Elucidation of lactose fine size and drug shape on rheological properties and aerodynamic behavior of dry powders for inhalation

Development of Novel Fluticasone/Salmeterol/Tiotropium-Loaded Dry Powder Inhaler and Bioequivalence Assessment to Commercial Products in Rats

Background/Objectives: Inhaler devices have been developed for the effective delivery of inhaled medications used in the treatment of pulmonary diseases. However, differing operating procedures across the devices can lead to user errors and reduce treatment efficacy, especially when patients use multiple devices simultaneously. To address this, we developed a novel dry powder inhaler (DPI), combining fluticasone propionate (FP), salmeterol xinafoate (SX), and tiotropium bromide (TB) into a single device designed for bioequivalent delivery compared to existing commercial products in an animal model. Methods: The micronized FP/SX/TB-loaded capsule was prepared by sieving, blending, and filling capsules. Capsule suitability of the drugs was investigated from the comparison of the stability of drugs within various capsule formulations to that of commercial products. The particle size of the drugs was adjusted using spiral air jet milling, and the ratio of lactose hydrate carriers was optimized by comparing the aerodynamic particle size distribution (APSD) with that of commercial products. To investigate the bioequivalence of micronized FP/SX/TB-loaded DPI to commercial products, the dissolution profile of FP/SX/TB particles and pharmacokinetics in rats were evaluated and compared to commercial products. Results: Capsules with hydroxypropyl methylcellulose (HPMC) without a gelling agent showed superior stability of the drugs compared to commercial products. The deposition pattern was influenced by the particle size of the drugs, and fine particle mass exhibited a significant correlation with the amount of fine carrier. Micronized FP/SX/TB-loaded DPI gave a similar APSD and dissolution profile compared to the commercial products and showed dose uniformity by the DPI device. Furthermore, micronized FP/SX/TB-loaded DPI exhibited bioequivalence to commercial products, as evidenced by no significant differences in pharmacokinetic parameters following intratracheal administration in rats. Conclusions: A novel triple-combination DPI containing FP/SX/TB was successfully developed, demonstrating comparable pharmacological performance to commercial products. Optimized FP/SX/TB-loaded DPI with HPMC capsule achieved bioequivalence in rat studies, suggesting its potential for improved patient compliance and therapeutic outcomes. This novel single-device DPI offers a promising alternative for triple therapy in pulmonary diseases.

Effect of lubricants type and particle size on the rheological properties and aerosolization behavior of dry powder inhalers

A commonly used strategy to improve aerosolization behavior of carrier-based dry powder inhalers (DPIs) is the addition of magnesium stearate as a lubricant, yet it may also negatively affect properties of DPIs. Thus, the aim of this study was to find lubricants that could be used as alternatives of magnesium stearate and meanwhile verify the applicability of using powder rheological properties to predict the performance of different lubricants in DPIs. Here, using fluticasone propionate as a model drug, LH200 as the carrier, influence of lubricants type and particle size, including magnesium stearate, sodium stearate, Leucine, sodium stearate fumarate, Compritol® 888 ATO, and Compritol® HD5 ATO, on the physicochemical properties, powder rheology and aerosolization behavior of the DPI formulations was characterized. Further, the relationship between powder rheological parameters and in-vitro drug deposition parameter, fine particle fraction (FPF), were explored, and the contribution of powder flowability and adhesion was evaluated using principal component analysis (PCA). The results showed that magnesium stearate, sodium stearate and smaller sized leucine significantly reduced the basic flowability energy, aeration energy and Permeability of the DPI formulations, leading to improved aerosolization behavior. A robust linear correlation was established between rheological parameters and FPF. PCA showed that in lubricants containing formulations, the contribution of flowability (74.69%) was greater than that of adhesion (25.31%). In conclusion, sodium stearate and smaller particle size Leucine can be considered as substitutes of magnesium stearate in DPI formulations.

siRNA Nanoparticle Dry Powder Formulation with High Transfection Efficiency and Pulmonary Deposition for Acute Lung Injury Treatment

Acute lung injury (ALI) is a severe inflammatory syndrome, which was caused by diverse factors. The COVID-19 pandemic has resulted in a higher mortality rate of these conditions. Currently, effective treatments are lacking. Although siRNA nucleotide-based drugs are promising therapeutic approaches, their poor stability and inability to efficiently reach target cells limit their clinical translation. This study identified a peptide from known cell-penetrating peptides that can form an efficient anti-inflammatory complex with TNF-α siRNA, termed SAR6EW/TNF-α siRNA. This complex can effectively transport TNF-α siRNA into the cytoplasm and achieve potent gene silencing in vitro as well as in vivo. By using lactose and triarginine as coexcipients and optimizing the spray-drying process, a powder was produced with micrometer-scale spherical and porous structures, enhancing aerosol release and lung delivery efficiency. The dry powder formulation and process preserve the stability and integrity of the siRNA. When administered intratracheally to ALI model mice, the complex powder demonstrated specific pulmonary gene silencing activity and significantly reduced inflammation symptoms caused by ALI, suggesting a potential strategy for the clinical therapeutic approach of respiratory diseases.

Understanding the role of swirling flow in dry powder inhalers: Implications for design considerations and pulmonary delivery

Dry powder inhalers (DPIs) are widely employed to treat respiratory diseases, offering numerous advantages such as high dose capacity and stable formulations. However, they usually face challenges in achieving sufficient pulmonary drug delivery and minimizing excessive oropharyngeal deposition. This review provides a new viewpoint to address these challenges by focusing on the role of swirling flow, a crucial yet under-researched aspect that induces strong turbulence. In the review, we comprehensively discuss both key classic designs (tangential inlet, swirling chamber, grid mesh, and mouthpiece) and innovative designs in inhalers, exploring how the induced swirling flow initiates powder dispersion and promotes delivery efficiency. Valuable design considerations to effectively coordinate inhalers with formulations and patients are also provided. It is highlighted that the delicate manipulation of swirling flow is essential to maximize benefits. By emphasizing the role of swirling flow and its potential application, this review offers promising insights for advancing DPI technology and optimizing therapeutic outcomes in inhaled therapy.

Fine excipient materials in carrier-based dry powder inhalation formulations: The interplay of particle size and concentration effects

The contributions of fine excipient materials to drug dispersibility from carrier-based dry powder inhalation (DPI) formulations are well recognized, although they are not completely understood. To improve the understanding of these contributions, we investigated the influences of the particle size of the fine excipient materials on characteristics of carrier-based DPI formulations. We studied two particle size grades of silica microspheres, with volume median diameters of 3.31 μm and 8.14 μm, as fine excipient materials. Inhalation formulations, each composed of a lactose carrier material, one of the fine excipient materials (2.5% or 15.0% w/w), and a drug (fluticasone propionate) material (1.5% w/w) were prepared. The physical microstructure, the rheological properties, the aerosolization pattern, and the aerodynamic performance of the formulations were studied. At low concentration, the large silica microspheres had a more beneficial influence on the drug dispersibility than the small silica microspheres. At high concentration, only the small silica microspheres had a beneficial influence on the drug dispersibility. The results reveal influences of fine excipient materials on mixing mechanics. At low concentration, the fine particles improved deaggregation and distribution of the drug particles over the surfaces of the carrier particles. The large silica microspheres were associated with a greater mixing energy and a greater improvement in the drug dispersibility than the small silica microspheres. At high concentration, the large silica microspheres kneaded the drug particles onto the surfaces of the carrier particles and thus impaired the drug dispersibility. As a critical attribute of fine excipient materials in carrier-based dry powder inhalation formulations, the particle size demands robust specification setting.

Critical attributes of fine excipient materials in carrier-based dry powder inhalation formulations: The particle shape and surface properties

The potential of fine excipient materials to improve the aerodynamic performance of carrier-based dry powder inhalation (DPI) formulations is well acknowledged but not fully elucidated. To improve the understanding of this potential, we studied two fine excipient materials: micronized lactose particles and silica microspheres. Inhalation formulations, each composed of a coarse lactose carrier, one of the two fine excipient materials (0.0-15.0 % w/w), and a spray-dried drug (fluticasone propionate) material (1.5 % w/w) were prepared. The physical structure, the flow behavior, the aerosolization behavior, and the aerodynamic performance of the formulations were studied. The two fine excipient materials similarly occupied carrier surface macropores. However, only the micronized lactose particles formed agglomerates and appeared to increase the tensile strength of the formulations. At 2.5 % w/w, the two fine excipient materials similarly improved drug dispersibility, whereas at higher concentrations, the micronized lactose material was more beneficial than the silica microspheres. The findings suggest that fine excipient materials improve drug dispersibility from carrier-based DPI formulations at low concentrations by filling carrier surface macropores and at high concentrations by forming agglomerates and/or enforcing fluidization. The study emphasizes critical attributes of fine excipient materials in carrier-based DPI formulations.

Impact of high shear blending on distribution of magnesium stearate on lactose for dry powder inhaled formulations

The use of magnesium stearate along with lactose in Dry Powder Inhaler (DPI) formulations is increasing. The impact of different conditions of high shear blending on the distribution of magnesium stearate on lactose particles was investigated in this study. The formulated blends were manufactured using high shear blending of pre-blended coarse and fine lactose particles with 1.0% (w/w) magnesium stearate under different blending conditions, specifically blending speed and time. The effects of blending conditions on the distribution of magnesium stearate on lactose particles were clearly identifiable by characterizing the formulated blends by means of rheological evaluations, scanning electron microscopy, and chemical surface analysis using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Rheological properties were significantly affected in blends with magnesium stearate compared to blends without magnesium stearate. Blending speed exhibited a strong influence on the distribution of magnesium stearate on lactose surface, while blending time had relatively minor effect.

Exploring the influence of magnesium stearate content and mixing modality on the rheological properties and in vitro aerosolization of dry powder inhaler

Since carrier-based dry powder inhalers (DPIs) suffer from inadequate drug deposition in the lung, an increasing number of marketed products have added magnesium stearate (MgSt) to improve the aerosolization, dispersion, and stability against moisture of DPI. However, for carrier-based DPI, there is a lack of examination of the optimal MgSt content as well as the mixing modality, and there is also a need to verify the applicability of rheological properties to predict the in vitro aerosolization of DPI formulations containing MgSt. Therefore, in this work, DPI formulations were prepared using fluticasone propionate as a model drug and commercial crystalline lactose Respitose® SV003 as a carrier within 1% MgSt content, the effect of MgSt content on the rheological and aerodynamic properties were investigated. After the optimal MgSt content was determined, the effects of mixing modality, mixing order, and carrier size on formulation properties were further investigated. Meanwhile, correlations were established between rheological parameters and in vitro drug deposition parameters, and the contribution of rheological parameters were determined using principal component analysis (PCA). The results showed that the optimal content of MgSt in DPI formulations is 0.25%-0.5% under both high-shear and low-shear, using medium-sized carriers (D50 around 70 μm) and low-shear mixing are beneficial for improving in vitro aerosolization. Good linear relationships between powder rheological parameters such as basic flow energy (BFE), specific energy (SE), Permeability and fine particle fraction (FPF) were established, PCA showed that both flowability and adhesion are key properties affecting FPF. In conclusion, both MgSt content and mixing modality can influence rheological properties of the DPI, which can be used as a screeing tool for DPI formuluation and preparation process optimization.

Predicting in vitro lung deposition behavior of combined dry powder inhaler via rheological properties

Dry powder inhaler (DPI) for pulmonary delivery is currently the primary treatment for asthma and COPD (chronic obstructive pulmonary disease), an increasing number of combined DPIs (containing two or more drugs in one inhaler) have been developed to complement the effect of single DPIs. Based on our previous studies, the rheological properties can be a potential tool used to predict the in vitro lung deposition behavior of DPI formulations. However, it is unknown whether such a prediction model is suitable for combination systems. Therefore, this study aimed to verify the applicability of using powder rheological properties to predict in vitro drug deposition behavior in combined DPI formulations. Two drugs (fluticasone propionate and salmeterol xinafoate) and their combination of DPI formulations were prepared using fine lactose content (in the range of 1%-20%) as a variable. The physicochemical properties of the powder mixtures such as particle size and content uniformity were characterized. The rheological properties of the powder mixtures were measured by FT4 rheometer, the aerodynamic behavior of the DPI formulations was evaluated by a new generation impactor (NGI), and the effect of flowability and adhesion on the deposition of the fine particle fraction (FPF) was investigated by principal component analysis (PCA). The results showed that the combined DPI formulations with larger particle interaction forces have certain differences from the aerodynamic behavior of the single DPI formulations. The regularity of rheological properties affecting FPF revealed in single DPI is still applicable to combined DPI, the parameters basic flowability energy (BFE), representing flowability, and flow factor (ff), Cohesion representing adhesion, can be well linearly related to the FPF. The results of the principal component analysis showed that better flowability and suitable adhesion contributed to higher in vitro deposition of the drug in the formulation, and the contribution of adhesion (75.42%) was greater than that of flowability (24.58%). In conclusion, rheological properties is an effective tool for predicting the deposition behavior of DPI not only in single but also in combined DPIs.