Two microparticle systems containing disodium cromoglycate (DSCG) alone or with polyvinyl alcohol (DSCG/PVA) were produced via spray drying and compared in terms of their physicochemical characteristics, aerosol performance and drug uptake across a pulmonary epithelial cell line (Calu-3), cultured under air interface conditions. The particle size distribution of DSCG and DSCG/PVA were similar, of spherical geometry, amorphous and suitable for inhalation purposes. Aerosolisation studies using a modified twin-stage impinger showed the DSCG/PVA to have greater aerosol performance than that of DSCG alone. Aerosol particles of DSCG and DSCG/PVA were deposited onto the surface of the Calu-3 air interface epithelium monolayer and the drug uptake from apical to basal directions measured over time. Drug uptake was measured across a range of doses to allow comparison of equivalent drug and powder mass deposition. Analysis of the data indicated that the percentage cumulative drug uptake was independent of the mass of powder deposited, but dependent on the formulation. Specifically, with the formulation containing DSCG, the diffusion rate was observed to change with respect to time (indicative of a concentration-dependent diffusion process), whilst DSCG/PVA showed a time-independent drug uptake (suggesting a zero-order depot release).

The aim of this study was to prepare lipid microparticles (LMs) loaded with the polar bronchodilator agent salbutamol, and designed for sustained release pulmonary delivery. The microparticles were produced by melt emulsification followed by a sonication step, using different biocompatible lipid carriers (tristearin, stearic acid and glyceryl behenate) and phosphatidylcholine as the surfactant. The use of salbutamol free base, rather than salbutamol sulphate, was necessary to obtain the incorporation of the drug in the lipid particle matrix. The prolonged release of salbutamol base was achieved only by the glyceryl behenate microparticles (40.9% of encapsulated drug being released after 8 h). The salbutamol loading was 4.2% ± 0.1 and the mass median diameter, determined by laser diffraction, ranged from 4.8 to 5.4 µm. The sustained release of LMs were formulated as a carrier-free dry powder for inhalation and exhibited a fine particle fraction of 17.3% ± 2.2, as measured by multi-stage liquid impinger.

Objectives: To evaluate physicochemical properties of two micronized drugs, salbutamol sulfate (SS) and beclomethasone dipropionate (BDP) prepared as dry powder inhalation physical blends. Methods: Five different blends of SS:BDP ratios of 0:100, 25:75, 50:50, 75:25, and 100:0 (w/w) were prepared. Aerosolization performance was evaluated using a multistage impinger and a Rotahaler® device. Results: The median SS particle diameter was larger than BDP (4.33 ± 0.37 µm compared to 2.99 ± 0.15 µm, respectively). The SS appeared to have a ribbon-like morphology, while BDP particles had plate-like shape with higher cohesion than SS. This was reflected in the aerosolization performance of the two drugs alone, where SS had a significantly higher fine particle fraction (FPF) than BDP (12.3%, 3.1% and 2.9%, 0.2%, respectively). The study of cohesion versus adhesion for a series of SS and BDP probes on SS and BDP substrates suggested both to be moderately adhesive, verified using scanning Raman microscopy, where a physical association between the two was observed. A plot of loaded versus emitted dose indicated that powder bed fluidization was significantly different when the drugs were tested individually. Furthermore, the FPF of the two drugs from the binary blends, at all three ratios, were similar. Conclusions: Such observations indicate that when these two drugs are formulated as a binary system, the resulting powder structure is altered and the aerosolization performance of each drug is not reflective of the individual drug performance. Such factors could have important implications and should be considered when developing combination dry powder inhalation systems.

Two combination dry powder inhalation formulations were engineered via spray drying and co-spray drying salbutamol base (SB) and beclomethasone dipropionate (BDP). The aerosol performances of the individual drugs, a physical mix and the co-spray-dried particle systems were investigated after blending with conventional lactose carrier, under realistic dose regimes. Furthermore, each system was evaluated in terms of the physicochemical properties and via high-throughput Raman microscopy (to study co-association and deposition patterns after in vitro aerosolisation studies). In general, analysis of the aerosol performance (measured using a next-generation impactor) of the single drug and physical mix formulations suggested that SB and BDP have significantly different stage-deposition profiles. Such observations were further substantiated by scanning electron microscopy, where SB–BDP agglomeration could be observed in the physical mix. Stage deposition from the SB–BDP co-spray-dried powders were different than that for the physical mix, wherein the amount of SB and BDP on each stage was equivalent; suggesting that the two drugs could be targeted and deposited at the same location on the lung epithelia. Raman microscopy of the physical mix and co-spray-dried formulations also confirmed the differences in stage deposition between formulations and co-localised deposition for the co-spray-dried formulation. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 101:4267–4276, 2012

Purpose

Conditions such as lung cancer currently lack non-invasively targetable and controlled release topical inhalational therapies. Superparamagnetic iron-oxide nanoparticles (SPIONs) have shown promising results as a targetable therapy. We aimed to fabricate and test the in-vitro performance of particles with SPION and drug within a lipid matrix as a potentially targetable and thermo-sensitive inhalable drug-delivery system.

Methods

Budesonide and SPIONs were incorporated into lipid particles using oil-in-water emulsification. Particles size, chemical composition, responsiveness to magnetic field, thermosensitiveness and inhalation performance in-vitro were investigated.

Results

Particles of average diameter 2–4 μm with budesonide and SPIONs inside the lipid matrix responded to a magnetic field with 100% extraction at a distance of 5 mm. Formulations were shown to have accelerated rate of drug release at hyperthermic temperatures (45°C)—controlled release. The produced inhalation dry powder presented promising inhalation performance, with an inhalable fine particle fraction of 30%.

Conclusions

The lipid system presented thermo-sensitive characteristics, suitable for controlled delivery, the model drug and SPION loaded lipid system was magnetically active and movable using simple permanent magnets, and the system demonstrates promise as an effective drug vehicle in targeted and controlled inhalation therapy.

Background: Inhaled dry powder mannitol has established in vivo therapeutic efficacy for enhancing mucociliary function. However, a single dose necessitates multiple inhalations of a sizeable powder mass. Nebulization of mannitol by vibrating mesh devices has recently been shown in vitro to impart similar dosing in a comparable or lesser treatment time. Nevertheless, the limited solubility of mannitol restricted fluid concentrations to 150 mg/mL. The present study examines the feasibility of higher solubility polyols that presumably possess similar therapeutic properties to mannitol but deliverable at higher concentrations to shorten treatment time. A secondary aim is to compare delivery by two commercially available mesh nebulizers—the Aeroneb® Go and PARI eFlow Rapid.

Methods: A series of formulations containing three polyols (mannitol, sorbitol, and xylitol) of increasing concentration in 1% w/v sodium chloride were nebulized. Aerosol characteristics and treatment times were determined primarily by laser diffraction.

Results: Results indicate viscosity is the primary determinant of vibrating mesh nebulizer performance. For both nebulizers, xylitol 334 mg/mL exhibits the greatest osmolar output—double that of 150 mg/mL mannitol.

Conclusions: A nebulized xylitol solution has potential clinical application for promoting rapid mucociliary clearance. Both vibrating mesh nebulizers facilitate quick treatment times. Future in vivo studies would compare the efficacy of nebulized xylitol to commercial hyperosmolar agents and establish any potential polyol-associated antibacterial activity.

Abstract

Objectives  Over the past 20 years, the inhalation drug delivery industry has undergone a quiet revolution after the phasing out of the chlorofluorocarbon propellants used to formulate pressure-metered dose inhalers (pMDIs). This review looks back to the creative landscape of those 20 years through a study of patent application trends. To this end, an analysis of the hydrofluoroalkane pMDIs patent landscape was undertaken.

Methods  A statistical analysis demonstrates that 20 years after the introduction of hydrofluoroalkanes in the inhalation delivery field, the original patent applications are coming to the end of their legal life.

Key findings  Detailed analysis revealed that, from a total of 971 of the patents identified, up to 2.3% will expire within the next 5 years, rising to up to 7.3% in the next 10 years. The UK and USA were the main patent destinations and locations of inventive activity, as measured by patent filing location. Interestingly, the UK was the first destination and location of inventive activity in Europe, largely due to the activity of GlaxoSmithKline, followed by Italy, thanks to the work of Trinity-Chiesi. The analysis also showed that patent assignees are not always major pharmaceutical companies, with suppliers of propellants, as well as companies without major inhalation activity (such as Novadel), making substantial contributions to the landscape.

Conclusions  These developments may have a significant impact on innovation trends and key company activity around novel pMDI formulations, in particular for generics manufacturers.

Abstract

Objectives  The formulation of multi-drug pressurised metered dose inhalers (pMDIs) opens up exciting therapeutic opportunities for the treatment of asthma and chronic obstructive pulmonary disease (COPD). We have investigated the formulation of a solution-based triple therapy pMDI containing ipratropium, formoterol, budesonide and ethanol as co-solvent.

Methods  This system was characterised for in-vitro performance and compared with marketed pMDIs (Atrovent and Symbicort).

Key findings  No significant difference was found in the stage deposition of each drug from the triple therapy formulation, suggesting that the droplets contained a fixed ratio of the three components used. Stage deposition of formoterol and budesonide from the suspension-based marketed Symbicort were significantly different, suggesting that the two drugs were deposited as separate entities. Calculation of the mass median aerodynamic diameter (MMAD) of each formulation suggested Atrovent (ipratropium, MMAD = 0.9 ± 0.0 µm) to have a small particle size, similar to the triple therapy formulation. Atrovent, like the triple therapy formulation was solution based and it contained ethanol as a co-solvent (triple therapy formulation, MMAD = 1.3 ± 0.0 µm).

Conclusions  This study demonstrated the feasibility of formulating a solution-based pMDI containing a triple therapy with identical deposition pattern for the treatment of several respiratory diseases where multi-drug cell targeting is required.

The deposition, dissolution and transport of salbutamol base (SB) and salbutamol sulfate (SS) inhalation powders were investigated using the Calu-3 air interface cell culture model and Franz diffusion cell. Drug uptake by cells was studied with respect to deposited dose, drug solubility and hydrophobicity. Furthermore, the role of active transport via organic cationic transporters (OCTs) was studied. SB and SS were processed to have similar diameters (3.09 ± 0.06 μm and 3.07 ± 0.03 μm, respectively) and were crystalline in nature. Analysis of drug wetting, dissolution and diffusion using a conventional in vitro Franz cell (incorporating a cell culture support Transwell polyester membrane) showed diffusion of SB to be slower than that of SS (98.57 ± 4.23 μg after 4 h for SB compared to 98.57 ± 4.01 μg after 15 min for SS). Such observations suggest dissolution to be the rate-limiting step. In comparison, the percentage transfer rate using the air interface Calu-3 cell model suggested SB transport to be significantly faster than SS transport (92.02 ± 4.47 μg of SB compared to 63.76 ± 8.84 μg of SS transported over 4 h), indicating that passive diffusion through the cell plays a role in transport. Furthermore, analysis of SB and SS transport, over a range of deposited doses, suggested the transport rate in the Franz diffusion cell to be limited by wetting of the particle and dissolution into the medium. However, for the cell monolayer, the cell membrane properties regulate the diffusion and transport rate. Analysis of the drug transport in the presence of triethylamine (TEA), a known inhibitor of OCTs, resulted in a significant decrease in drug transport, suggesting an active transport mechanism. The presence of OCTs in this cell line was further validated by Western blot analysis. Finally, the transport of SS from a commercial product (Ventolin Rotacaps) was studied and showed good agreement with the model SS system studied here.

Control of cell–matrix interactions plays a role in the regulation of stem cell function. In this study basic fibroblast growth factor (bFGF) linked to maltose-binding protein (MBP) was designed as a matrix for cell adhesion. MBP–FGF was immobilized on polystyrene (PS) surfaces by spontaneous adsorption. The amount of MBP–bFGF immobilized on the PS surface increased with increasing protein concentration, being 158 ng cm−2 at 10 μg ml−1 protein. Human adipose-derived stem cell (hASC) adhesion to MBP–bFGF immobilized on a PS surface (PS–MBP–bFGF) was inhibited by heparin. Integrin signaling and cell spreading of hASC on PS–MBP–bFGF were down-regulated compared with those on fibronectin-coated surfaces or tissue culture polystyrene (TCP). hASC differentiated into adipocytes, which stained positive for lipid vacuoles with Oil Red, more readily on PS–MBP–bFGF than on TCP. In contrast, hASC hardly differentiated into osteoblast on PS–MBP–bFGF or on TCP. These results suggest that the mechanism of hASC adhesion to MBP–bFGF immobilized on a PS substrate is mediated by a specific interaction between bFGF and heparin, and that the adhesion mechanism might provide an insight into the design of biomaterials to control the fate of stem cells.

This study investigates the use of Monte Carlo simulation for the determination of release properties from cubic inert matrices. Specifically, the study has focused on factors including porosity, surface area and tortuosity. The release platform was formed by simulating matrices with different ratios of drug and excipient, which undergo drug release in a uni-directional (two-face) or omni-directional (six-face) process. Upon completion of each simulation the matrix ‘carcass’ was examined and porosity and tortuosity of the medium evaluated. The tortuosity of the medium was evaluated directly by a blind random walk algorithm. These parameters as well as the release profile were then studied with respect to common mathematical models describing drug diffusion (the square-root, power and Weibull models). It was found that, depending on their composition, the matrices systems were either homogeneous or heterogeneous in nature. Furthermore, it was found that the physical parameters could be successfully fitted to the a and b constants of the Weibull model. This approach allows the prediction of drug release from an inert matrix system with the knowledge of a few physical parameters.

Computational Fluid Dynamics (CFD) and Discrete Element Modelling (DEM) studies relevant to inhaled drug delivery are reviewed. CFD is widely used in device design to determine airflow patterns and turbulence levels. CFD is also used to simulate particles and droplets, which are subjected to various forces, turbulence and wall interactions. These studies can now be performed routinely because of the availability of commercial software containing high quality turbulence and particle models.

DEM allows for the modelling of agglomerate break-up upon interaction with a wall or due to shear in the flow. However, the computational cost is high and the number of particles that can be simulated is minimal compared with the number present in typical inhaled formulations. Therefore DEM is currently limited to fundamental studies of break-up mechanisms.

With decreasing computational limitations, simulations combining CFD and DEM that can address outstanding issues in agglomerate break-up and dispersion will be possible.

Inverse gas chromatography (IGC) is a sensitive technique for the measurement of powder surface properties, especially surface energetics. Given the importance of these characteristics to the performance of dry powder inhaler formulations (DPIs), it is unsurprising that IGC has been applied to the study of these systems. Monitoring batch-to-batch variation and the effects of processing steps are established uses of IGC in this field and the relevant studies are discussed. A less established use of IGC is for the prediction of DPI performance. Although some groups have found a negative relationship between the dispersive surface energy of one formulation component and fine particle delivery, such studies often have a number of limitations. More complex approaches have failed to produce consistent results. Further, more carefully designed, studies are required in this area. In the final section of this article, some areas for on-going research are discussed, including the need to critically assess the best method for the calculation of the specific free energy of adsorption with pharmaceutical materials.