave radiation and caused the compact to deform. Furthermore, CCX was found to recrystallize upon cooling in PEG-based formulations. Hence, a mixture of PEG and PVP was used, where the presence of PVP preserved the physical shape of the compact, and the physical state of the amorphous solid dispersion. To study the impact of the polymer mixture, different compact compositions of CCX, PEG and PVP were prepared. When exposing the compacts to microwave radiation, it was found that the PEG:PVP ratio was critical for in situ amorphization and that complete amorphization was only achieved above a certain temperature threshold.

Different BCS Class II Drug-Gelucire Solid Dispersions Prepared by Spray Congealing: Evaluation of Solid State Properties and In Vitro Performances

Delivery of poorly water soluble active pharmaceutical ingredients (APIs) by semi-crystalline solid dispersions prepared by spray congealing in form of microparticles (MPs) is an emerging method to increase their oral bioavailability. In this study, solid dispersions based on hydrophilic Gelucires^® (Gelucire^® 50/13 and Gelucire^® 48/16 in different ratio) of three BCS class II model compounds (carbamazepine, CBZ, tolbutamide, TBM, and cinnarizine, CIN) having different physicochemical properties (logP, pKa, Tm) were produced by spray congealing process. The obtained MPs were investigated in terms of morphology, particles size, drug content, solid state properties, drug-carrier interactions, solubility, and dissolution performances. The solid-state characterization showed that the properties of the incorporated drug had a profound influence on the structure of the obtained solid dispersion: CBZ recrystallized in a different polymorphic form, TBM crystallinity was significantly reduced as a result of specific interactions with the carrier, while smaller crystals were observed in case of CIN. The in vitro tests suggested that the drug solubility was mainly influenced by carrier composition, while the drug dissolution behavior was affected by the API solid state in the MPs after the spray congealing process. Among the tested APIs, TBM-Gelucire dispersions showed the highest enhancement in drug dissolution as a result of the reduced drug crystallinity.

Polymorphism in Solid Dispersions

Solid dispersions embed active pharmaceutical ingredients in polymeric carriers to improve their solubility. Three solid dispersion preparation techniques are typically employed: solvent evaporation, solvent-fusion, and fusion methods. Although these are also widely recommended as preparative methods for phase diagram determination, few examples exist concerning their effect on the resulting polymorph, once the solid dispersion is produced. In this study, the influence of these methods on the polymorphic form obtained in crystalline solid dispersions (CSDs) composed of flufenamic acid (FFA) and poly(ethylene glycol) was investigated. The physical mixtures and CSDs were characterized by powder X-ray diffraction, infrared spectroscopy, and differential scanning calorimetry. The results reveal that the fusion method leads to concomitant polymorphs (mainly FFA I and III) in the CSDs. In contrast, the solvent evaporation and solvent-fusion methods lead to FFA III. Collectively, these results demonstrate that preparative methods have a significant influence on the phase diagrams determined (average relative deviation ≤8%), which are often used to justify the design space of manufacturing processes, including those deemed "continuous." Consequently, choosing a preparation method that results in the desired polymorph is crucial to ensure accurate determination of phase diagrams and critical quality attributes of formulations.

Molecular Understanding and Implication of Structural Integrity in the Deformation Behavior of Binary Drug-Drug Eutectic Systems

In eutectic, a lamellar microstructure offers better tableting than that of the nonreacted physical mixture. However, bulk deformation remains elusive in two binary eutectics. We hypothesized that the binary eutectic of a drug with different components, having different H-bonding dimensionalities and crystal structure, shall allow the understanding of the structural integrity in the bulk deformation behavior. The shearing molecular solid (FXT Q) shared a common composition with the viscoelastic crystal (ASP I) and brittle (PCM I), forming EM-1 (ϕ₁ = 41.27:58.73% w/w) and EM-2 (ϕ₂ = 41.10:58.90% w/w), respectively. The excess thermodynamic functions were contributed by high energy microstructures (nonbonding interactions) along incoherent phase boundaries (visualized under CLSM). The energy dispersive analysis enabled the recognition of the relative distribution of higher atoms over the heterogeneous surface. EM-1 (FXT Q-ASP I) demonstrated higher compressibility, tensile strength, and compactibility (CTC profile) compared to those of EM-2 (FXT Q-PCM I) over a range of applied compaction pressures. The lower true yield strength (σ_0(EM-1) = 138.66 MPa) of EM-1 as compared to that of EM-2 (σ_0(EM-2) = 166.66 MPa) suggested a better deformation performance and incipient plasticity quantified from the "out-of-die" Heckel analysis. From Ryshkewitch analysis, the tensile strength at zero porosity (τ₀₁ = 3.83 MPa) was predicted to be higher for EM-1 than EM-2 (τ₀₂ = 2.54 MPa). The higher bonding strength of EM-1 was contributed to the additional influence of true density and isotropic van der Waals interactions of ASP I (0D). In contrast, EM-2 demonstrated lower compressibility and compactibility, having herringbone molecular packing of PCM I (1D) with a common shearing component (FXT Q (1D)). This study confirmed that the intrinsic deformational and chemical nature of the second component defined the compressibility and compactibility tendency to a greater extent in the tableting performance of conglomerates of crystalline solid solution.

Revealing Polymorphic Phase Transformations in Polymer-Based Hot Melt Extrusion Processes

The inadvertent occurrence of polymorphic phase transformations in active pharmaceutical ingredients (APIs) during hot melt extrusion (HME) processes has been claimed to limit the application of this technique. Hence, the control of polymorphism would need to be addressed if there is any prospect of HME to be successfully implemented as an alternative solid dosage formulation strategy in integrated, continuous end-to-end pharmaceutical manufacturing settings. This work demonstrates that flufenamic acid (FFA), one of the most polymorphic APIs known, thus far, can be processed using temperature-simulated HME with polyethylene glycol (PEG) as polymeric carrier. At temperatures above the transition point of FFA forms III and I (42 °C), the induction time of the polymorphic phase transformation is longer than the average reported residence time in conventional HME processes (5 min). Moreover, it was demonstrated that thorough understanding of the thermodynamic and kinetic design space for the PEG-FFA system leads to polymorphic control in the produced crystalline solid dispersions. Ultimately, this investigation helps to gain fundamental understanding of the processing needs of crystalline solid dispersions, which will lead to the broader application of HME as a continuous manufacturing strategy for drug products containing APIs prone to polymorphism, representing about 80% of all APIs.

Dissolution evaluation in vitro and bioavailability in vivo of self-microemulsifying drug delivery systems for pH-sensitive drug loratadine

The aim of this study was to improve the oral absorption of loratadine, a pH-sensitive drug, by self-microemulsifying drug delivery systems (SMEDDSs). The optimal SMEDDS was analysed and evaluated after emulsification in distilled water with diameter of 26.57 ± 0.71 nm and zeta potential of -30.5 ± 4.5 mV. Dissolution experiments in vitro were carried out in different released media of pH values and the SMEDDS formulations were able to release loratadine completely in different media while market tablets just performed similarly in the media of pH 1.2. Furthermore, the oral bioavailability and the pharmacokinetic behaviour of loratadine formulations in vivo were studied after a single dose of 1 mg/kg loratadine in beagle dogs. The SMEDDS formulations displayed higher Cmax and AUC, approximately 9 and 5 times increase than those of market tablets (p < 0.01) respectively. These results demonstrated that SMEDDS formulations had significantly increased the oral absorption of loratadine in beagle dogs.

Strategies to address low drug solubility in discovery and development

Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.