Formulation Design of Dry Powders for Inhalation

Generation of High Dose Inhalable Effervescent Dispersions against Pseudomonas aeruginosa Biofilms

PURPOSE

Novel particle engineering approach was used in this study to generate high dose inhalable effervescent particles with synergistic effects against Pseudomonas aeruginosa biofilms.

METHODS

Spray dried co-amorphous salt of ciprofloxacin (CFX) and tartaric acid (TA) was prepared and coated with external layer of sodium bicarbonate and silica coated silver nanobeads. Design of experiments (DOE) was used to optimize physicochemical properties of particles for enhanced lung deposition.

RESULTS

Generated particles were co-amorphous CFX/TA showing that CFX lost its zwitterionic form and exhibiting distinct properties to CFX/HCl as assessed by FTIR and thermal analysis. Particles exhibited mass mean aerodynamic diameter (MMAD) of 3.3 μm, emitted dose of 78% and fine particle dose of 85%. Particles were further evaluated via antimicrobial assessment of minimum inhibitory concentrations (MIC) and minimum biofilm eradication concentration (MBEC). MIC and MBEC results showed that the hybrid particles were around 3-5 times more effective when compared to CFX signifying that synergistic effect was achieved. Diffusing wave spectroscopy results showed that the silver containing particles had a disruptive effect on rheological properties as opposed to silver free particles.

CONCLUSIONS

Overall, these results showed the potential to use particle engineering to generate particles that are highly disruptive of bacterial biofilms.

Performance tuning of particle engineered mannitol in dry powder inhalation formulations

Typically, smooth lactose particles are used as carrier in dry powder formulations for inhalation. Two classical approaches to improve their aerodynamic behaviour are the addition of fines (milled lactose) or magnesium stearate (MgSt). Mannitol (Parteck® M DPI) as an alternative carrier was used in this study. It has an irregular particle size distribution and a large and rough surface. This could be challenging for the detachment of micronised drug upon inhalation and it is unclear whether classic strategies for the optimisation of aerodynamic performance can be applied. In contrast, its rough surface could be an advantage in terms of drug load. To address these questions, the mannitol carrier was blended with two different drugs using various concentrations up to 50%. Self-produced mannitol fines and MgSt in different amounts and in combination were added. Blends were investigated regarding their in vitro aerodynamic performance, dosing behaviour and powder rheology. An addition of up to 30% drug load was possible while retaining good flowability and constant dosing behaviour. Despite the rough and indented carrier surface of the mannitol carrier, the addition of fines or MgSt increased the inhalable fraction, but higher concentrations of fines, as used for lactose blends, were necessary.

Computational Fluid Dynamics (CFD) Simulations of Spray Drying: Linking Drying Parameters with Experimental Aerosolization Performance

PURPOSE

The purpose of this study was to develop a new computational fluid dynamics (CFD)-based model of the complex transport and droplet drying kinetics within a laboratory-scale spray dryer, and relate CFD-predicted drying parameters to powder aerosolization metrics from a reference dry powder inhaler (DPI).

METHODS

A CFD model of the Buchi Nano Spray Dryer B-90 was developed that captured spray dryer conditions from a previous experimental study producing excipient enhanced growth powders with L-leucine as a dispersion enhancer. The CFD model accounted for two-way heat and mass transfer coupling between the phases and turbulent flow created by acoustic streaming from the mesh nebulizer. CFD-based drying parameters were averaged across all droplets in each spray dryer case and included droplet time-averaged drying rate (κ_avg), maximum instantaneous drying rate (κ_max) and precipitation window.

RESULTS

CFD results highlighted a chaotic drying environment in which time-averaged droplet drying rates (κ_avg) for each spray dryer case had high variability with coefficients of variation in the range of 60-70%. Maximum instantaneous droplet drying rates (κ_max) were discovered that were two orders of magnitude above time-averaged drying rates. Comparing CFD-predicted drying parameters with experimentally determined mass median aerodynamic diameters (MMAD) and emitted doses (ED) from a reference DPI produced strong linear correlations with coefficients of determination as high as R² = 0.98.

CONCLUSIONS

For the spray dryer system and conditions considered, reducing the CFD-predicted maximum drying rate experienced by droplets improved the aerosolization performance (both MMAD and ED) when the powders were aerosolized with a reference DPI.

Naringenin-Loaded Dipalmitoylphosphatidylcholine Phytosome Dry Powders for Inhaled Treatment of Acute Lung Injury

Background: Acute lung injury is a severe respiratory disorder characterized by overwhelming lung inflammation. Dipalmitoylphosphatidylcholine (DPPC) is the major lipid component of pulmonary surfactant, which here acts as a carrier delivery system for drugs, while also preserving surface tension in the lung. The clinical development of naringenin (NG) is limited by its low solubility and bioavailability. Methods: Novel NG-loaded DPPC phytosomes for dry powder inhalation (NPDPIs) were prepared by solvent evaporation and a freeze-drying method. The particle size, electric potential, in vitro release, and lung deposition were characterized. A rat model of acute lung injury was established and used for pharmacodynamic evaluations. Results: A mixture of NG/DPPC 1:2 (w/w) formed stable phytosomes with the addition of appropriate ethanol. The phytosomes had high complexation efficiency (92.1% ± 1.87%) with NG, a small mean size (150.8 ± 6.9 nm), and a high zeta potential (20.97 ± 0.55 mV). NPDPIs composed of mannitol/DPPC/NG (4:2:1, w/w/w) presented a satisfactory appearance, good fluidity, quick reconstitution to naringenin phytosomes (NGPs), and small (167.2 nm) reconstituted NGPs. The aerodynamic diameter (12.48 μm) and fine particle fraction (23.90%) were suitable for pulmonary delivery by inhalation. The in vivo NPDPIs demonstrated efficacy in a rat model of acute lung injury. NPDPIs significantly inhibited the phosphorylation of P38 in the mitogen-activated protein kinase pathway and suppressed oxidative stress. Surprisingly, the DPPC vehicle exhibited potential effects against acute lung injury by protecting respiratory function. Conclusions: NPDPIs were developed for sustained drug release, promoting pulmonary bioavailability of drug and protecting against acid-induced acute lung injury in rats by pulmonary delivery. NPDPIs are a promising dry powder inhaler for clinical application in acute lung injury.

Comparison of Phospholipid-Based Particles for Sustained Release of Ciprofloxacin Following Pulmonary Administration to Bronchiectasis Patients

The rapid clearance of ciprofloxacin hydrochloride from the lungs following administration as an aerosol leads to poor efficacy in the treatment of pulmonary infections. The development of formulations capable of sustaining ciprofloxacin concentrations in the lungs has the potential to significantly improve antibacterial activity. The present review compares two approaches for sustaining levels of ciprofloxacin in the lungs, a liposomal formulation where ciprofloxacin is encapsulated in small unilamellar vesicles, and a dry powder formulation of the practically insoluble zwitterionic form of the drug. These two formulations recently completed large multicenter, phase 3 clinical studies in bronchiectasis patients. As such, they present a unique opportunity to examine the chemistry, manufacturing, and control of the dosage forms in addition to their tolerability and efficacy in more than 1000 bronchiectasis patients. Both formulations were generally well tolerated with most adverse events found to be mild to moderate in intensity. While the formulations were effective in reducing and/or eradicating infections, this did not lead to reductions in pulmonary exacerbations, the primary endpoint. The failures speak more to the heterogeneous nature of the disease and the difficulty in identifying bronchiectasis patients likely to exacerbate, rather than an inherent limitation of the formulations. While the formulations are similar in many respects, they also present some interesting differences. This review explores the implications of these differences on the treatment of respiratory infections.

Effect of Particle Formation Process on Characteristics and Aerosol Performance of Respirable Protein Powders

Pulmonary delivery of biopharmaceuticals may enable targeted local therapeutic effect and noninvasive systemic administration. Dry powder inhaler (DPI) delivery is an established patient-friendly approach for delivering large molecules to the lungs; however, the complexities of balancing protein stability with aerosol performance require that the design space of biopharmaceutical DPI formulations is rigorously explored. Utilizing four rationally selected formulations obtained using identical atomization conditions, an extensive study of the effect of the particle formation process (spray drying or spray freeze-drying) on powder properties, aerosol performance, and protein stability was performed. Multiple linear regression analysis was used to understand the relationship between powder properties, device dispersion mechanism, and aerosol performance. Spray drying and spray freeze-drying, despite the same spraying conditions, produced powders with vastly different physical characteristics, though similar aerosol performance. The resulting regression model points to the significance of particle size, density, and surface properties on the resulting aerosol performance, with these factors weighing differently according to the device dispersion mechanism utilized (shear-based or impaction-based). The physical properties of the produced spray dried and spray freeze-dried powders have differing implications for long-term stability, which will be explored extensively in a future study.

Sustained release of a model water-soluble compound via dry powder aerosolizable acetalated dextran microparticles

Objective: To design and characterize aerosol microparticles (MP) to provide sustained release of the water-soluble compound sulforhodamine B (SRB) and achieve effective aerosol dispersion. Significance: Modulating the release of water-soluble compounds remains a challenge in pulmonary drug delivery. Methods: SRB and water made up an aqueous solution, while acetalated dextran (Ac-Dex) and isopropyl alcohol made up an organic solution. The two solutions were mixed together, and the solution was spray dried to produce MP. MP were characterized for morphology, size, release kinetics, aerosol dispersion, and cellular interactions. Results: Ac-Dex MP exhibited corrugated morphology and aerodynamic diameters from 2.06 to 2.86 μm. MP deposited in all stages of a Next Generation Impactor, with >90% fine particle fraction. MP exhibited encapsulation efficiencies >129% with SRB loading values up to 16.7 μg SRB/mg MP. MP exhibited sustained release of SRB at pH 7 and fast release at pH 5. In vitro experiments showed minimal cytotoxicity, successful uptake of MP in epithelial cells, and no disruption to the integrity of epithelial monolayers. Conclusions: Ac-Dex MP systems demonstrated the ability to provide sustained the release of a water-soluble therapeutic in addition to effective aerosol dispersion for pulmonary applications.

A Design of Experiment (DoE) approach to optimise spray drying process conditions for the production of trehalose/leucine formulations with application in pulmonary delivery

The present study evaluates the effect of L-leucine concentration and operating parameters of a laboratory spray dryer on characteristics of trehalose dry powders, with the goal of optimizing production of these powders for inhaled drug delivery. Trehalose/L-leucine mixtures were spray dried from aqueous solution using a laboratory spray dryer. A factorial design of experiment (DoE) was undertaken and process parameters adjusted were: inlet temperature, gas flow rate, feed solution flow rate (pump setting), aspiration setting and L-leucine concentration. Resulting powders were characterised in terms of particle size, yield, residual moisture content, and glass transition temperature. Particle size was mainly influenced by gas flow rate, whereas product yield and residual moisture content were found to be primarily affected by inlet temperature and spray solution feed rate respectively. Interactions between a number of different process parameters were elucidated, as were relationships between different responses. The leucine mass ratio influenced the physical stability of powders against environmental humidity, and a high leucine concentration (30% w/w) protected amorphous trehalose from moisture induced crystallization. High weight ratio of leucine in the formulation, however, negatively impacted the aerosol performance. Thus, in terms of L-leucine inclusion in a formulation designed for pulmonary delivery, a balance needs to be found between physical stability and deposition characteristics.

Linking carrier morphology to the powder mechanics of adhesive mixtures for dry powder inhalers via a blend-state model

The aim of this study was to investigate how the carrier morphology affects the expression of blend states in adhesive mixtures as a function of surface coverage ratio (SCR) and to identify where transitions between the different states occur. Adhesive mixtures of five lactose carriers with varying contents of lactose fines, corresponding to blends with different SCR ranging from 0 to 6, were produced by low-shear mixing. The powder mechanics of the mixtures were characterized by bulk density, compressibility and permeability. The appearance of the carriers and blends was studied by scanning electron microscopy, light microscopy and atomic force microscopy. The size and morphology of the carriers had a crucial impact on the evolution of the blend state, and affected the powder mechanical properties of the mixtures. It was found that smaller carriers with little or no surface irregularities were more sensitive to additions of fines resulting in self-agglomeration of fines at relatively low SCR values. On the contrary, carriers with irregular surface structures and larger sizes were able to reach higher SCR values before self-agglomeration of fines occurred. This could be attributed to an increased deagglomeration efficiency of irregular and larger carriers and to fines predominantly adhering to open pores.

Spray-Dried PulmoSphere™ Formulations for Inhalation Comprising Crystalline Drug Particles

Over the past 20 years, solution-based spray dried powders have transformed inhaled product development, enabling aerosol delivery of a wider variety of molecules as dry powders. These include inhaled proteins for systemic action (e.g., Exubera®) and high-dose inhaled antibiotics (e.g., TOBI® Podhaler™). Although engineered particles provide several key advantages over traditional powder processing technologies (e.g., spheronized particles and lactose blends), the physicochemical stability of the amorphous drug present in these formulations brings along its own unique set of constraints. To this end, a number of approaches have been developed to maintain the crystallinity of drugs throughout the spray drying process. One approach is to spray dry suspensions of micronized drug(s) from a liquid feed. In this method, minimization of drug particle dissolution in the liquid feed is critical, as dissolved drug is converted into amorphous domains in the spray-dried drug product. The review explores multiple formulation and engineering strategies for decreasing drug dissolution independent of the physicochemical properties of the drug(s). Strategies to minimize particle dissolution include spray blending of particles of different compositions, formation of respirable agglomerates of micronized drug with small porous carrier particles, and use of common ions. The formulations extend the range of doses that can be delivered with a portable inhaler from about 100 ng to 100 mg. The spray-dried particles exhibit significant advantages in terms of lung targeting and dose consistency relative to conventional lactose blends, while still maintaining the crystallinity of drug(s) in the formulated drug product.

Pulmonary drug delivery to older people

Pulmonary diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are common in older people. Treatment principles are well established in this group of patients; however, inadequate training and improper inhaler techniques often results in poor treatment outcomes. Healthcare professionals often do not have the required knowledge about the most common inhaler devices. Age-related conditions like cognitive ability and physical strength would also impact on the inhaler usage. Pharmacokinetics and pharmacodynamics may be affected by physiological changes, like impaired renal and hepatic functions and reduced lung functions. Adjusting and optimizing the inhaler device to the patient preferences, improvement of the drug formulation and inhalers, and using different adherence strategies might improve the treatment outcomes in elderly patients.

Improved Physical Stability and Aerosolization of Inhalable Amorphous Ciprofloxacin Powder Formulations by Incorporating Synergistic Colistin

This study aimed to develop dry powder inhaler (DPI) combination formulations of ciprofloxacin and colistin for use in respiratory infections. Effects of colistin on physical stability and aerosolization of spray-dried ciprofloxacin were examined. The combination DPI formulations were produced by co-spray drying colistin and ciprofloxacin in mass ratios of 1:1, 1:3, and 1:9. Colistin and ciprofloxacin were also co-sprayed with l-leucine in the mass ratio of 1:1:1. The physical and aerosolization stability of the selected co-sprayed formulations stored at 20, 55, and 75% relative humidity (RH) were examined. Formulation characterizations were carried out using powder X-ray diffraction (PXRD) for crystallinity, scanning electron microscopy for morphology and particle size distribution, and dynamic vapor sorption for moisture sorption. Particle surface analysis was performed using X-ray photoelectron spectroscopy, energy dispersive X-ray spectrometry, and nano-time-of-flight secondary ion mass spectrometry. Potential intermolecular interactions were studied using Fourier-transform infrared spectroscopy (FTIR). Aerosol performance was evaluated using a multistage liquid impinger with a RS01 monodose inhaler device. PXRD diffractograms showed that the co-spray-dried colistin-ciprofloxacin formulation in the mass ratio (1:1) was amorphous at 55% RH for up to 60 days; whereas the co-spray-dried colistin-ciprofloxacin (1:3) and colistin-ciprofloxacin (1:9) crystallized after storage for 3 days at 55% RH. However, the extent of crystallization for the combination formulations was less as compared to the spray-dried ciprofloxacin alone formulation. Surface morphology of the co-spray-dried formulations at different concentrations did not change even after storage at 55% RH for 60 days, unlike the spray-dried ciprofloxacin alone powder which became rougher after 3 days of storage at 55% RH. Surface analysis data indicated surface enrichment of colistin in the co-spray-dried formulations. Increasing colistin concentration on the composite particles surfaces improved aerosol performance of ciprofloxacin. FTIR data demonstrated intermolecular interactions between colistin and ciprofloxacin, thereby delaying and/or preventing crystallization of ciprofloxacin when co-spray-dried. Co-spray drying ciprofloxacin with colistin in the mass ratio (1:1) completely prevented crystallization of ciprofloxacin at 55% RH for up to 60 days. However, the colistin-ciprofloxacin formulation (1:1) began to fuse when stored at 75% RH due to moisture absorption resulting in a compromised aerosol performance. In contrast, the colistin-ciprofloxacin-leucine (1:1:1) formulation demonstrated no particle fusion, enabling a stable aerosol performance at 75% RH for 7 days. This study demonstrated that incorporation of colistin in the spray-dried formulations can improve physical stability and aerosolization of amorphous ciprofloxacin at 55% RH. At 75% RH, further addition of l-leucine in the formulation prevented particle fusion and deterioration in aerosol performance, attributed to the enrichment of nonhygroscopic l-leucine on the particle surface.

Formulation of High-Performance Dry Powder Aerosols for Pulmonary Protein Delivery

PURPOSE

Pulmonary delivery of biologics is of great interest, as it can be used for the local treatment of respiratory diseases or as a route to systemic drug delivery. To reach the full potential of inhaled biologics, a formulation platform capable of producing high performance aerosols without altering protein native structure is required.

METHODS

A formulation strategy using Particle Replication in Non-wetting Templates (PRINT) was developed to produce protein dry powders with precisely engineered particle morphology. Stability of the incorporated proteins was characterized and the aerosol properties of the protein dry powders was evaluated in vitro with an Andersen Cascade Impactor (ACI).

RESULTS

Model proteins bovine serum albumin (BSA) and lysozyme were micromolded into 1 μm cylinders composed of more than 80% protein, by mass. Extensive characterization of the incorporated proteins found no evidence of alteration of native structures. The BSA formulation produced a mass median aerodynamic diameter (MMAD) of 1.77 μm ± 0.06 and a geometric standard deviation (GSD) of 1.51 ± 0.06 while the lysozyme formulation had an MMAD of 1.83 μm ± 0.12 and a GSD of 1.44 ± 0.03.

CONCLUSION

Protein dry powders manufactured with PRINT could enable high-performance delivery of protein therapeutics to the lungs.

Drying Technologies for the Stability and Bioavailability of Biopharmaceuticals

Solid dosage forms of biopharmaceuticals such as therapeutic proteins could provide enhanced bioavailability, improved storage stability, as well as expanded alternatives to parenteral administration. Although numerous drying methods have been used for preparing dried protein powders, choosing a suitable drying technique remains a challenge. In this review, the most frequent drying methods, such as freeze drying, spray drying, spray freeze drying, and supercritical fluid drying, for improving the stability and bioavailability of therapeutic proteins, are discussed. These technologies can prepare protein formulations for different applications as they produce particles with different sizes and morphologies. Proper drying methods are chosen, and the critical process parameters are optimized based on the proposed route of drug administration and the required pharmacokinetics. In an optimized drying procedure, the screening of formulations according to their protein properties is performed to prepare a stable protein formulation for various delivery systems, including pulmonary, nasal, and sustained-release applications.

Formulation techniques for high dose dry powders

Delivery of drugs to the lungs via dry powder inhaler (DPI) is a promising approach for the treatment of both local pulmonary conditions and systemic diseases. Though DPIs are widely used for the pulmonary deposition of potent bronchodilators, anticholinergics, and corticosteroids, there is growing interest in the utilization of this delivery system for the administration of high drug doses to the lungs, as made evident by recent regulatory approvals for anti-microbial, anti-viral and osmotic agents. However, the formulation of high dose DPIs carries several challenges from both a physiological and physicochemical standpoint. This review describes the various formulation techniques utilized to overcome the barriers associated with the pulmonary delivery of high dose powders.

Relationships between surface coverage ratio and powder mechanics of binary adhesive mixtures for dry powder inhalers

The aim of this paper was to study relationships between the content of fine particles and the powder mechanics of binary adhesive mixtures and link these relationships to the blend state. Mixtures with increasing amounts of fine particles (increasing surface coverage ratios (SCR)) were prepared using Lactopress SD as carrier and micro particles of lactose as fines (2.7 µm). Indicators of unsettled bulk density, compressibility and flowability were derived and the blend state was visually examined by imaging. The powder properties studied showed relationships to the SCR characterised by stages. At low SCR, the fine particles predominantly gathered in cavities of the carriers, giving increased bulk density and unchanged or improved flow. Thereafter, increased SCR gave a deposition of particles at the enveloped carrier surface with a gradually more irregular adhesion layer leading to a reduced bulk density and a step-wise reduced flowability. The mechanics of the mixtures at a certain stage were dependent on the structure and the dynamics of the adhesion layer and transitions between the stages were controlled by the evolution of the adhesion layer. It is advisable to use techniques based on different types of flow in order to comprehensively study the mechanics of adhesive mixtures.

Protective effect of sodium stearate on the moisture-induced deterioration of hygroscopic spray-dried powders

Amorphous powders are thermodynamically unstable, significantly impacting the processing, storage and performance of a product. Therefore, stabilization of the amorphous contents is in demand. In this study, disodium cromoglycate (DSCG) powder was chosen as a model drug because it is amorphous and highly hygroscopic after spray drying. Sodium stearate (NaSt) was co-spray dried with DSCG at various concentrations (10, 50 and 90% w/w) to investigate its effect against moisture-induced deterioration on the in vitro aerosolization performance of DSCG. Particle size distribution and morphology were measured by laser diffraction and scanning electron microscopy (SEM). Physicochemical properties of the powders were analysed by X-ray powder diffraction (XRPD) and dynamic vapour sorption (DVS). Particle surface chemistry was analysed by the time-of-flight secondary ion mass spectrometry (ToF-SIMS). In vitro dissolution behaviours of the spray-dried (SD) powders were tested by the Franz cell apparatus. In vitro aerosolization performance of SD formulations stored at different relative humidity (RH) was evaluated by a multi-stage liquid impinger (MSLI), using an Osmohaler® at 100 L/min. Results showed that adding NaSt in the formulation not only increased the aerosolization performance of DSCG significantly, but also effectively reduced the deleterious impact of moisture. No significant difference was found in the fine particle fraction (FPF) of formulations containing NaSt before and after storage at both 60% and 75% RH for one week. However, after one month storage at 75% RH, SD formulation containing 10% NaSt showed a reduction in FPF, while formulations containing 50% or 90% NaSt showed no change. The underlying mechanism was that NaSt increased the crystallinity of the powders and its presence on the particle surface reduced particle aggregations and cohesiveness. However, NaSt at high concentration could reduce dissolution rate, which needs to be taken into consideration.

Electrohydrodynamic methods for the development of pulmonary drug delivery systems

Electrospinning and electrospraying are two highly versatile and scalable electrohydrodynamic methods, which have attracted considerable attention during the last years towards the fabrication of polymer-based drug delivery systems. The latter may be obtained in the form of nano- or microfibers (via electrospinning) or as drug-loaded nano- and microparticles (via electrospraying). This review article begins with an introduction on the basic principles and the important influencing parameters governing the electrospinning/electrospraying processes, followed by an overview on their use for the development of nano/microfibers and nano/microparticles destined for use in pharmaceutical applications. Focus is given on research efforts targeting in the formulation of drug delivery systems and devices designed for pulmonary drug delivery applications thus emphasizing on the potential use of electrospinning and electrospraying in the area of inhaled medicines.

Protection of hydrophobic amino acids against moisture-induced deterioration in the aerosolization performance of highly hygroscopic spray-dried powders

BACKGROUND

Inhalable particles containing amorphous form of drugs or excipients may absorb atmospheric moisture, causing powder aggregation and recrystallization, adversely affecting powder dispersion and lung deposition. The present study aims to explore hydrophobic amino acids for protection against moisture in spray-dried amorphous powders, using disodium cromoglycate (DSCG) as a model drug.

MATERIALS AND METHODS

DSCG powders were produced by co-spray drying with isoleucine (Ile), valine (Val) and methionine (Met) in various concentrations (10, 20 and 40%w/w). Particle size distribution and morphology were measured by laser diffraction and scanning electron microscopy (SEM). Physiochemical properties of the powders were characterized by X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic vapor sorption (DVS). Particle surface chemistry was analyzed by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). In vitro aerosolization performance was evaluated by a next generation impactor (NGI) after the powders were stored at 60% or 75% relative humidity (RH) for one month and three months.

RESULTS AND DISCUSSION

Ile, Val and Met significantly reduced the deleterious effect of moisture on aerosol performance, depending on the amount of amino acids in the formulation. Formulations containing 10% or 20% of Ile, Val and Met showed notable deterioration in aerosol performance, with fine particle fraction (FPF) reduced by 6-15% after one-month storage at both 60% and 75% RH. However, 40% Ile was able to maintain the aerosol performance of DSCG stored at 75% RH for one month, while the FPF dropped by 7.5% after three months of storage. In contrast, 40% Val or Met were able to maintain the aerosol performance at 60% RH storage but not at 75% RH. At 40%w/w ratio, these formulations had particle surface coverage of 94.5% (molar percent) of Ile, 87.1% of Val and 84.6% of Met, respectively, which may explain their moisture protection effects.

CONCLUSION

Ile, Val and Met showed promising moisture protection effect on aerosol performance. The results broaden the understanding on the use of hydrophobic amino acids as an excipient for long-term storage of inhalation powders formulations that are hygroscopic.

The Impact of Inspiratory Flow Rate on Drug Delivery to the Lungs with Dry Powder Inhalers

Current marketed dry powder inhalers utilize the energy from patient inspiration to fluidize and disperse bulk powder agglomerates into respirable particles. Variations in patient inspiratory flow profiles can lead to marked differences in total lung dose (TLD), and ultimately patient outcomes for an inhaled therapeutic. The present review aims to quantitate the flow rate dependence in TLD observed for a number of drug/device combinations using a new metric termed the Q index. With this data in hand, the review explores key attributes in the design of the formulation and device that impact flow rate dependence. The review also proposes alternative in vitro methods to assess flow rate dependence that more closely align with in vivo observations. Finally, the impact of variations in flow rate on lung function for inhaled bronchodilators is summarized.

Development of a microparticle-based dry powder inhalation formulation of ciprofloxacin hydrochloride applying the quality by design approach

Pulmonary drug delivery of ciprofloxacin hydrochloride offers effective local antibacterial activity and convenience of easy application. Spray drying is a trustworthy technique for the production of ciprofloxacin hydrochloride microparticles. Quality by design (QbD), an up-to-date regulatory-based quality management method, was used to predict the final quality of the product. According to the QbD-based theoretical preliminary parameter ranking and priority classification, dry powder inhalation formulation tests were successfully performed in practice. When focusing on the critical parameters, the practical development was more effective and was in correlation with our previous findings. Spray drying produced spherical microparticles. The dry powder formulations prepared were examined by particle size analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray powder diffraction, differential scanning calorimetry, and in vitro drug release and aerodynamic particle size analyses were also performed. These formulations showed an appropriate particle size ranging between 2 and 4 μm and displayed an enhanced aerosol performance with fine particle fraction up to 80%.

L-Leucine as an excipient against moisture on in vitro aerosolization performances of highly hygroscopic spray-dried powders

L-Leucine (LL) has been widely used to enhance the dispersion performance of powders for inhalation. LL can also protect powders against moisture, but this effect is much less studied. The aim of this study was to investigate whether LL could prevent moisture-induced deterioration in in vitro aerosolization performances of highly hygroscopic spray-dried powders. Disodium cromoglycate (DSCG) was chosen as a model drug and different amounts of LL (2-40% w/w) were added to the formulation, with the aim to explore the relationship between powder dispersion, moisture protection and physicochemical properties of the powders. The powder formulations were prepared by spray drying of aqueous solutions containing known concentrations of DSCG and LL. The particle sizes were measured by laser diffraction. The physicochemical properties of fine particles were characterized by X-ray powder diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic vapor sorption (DVS). The surface morphology and chemistry of fine particles were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). In vitro aerosolization performances were evaluated by a next generation impactor (NGI) after the powders were stored at 60% or 75% relative humidity (RH), and 25°C for 24h. Spray-dried (SD) DSCG powders were amorphous and absorbed 30-45% (w/w) water at 70-80% RH, resulting in deterioration in the aerosolization performance of the powders. LL did not decrease the water uptake of DSCG powders, but it could significantly reduce the effect of moisture on aerosolization performances. This is due to enrichment of crystalline LL on the surface of the composite particles. The effect was directly related to the percentage of LL coverage on the surface of particles. Formulations having 61-73% (molar percent) of LL on the particle surface (which correspond to 10-20% (w/w) of LL in the bulk powders) could minimize moisture-induced deterioration in the aerosol performance. In conclusion, particle surface coverage of LL can offer short-term protection against moisture on dispersion of hygroscopic powders.