Exploring the influence of drug content on DPI powder properties and potential prediction of pulmonary drug deposition

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.

Potential of Powder Rheology for Detecting Unforeseen Cross-Contamination of Foreign Active Pharmaceutical Ingredients

Unexpected cross-contamination by foreign components during the manufacturing and quality control of pharmaceutical products poses a serious threat to the stable supply of drugs and the safety of customers. In Japan, in 2020, a mix-up containing a sleeping drug went undetected by liquid chromatography during the final quality test because the test focused only on the main active pharmaceutical ingredient (API) and known impurities. In this study, we assessed the ability of a powder rheometer to analyze powder characteristics in detail to determine whether it can detect the influence of foreign APIs on powder flow. Aspirin, which was used as the host API, was combined with the guest APIs (acetaminophen from two manufacturers and albumin tannate) and subsequently subjected to shear and stability tests. The influence of known lubricants (magnesium stearate and leucine) on powder flow was also evaluated for standardized comparison. Using microscopic morphological analysis, the surface of the powder was observed to confirm physical interactions between the host and guest APIs. In most cases, the guest APIs were statistically detected due to characteristics such as their powder diameter, pre-milling, and cohesion properties. Furthermore, we evaluated the flowability of a formulation incorporating guest APIs for direct compression method along with additives such as microcrystalline cellulose, potato starch, and lactose. Even in the presence of several additives, the influence of the added guest APIs was successfully detected. In conclusion, powder rheometry is a promising method for ensuring stable product quality and reducing the risk of unforeseen cross-contamination by foreign APIs.

Drug combinations for inhalation: Current products and future development addressing disease control and patient compliance

Pulmonary delivery is an alternative route of administration with numerous advantages over conventional routes of administration. It provides low enzymatic exposure, fewer systemic side effects, no first-pass metabolism, and concentrated drug amounts at the site of the disease, making it an ideal route for the treatment of pulmonary diseases. Owing to the thin alveolar-capillary barrier, and large surface area that facilitates rapid absorption to the bloodstream in the lung, systemic delivery can be achieved as well. Administration of multiple drugs at one time became urgent to control chronic pulmonary diseases such as asthma and COPD, thus, development of drug combinations was proposed. Administration of medications with variable dosages from different inhalers leads to overburdening the patient and may cause low therapeutic intervention. Therefore, products that contain combined drugs to be delivered via a single inhaler have been developed to improve patient compliance, reduce different dose regimens, achieve higher disease control, and boost therapeutic effectiveness in some cases. This comprehensive review aimed to highlight the growth of drug combinations by inhalation over time, obstacles and challenges, and the possible progress to broaden the current options or to cover new indications in the future. Moreover, various pharmaceutical technologies in terms of formulation and device in correlation with inhaled combinations were discussed in this review. Hence, inhaled combination therapy is driven by the need to maintain and improve the quality of life for patients with chronic respiratory diseases; promoting drug combinations by inhalation to a higher level is a necessity.

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.

Sodium hyaluronate dry powder inhalation in combination with sodium cromoglycate prepared using optimized spray drying conditions

Sodium hyaluronate (SHA) is an anti-inflammatory and protective agent against bronchoconstriction, and sodium cromoglicate (SCG) prevents exercise-induced bronchoconstriction and inflammation. Based on the pharmacological properties of both substances, this study aimed to develop a dry powder inhaler (DPI) of SHA alone and in combination with SCG. The target of the study was to develop flowable formulations without any surfactants by using the spray drying method. To obtain respirable SHA and SCG:SHA particles, variables of the spray dryer, such as inlet temperature, atomized air flow, and feed solution, were changed. The particles 1-8 μm in size were produced with high yield by spray drying and increasing the ethanol percentage of the feed solution (60%), which is the most remarkable parameter. After that, physicochemical characterizations were performed. The aerosol performance of DPI formulations prepared using lactose was evaluated using Handihaler® DPI. The fine particle fraction (FPF) was 36% for the SHA formulation, whereas it was 52 and 53% for SCG and SHA, respectively, in the SCG:SHA formulation. Consequently, both particles were produced reproducibly by spray drying, and inhaled SHA and SCG:SHA dry powder formulations were developed due to their high FPF and flowability with lactose.

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.

The Study of Spray-Freeze-Drying Technique for Development of Novel Combination pMDIs, Part I: Study on the Preparation Method

Clinically available pressurized metered-dose inhalers (pMDIs) mainly directly use micronized drugs as inhalable microparticles. Although technology for preparing pMDIs has proven to obtain clinically appropriate aerosol performance, the fine particle fraction and delivered dose content uniformity (DDCU) of pMDIs still need to be improved. DDCU problem is usually exacerbated by patients' handling errors prior to taking a dose. In this study, novel phospholipid microparticle inhalation pMDIs were prepared by a spray-freeze-drying process using mometasone furoate and formoterol fumarate dihydrate as model drugs and distearoylphosphatidylcholine as an excipient. Combined with the material composition, the atomization and freeze-drying processes were also studied. Our data showed that both atomization parameters of gas–liquid ratio and freeze-drying curve settings met the requirements of drug design. According to aerodynamic performance in vitro and DDCU evaluation, the performance of the phospholipid microparticle inhalation pMDI was better than that of the micronized drug microparticle pMDI. In conclusion, preparing pMDIs with particle engineering has the potential to ensure accuracy of quantification and to improve the efficiency of drug deposition in lungs in clinical practice.

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

Pulmonary drug delivery has gained great attention in local or systemic diseases therapy, however it is still difficult to scale-up DPI production due to the complexity of interactions taking place in DPI systems and limited understanding between flowability and inter-particle interactions in DPI formulations. Therefore, finding some quantitative parameters related to DPI delivery performance for predicting the in vitro drug deposition behavior is essential. Therefore, this study introduces a potential model for predicting aerodynamic performance of carrier-based DPIs, as well to find more relevant fine powder size and optimal shape to improve aerodynamic performance. Using salbutamol sulfate as a model drug, Lactohale®206 as coarse carrier, Lactohale®300, Lactohale®230, and Lactohale®210 as third fine components individually, the mixtures were prepared at 1% (w/w) drug content accompanied with carriers and the third component (ranging from 3 - 7%), influence of lactose fines size on DPI formulation's rheological and aerodynamic properties was investigated. The optimum drug particle shape was also confirmed by computer fluid dynamics model. This study proved that pulmonary deposition efficiency could be improved by decreasing lactose fines size. Only fines in the size range of 0-11 μm have a good linear relationship with FPF, attributed to the fluidization energy enhancement and aggregates mechanism. Once exceeding 11 μm, fine lactose would act as a second carrier, with increased drug adhesion. Computational fluid dynamics (CFD) models indicated fibrous drug particles were beneficial to transfer to the deep lung. Furthermore, good correlations between rheological parameters and FPF of ternary mixtures with different lactose fines were established, and it was disclosed that the FPF was more dependent on interaction parameters than that of flowability.

Development of a Spray-Dried Formulation of Peptide-Dna Nanoparticles into a Dry Powder for Pulmonary Delivery Using Factorial Design

Background

Gene therapy via pulmonary delivery holds the potential to treat various lung pathologies. To date, spray drying has been the most promising method to produce inhalable powders. The present study determined the parameters required to spray dry nanoparticles (NPs) that contain the delivery peptide, termed RALA (N-WEARLARALARALARHLARALARALRACEA-C), complexed with plasmid DNA into a dry powder form designed for inhalation.

Methods

The spray drying process was optimised using full factorial design with 19 randomly ordered experiments based on the combination of four parameters and three centre points per block. Specifically, mannitol concentration, inlet temperature, spray rate, and spray frequency were varied to observe their effects on process yield, moisture content, a median of particle size distribution, Z-average, zeta potential, encapsulation efficiency of DNA NPs, and DNA recovery. The impact of mannitol concentration was also examined on the spray-dried NPs and evaluated via biological functionality in vitro.

Results

The results demonstrated that mannitol concentration was the strongest variable impacting all responses apart from encapsulation efficiency. All measured responses demonstrated a strong dependency on the experimental variables. Furthermore, spray drying with the optimal variables in combination with a low mannitol concentration (1% and 3%, w/v) produced functional RALA/pDNA NPs.

Conclusion

The optimal parameters have been determined to spray dry RALA/pDNA NPs into an dry powder with excellent biological functionality, which have the potential to be used for gene therapy applications via pulmonary delivery.

Elucidating the Effect of Fine Lactose Ratio on the Rheological Properties and Aerodynamic Behavior of Dry Powder for Inhalation

Dry powder inhaler (DPI) is recognized as the first choice for lung diseases' treatment. However, it lacks a universal way for DPI formulation development. Fine lactose is commonly added in DPIs to improve delivery performance; however, the fine ratio-dependent mechanism is unclear. Therefore, the objective of this study is to explore the influence of fine lactose ratio on DPI powder properties and aerodynamic behavior, and the fine lactose ratio-dependent mechanism involved during powder fluidization and lung deposition. Here salbutamol sulfate was used as a model drug, Lactohale® 206 as coarse carrier, and Lactohale® 300 as fine component; the mixtures were prepared at 1% drug content, with fine content up to 20%. It was shown that with the fine addition, flowability of the mixtures was improved, interaction among particles was increased, and the presence of fines could help to improve DPI's aerosolization performance. When the fines added were less than 3%, the "active site" hypothesis played a leading role. When the added fines were over 3% but less than 10%, fluidization enhancement mechanism was more important. After the added fines reaching 10%, aggregate mechanism started to dominate. However, FPF cannot be further increased once the fines reached 20%. Moreover, the correlations between FPF and dynamic powder parameters were verified in ternary mixtures, and cohesion had a greater impact on FPF than that of flowability. In conclusion, adding lactose fines is an effective way to improve lung deposition of DPI, with the concrete mechanism lactose fine ratio dependent.

On the relationship between blend state and dispersibility of adhesive mixtures containing active pharmaceutical ingredients

The objectives of this investigation were to study the evolution in blend state of adhesive mixtures containing the active pharmaceutical ingredients (APIs) salbutamol, budesonide and AZD5423 and to study the relationship between blend state and dispersibility of the mixtures, as assessed by the fine particle fraction (FPF). A series of adhesive mixtures of varied fines concentration were prepared for each API using the same type of carrier. Based on visual examination and powder mechanics, blend states were identified and summarized as blend state maps for each API. The dispersibility of the mixtures was studied using a Fast Screening Impactor (FSI) equipped with a ScreenHaler. The evolution in blend state differed between the APIs in terms of the width of the blend states. The structure of the adhesion layer also differed between the APIs, from relatively uniform to a heterogeneous layer with small agglomerates dispersed on the carrier surface. All three APIs expressed a similar type of bended relationship between FPF and fines concentration. However, the initial rate of increase and the fines concentration of the plateau differed between the APIs. The adhesive mixtures of all APIs followed the three main states in terms of structural evolution and the overall shape of the FPF-fines concentration profiles could be explained by the evolution in blend state. It is proposed that the structure of the adhesion layer is an important factor explaining the differences in blend state - blend dispersibility relationships between the APIs.

Development of solid lipid microparticles by melt-emulsification/spray-drying processes as carriers for pulmonary drug delivery

The aim of this study was to optimize the parameters of the complex melt-emulsification process coupled with the spray-drying, in order to maintain the balance between solid lipid microparticles (SLMs) powders aerodynamic performance and salbutamol sulfate release rate. Quality target product profile was identified and risk management and principal component analysis were used to guide formulation development. Obtained dry powders for inhalation (DPIs) were evaluated in terms of SLMs size distribution, morphology, true density, drug content, solid state characterization studies, in vitro aerosol performance and in vitro drug release. SLMs micrographs indicated spherical, porous particles. Selected powders showed satisfactory aerosol performance with a mean mass aerodynamic diameter of around 3 μm and acceptable fine particle fraction (FPF). Addition of trehalose positively affected SLMs aerodynamic properties. The results of in vitro dissolution testing indicated that salbutamol sulfate release from the tested SLMs formulations was modified, in comparison to the raw drug release. In conclusion, SLMs in a form of DPIs were successfully developed and numerous factors that affects SLMs properties were identified in this study. Further research is required for full understanding of each factor's influence on SLMs properties and optimization of DPIs with maximized FPFs.

Exploring the potential influence of drug charge on downstream deposition behaviour of DPI powders

Dry powder inhaler (DPI) development is limited by the time- and labor-consuming in vitro lung deposition test. It's highly desirable to find an easy tool for DPI formulation screening. Dynamic powder rheological properties seem to present many advantages, however, the adoptability needs to be verified. Drug charge is an important parameter especially for DPI formulation design but how it affects the process of pulmonary drug delivery is unavailable. Therefore, the objective of this study is to explore the influence of drug charge on DPI powders, further testing the potentials of powder properties for downstream deposition behavior prediction. Taking five differently charged drugs as model, influence of drug charge on uniformity, rheological and aerodynamic properties of the mixtures were investigated systemically. It was found that mometasone furoate with near neutral charge presented better content homogeneity, while significantly decreased recovery was noted for charged drugs, such as positively charged drug (salbutamol sulphate and indacaterol maleate) mixtures and negatively charged drug (budesonide and fluticasone propionate) mixtures. Moreover, drug charge also influenced flowability and cohesion of their admixture with lactose. As for the downstream deposition, neutral drugs presented higher fine particle fraction (FPF), followed by positively charged drugs and negatively charged drugs. Good correlations between basic flowability energy, aeration energy, Permeability and FPF were established irrespective of different drugs. Principal component analysis results suggested flowability had a greater influence on FPF when mixtures were less cohesive. In conclusion, this study demonstrated drug charge can influence physicochemical, rheological and aerodynamic properties of the admixture, and DPIs' dynamic properties could be used as potential tools to predict downstream deposition with good accuracy.