Fast dissolution of poorly water soluble drugs from fluidized bed coated nanocomposites: Impact of carrier size

Systematic Screening Study for the Selection of Proper Stabilizers to Produce Physically Stable Canagliflozin Nanosuspension by Wet Milling Method

One of the crucial approaches to managing the low solubility and weak bioavailability of drugs is via nanocrystal technology. Through this technology, drug particles have an increased solubility and a faster dissolution rate due to high surface free energy, which requires an appropriate stabilizer(s) to prevent instabilities during the manufacturing process and storage of the nanosuspension. This study aimed to establish a scientific predictive system for properly selecting stabilizers or to reduce the attempts on a trial-and-error basis in the wet-milling method. In total, 42 experiments were performed to examine the effect of critical material attributes on the wettability of the drug, the saturation solubility in the stabilizer solutions or combinations thereof and the dynamic viscosity of stabilizer solutions. All data were evaluated by Minitab 19® and an optimization study was performed. The optimized formulation at a certain concentration of stabilizer combination was ground by Dyno Mill® with 0.3 mm beads for one hour. The optimized nanosuspension with a particle size of 204.5 nm was obtained in short milling time and offered 3.05- and 3.51 times better dissolution rates than the marketed drug product (Invokana® 100 mg) in pH 4.5 and pH 6.8 as non-sink conditions, respectively. The formulation was monitored for three months at room temperature and 4 °C. The parameters were 261.30 nm, 0.163, -14.1 mV and 261.50 nm, 0.216 and -17.8 mV, respectively. It was concluded that this approach might indicate the appropriate selection of stabilizers for the wet-milling process.

3D Raman mapping as an analytical tool for investigating the coatings of coated drug particles

The properties of dry-coated paracetamol particles (fast-dissolving model drug) with carnauba wax particles as the coating agent (dissolution retardant) were investigated. Raman mapping technique was used to non-destructively examine the thickness and homogeneity of coated particles. The results showed that the wax existed in two forms on the surface of the paracetamol particles, forming a porous coating layer: i) whole wax particles on the surface of paracetamol and glued together with other wax surface particles, and ii) deformed wax particles spread on the surface. Regardless of the final particle size fraction (between 100 and 800 μm), the coating thickness had high variability, with average thickness of 5.9 ± 4.2 μm. The ability of carnauba wax to decrease the dissolution rate of paracetamol was confirmed by dissolution of powder and tablet formulations. The dissolution was slower for larger coated particles. Tableting further reduced the dissolution rate, clearly indicating the impact of subsequent formulation processes on the final quality of the product.

Preparation of Free-Flowing Spray-Dried Amorphous Composites Using Neusilin®

A highly porous additive, Neusilin^®, with high adsorption capability is investigated to improve bulk properties, hence processability of spray-dried amorphous solid dispersions (ASDs). Griseofulvin (GF) is applied as a model BCS class 2 drug in ASDs. Two grades of Neusilin^®, US2 (coarser) and UFL2 (finer), were used as additives to produce spray-dried amorphous composite (AC) powders, and their performance was compared with the resulting ASDs without added Neusilin^®. The resulting AC powders that included Neusilin^® had greatly enhanced flowability (flow function coefficient (FFC) > 10) comparable to larger particles (100 μm) yet had finer particle size (< 50 μm), hence retaining the advantage of fast dissolution rate of finer sizes. Dissolution results demonstrated that achieved GF supersaturation for AC powders with Neusilin^® was as high as 3 times that of crystalline GF concentration and was achieved within 30 min. In addition, 80% of drug was released within 4 min. The flowability improvement for AC powders with Neusilin^® was more significant as compared to spray-dried ASDs without Neusilin^®. Thus, the role of Neusilin^® in flowability improvement was evident, considering that spray-dried AC with Neusilin^® UFL2 has higher FFC than ASDs having a similar size. Lastly, the AC powders retained a fully amorphous state of GF after 3-month ambient storage. The overall results conveyed that the improved flowability and dissolution rate could outweigh the loss of drug loading resulted by addition of Neusilin^®.

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.

Itraconazole Nanosuspensions via Dual Centrifugation Media Milling: Impact of Formulation and Process Parameters on Particle Size and Solid-State Conversion as Well as Storage Stability

Nanocrystal suspensions proved to be a potent enabling principle for biopharmaceutics classification system class II drugs with dissolution limited bioavailability. In the example of itraconazole (ITZ) as a model drug combined with electrosteric stabilization using hydroxypropyl cellulose (HPC-SL), sodium dodecyl sulfate (SDS) and polysorbate 80 (PS80), the impacts of formulation and process parameters of a dual centrifugal mill on material attributes such as particle size, zeta potential, particle morphology, storage stability and especially solid-state characteristics were evaluated. A minimal concentration of 0.9% (w/w) HPC-SL, 0.14% (w/w) SDS and 0.07% (w/w) PS80 was necessary for sufficient nanoparticle stabilization. Despite the minor effect of PS80, its presence was beneficial for electrosteric stabilization. Choosing lower stabilizer concentrations resulted in a pronounced increase in particle size due to agglomeration, which was confirmed by SEM imaging and a decrease in zeta potential in combination with an amorphization of the particles. Milling temperature had no significant impact on the particle size, whereas milling speed and the size of the milling beads used were found to have a strong impact on the critical material attributes such as particle size and polydispersity index. The smallest particle sizes could be obtained by using the smallest milling bead size. However, the smallest obtainable particle size could only be achieved by using two-fold stabilizer concentrations, as smaller particles exhibit a larger specific surface area.

Production and isolation of pharmaceutical drug nanoparticles

Nanosizing of pharmaceutical drug particles is one of the most important drug delivery platforms approaches for the commercial development of poorly water-soluble drug molecules. Though nanosizing of drug particles has been proven to greatly enhance drugs dissolution rate and apparent solubility, nanosized materials have presented significant challenges for their formulation as solid dosage forms (e.g. tablets, capsules). This is due to the strong Van der Waals attraction forces between dry nanoparticles leading to aggregation, cohesion, and consequently poor flowability. In this review, the broad area of nanomedicines is overviewed with the primary focus on drug nanocrystals and the top-down and bottom-up methods used in their fabrication. The review also looks at how nanosuspensions of pharmaceutical drugs are generated and stabilised, followed by subsequent strategies for isolation of the nanoparticles. A perspective on the future outlook for drug nanocrystals is also presented.

Nanosuspensions of a poorly soluble investigational molecule ODM-106: Impact of milling bead diameter and stabilizer concentration

Aqueous solubility of a drug substance is an important attribute affecting oral bioavailability. Nanonization, particle size reduction to submicron level, is an elegant approach to improve drug solubility and dissolution by increasing the surface energy, which in turn necessitates the use of stabilizers. The purpose of this study was to develop a nanosuspension of a practically water-insoluble investigational molecule by nanomilling approach using wet media milling. A variety of polymeric and surface active excipients were tested for their wettability. A combination of hydroxypropyl methylcellulose and sodium lauryl sulfate (SLS) were selected as stabilizers on the bases of compatibility studies and efficient wettability behaviour in contact angle measurements (≈80˚). A factorial design set-up was used to study the effect of milling bead diameter and stabilizer concentration on the efficiency of particle size reduction. Nanonization outcome was different when milling beads of 0.5 mm and 1 mm diameter were used at different concentrations of the stabilizers, which demonstrated the complex nature of the whole system. Storage of the nanosuspensions under different temperature conditions resulted only in minor changes of the particle size fractions.

Insoluble Polymers in Solid Dispersions for Improving Bioavailability of Poorly Water-Soluble Drugs

In recent decades, solid dispersions have been demonstrated as an effective approach for improving the bioavailability of poorly water-soluble drugs, as have solid dispersion techniques that include the application of nanotechnology. Many studies have reported on the ability to change drug crystallinity and molecular interactions to enhance the dissolution rate of solid dispersions using hydrophilic carriers. However, numerous studies have indicated that insoluble carriers are also promising excipients in solid dispersions. In this report, an overview of solid dispersion strategies involving insoluble carriers has been provided. In addition to the role of solubility and dissolution enhancement, the perspectives of the use of these polymers in controlled release solid dispersions have been classified and discussed. Moreover, the compatibility between methods and carriers and between drug and carrier is mentioned. In general, this report on solid dispersions using insoluble carriers could provide a specific approach and/or a selection of these polymers for further formulation development and clinical applications.

Conversion of indomethacin nanosuspensions into solid dosage forms via fluid bed granulation and compaction

Preparation of pharmaceutical nanosuspensions is a popular technique to increase the dissolution velocity of poorly water-soluble drugs. Subsequent drying into a compaction-ready powder or granule is a critical process due to possible adverse solid characteristics and the risk of growth of nanoparticles. This work evaluated the drying of nanosuspensions via fluid bed granulation with focus on the binder selection and used concentrations, as well as the parameters spray rate and atomization pressure. Design of experiments was used to identify significant parameters. Indomethacin nanosuspensions were prepared by wet media milling and dried on a carrier consisting of lactose, microcrystalline cellulose, and crospovidone with and without additional binder during granulation. Resulting granules were compacted into tablets and their in vitro dissolution performances were characterized. A higher content of binder PVP and a higher spray rate led to less growth of resuspended nanoparticles. Finally, indomethacin nanoparticle tablets showed a superior dissolution performance in contrast to raw indomethacin tablets.

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.

Formulation of Ketoconazole Nanocrystal-Based Cryopellets

Commercial development of nanosuspensions for oral drug delivery generally involves a drying step which aims to generate a stable product that rapidly releases the nanocrystals once rehydrated and can be easily processed into a final dosage form (e.g., filled into hard capsule). Cryopelletisation is a freeze drying technique allowing the production of lyophilised micrometric spheres with good flowability. In the current work, the possibility to formulate redispersible ketoconazole nanocrystal-based cryopellets able to withstand intensive handling was investigated. Cryopellets were generated by first freezing regular droplets of nanosuspension using liquid nitrogen followed by water removal by sublimation in a standard freeze dryer. Low-friable cryopellets (< 1%) were produced by embedding the nanocrystals in a stabilizing hydroxypropyl cellulose SSL grade matrix, thus proving that these structures can withstand intensive handling. A threshold quantity of hydroxypropyl cellulose SSL grade (5/20 hydroxypropyl cellulose SSL grade-to-drug mass ratio) was required in combination with D-α-tocopherol polyethylene glycol 1000 succinate (vitamin E TPGS) to successfully recover the nanocrystals over storage. A further addition of micronised crospovidone has shown a positive effect on the dissolution performance of cryopellets. Altogether, this study demonstrated that the design of cryopellets combining the strengths of freeze-dried powders (porous internal structure, low residual humidity) and pellets (free-flowing units, mechanical resistance during handling) can potentially improve the nanocrystal's redispersibility compared with other drying techniques while facilitating the downstream processing.

Fenofibrate Nanocrystal Composite Microparticles for Intestine-Specific Oral Drug Delivery System

Hydrophobic drug nanocrystals (NCs) manufactured by particle engineering have been extensively investigated for enhanced oral bioavailability and therapeutic effectiveness. However, there are significant drawbacks, including fast dissolution of the nanocrystals in the gastric environment, leading to physicochemical instability. To solves this issue, we developed an innovative technique that involves the encapsulation of nanocrystals in composite spherical microparticles (NCSMs). Fenofibrate (FNB) NCs (FNB-NCs) manufactured by a wet stirred media milling (WSMM) technique and an ionotropic crosslinking method were used for FNB-NC encapsulation within gastroresistant NCSMs. Various solid-state methods were used for characterizing NCSMs. The pH-sensitive NCSMs showed a site-specific release pattern at alkaline pH and nearly 0% release at low pH (gastric environment). This phenomenon was confirmed by a real-time in situ UV-imaging system known as the surface dissolution imager (SDI), which was used to monitor drug release events by measuring the color intensity and concentration gradient formation. All these results proved that our NCSM approach is an innovative idea in oral drug delivery systems, as it resolves significant challenges in the intestine-specific release of hydrophobic drugs while avoiding fast dissolution or burst release.

Study on Formulation, in vivo Exposure, and Passive Targeting of Intravenous Itraconazole Nanosuspensions

The pharmacokinetic profile of a drug can be different when delivered as a nanosuspension compared with a true solution, which may in turn affect the therapeutic effect of the drug. The goal of this study was to prepare itraconazole nanosuspensions (ITZ-Nanos) stabilized by an amphipathic polymer, polyethylene glycol-poly (benzyl aspartic acid ester) (PEG-PBLA), by the precipitation-homogenization, and study the pharmacokinetic profile of the ITZ-Nanos. The particle size and morphology of nanosuspensions were determined by Zetasizer and field emission scanning electron microscope (SEM), respectively. The dissolution profile was evaluated using a paddle method according to Chinese Pharmacopoeia 2015. The level of ITZ in plasma and tissues was measured by a HPLC method. The optimized ITZ-Nanos had an average particle size of 268.1 ± 6.5 nm and the particles were in a rectangular form. The dissolution profile of ITZ-Nanos was similar to that of commercial ITZ injections, with nearly 90% ITZ released in the first 5 min. The ITZ-Nanos displayed different pharmacokinetic properties compared with the commercial ITZ injections, including a decreased initial drug concentration, increased plasma half-life and mean residence time (MRT), and increased concentration in the liver, lung, and spleen. The ITZ-Nanos can change the in vivo distribution of ITZ and result in passive targeting to the organs with mononuclear phagocyte systems (MPS).

Combination of Roll Grinding and High-Pressure Homogenization Can Prepare Stable Bicelles for Drug Delivery

To improve the solubility of the drug nifedipine (NI), NI-encapsulated lipid-based nanoparticles (NI-LNs) have been prepared from neutral hydrogenated soybean phosphatidylcholine and negatively charged dipalmitoylphosphatidylglycerol at a molar ratio of 5/1 using by roll grinding and high-pressure homogenization. The NI-LNs exhibited high entrapment efficiency, long-term stability, and enhanced NI bioavailability. To better understand their structures, cryo transmission electron microscopy and atomic force microscopy were performed in the present study. Imaging from both instruments revealed that the NI-LNs were bicelles. Structures prepared with a different drug (phenytoin) or with phospholipids (dimyristoylphosphatidylcholine, dipalmitoylphosphatidylcholine, and distearoylphosphatidylcholine) were also bicelles. Long-term storage, freeze-drying, and high-pressure homogenization did not affect the structures; however, different lipid ratios, or the presence of cholesterol, did result in liposomes (5/0) or micelles (0/5) with different physicochemical properties and stabilities. Considering the result of long-term stability, standard NI-LN bicelles (5/1) showed the most long-term stabilities, providing a useful preparation method for stable bicelles for drug delivery.

Bioavailability Enhancement of Poorly Water-Soluble Drugs via Nanocomposites: Formulation⁻Processing Aspects and Challenges

Drug nanoparticles embedded in a dispersant matrix as a secondary phase, i.e., drug-laden nanocomposites, offer a versatile delivery platform for enhancing the dissolution rate and bioavailability of poorly water-soluble drugs. Drug nanoparticles are prepared by top-down, bottom-up, or combinative approaches in the form of nanosuspensions, which are subsequently dried to prepare drug-laden nanocomposites. In this comprehensive review paper, the term &ldquo;nanocomposites&rdquo; is used in a broad context to cover drug nanoparticle-laden intermediate products in the form of powders, cakes, and extrudates, which can be incorporated into final oral solid dosages via standard pharmaceutical unit operations, as well as drug nanoparticle-laden strip films. The objective of this paper is to review studies from 2012⁻2017 in the field of drug-laden nanocomposites. After a brief overview of the various approaches used for preparing drug nanoparticles, the review covers drying processes and dispersant formulations used for the production of drug-laden nanocomposites, as well as various characterization methods including quiescent and agitated redispersion tests. Traditional dispersants such as soluble polymers, surfactants, other water-soluble dispersants, and water-insoluble dispersants, as well as novel dispersants such as wet-milled superdisintegrants, are covered. They exhibit various functionalities such as drug nanoparticle stabilization, mitigation of aggregation, formation of nanocomposite matrix⁻film, wettability enhancement, and matrix erosion/disintegration. Major challenges such as nanoparticle aggregation and poor redispersibility that cause inferior dissolution performance of the drug-laden nanocomposites are highlighted. Literature data are analyzed in terms of usage frequency of various drying processes and dispersant classes. We provide some engineering considerations in comparing drying processes, which could account for some of the diverging trends in academia vs. industrial practice. Overall, this review provides rationale and guidance for drying process selection and robust nanocomposite formulation development, with insights into the roles of various classes of dispersants.

Novel nanocrystal-based solid dispersion with high drug loading, enhanced dissolution, and bioavailability of andrographolide

Objective

The current study sought to design a quickly dissolving, high drug loading nanocrystal-based solid dispersion (NC-SD) in order to improve the dissolution of poorly soluble drugs.

Methods

The NC-SD was prepared by means of combination of homogenization and spray-drying. Polymer hydroxypropylmethylcellulose (HPMC) was used as baseline dispersant for NC-SD of the model drug – andrographolide (AG). Three superdisintegrants cohomogenized with HPMC were used as codispersant for AG-NC-SD and compared to common water-soluble dispersants – mannitol and lactose. The dissolution characterization and oral bioavailability of AG-NC-SD were evaluated.

Results

The AG-NC-SD with the higher concentration of HPMC exhibited fast dissolution due to the enhanced wettability of HPMC. The water-soluble codispersants (mannitol and lactose) did not completely prevent AG-NC from aggregation during spray-drying. To achieve much faster AG release, cohomogenized superdisintegrants at a level of 20% must be used along with 25% HPMC. Compared with water-soluble dispersants like mannitol and lactose, superdisintegrants with high swelling capacity were much more effective dispersants for enhancing fast redispersion/dissolution of AG-NC-SD via a swelling-triggered erosion/disintegration mechanism. Surfactant-free AG-NC-SD with 15% cohomogenized sodium carboxymethyl starch combined with 15% HPMC and 10% lactose enhanced the dissolution further, without comprising drug loading, exhibited a barely compromised dissolution rate compared to precursor NC suspensions (f₂>50), and possessed drug loading up to 67.83%±1.26%. The pharmacokinetics results also demonstrated that the AG-NC-SD significantly improved the bioavailability in vivo of AG (P<0.05), compared with to the coarse AG.

Conclusion

This study illustrates that a quickly dissolving, high drug load, surfactant-free NC-SD can be prepared by using a superdisintegrant as codispersant, and provides a feasible strategy to improve the oral bioavailability of poorly soluble drugs.

Quiescent and Agitated Redispersion as a Tool for Evaluating Dispersant Effectiveness in Dissolution Enhancement of Drug-Laden Nanocomposites

Nanocomposite microparticles (NCMPs) have been used in various solid dosage forms with the goal of enhancing the dissolution rate and bioavailability of poorly water-soluble drugs. Nanoparticle recovery from NCMPs, i.e., redispersion, is the preliminary step in drug dissolution. This study aims at exploring aqueous redispersion of NCMPs with various dispersants under quiescent vs. agitated conditions as potential dispersant screening tool in the development of fast-dissolving NCMP formulations. NCMPs were prepared by coating wet-milled suspensions of a poorly water-soluble drug, griseofulvin (GF), formulated with the dispersants hydroxypropyl cellulose (HPC), sodium dodecyl sulfate (SDS), as-received/wet co-milled croscarmellose sodium (CCS), and mannitol, onto Pharmatose® carrier particles in a fluidized bed dryer. The NCMPs were added to quiescent water kept in a cuvette, and the redispersion was visualized and investigated by turbidimetry and dynamic light scattering. The morphological evolution of a single NCMP exposed to a drop of water was studied via optical microscopy, which provided further insight into the self-redispersibility. As a comparison, the NCMPs were also redispersed in water agitated by a paddle stirrer followed by centrifugation and drug assay of the resultant supernatant, which yielded the percentage of GF recovered as nanoparticles. Both quiescent and agitated redispersion methods yielded similar rank-ordering of the dispersants: NCMPs with either HPC/SDS or HPC/CCS exhibited effective nanoparticle recovery and fast dissolution, whereas those with HPC or HPC/mannitol led to poor redispersibility and slow dissolution. This study demonstrates that both quiescent and agitated redispersion tests could be used for screening/optimizing dispersants for fast-dissolving drug NCMP formulations.