Ranking Itraconazole Formulations Based on the Flux through Artificial Lipophilic Membrane.

PURPOSE: The goal of the study was to evaluate a miniaturized dissolution-permeation apparatus (µFLUX™ apparatus) for its ability to benchmark several itraconazole (ITZ) formulations for which in vivo PK data was available in the literature. METHOD: Untreated and micronized powders of ITZ and various enabling formulations of ITZ (commercial Sporanox® solid dispersion, a Soluplus®-based solid dispersion and a nanosuspension) were introduced to the donor compartment of µFLUX™ apparatus. Donor and acceptor chambers were divided from each other by a lipophilic membrane. In addition to the flux evaluations, changes in solid state as a function of time were investigated to gain further insight into the flux changes observed over time for the solid dispersion formulations. RESULTS: Initial flux values from Sporanox®, the nanosuspension and the micronized ITZ showed ratios of 52/4/1 with a decreasing flux from nanosuspension and both solid dispersions after 2.5-3 h. Although the initial flux from the Soluplus® formulation was 2.2 times lower than the one observed for Sporanox®, the decrease in flux observed was milder and became ~ 2 times higher than Sporanox® after approximately 2.5 h. The total amounts of ITZ in the receiver compartment after 240 min showed the same rank order as the rodent AUCs of these formulations reported in literature. CONCLUSIONS: It was demonstrated that in vitro flux measurements using lipophilic artificial membranes could correctly reproduce the rank order of PK results for ITZ formulations. The drop in flux over time for solid dispersions could be backed by experimental indications of crystallization.

Classification of the crystallization behavior of amorphous active pharmaceutical ingredients in aqueous environments.

PURPOSE: To classify the crystallization behavior of amorphous active pharmaceutical ingredients (API) exposed to aqueous environments. METHODS: A set of approximately 50 chemically and physically diverse active pharmaceutical ingredients (APIs) was selected for this study. Two experimental setups were employed to characterize the crystallization behavior of the amorphous API in an aqueous environment. For the first approach, precipitation, as evidenced by the development of turbidity, was induced using the solvent shift method, by mixing concentrated API solutions in DMSO with an aqueous buffer in a capillary. Subsequently, crystallization was monitored in situ over time using synchrotron radiation (simultaneous SAXS/WAXS beamline 12-ID-B at the Advanced Photon Source, Argonne National Laboratories, Argonne, IL). In the second approach, amorphous films were prepared by melt quenching; after adding buffer, crystallization was monitored with time using polarized light microscopy. RESULTS: In general, the crystallization behavior of a given compound was similar irrespective of the experimental method employed. However, the crystallization behavior among different compounds varied significantly, ranging from immediate and complete crystallization to no observable crystallization over biorelevant time scales. Comparison of the observed behavior with previous studies of crystallization tendency in non-aqueous environments revealed that the crystallization tendency of individual APIs was somewhat similar regardless of the crystallization environment. CONCLUSIONS: API properties, rather than the method by which amorphous materials are generated, tend to dictate crystallization behavior in aqueous media.

Rapid insight into heating-induced phase transformations in the solid state of the calcium salt of atorvastatin using multivariate data analysis.

PURPOSE: To investigate the heating-induced dehydration and melting behavior of the trihydrate phase of the calcium salt of atorvastatin. METHODS: Multivariate curve resolution (MCR) was used to decompose a variable-temperature synchrotron X-ray powder diffraction (VT-XRPD) data matrix into diffraction patterns and concentration profiles of pure drug phases. RESULTS: By means of the MCR-estimated diffraction patterns and concentration profiles, the trihydrate phase of the drug salt was found to dehydrate sequentially into two partially dehydrated hydrate structures upon heating from 25 to 110°C, with no associated breakage of the original crystal lattice. During heating from 110 to 140°C, the remaining water was lost from the solid drug salt, which instantly collapsed into a liquid crystalline phase. An isotropic melt was formed above 155°C. Thermogravimetric analysis, hot-stage polarized light microscopy, and hot-stage Raman spectroscopy combined with principal component analysis (PCA) was shown to provide consistent results. CONCLUSIONS: This study demonstrates that MCR combined with VT-XRPD is a powerful tool for rapid interpretation of complex dehydration behavior of drug hydrates, and it is also the first report on a liquid crystalline phase of the calcium salt of atorvastatin.

Nanoscale mid-infrared evaluation of the miscibility behavior of blends of dextran or maltodextrin with poly(vinylpyrrolidone).

Determining the extent of miscibility of amorphous components is of great importance for certain pharmaceutical systems, in particular for polymer-polymer and polymer-small molecule blends. In this study, the application of standard atomic force microscopy (AFM) measurements combined with nanoscale mid-infrared (mid-IR) spectroscopy was explored to evaluate miscibility in binary polymer blends. The miscibility characteristics of a set of 50/50 (w/w) polymer blends comprising of poly(vinylpyrrolidone) (PVP) with dextran or maltodextrin (DEX) of varying molecular weights (MWs) were investigated. Standard AFM characterization results show good agreement with inferences drawn from differential scanning calorimetry (DSC) analysis in terms of forming either single or two phase systems. AFM analysis also provided insight into the microstructure of the two phase systems and how domain sizes varied as a function of polymer MWs. Nanoscale mid-IR evaluation of the blends, performed by collecting local mid-IR spectra or spectral maps, provided an extra dimension of information about the dependence of polymer MWs on chemical composition of the different phases. AFM, combined with nanoscale mid-infrared analysis, thus appears to be a promising technique for the evaluation of miscibility in certain pharmaceutical blends.

Molecular weight effects on the miscibility behavior of dextran and maltodextrin with poly(vinylpyrrolidone).

PURPOSE: To characterize and interpret the miscibility of dextran and maltodextrin with poly(vinylpyrrolidone) (DEX-PVP) as a function of polymer molecular weights. METHODS: Blend miscibility was studied using 4 different molecular weight (MW) grades of DEX combined with 5 MW grades of PVP, over a broad compositional range. Miscibility was evaluated by inspection of glass transition events measured by differential scanning calorimetry (DSC). Fourier transform mid-infrared spectroscopy (FTIR), combined with curve fitting, was performed to characterize the extent of hydrogen bonding. The observed miscibility behavior was further interpreted in terms of mixing thermodynamics. RESULTS: Miscibility of the blends ranged from fully miscible to completely immiscible with multiple partially miscible systems observed. Increasing polymer molecular weight decreased miscibility. For the lowest DEX grade, hydrogen bonding was independent of PVP MW, as expected since all systems were completely miscible. Higher molecular weights of DEX resulted in reduced intermolecular hydrogen bonding and decreased miscibility, increasingly so for higher MW PVP grades. Evaluation of the mixing thermodynamics supported these findings. CONCLUSIONS: With higher combined molecular weights of DEX-PVP blends, phase behavior evolves from completely miscible to virtually immiscible. Concurrently, DEX-PVP hydrogen bonding decreases. From a thermodynamic perspective, the combinatorial mixing entropy was observed to decrease as the molecular weight of the polymers increased, providing a reduced counterbalance to the unfavorable mixing enthalpy thought to accompany this polymer combination.

pH-Induced precipitation behavior of weakly basic compounds: determination of extent and duration of supersaturation using potentiometric titration and correlation to solid state properties.

PURPOSE: To examine the precipitation and supersaturation behavior of ten weak bases in terms of the relationship between pH-concentration-time profiles and the solid state properties of the precipitated material. METHODS: Initially the compound was dissolved at low pH, followed by titration with base to induce precipitation. Upon precipitation, small aliquots of acid or base were added to induce slight subsaturation and supersaturation respectively and the resultant pH gradient was determined. The concentration of the unionized species was calculated as a function of time and pH using mass and charge balance equations. RESULTS: Two patterns of behavior were observed in terms of the extent and duration of supersaturation arising following an increase in pH and this behavior could be rationalized based on the crystallization tendency of the compound. For compounds that did not readily crystallize, an amorphous precipitate was formed and a prolonged duration of supersaturation was observed. For compounds that precipitated to crystalline forms, the observed supersaturation was short-lived. CONCLUSION: This study showed that supersaturation behavior has significant correlation with the solid-state properties of the precipitate and that pH-metric titration methods can be utilized to evaluate the supersaturation behavior.

Evaluation of the Formulation Parameter-Dependent Redispersibility of API Nanoparticles from Fluid Bed Granules.

The production of nanosuspensions of poorly soluble active pharmaceutical ingredients (API) is a popular technique to counteract challenges regarding bioavailability of such active substances. A subsequent drying of the nanosuspensions is advantageous to improve the long-term stability and the further processing into solid oral dosage forms. However, associated drying operations are critical, especially with regard to nanoparticle growth, loss in redispersibility and associated compromised bioavailability. This work extends a previous study regarding the applicability of an API (itraconazole) nanosuspension as a granulation liquid in a fluidized bed process with focus on the influence of applied formulation parameters on the structure of obtained nanoparticle-loaded granules and their nanoparticle redispersibility. Generally, a higher dissolution rate of the carrier material (glass beads, lactose, mannitol or sucrose) and a higher content of a matrix former/hydrophilic polymer (PVP/VA or HPMC) in the granulation liquid resulted in the formation of coarser and more porous granules with improved nanoparticle redispersibility. HPMC was found to have advantages as a polymer compared with PVP/VA. In general, a better redispersibility of the nanoparticles from the granules could be associated with better dispersion of the API nanoparticles at the surface of the granules as deduced from the thickness of nanoparticle-loaded layers around the granules. The layer thickness on granules was assessed by means of confocal Raman microscopy. Finally, the dispersion of the nanoparticles in the granule layers was exemplarily described by calculation of theoretical mean nanoparticle distances in the granule layers and was correlated with data obtained from redispersibility studies.

Influence of particle size on the ultraviolet spectrum of particulate-containing solutions: implications for in-situ concentration monitoring using UV/Vis fiber-optic probes.

PURPOSE: To critically evaluate the effect of submicron and micron-sized organic particulates on the ultraviolet (UV) absorption spectra of aqueous systems and assess the applicability of UV/Vis fiber-optic probes for in-situ concentration monitoring in the presence of particles of different sizes. METHODS: UV absorbance spectra were obtained for aqueous felodipine suspensions containing a range of particle sizes (300 nm-400 µm) and suspension concentrations and for methanolic solutions of different concentrations and amorphous films of different thicknesses. Select suspensions were further characterized using nuclear magnetic resonance (NMR) experiments. Mie theory was used to provide insight into the role of particle size on scattering and absorption of UV radiation. RESULTS: Large increases in absorbance as a function of total suspension concentration were observed for nanosuspensions but not for the other particle sizes evaluated. NMR measurements of solution concentration indicated that the observed increases in UV absorbance values for these systems were not caused by increases in the concentration of dissolved molecules, implying that nanoparticles of felodipine might absorb UV light. Mie theory-based calculations enabled reconstruction of the experimental observations and supported this hypothesis. CONCLUSIONS: For solutions containing small (submicron) felodipine particles, UV spectra were influenced by absorption of the particles and contributions from absorption of dissolved molecules and scattering of the particles. Caution should be applied when using in situ UV/VIS-probes to monitor the amount of dissolved material during dissolution, in particular when small particles are present (e.g. dissolution of nanoparticulate formulations) or generated (e.g. precipitation of supersaturated solutions) in the dissolution medium.

Understanding the tendency of amorphous solid dispersions to undergo amorphous-amorphous phase separation in the presence of absorbed moisture.

Formulation of an amorphous solid dispersion (ASD) is one of the methods commonly considered to increase the bioavailability of a poorly water-soluble small-molecule active pharmaceutical ingredient (API). However, many factors have to be considered in designing an API-polymer system, including any potential changes to the physical stability of the API. In this study, the tendency of ASD systems containing a poorly water-soluble API and a polymer to undergo amorphous-amorphous phase separation was evaluated following exposure to moisture at increasing relative humidity. Infrared spectroscopy was used as the primary method to investigate the phase behavior of the systems. In general, it was observed that stronger drug-polymer interactions, low-ASD hygroscopicity, and a less hydrophobic API led to the formation of systems resistant to moisture-induced amorphous-amorphous phase separation. Orthogonal partial least squares analysis provided further insight into the systems, confirming the importance of the aforementioned properties. In order to design a more physically stable ASD that is resistant to moisture-induced amorphous-amorphous phase separation, it is important to consider the interplay between these properties.

Small scale screening to determine the ability of different polymers to inhibit drug crystallization upon rapid solvent evaporation.

In this study, the ability of 7 chemically diverse polymers [Eudragit E100 (E100), poly(acrylic acid) (PAA), poly(vinylpyrrolidone) (PVP), poly(vinylpyrrolidone-vinyl acetate) (PVPVA), poly(styrene sulfonic acid) (PSSA), hydroxypropylmethylcellulose (HPMC) and hydroxypropylmethylcellulose acetate succinate (HPMCAS)] to inhibit the crystallization of 8 readily crystallizable model compounds [benzamide (BD), phenacetin (PH), flurbiprofen (FB), flufenamic acid (FFA), chlorpropamide (CP), chlorzoxazone (CZ), bifonazole (BI) and lidocaine (LI)] was investigated. Films of the different drug-polymer combinations were prepared by rapid evaporation from solution, using a spin coating method. A total of 7 different drug/polymer weight ratios [90/10, 75/25, 60/40, 50/50, 40/60, 25/75 and 10/90 (w/w)] were evaluated for each drug-polymer combination. Crystallization behavior of the films was monitored using polarized light microscopy over 7 days of room temperature storage under dry conditions. It was observed that compounds having a higher crystallization tendency for the pure compound tended to be more difficult to stabilize using the polymeric additives; more polymer was required. In addition, the stabilizing ability of the polymers varied considerably for the individual compounds, with the acidic polymers PAA and PSSA showing the most extreme behavior. The acidic polymers were good stabilizers for the drugs with basic and amide functional groups, but extremely poor stabilizers for acidic drugs. A reasonable correlation between crystallization inhibition in spin coated films versus bulk powders (prepared by rotary evaporation) was observed. The small scale screening method is thus a potentially useful technique to evaluate the role of drug-polymer chemistry in the stabilization of amorphous solid dispersions.

Solubility increases associated with crystalline drug nanoparticles: methodologies and significance.

In this manuscript, the determination of solubility of crystalline drug nanosuspensions by a range of methods is critically investigated. As the determinations of solubility were performed in the presence of the solubilizing nanosuspension stabilizer d-α-tocopherol polyethylene glycol 1000 succinate (TPGS), the potential effects of this excipient on the measurements were studied first. Solubility data of nanosuspensions of itraconazole, loviride, phenytoin and naproxen were generated using different methodologies. Data obtained using separation-based methodologies (centrifugation, filtration and ultracentrifugation) proved to be of limited use, due to poor nanoparticle separation efficiencies and/or significant adsorption of TPGS onto the nanoparticle surfaces. Light scattering and turbidity were found to be more suitable for the determination of nanosuspension solubility. The obtained data show that, unlike earlier reports, the solubility increases due to nanosizing are small, with measured increases of only 15%. These solubility increases are in fair agreement with what would be predicted based on the Ostwald-Freundlich equation.

2-(Biphenyl-4-yl)acetic acid (felbinac).

The structure of the title compound, C(14)H(12)O(2), displays the expected inter-molecular hydrogen bonding of the carb-oxy-lic acid groups, forming dimers. The dihedral angle between the two aromatic rings is 27.01 (7)°.

1-[(Biphenyl-4-yl)(phen-yl)meth-yl]-1H-imidazole (bifonazole).

In the title compound, C(22)H(18)N(2), the dihedral angles formed by the imidazole ring with the phenyl ring and the benzene ring of the biphenyl group are 87.02 (5) and 78.20 (4)°, respectively. In the crystal, mol-ecules inter-act through inter-molecular C-H⋯N hydrogen bonds, forming chains parallel to the b axis. These chains are further linked into a three-dimensional network by C-H⋯π stacking inter-actions.

2-But-oxy-N-[2-(diethyl-amino)-eth-yl]quinoline-4-carboxamide (dibucaine).

The mol-ecular conformation of the title compound, C(20)H(29)N(3)O(2), is stabilized by an intra-molecular C-H⋯O hydrogen bond. The orientation of the amide group to the ring system is characterized by a C-C-C-O dihedral angle of 137.5 (3)°. In the crystal, inter-molecular N-H⋯O hydrogen bonds between the amide groups form C(4) chains running parallel to the a axis.

Influence of Formulation Parameters on Redispersibility of Naproxen Nanoparticles from Granules Produced in a Fluidized Bed Process.

The particle size reduction of active pharmaceutical ingredients is an efficient method to overcome challenges associated with a poor aqueous solubility. With respect to stability and patient's convenience, the corresponding nanosuspensions are often further processed to solid dosage forms. In this regard, the influence of several formulation parameters (i.e., type of carrier material, type and amount of additional polymeric drying excipient in the nanosuspension) on the redispersibility of naproxen nanoparticle-loaded granules produced in a fluidized bed process was investigated. The dissolution rate of the carrier material (i.e., sucrose, mannitol, or lactose) was identified as a relevant material property, with higher dissolution rates (sucrose > mannitol > lactose) resulting in better redispersibility of the products. Additionally, the redispersibility of the product granules was observed to improve with increasing amounts of polymeric drying excipient in the nanosuspension. The redispersibility was observed to qualitatively correlate with the degree of nanoparticle embedding on the surface of the corresponding granules. This embedding was assumed to be either caused by a partial dissolution and subsequent resolidification of the carrier surface dependent on the dissolution rate of the carrier material or by resolidification of the dissolved polymeric drying excipient upon drying. As the correlation between the redispersibility and the morphology of the corresponding granules was observed for all investigated formulation parameters, it may be assumed that the redispersibility of the nanoparticles is determined by their distance in the dried state.

Spray drying of API nanosuspensions: Importance of drying temperature, type and content of matrix former and particle size for successful formulation and process development.

Active pharmaceutical ingredient (API) nanosuspensions from naproxen (Nap) and itraconazole (Itra) stabilized with Kollidon®VA64 (KVA) and sodium dodecyl sulfate (SDS) were produced in two different size classes each by wet media milling. These API nanosuspensions were spray dried with lactose, trehalose and sucrose as matrix formers in different proportions and at different drying temperatures (Toutlet). Toutlet as well as the API content significantly influenced the redispersibility of the API nanoparticles. It could be shown that these two parameters are related to each other, with an increasing API content leading to a decreasing maximum applicable Toutlet (Tcritical). Drying above Tcritical always led to an alteration of the size characteristics of the API nanoparticles and thus to a non-redispersible product with respect to the defined quality criteria. For each proportion of API to matrix former, a Tcritical could be found. Tcritical showed a linear relation to the API content. The linear regression of this relation was defined as process boundary. The y-intercept of the process boundary correlated well with the glass transition temperature (Tg) of the pure matrix former used for spray drying. The two APIs under investigation led to virtually identical behaviour if other parameters were kept constant. The particle size of the initial nanosuspension had an important influence. Nanosuspensions with comparatively small particle sizes led to a significantly stronger decrease of the process boundaries compared to the use of larger particle sizes. The maximum API content that leads to a redispersible product is thus decisively determined by Toulet of the spray dryer, Tg as well as the proportion of the matrix former and by the particle size of the API nanoparticles used.

Downscaling drug nanosuspension production: processing aspects and physicochemical characterization.

In this study, scaling down nanosuspension production to 10 mg of drug compound and evaluation of the nanosuspensions to 1 mg of drug compound per test were investigated. Media milling of seven model drug compounds (cinnarizine-indomethacin-itraconazole-loviride-mebendazole-naproxen-phenytoin) was evaluated in a 96-well plate setup (10, 20, and 30 mg) and a glass-vial-based system in a planetary mill (10, 100, and 1,000 mg). Physicochemical properties evaluated on 1 mg of drug compound were drug content (high-performance liquid chromatography), size [dynamic light scattering (DLS)], morphology (scanning electron microscopy), thermal characteristics (differential scanning calorimetry), and X-ray powder diffraction (XRPD). Scaling down nanosuspension production to 10 mg of drug compound was feasible for the seven model compounds using both designs, the planetary mill design being more robust. Similar results were obtained for both designs upon milling 10 mg of drug compound. Drug content determination was precise and accurate. DLS was the method of choice for size measurements. Morphology evaluation and thermal analysis were feasible, although sample preparation had a big influence on the results. XRPD in capillary mode was successfully performed, both in the suspended state and after freeze-drying in the capillary. Results obtained for the latter were superior. Both the production and the physicochemical evaluation of nanosuspensions can be successfully downscaled, enabling nanosuspension screening applications in preclinical development settings.

New Potent DOT1L Inhibitors for in Vivo Evaluation in Mouse.

In MLL-rearranged cancer cells, disruptor of telomeric silencing 1-like protein (DOT1L) is aberrantly recruited to ectopic loci leading to local hypermethylation of H3K79 and consequently misexpression of leukemogenic genes. A structure-guided optimization of a HTS hit led to the discovery of DOT1L inhibitors with subnanomolar potency, allowing testing of the therapeutic principle of DOT1L inhibition in a preclinical mouse tumor xenograft model. Compounds displaying good exposure in mouse and nanomolar inhibition of target gene expression in cells were obtained and tested in vivo.

Microcrystalline cellulose, a useful alternative for sucrose as a matrix former during freeze-drying of drug nanosuspensions - a case study with itraconazole.

Itraconazole nanosuspensions, stabilized with 10% TPGS (relative to the weight of itraconazole), were transformed into nanoparticulate powders by freeze-drying. The crystalline itraconazole nanoparticles showed peak broadening in the X-ray powder diffraction spectra and a lower melting point as inferred from differential scanning calorimetry. As it was found that freeze-drying compromised dissolution behavior, sucrose was added as a matrix, former (50,100 and 200%, relative to the weight of itraconazole). Higher amounts of sucrose unexpectedly resulted in a decrease in the dissolution rate. After thorough evaluation of the powders, it was found that whereas higher sucrose content showed a cryoprotective effect, agglomeration during the final phase of the subsequent drying step tended to increase with higher amounts of sucrose. Therefore, microcrystalline cellulose (MCC) was evaluated as an alternative matrix former. The inclusion of MCC resulted in fast dissolution that increased with increasing amounts of MCC [for powders containing 50%,100% and 200% MCC, (relative to the weight of itraconazole), the times required for 63.2% release were 10.5+/-0.7, 6.4+/-1.2 and 3.1+/-0.5min, respectively]. The dissolution profiles showed an initial phase of burst dissolution, followed by a phase of slower release. As the fraction showing burst dissolution increased with higher MCC content, the system holds promise to maintain the dissolution enhancing properties of nanoparticles in the dry form.

Alternative matrix formers for nanosuspension solidification: Dissolution performance and X-ray microanalysis as an evaluation tool for powder dispersion.

Four alternative matrix formers [Avicel PH101, Fujicalin (CaHPO(4)), Aerosil 200 (SiO(2)) and Inutec SP1] were evaluated for their capability in preserving rapid dissolution after spray-drying of nanosuspensions. Model drug compounds selected were cinnarizine (CIN), itraconazole (ITR) and phenylbutazone (PHB) as they showed a decrease in dissolution rate upon spray-drying in the absence of additional matrix formers, yielding release values after 5min of dissolution (release(5min)) of 57.7+/-1.0% (CIN), 56.3+/-3.8% (ITR) and 67.4+/-1.3% (PHB). Compared to the situation without matrix former inclusion, the performance of Avicel PH101 was good for CIN (release(5min)=90.9+/-7.7%), intermediate for PHB (release(5min)=81.0+/-6.4%) and poor for ITR (release(5min)=42.1+/-4.2%). For Fujicalin, intermediate (PHB: release(5min)=87.7+/-3.0%) or poor (CIN: release(5min)=66.1+/-3.4%; ITR: release(5min)=55.9+/-5.2%) performance was seen. Results for Aerosil 200 were good for all compounds (CIN: release(5min)=91.5+/-2.5%; ITR: release(5min)=83.8+/-3.4%; PHB: release(5min)=95.5+/-2.4%), indicating that the large specific surface area was in this case translated into good matrix forming capabilities. Finally, the best results were obtained for Inutec SP1 (CIN: release(5min)=88.7+/-1.2%; ITR: release(5min)=93.4+/-2.4%; PHB: release(5min)=101.3+/-4.9%). Except for Avicel PH101, Cl-maps from X-ray microanalysis of the itraconazole powders supported the hypothesis that better dispersion of drug in the powders results in faster dissolution.