Solid state properties and drug release behavior of co-amorphous indomethacin-arginine tablets coated with Kollicoat® Protect

Development and characterization of co-amorphous griseofulvin/L-leucin by modified solvent processing hot-melt extrusion

Co-amorphous systems (CAMS) were developed between griseofulvin (GRI) and L-leucine (LEU) at 2:1 wt ratio, by application of a novel solvent assisted hot-melt extrusion (HME) method that involved wet processing/drying of the feeds prior to extrusion. CAMS formation was confirmed by powder crystallography (pXRD) and thermal analysis (DSC). Intermolecular H-bonding between the carbonyl groups of GRI and the hydroxyl and amino groups of LEU were identified by vibrational spectroscopy (ATR-FTIR). The measured glass transition temperatures (Tg) of the extrudates from feeds processed with aqueous acetic acid (AcOH) were markedly lower than that of neat amorphous GRI and values predicted from Gordon-Taylor equation, indicating plasticizing action of AcOH. Drug concentrations during dissolution of CAMS under non-sink conditions (Sink Index 0.0115) were up to x82 higher at plateau compared to crystalline drug solubility. The degree of supersaturation lasted for at least 24 h. Plasticizer (Compritol®/Kolliphor® 75/25) added before extrusion did not impact significantly on CAMS formation but altered the dissolution profile from a spring-and-parachute profile to gradual rise to maximum. These findings reinforce the application of drug/amino acid-based CAMS in formulation, particularly for high-dose drugs, for which polymers are unsuited due to the required large proportions.

Rapid screening of ternary amorphous formulations by a spray drying robot

Spray drying is commonly used for producing amorphous solid dispersions to improve drug solubility. The development of such formulations typically relies on comprehensive excipient and composition screening, which requires the preparation of many spray-dried powder samples. This is both labour-intensive and time-consuming when carried out manually. In the present work, the formulation screening task was automated by coupling a laboratory spray dryer operated in a semi-continuous mode with custom-made add-ons, allowing for rapid, computer-controlled production of formulation samples with systematically varying composition. The practical use of the spray drying robot in formulation development was demonstrated on a case study of poorly water-soluble model drugs simvastatin and ezetimibe. Six different polymers and several drug:polymer ratios were screened for the enhancement of dissolution properties. From a pool of 28 spray-dried samples, ternary compositions containing Eudragit L100-55 were identified as the most suitable ones for further processing and characterisation. The ability to populate the formulation design space rapidly and automatically made it possible to construct maps of physico-chemical properties such as glass transition temperature or dissolution rate. The spray drying robot thus enables the acceleration of early formulation development and a deeper understanding of composition-property relationships for multi-component spray dried powders.

Role of Heteronucleants in Melt Crystallization of Crystalline Solid Dispersions

Few publications exist concerning polymorphic control during melt crystallization, particularly when employing heteronucleants. Here, the influence of a polymeric thin film (polyethylene terephthalate, PET) on the crystallization from melt of the polymorphic compound acetaminophen (ACM) in polyethylene glycol (PEG) was investigated. Molten ACM-PEG at different compositions was monitored using in situ Raman spectroscopy for nucleation induction time measurements and phase identification. Furthermore, X-ray diffraction (XRD) served to analyze the preferred orientation (PO) of the pastilles (solidified melt droplets) on PET-coated and uncoated substrates. The results indicate that PET-coated substrates qualitatively accelerate the nucleation of ACM form II (ACM II) in PEG compared to uncoated glass substrates. Additionally, the occurrence of ACM II in PEG was increased by an average of 10% when crystallized on PET-coated substrates compared to uncoated substrates. Overall, these results suggest that ACM can interact through hydrogen bonding with the PET-coated substrate, leading to faster nucleation. This investigation illustrates the effect of PET-coated substrates in the selective crystallization of ACM II in PEG as crystalline solid dispersions (CSDs). Ultimately, the results suggest the implementation of polymeric heteronucleants in melt crystallization processes, specifically, in advanced polymer-based formulation processes for the enhanced polymorphic form control of pharmaceutical compounds in CSDs.

Dose Titration of Solid Dosage Forms via FDM 3D-Printed Mini-Tablets

The robustness of 3D-printed mini-tablets as a platform to administer milligram dosages, intended for age-specific therapy, without the need of tablet splitting while maintaining similar release profiles, was investigated. Griseofulvin, as a model poorly water-soluble drug, and hydroxypropyl cellulose along with Kollicoat Protect as polymers were used to prepare filaments at 1-20% drug concentrations via hot-melt extrusion (HME). Higher drug concentrations served for testing the feasibility of a reduced number of mini-tablets to be administered. A reliable dose titration in the range 0.19-3.91 mg at a high accuracy (R2 of 0.999) was achieved through composite unit (multi-unit) mini-tablets. All mini-tablets produced had excellent content uniformity and their label claim values were within the acceptable range, proving that HME processing followed by 3D printing promotes content uniformity even for mini-tablets containing low drug doses (0.19 mg). Remarkably, the proposed approach allowed achieving similar drug release profiles via composite unit mini-tablets as well as single mini-tablets at high drug concentrations. In contrast, split tablets demonstrated different release behaviors, attributed to their size and shape differences. Overall, the distinct advantages of mini-tablets to provide dose flexibility while maintaining similar release profiles was demonstrated.

Co-amorphous Systems of Sinomenine with Platensimycin or Sulfasalazine: Physical Stability and Excipient-Adjusted Release Behavior

There is strong interest to develop affordable treatments for the infection-associated rheumatoid arthritis (RA). Here, we present a drug-drug co-amorphous strategy against RA and the associated bacterial infection by the preparation and characterization of two co-amorphous systems of sinomenine (SIN) with platensimycin (PTM) or sulfasalazine (SULF), two potent antibiotics. Both of them were comprehensively characterized using powder X-ray diffraction, temperature-modulated differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The co-amorphous forms of SIN-PTM and SIN-SULF exhibited high T_gs at 139.10 ± 1.0 and 153.3 ± 0.2 °C, respectively. After 6 months of accelerated tests and 1 month of drug-excipient compatibility experiments, two co-amorphous systems displayed satisfactory physical stability. The formation of salt and strong intermolecular interactions between SIN and PTM or SULF, as well as the decreased molecular mobility in co-amorphous systems, may be the intrinsic mechanisms underlying the excellent physical stability of both co-amorphous systems. In dissolution tests, two co-amorphous systems displayed distinct reduced SIN-accumulative releases (below 20% after 6 h of release experiments), which may lead to its poor therapeutic effect. Hence, we demonstrated a controlled release strategy for SIN by the addition of a small percentage of polymers and a small-molecule surfactant to these two co-amorphous samples as convenient drug excipients, which may also be used to improve the unsatisfactory dissolution behaviors of the previously reported SIN co-amorphous systems. Several hydrogen bonding interactions between SIN and PTM or SULF could be identified in NMR experiments in DMSO-d₆, which may be underlying reasons of decreased dissolution behaviors of both co-amorphous forms. These drug-drug co-amorphous systems could be a potential strategy for the treatment of infection-associated RA.

Amorphous and Co-Amorphous Olanzapine Stability in Formulations Intended for Wet Granulation and Pelletization

The preparation of amorphous and co-amorphous systems (CAMs) effectively addresses the solubility and bioavailability issues of poorly water-soluble chemical entities. However, stress conditions imposed during common pharmaceutical processing (e.g., tableting) may cause the recrystallization of the systems, warranting close stability monitoring throughout production. This work aimed at assessing the water and heat stability of amorphous olanzapine (OLZ) and OLZ-CAMs when subject to wet granulation and pelletization. Starting materials and products were characterized using calorimetry, diffractometry and spectroscopy, and their performance behavior was evaluated by dissolution testing. The results indicated that amorphous OLZ was reconverted back to a crystalline state after exposure to water and heat; conversely, OLZ-CAMs stabilized with saccharin (SAC), a sulfonic acid, did not show any significant loss of the amorphous content, confirming the higher stability of OLZ in the CAM. Besides resistance under the processing conditions of the dosage forms considered, OLZ-CAMs presented a higher solubility and dissolution rate than the respective crystalline counterpart. Furthermore, in situ co-amorphization of OLZ and SAC during granule production with high fractions of water unveils the possibility of reducing production steps and associated costs.

Preformulation Studies of Ezetimibe-Simvastatin Solid Dispersions in the Development of Fixed-Dose Combinations

Two active pharmaceutical ingredients (APIs) with limited solubility, simvastatin and ezetimibe, prepared as a drug-drug solid dispersion (SD) was evaluated for physicochemical, microstructural, and aqueous dissolution properties. The simvastatin-ezetimibe SD was prepared using the co-grinding method in a wide range of weight fractions and differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD) were used to perform the phase composition analysis. DSC studies confirmed that simvastatin and ezetimibe form a simple eutectic phase equilibrium diagram. Analysis of Fourier transform infrared spectroscopy (FTIR) studies excluded strong interactions between the APIs. Our investigations have revealed that all studied dispersions are characterized by substantially improved ezetimibe dissolution regardless of simvastatin content, and are best when the composition oscillates near the eutectic point. Data obtained in our studies provide an opportunity for the development of well-formulated, ezetimibe-simvastatin fixed-dose combinations (for hypercholesterolemia treatment) with reduced ezetimibe dosages based on its dissolution improvement.

Supersaturating drug delivery systems containing fixed-dose combination of two antihypertensive drugs: Formulation, in vitro evaluation and molecular metadynamics simulations

The purpose of this study was to associate the poorly water-soluble antihypertensive drugs candesartan cilexetil (CC) and hydrochlorothiazide (HCTZ) as fixed-dose combination, in the form of ternary Amorphous Solid Dispersions (ASD), using hydroxypropylmethylcellulose acetate succinate (HPMCAS) type M as polymeric carrier. The potential of the system to generate and to maintain supersaturation of both drugs was also evaluated. The ASDs were prepared by ball milling technique and solid-state characterization was performed by differential scanning calorimetry (DSC), Fourier transformed infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD). Interaction between drugs and polymer in solid-state was evaluated by molecular metadynamics simulations. In vitro supersaturation profiles were determined in biorelevant medium. Physicochemical stability of ASDs was also evaluated under different storage conditions. Amorphization of both drugs was confirmed by solid-state characterization techniques. Molecular metadynamics simulations indicated that CC has stronger interaction with HMPCAS than HCTZ. In vitro supersaturation studies have shown that ternary ASDs could generate and maintain supersaturation of both drugs in biorelevant medium. The polymer reduced the desupersaturation of both drugs. Ternary ASDs also showed physicochemical stability over a period of 90 days, demonstrating the potential of the polymer in reducing the drugs recrystallization over the time. Ternary ASDs of CC, HCTZ and HPMCAS can be considered a promising system to associate the drugs as fixed-dose combinations. Also, these systems generate and maintain supersaturation of both drugs in biorelevant medium, with great storage stability. HPMCAS M was a good carrier for reducing the desupersaturation of associated HCTZ and CC.

Co-Amorphous Drug Formulations in Numbers: Recent Advances in Co-Amorphous Drug Formulations with Focus on Co-Formability, Molar Ratio, Preparation Methods, Physical Stability, In Vitro and In Vivo Performance, and New Formulation Strategies

Co-amorphous drug delivery systems (CAMS) are characterized by the combination of two or more (initially crystalline) low molecular weight components that form a homogeneous single-phase amorphous system. Over the past decades, CAMS have been widely investigated as a promising approach to address the challenge of low water solubility of many active pharmaceutical ingredients. Most of the studies on CAMS were performed on a case-by-case basis, and only a few systematic studies are available. A quantitative analysis of the literature on CAMS under certain aspects highlights not only which aspects have been of great interest, but also which future developments are necessary to expand this research field. This review provides a comprehensive updated overview on the current published work on CAMS using a quantitative approach, focusing on three critical quality attributes of CAMS, i.e., co-formability, physical stability, and dissolution performance. Specifically, co-formability, molar ratio of drug and co-former, preparation methods, physical stability, and in vitro and in vivo performance were covered. For each aspect, a quantitative assessment on the current status was performed, allowing both recent advances and remaining research gaps to be identified. Furthermore, novel research aspects such as the design of ternary CAMS are discussed.

Eutectic mixtures as an approach to enhance solubility, dissolution rate and oral bioavailability of poorly water-soluble drugs

Eutectic mixtures have been known for a long time in the pharmaceutical field. However, its potential as a system to improve the solubility and dissolution of poorly water-soluble drugs remains little explored. Studies involving the microstructural characterization and the preparation of solid dosage forms containing eutectic mixtures are also an issue to be developed. Recently, the number of studies involving the preparation of eutectic mixtures to improve the solubility and oral bioavailability of poorly soluble drugs has increased considerably, including drug-carrier and drug-drug mixtures. In this review is discussed the potential of eutectic mixtures as an alternative pharmaceutical solid system to enhance drugs solubility, dissolution rate or oral bioavailability. Different aspects like history, physico-chemical, microstructural properties, preparation methods, mechanisms involved in solubility/dissolution enhancement, techniques for solid state characterization, in vivo studies, advantages, limitations and formulation perspective are also discussed.

Microwave-Induced In Situ Amorphization: A New Strategy for Tackling the Stability Issue of Amorphous Solid Dispersions

The thermodynamically unstable nature of amorphous drugs has led to a persistent stability issue of amorphous solid dispersions (ASDs). Lately, microwave-induced in situ amorphization has been proposed as a promising solution to this problem, where the originally loaded crystalline drug is in situ amorphized within the final dosage form using a household microwave oven prior to oral administration. In addition to circumventing issues with physical stability, it can also simplify the problematic downstream processing of ASDs. In this review paper, we address the significance of exploring and developing this novel technology with an emphasis on systemically reviewing the currently available literature in this pharmaceutical arena and highlighting the underlying mechanisms involved in inducing in situ amorphization. Specifically, in order to achieve a high drug amorphicity, formulations should be composed of drugs with high solubility in polymers, as well as polymers with high hygroscopicity and good post-plasticized flexibility of chains. Furthermore, high microwave energy input is considered to be a desirable factor. Lastly, this review discusses challenges in the development of this technology including chemical stability, selection criteria for excipients and the dissolution performance of the microwave-induced ASDs.

Influences of different Fe sources on Fe bioavailability and homeostasis in SD rats

The purpose of this study was to determine whether the enteric coating process affects growth performance, Fe bioavailability, and gene expression levels that maintain iron balance in the body. The test was divided into the control group, ferrous sulfate group, ferrous fumarate group, ferrous glycine chelate(1:1) (Fe-Gly(1:1)) group, ferrous glycine chelate(2:1) (Fe-Gly(2:1)) group, enteric-coated Fe-Gly(1:1) group, and enteric-coated Fe-Gly(2:1) group. The results showed that the growth performance of the rats in each iron supplement group was no significant difference among them. The results of serum biochemical indicators showed that the antioxidant capacity of the rats in the iron supplement group after enteric coating increased. The iron supplementation effect of Fe-Gly(1:1) and Fe-Gly(2:1) was better than that of ferrous sulfate, and the effect of Fe-Gly(1:1) after enteric coating was enhanced. The expression levels of IRP1 and IRP2 in the genes of enteric-coated Fe-Gly(1:1) and enteric-coated Fe-Gly(2:1) were significantly higher than those of ferrous sulfate. The expression levels of IRP1 and IRP2 in the protein of enteric-coated Fe-Gly(1:1) group were significantly higher than those in the Fe-Gly(1:1) group. The above results show that Fe-Gly can improve the bioavailability and antioxidant capacity of iron and reduce the iron output of feces after enteric coating.

Application of Co-Amorphous Technology for Improving the Physicochemical Properties of Amorphous Formulations

Co-amorphous technology was recently introduced to stabilize drugs in the amorphous state for drug development. We examined the predictability of the formation of co-amorphous systems and identified two reliable indicators of successful formation: (1) a negative Δ H_mix value and (2) small Δlog P between components. Moreover, we found that the stability of co-amorphous systems was improved when (1) Δ H_mix was negative and (2) amorphous forms of the constituent compounds were stable. Furthermore, we concluded that co-amorphous systems with small (negatively large) Δ H_mix values had lower hygroscopicity. Typically, amorphous solid dispersions exhibit hygroscopicity because polymers exhibit large hygroscopicity. We proved the superiority of co-amorphous technology over amorphous solid dispersion in this respect. Our results provide methods for (1) establishing a screening method and (2) improving hygroscopicity, which may make co-amorphous technology more useful than amorphous solid dispersion technology.

Preparation and characterization of multi-component tablets containing co-amorphous salts: Combining multimodal non-linear optical imaging with established analytical methods

Co-amorphous mixtures have rarely been formulated as oral dosage forms, even though they have been shown to stabilize amorphous drugs in the solid state and enhance the dissolution properties of poorly soluble drugs. In the present study we formulated tablets consisting of either spray dried co-amorphous ibuprofen-arginine or indomethacin-arginine, mannitol or xylitol and polyvinylpyrrolidone K30 (PVP). Experimental design was used for the selection of tablet compositions, and the effect of tablet composition on tablet characteristics was modelled. Multimodal non-linear imaging, including coherent anti-Stokes Raman scattering (CARS) and sum frequency/second harmonic generation (SFG/SHG) microscopies, as well as scanning electron microscopy, X-ray diffractometry and Fourier-transform infrared spectroscopy were utilized to characterize the tablets. The tablets possessed sufficient strength, but modelling produced no clear evidence about the compaction characteristics of co-amorphous salts. However, co-amorphous drug-arginine mixtures resulted in enhanced dissolution behaviour, and the PVP in the tableting mixture stabilized the supersaturation. The co-amorphous mixtures were physically stable during compaction, but the excipient selection affected the long term stability of the ibuprofen-arginine mixture. CARS and SFG/SHG proved feasible techniques in imaging the component distribution on the tablet surfaces, but possibly due to the limited imaging area, recrystallization detected with x-ray diffraction was not detected.

Impact of Drug Physicochemical Properties on Lipolysis-Triggered Drug Supersaturation and Precipitation from Lipid-Based Formulations

In this study we investigated lipolysis-triggered supersaturation and precipitation of a set of model compounds formulated in lipid-based formulations (LBFs). The purpose was to explore the relationship between precipitated solid form and inherent physicochemical properties of the drug. Eight drugs were studied after formulation in three LBFs, representing lipid-rich (extensively digestible) to surfactant-rich (less digestible) formulations. In vitro lipolysis of drug-loaded LBFs were conducted, and the amount of dissolved and precipitated drug was quantified. Solid form of the precipitated drug was characterized with polarized light microscopy (PLM) and Raman spectroscopy. A significant solubility increase for the weak bases in the presence of digestion products was observed, in contrast to the neutral and acidic compounds for which the solubility decreased. The fold-increase in solubility was linked to the degree of ionization of the weak bases and thus their attraction to free fatty acids. A high level of supersaturation was needed to cause precipitation. For the weak bases, the dose number indicated that precipitation would not occur during lipolysis; hence, these compounds were not included in further studies. The solid state analysis proved that danazol and griseofulvin precipitated in a crystalline form, while niclosamide precipitated as a hydrate. Felodipine and indomethacin crystals were visible in the PLM, whereas the Raman spectra showed presence of amorphous drug, indicating amorphous precipitation that quickly crystallized. The solid state analysis was combined with literature data to allow analysis of the relationship between solid form and the physicochemical properties of the drug. It was found that low molecular weight and high melting temperature increases the probability of crystalline precipitation, whereas precipitation in an amorphous form was favored by high molecular weight, low melting temperature, and positive charge.

Co-Amorphous Solid Dispersions for Solubility and Absorption Improvement of Drugs: Composition, Preparation, Characterization and Formulations for Oral Delivery

The amorphous solid state offers an improved apparent solubility and dissolution rate. However, due to thermodynamic instability and recrystallization tendencies during processing, storage and dissolution, their potential application is limited. For this reason, the production of amorphous drugs with adequate stability remains a major challenge and formulation strategies based on solid molecular dispersions are being exploited. Co-amorphous systems are a new formulation approach where the amorphous drug is stabilized through strong intermolecular interactions by a low molecular co-former. This review covers several topics applicable to co-amorphous drug delivery systems. In particular, it describes recent advances in the co-amorphous composition, preparation and solid-state characterization, as well as improvements of dissolution performance and absorption are detailed. Examples of drug-drug, drug-carboxylic acid and drug-amino acid co-amorphous dispersions interacting via hydrogen bonding, π−π interactions and ionic forces, are presented together with corresponding final dosage forms.

Undesired co-amorphisation of indomethacin and arginine during combined storage at high humidity conditions

The use of co-amorphous systems for solubility enhancement of poorly water-soluble drugs has recently gained interest in the field of pharmaceutical technology. However, undesired co-amorphisation of a drug may lead to an alteration of the performance of the drug product, e.g. the previously observed co-amorphisation of indomethacin and arginine upon storage of tablets containing both components in an initially crystalline form at room temperature (RT) and 75% relative humidity (RH). Therefore, the aim of the present study was to further investigate this unintended co-amorphisation by storing plain crystalline γ-indomethacin and arginine as well as physical mixtures of both components at RT and three different RH levels (28, 58, and 75% RH). After storage for up to 101 days, their properties were analysed by X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and HPLC. Results showed that the solid state of plain γ-indomethacin did not change during storage at all three storage conditions. In contrast, arginine was found to form a dihydrate upon storage at RT/58% RH and RT/75% RH. The physical mixtures, stored at RT/28% RH and RT/58% RH, remained crystalline and were chemically stable, while the formation of a co-amorphous salt between indomethacin and arginine as well as basic hydrolysis of indomethacin started already 1 day after exposure to RT/75% RH. Moreover, formation of a crystalline salt of indomethacin and arginine upon storage at RT/75% RH was observed. As neither of these instabilities occurred, if indomethacin was stored separately, the simultaneous effects of arginine and moisture on the solid state properties and chemical stability of indomethacin should be taken into account, if selecting arginine as excipient.