Tailored ASD destabilization - Balancing shelf life stability and dissolution performance with hydroxypropyl cellulose.

Amorphous solid dispersion (ASD) formulations are preferred enabling formulations for poorly water soluble active pharmaceutical ingredients (API) as they reliably enhance the dissolution behavior and solubility. Balancing a high stability against unwanted transformations such as crystallization and amorphous phase separation during storage on the one hand and optimizing the dissolution behavior of the formulation (high supersaturation and maintenance for long time) on the other hand are essential during formulation development. This study assessed the potential of ternary ASDs (one API and two polymers) containing the polymers hydroxypropyl cellulose together with poly(vinylpyrrolidone-co-vinyl acetate) (PVP VA64) or hydroxypropyl cellulose acetate succinate to stabilize the amorphously embedded APIs fenofibrate and simvastatin during storage and to enhance the dissolution performance. Thermodynamic predictions using the PC-SAFT model revealed for each combination of polymers the optimal polymer ratio, maximum API load that is thermodynamically stable as well as miscibility of the two polymers. The stability predictions were validated by three months enduring stability tests, followed by a characterization of the dissolution behavior. The thermodynamically most stable ASDs were found to be the ASDs with deteriorated dissolution performance. Within the investigated polymer combinations, physical stability and dissolution performance opposed each other.

Physiological Buffer Effects in Drug Supersaturation - A Mechanistic Study of Hydroxypropyl Cellulose as Precipitation Inhibitor.

Phosphate buffer is predominantly used instead of the more physiological bicarbonate buffer, as the latter requires a technical solution of adequate gas mixing. Recent pioneering work on how bicarbonate buffer affected drug supersaturation revealed interesting effects that call for more mechanistic understanding. Therefore, this study used hydroxypropyl cellulose as a model precipitation inhibitor and real-time desupersaturation testing was conducted with the drugs bifonazole, ezetimibe, tolfenamic acid and triclabendazole. Specific buffer effects for the different compounds were noted and overall, statistical significance was found for the precipitation induction time (p = 0.0088). Interestingly, molecular dynamics simulation revealed a conformational effect of the polymer in the presence of the different buffer types. Subsequent molecular docking trials suggested a stronger interaction energy of drug and polymer in the presence of phosphate compared to bicarbonate buffer (p =0.0010). In conclusion, a better mechanistic understanding of how different buffers affect drug-polymer interactions regarding drug supersaturation was achieved. Further mechanisms may account for the overall buffer effects and additional research on drug supersaturation is certainly needed, but it can already be concluded that bicarbonate buffering should be used more often for in vitro testing in drug development.

Phase homogeneity in ternary amorphous solid dispersions and its impact on solubility, dissolution and supersaturation - Influence of processing and hydroxypropyl cellulose grade.

As performance of ternary amorphous solid dispersions (ASDs) depends on the solid-state characteristics and polymer mixing, a comprehensive understanding of synergistic interactions between the polymers in regard of dissolution enhancement of poorly soluble drugs and subsequent supersaturation stabilization is necessary. By choosing hot-melt extrusion (HME) and vacuum compression molding (VCM) as preparation techniques, we manipulated the phase behavior of ternary efavirenz (EFV) ASDs, comprising of either hydroxypropyl cellulose (HPC)-SSL or HPC-UL in combination with Eudragit® L 100-55 (EL 100-55) (50:50 polymer ratio), leading to single-phased (HME) and heterogeneous ASDs (VCM). Due to higher kinetic solid-state solubility of EFV in HPC polymers compared to EL 100-55, we visualized higher drug distribution into HPC-rich phases of the phase-separated ternary VCM ASDs via confocal Raman microscopy. Additionally, we observed differences in the extent of phase-separation in dependence on the selected HPC grade. As HPC-UL exhibited decisive lower melt viscosity than HPC-SSL, formation of partially miscible phases between HPC-UL and EL 100-55 was facilitated. Consequently, as homogeneously mixed polymer phases were required for optimal extent of solubility improvement, the manufacturing-dependent differences in dissolution performances were smaller using HPC-UL, instead of HPC-SSL, i.e. using HPC-UL was less demanding on shear stress provided by the process.

Boost of solubility and supersaturation of celecoxib via synergistic interactions of methacrylic acid-ethyl acrylate copolymer (1:1) and hydroxypropyl cellulose in ternary amorphous solid dispersions.

A current trend in the development of amorphous solid dispersions (ASDs) is the combination of two polymers for synergistic enhancement in supersaturation of poorly soluble drugs. We investigated the supersaturation potential of celecoxib (CXB) using combinations of methacrylic acid-ethyl acrylate copolymer (1:1) (EL 100-55) and hydroxypropyl cellulose (HPC) SSL. Initially, the supersaturation potential of single polymers and combinations in various ratios was assessed. While EL 100-55 and HPC SSL alone showed limited potential in solubility enhancement of CXB the combination of both polymers led to a boost of CXB solubility, whereby most promising results were obtained using a 50:50 polymer ratio. Binary and ternary CXB ASDs (10% drug load) were prepared via vacuum compressing molding (VCM) and hot melt extrusion (HME). ASDs were studied by exploring the miscibility and intermolecular interactions and tested for their dissolution performance. HPC SSL was identified to be a suitable precipitation inhibitor when added to a fast dissolving CXB: EL 100-55 ASD. Ternary ASDs showed even further dissolution improvement, when processed by HME. The combination of heat and shear stress led to a homogeneous and intimate mixture of EL 100-55 and HPC SSL, resulting in formation of synergistic interactions with pronounced impact on CXB supersaturation.

Hydroxypropyl Cellulose for Drug Precipitation Inhibition: From the Potential of Molecular Interactions to Performance Considering Microrheology.

There has been recent interest in using hydroxypropyl cellulose (HPC) for supersaturating drug formulations. This study investigated the potential for molecular HPC interactions with the model drug celecoxib by integrating novel approaches in the field of drug supersaturation analysis. Following an initial polymer characterization study, quantum-chemical calculations and molecular dynamics simulations were complemented with results of inverse gas chromatography and broadband diffusing wave spectroscopy. HPC performance was studied regarding drug solubilization and kinetics of desupersaturation using different grades (i.e., HPC-UL, SSL, SL, and L). The results suggested that the potential contribution of dispersive interactions and hydrogen bonding depended strongly on the absence or presence of the aqueous phase. It was proposed that aggregation of HPC polymer chains provided a complex heterogeneity of molecular environments with more or less excluded water for drug interaction. In precipitation experiments at a low aqueous polymer concentration (i.e., 0.01%, w/w), grades L and SL appeared to sustain drug supersaturation better than SSL and UL. However, UL was particularly effective in drug solubilization at pH 6.8. Thus, a better understanding of drug-polymer interactions is important for formulation development, and polymer blends may be used to harness the combined advantages of individual polymer grades.

In vitro and in vivo assessment of hydroxypropyl cellulose as functional additive for enabling formulations containing itraconazole.

Using polymers as additives to formulate ternary amorphous solid dispersions (ASDs) has successfully been established to increase the bioavailability of poorly soluble drugs, when one polymer is not able to provide both, stabilizing the drug in the matrix and the supersaturated solution. Therefore, we investigated the influence of low-viscosity hydroxypropyl cellulose (HPC) polymers as an additive in HPMC based ternary ASD formulations made by hot-melt extrusion (HME) on the bioavailability of itraconazole (ITZ). The partitioning potential of the different HPC grades was screened in biphasic supersaturation assays. Solid-state analytics were performed using differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD). The addition of HPCs, especially HPC-UL, resulted in a superior partitioned amount of ITZ in biphasic supersaturation assays. Moreover, the approach in using HPCs as an additive in HPMC based ASDs led to an increase in partitioned ITZ compared to Sporanox® in biorelevant biphasic dissolution studies. The results from the biphasic dissolution experiments correlated well with the in vivo studies, which revealed the highest oral bioavailability for the ternary ASD comprising HPC-UL and HPMC.

Phase behavior of ASDs based on hydroxypropyl cellulose.

Novel polymeric carriers for amorphous solid dispersions (ASDs) are highly demanded in pharmaceutical industry to improve the bioavailability of poorly-soluble drug candidates. Besides established polymer candidates, hydroxypropyl celluloses (HPC) comes more and more into the focus of ASD production since they have the availability to stabilize drug molecules in aqueous media against crystallization. The thermodynamic long-term stability of HPC ASDs with itraconazole and fenofibrate was predicted in this work with PC-SAFT and compared to three-months enduring long-term stability studies. The glass-transition temperature is a crucial attribute of a polymer, but in case of HPC hardly detectable by differential scanning calorimetry. By investigating the glass transition of HPC blends with a miscible polymer, we were for the first time able to estimate the HPC glass transition. Although both, fenofibrate and itraconazole reveal a very low crystalline solubility in HPC regardless of the HPC molecular weight, we observed that low-molecular weight HPC grades such as HPC-UL prevent fenofibrate crystallization for a longer period than the higher molecular weight HPC grades. As predicted, the ASDs with higher drug load underwent amorphous phase separation according to the differential scanning calorimetry thermograms. This work thus showed that it is possible to predict critical drug loads above which amorphous phase separation and/or crystallization occurs in HPC ASDs.

3D printed opioid medicines with alcohol-resistant and abuse-deterrent properties.

In the past decade, prescriptions for opioid medicines have been exponentially increasing, instigating opioid abuse as a global health crisis associated with high morbidity and mortality. In particular, diversion from the intended mode of opioid administration, such as injecting and snorting the opioid, is a major problem that contributes to this epidemic. In light of this, novel formulation strategies are needed to support efforts in reducing the prevalence and risks of opioid abuse. Here, modified release tramadol printlets (3D printed tablets) with alcohol-resistant and abuse-deterrent properties were prepared by direct powder extrusion three-dimensional (3D) printing. The printlets were fabricated using two grades of hydroxypropylcellulose (HPC). Both formulations displayed strong ethanol-resistance and had moderate abuse-deterrent properties. Polyethylene oxide (PEO) was subsequently added into the formulations, which improved the printlets' resistance to physical tampering in nasal inhalation tests and delayed their dissolution in solvent extraction tests. Overall, this article reports for the first time the use of direct powder extrusion 3D printing to prepare drug products with both alcohol-resistant and abuse-deterrent properties. These results offer a novel approach for the safe and effective use of opioids that can contribute to the advantages that 3D printing provides in terms of on-demand dose personalisation.

Direct powder extrusion 3D printing: Fabrication of drug products using a novel single-step process.

Three-dimensional (3D) printing is revolutionising how we envision manufacturing in the pharmaceutical field. Here, we report for the first time the use of direct powder extrusion 3D printing: a novel single-step printing process for the production of printlets (3D printed tablets) directly from powdered materials. This new 3D printing technology was used to prepare amorphous solid dispersions of itraconazole using four different grades of hydroxypropylcellulose (HPC - UL, SSL, SL and L). All of the printlets showed good mechanical and physical characteristics and no drug degradation. The printlets showed sustained drug release characteristics, with drug concentrations higher than the solubility of the drug itself. The printlets prepared with the ultra-low molecular grade (HPC - UL) showed faster drug release compared with the other HPC grades, attributed to the fact that itraconazole was found in a higher percentage as an amorphous solid dispersion. This work demonstrates the potential of this innovate technology to overcome one of the major disadvantages of fused deposition modelling (FDM) 3D printing by avoiding the need for preparation of filaments by hot melt extrusion (HME). This novel single-step technology could revolutionise the preparation of amorphous solid dispersions as final formulations and it may be especially suited for preclinical studies, where the quantity of drugs is limited and without the need of using traditional HME.

Powder bed 3D-printing of highly loaded drug delivery devices with hydroxypropyl cellulose as solid binder.

3D-printing is a promising tool to pave the way to the widespread adaption of individualized medicine. Several printing techniques have been investigated and introduced to pharmaceutical research. Until now, only one 3D-printed medicine is approved on the US market. The medicine is manufactured via drop-on-powder deposition, which uses inkjet printing to jet a liquid binder on a powder bed to create 3D objects. However, inkjet processes are prone to nozzle clogging when binders or active pharmaceutical ingredients (APIs) are included in the printing ink. This renders the formulation development of the ink the most challenging step. In this study, different hydroxypropyl cellulose (HPC) grades were investigated as solid binders in the powder formulation on a commercially available DoP printer. The printed ink only consisted of a water/ethanol mixture. Formulations containing 70% caffeine as model API were developed and tablets printed. It was found that the friability of the tablets greatly depends on the particle size of the employed binder, whereas disintegration time and dissolution properties mainly depend on the viscosity of the employed binders. Higher viscous binders led to slower disintegration and dissolution whereas lower viscous binders led to faster disintegration and dissolution. The study demonstrates that HPC is a suitable solid binder for DoP printing and that 3D-DoP printing can be used to print robust dosage forms.

Competing for water: A new approach to understand disintegrant performance.

The understanding of tablet disintegration is still incomplete as not all involved factors and processes are known or accounted for. E.g., the negative influence of soluble fillers, on disintegration is usually attributed to increased viscosity due to dissolved filler. When the most common filler, lactose, dissolves, the viscosity increases only slightly. The impact of binders has hardly been studied systematically. In this study, water uptake and force development as well as water sorption experiments were performed of tablets containing either a soluble or an insoluble filler, one of four different binders, and one of four different disintegrants. For both fillers, one disintegrant performed distinctly worse than the others. For the insoluble filler, dibasic calcium phosphate (DCP), sodium starch glycolate resulted in the longest disintegration, for the soluble filler, lactose, croscarmellose sodium performed worst. Based on the experimental results, the authors introduce the competition-for-water hypothesis, which takes into consideration the amount of freely available water molecules and hydration kinetics of excipients. Soluble fillers bind a large number of water molecules in hydrate shells and prevent, therefore, proper disintegrant action. Previously inconsistent observations can be approached with this hypothesis and a better understanding of the underlying processes and explanations is possible.

Fries rearrangement of aryl formates: a mechanistic study by means of 1H, 2H, and 11B NMR spectroscopy and DFT calculations.

1H, 2H, and 11B NMR spectroscopy has been used to study the mechanism of the Fries rearrangement of aryl formates promoted by boron trichloride by monitoring both the substrate and the Lewis acid. DFT calculations were employed to investigate the energetics of several reaction paths and to calculate NMR chemical shifts of key intermediates and products. After the formation of a 1:1 substrate-Lewis acid adduct, the rearrangement proceeds in two steps, beginning with the cleavage of the ester bond and the release of formyl chloride in situ, which, in turn, acts as a formylating agent, introducing an aldehydic functionality into the aromatic ring. The high regioselectivity (only the ortho product is obtained) is also accounted for by the proposed intermolecular, Lewis acid-assisted mechanism.

Charge separation and efficient light energy conversion in sensitized mesoscopic solar cells based on binary ionic liquids.

A 7.4% power conversion efficiency at air mass (AM) 1.5 full sunlight was reached with a mesoscopic solar cell employing a new binary ionic liquid electrolyte composed of 1-propyl-3-methylimidazolium iodide and 1-ethyl-3-methylimidazolium tricyanomethanide in conjunction with the amphiphilic ruthenium complex NaRu(4-carboxylic acid-4'-carboxylate)(4,4'-dinonyl-2,2'-bipyridine)(NCS)(2), coded as Z-907Na. Ultramicroelectrode voltammetric, nanosecond laser transient absorbance, and photovoltaic measurements show that a high iodide concentration is required for dye regeneration to compete efficiently with charge recombination. A surprisingly fast reductive quenching process is turned on in pure iodide melts. This channel is unproductive, explaining the lower photocurrents observed under these conditions.

Pechmann reaction promoted by boron trifluoride dihydrate.

The Pechmann reaction of substituted phenols 1a-e with methyl acetoacetate (2) can be activated by boron trifluoride dihydrate (3) to give the corresponding 4-methyl- coumarin derivatives 4a-e in excellent yield (98-99 %).

Convenient replacement of the hydroxy by an amino group in 4 hydroxycoumarin and 4-hydroxy-6-methyl-2-pyrone under microwave irradiation.

The reaction of 4-hydroxycoumarin (1) with some primary amines 2a-h and morpholine (2i) under microwave irradiation occurred without opening of the lactone ring to give N-substituted 4-aminocoumarins 3a-i in excellent yields. Under the same experimental conditions, 4-hydroxy-6-methyl-2-pyrone (4) reacted with benzylamine (2e) or 2-phenyl- ethylamine (2f) to give the corresponding N,N'-disubstituted 4-amino-6-methyl-2-pyridones 5e,f. The main advantages of this procedure are dramatically shortened reaction times, higher amine utilization and considerably improved yields.

Efficient liquid-phase synthesis of 2'-hydroxychalcones.

The condensation of 2'-hydroxyacetophenone (1) with aromatic aldehydes (2) in a well closed vessel using microwave irradiation or classical heating at 132 degrees C, provides a fast and simple method for the liquid-phase synthesis of 2'-hydroxychalcones without formation of by-products. Antiproliferative activity of these compounds were evaluated using MCF-7 cells.