Comparison of the Application of Vibrating Mesh Nebulizer and Jet Nebulizer in Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-analysis.

Objective: To comparison of the application of Vibrating Mesh Nebulizer and Jet Nebulizer in chronic obstructive pulmonary disease (COPD). Research Methods: This systematic review and meta-analysis was conducted following the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) statements. The primary outcome measures analyzed included: The amount of inhaler in the urine sample at 30 minutes after inhalation therapy (USAL0.5), The total amount of inhaler in urine sample within 24 hours (USAL24), Aerosol emitted, Forced expiratory volume in 1 second (FEV1), Forced vital capacity (FVC). Results: Ten studies were included with a total of 314 study participants, including 157 subjects in the VMN group and 157 subjects in the JN group. The data analysis results of USAL0.5, MD (1.88 [95% CI, 0.95 to 2.81], P = 0.000), showed a statistically significant difference. USAL24, MD (1.61 [95% CI, 1.14 to 2.09], P = 0.000), showed a statistically significant difference. The results of aerosol emitted showed a statistically significant difference in MD (3.44 [95% CI, 2.84 to 4.04], P = 0.000). The results of FEV1 showed MD (0.05 [95% CI, -0.24 to 0.35], P=0.716), the results were not statistically significant. The results of FVC showed MD (0.11 [95% CI, -0.18 to 0.41], P=0.459), the results were not statistically significant. It suggests that VMN is better than JN and provides higher aerosols, but there is no difference in improving lung function between them. Conclusion: VMN is significantly better than JN in terms of drug delivery and utilization in the treatment of patients with COPD. However, in the future use of nebulizers, it is important to select a matching nebulizer based on a combination of factors such as mechanism of action of the nebulizer, disease type and comorbidities, ventilation strategies and modes, drug formulations, as well as cost-effectiveness, in order to achieve the ideal treatment of COPD.

Liposomes for Inhalation.

Inhalation of liposomes formulated with phospholipids similar to endogenous lung surfactants and lipids offers biocompatibility and versatility within the pulmonary medicine field to treat a range of diseases such as lung cancer, cystic fibrosis and lung infections. Manipulation of the physicochemical properties of liposomes enables innovative design of the carrier to meet specific delivery, release and targeting requirements. This delivery system offers several benefits: improved pharmacokinetics with reduced toxicity, enhanced therapeutic efficacy, increased delivery of poorly soluble drugs, taste masking, biopharmaceutics degradation protection and targeted cellular therapy. This section provides an overview of liposomal formulation and delivery, together with their applications for different disease states in the lung.

Developing Dry Powder Inhaler Formulations.

This section aims to provide a concise and contemporary technical perspective and reference resource covering dry powder inhaler (DPI) formulations. While DPI products are currently the leading inhaled products in terms of sales value, a number of confounding perspectives are presented to illustrate why they are considered surprisingly, and often frustratingly, poorly understood on a fundamental scientific level, and most challenging to design from first principles. At the core of this issue is the immense complexity of fine cohesive powder systems. This review emphasizes that the difficulty of successful DPI product development should not be underestimated and is best achieved with a well-coordinated team who respect the challenges and who work in parallel on device and formulation and with an appreciation of the handling environment faced by the patient. The general different DPI formulation types, which have evolved to address the challenges of aerosolizing fine cohesive drug-containing particles to create consistent and effective DPI products, are described. This section reviews the range of particle engineering processes that may produce micron-sized drug-containing particles and their subsequent assembly as either carrier-based or carrier-free compositions. The creation of such formulations is then discussed in the context of the material, bulk, interfacial and ultimately drug-delivery properties that are considered to affect formulation performance. A brief conclusion then considers the future DPI product choices, notably the issue of technology versus affordability in the evolving inhaler market.

Clinical Burden of Chronic Obstructive Pulmonary Disease in Patients with Suboptimal Peak Inspiratory Flow.

Introduction: Many patients with chronic obstructive pulmonary disease (COPD) may derive inadequate benefit from dry powder inhalers (DPIs) because of suboptimal peak inspiratory flow (sPIF). Objectives: To assess the clinical burden of COPD by characterizing the clinical characteristics of participants with sPIF against medium-low resistance DPIs versus those with optimal PIF (oPIF) from two phase 3 clinical trials. Methods: Baseline data were collected from two randomized, controlled, phase 3 trials (NCT03095456; NCT02518139) in participants with moderate-to-severe COPD. oPIF (60 L/min) against the medium-low resistance DPIs was used as the threshold for defining the PIF subgroups (<60 L/min (sPIF) vs ≥60 L/min (oPIF)). Results: Most participants included in this analysis were White (92%) and male (63%); the mean (range) age was 65 (43-87) years. Participants with sPIF had significantly greater dyspnea than those with oPIF as measured using the modified Medical Research Council scoring (mean (95% CI): 2.1 (2.0-2.2) vs 1.6 (1.4-1.7); P < 0.001) and baseline dyspnea index (mean (95% CI): 5.1 (4.9-5.4) vs 6.1 (5.8-6.3); P < 0.001). Based on COPD Assessment Test scores, participants with sPIF had a higher COPD symptom burden than those with oPIF (mean (95% CI): 21.5 (19.7-23.3) vs 19.5 (18.6-20.4); P = 0.05). Conclusion: In these trials, participants with COPD who had sPIF against the medium-low resistance DPIs had more dyspnea and worse health status than those with oPIF. These results demonstrate that sPIF is associated with a higher clinical burden as measured by patient-reported outcomes.

[Diagnosis and therapy of patients with asthma in Germany. Results of the care study RELEVANT]. / Diagnostik und Therapie von Patienten mit Asthma in Deutschland : Ergebnisse der Versorgungsstudie RELEVANT.

BACKGROUND: Diagnostic and therapeutic options for asthma have improved with asthma control and remission being of central importance. The RELEVANT study aimed for a nationwide snapshot of current asthma diagnosis and treatment in general practice and specialty care for identification of further aspects for optimization. METHOD: RELEVANT is a nationwide cross-sectional study using a structured questionnaire. This comprised 14 questions on asthma-related topics covering diagnostics and therapy. Participants were general practitioners/internal medicine specialists and pulmonologists. RESULTS: A total of 1,558 persons took part in the survey. Regarding relevant specific diagnostic procedures for asthma, GPs/internists almost exclusively mentioned pulse oximetry. Among the pulmonologists, fractional exhaled nitric oxide (FeNO) measurement was mentioned, among others. FeNO and blood eosinophils were only mentioned by the pulmonologists as diagnostic and treatment-relevant markers. A total of more than 60% of the GPs/internists surveyed stated that only around 25% or fewer of their patients would voluntarily report restrictions in their everyday lives. Regarding drug treatment, the majority stated that they recognized differences between various ICS/LABA combination therapies. CONCLUSIONS: The results indicate a need for optimization, particularly regarding asthma control. This involves both a better assessment by patients' everyday life restrictions and modern ways of assessing asthma control in cooperation between GPs/internal medicine specialists and pulmonologists. One fifth of respondents do not see any differences between various ICS/LABA combinations in daily practice, although there are pharmacodynamic and pharmacokinetic differences.

Tobramycin Systemic Absorption in Lung Transplant Recipients Treated With Inhaled Tobramycin: A Cohort Study.

Inhaled tobramycin treatment has been associated with nephrotoxicity in some case reports, but limited data are available about serum levels and its possible systemic absorption in lung transplant recipients (LTR). We conducted a single-center, observational and retrospective study of all adult (>18 years old) LTR treated with inhaled tobramycin for at least 3 days between June 2019 and February 2022. Trough serum levels were collected and >2 µg/mL was considered a high drug level. The primary outcome assessed the presence of detectable trough levels, while the secondary outcome focused on the occurrence of acute kidney injury (AKI) in individuals with detectable trough levels. Thirty-four patients, with a median age of 60 years, were enrolled. The primary indications for treatment were donor bronchial aspirate bacterial isolation (18 patients) and tracheobronchitis (15 patients). In total, 28 patients (82%) exhibited detectable serum levels, with 9 (26%) presenting high levels (>2 µg/mL). Furthermore, 9 patients (26%) developed acute kidney injury during the treatment course. Median trough tobramycin levels were significantly elevated in invasively mechanically ventilated patients compared to non-ventilated individuals (2.5 µg/mL vs. 0.48 µg/mL) (p < 0.001). Inhaled tobramycin administration in LTRs, particularly in those requiring invasive mechanical ventilation, may result in substantial systemic absorption.

On the Feasibility of Rugose Lipid Microparticles in Pressurized Metered Dose Inhalers with Established and New Propellants.

Pressurized metered dose inhalers (pMDIs) require optimized formulations to provide stable, consistent lung delivery. This study investigates the feasibility of novel rugose lipid particles (RLPs) as potential drug carriers in pMDI formulations. The physical stability of RLPs was assessed in three different propellants: the established HFA-134a and HFA-227ea and the new low global-warming-potential (GWP) propellant HFO-1234ze. A feedstock containing DSPC and calcium chloride was prepared without pore forming agent to spray dry two RLP batches at inlet temperatures of 55 °C (RLP55) and 75 °C (RLP75). RLPs performance in pMDI formulations was compared to two reference samples that exhibit significantly different performance when suspended in propellants: well-established engineered porous particles and particles containing 80% trehalose and 20% leucine (80T20L). An accelerated stability study at 40 °C and relative humidity of 7% ± 5% was conducted over 3 months. At different time points, a shadowgraphic imaging technique was used to evaluate the colloidal stability of particles in pMDIs. Field emission electron microscopy with energy dispersive X-ray spectroscopy was used to evaluate the morphology and elemental composition of particles extracted from the pMDIs. After 2 weeks, all 80T20L formulations rapidly aggregated upon agitation and exhibited significantly inferior colloidal stability compared to the other samples. In comparison, both the RLP55 and RLP75 formulations, regardless of the propellant used, retained their rugose structure and demonstrated excellent suspension stability comparable with the engineered porous particles. The studied RLPs demonstrate great potential for use in pMDI formulations with HFA propellants and the next-generation low-GWP propellant HFO-1234ze.

Biological treatment of obstructive lung diseases.

In the last 30 years, the treatment of obstructive lung diseases, such as asthma and COPD, has seen significant advancements. Introduction of inhaled corticosteroids (ICS) and, more recently, biological treatments has revolutionized care. Biological treatments are very successful in severe asthma and are expected to be approved for COPD soon. Systematic assessment and multidimensional treatment approaches are crucial in both conditions. Future care may involve specialized centres for severe obstructive lung diseases, focusing on personalized approaches and monitoring, as argued in this review.

Safety, immunogenicity, and protective effective of inhaled COVID-19 vaccines: A systematic review and meta-analysis.

This study aimed to examine the safety, immunogenicity and protective effective of inhaled COVID-19 vaccines (ICVs). Literature research was done through EMBASE, Cochrane, PubMed, and Web of Science up to 10 March 2024. Pooled estimates with corresponding 95% confidence intervals (CI) were computed and compared using the random effects and common effects model. Of the 15 studies, 11 analyzed safety, 13 analyzed immunogenicity, and 3 analyzed protective effective. The results showed a favorable safety profile of ICVs for primary vaccination series, however it does not always seem to produce the expected immune response and protective effective. Meta-analysis of ICVs booster vaccinations (BVs) showed that the levels of neutralizing antibody Geometric mean titer (nAb-GMT) with aerosolised Ad5-nCoV (AAd5-nCoV) were all higher than those with inactivated vaccine (INA-nCoV) (standard mean difference (SMD) = 2.32; 95% CI: 1.96-2.69) and intramuscular Ad5-nCoV (IMAd5-nCoV) (SMD = 0.31; 95% CI: 0.14-0.48) against the original strain of SARS-CoV-2. Importantly, we also observed similar results in the omicron variant. In addition, ICV in BVs has high mucosal immunity to IgA antibodies. The risk of adverse events was comparable or lower for AAd5-nCoV compared to INA-nCoV or IMAd5-nCoV. Current evidence shows that the safety profile of ICVs were well. The booster dose of AAd5-nCoV had a high immune response (including mucosal immunity) and provided protection against COVID-19 caused by the SARS-CoV-2 omicron variant. Further studies are needed to investigate the long-term safety of intranasal vaccine booster protection and various types of ICVs.

Characteristics of Users and New Initiators of Single- and Multiple-Inhaler Triple Therapy for Chronic Obstructive Pulmonary Disease in Germany.

Purpose: To assess patient characteristics of users and new initiators of triple therapy for chronic obstructive pulmonary disease (COPD) in Germany. Patients and Methods: Retrospective cohort study of patients with COPD and ≥1 prescription for single-inhaler triple therapy (SITT; fluticasone furoate/umeclidinium/vilanterol [FF/UMEC/VI] or beclomethasone dipropionate/glycopyrronium bromide/formoterol [BDP/GLY/FOR]) or multiple-inhaler triple therapy (MITT), using data from the AOK PLUS German sickness fund (1 January 2015-31 December 2019). The index date was the first date of prescription for FF/UMEC/VI or BDP/GLY/FOR (SITT users), or the first date of overlap of inhaled corticosteroid, long-acting ß2-agonist, and long-acting muscarinic antagonist (MITT users). Two cohorts were defined: the prevalent cohort included all identified triple therapy users; the incident cohort included patients newly initiating triple therapy for the first time (no prior use of MITT or SITT in the last 2 years). Patient characteristics and treatment patterns were assessed on the index date and during the 24-month pre-index period. Results: In total, 18,630 patients were identified as prevalent triple therapy users (MITT: 17,945; FF/UMEC/VI: 700; BDP/GLY/FOR: 908; non-mutually exclusive) and 2932 patients were identified as incident triple therapy initiators (MITT: 2246; FF/UMEC/VI: 311; BDP/GLY/FOR: 395; non-mutually exclusive). For both the prevalent and incident cohorts, more than two-thirds of patients experienced ≥1 moderate/severe exacerbation in the preceding 24 months; in both cohorts more BDP/GLY/FOR users experienced ≥1 moderate/severe exacerbation, compared with FF/UMEC/VI and MITT users. Overall, 97.9% of prevalent triple therapy users and 86.4% of incident triple therapy initiators received maintenance treatment in the 24-month pre-index period. Conclusion: In a real-world setting in Germany, triple therapy was most frequently used after maintenance therapy in patients with recent exacerbations, in line with current treatment recommendations.

Triple therapy (a combination of three different respiratory inhaled medications) is recommended for patients with chronic obstructive pulmonary disease (COPD) who experience repeated short-term symptom flare-ups when taking dual therapy (a combination of two different respiratory medications). Previously, patients had to take triple therapy using two or three separate inhalers. More recently, single-inhaler triple therapies have been developed, meaning patients can take all three different medications at the same time via one single inhaler. This study assessed the characteristics of patients who were already receiving triple therapy, or who started triple therapy (either via multiple inhalers or a single inhaler), in Germany between January 2015 and December 2019. In total, 18,630 patients who were already receiving triple therapy during the study period, and 2932 patients who newly started using triple therapy were included. The study reported that more than two-thirds of included patients had experienced at least one flare-up of COPD symptoms in the 2 years before starting triple therapy. Most patients had also received another therapy for COPD before starting triple therapy. A small proportion of patients started taking triple therapy after receiving no other therapy for COPD in the previous 2 years. The results of the study suggest that triple therapy for COPD in Germany is most often used in accordance with recommendations (patients already receiving therapy and experiencing repeated symptom flare-ups).

An in-hospital intervention to reduce the proportion of misused inhalers at hospital discharge among patients with COPD: a non-randomised intervention study.

AIMS OF THE STUDY: Misuse of inhalers during chronic obstructive pulmonary disease (COPD) treatment is common and may result from errors in inhalation technique or insufficient peak inspiratory flow (PIF). We aimed to evaluate the impact of an in-hospital intervention to reduce inhaler misuse at hospital discharge among patients with COPD. METHODS: We conducted a monocentric, non-randomised intervention study to compare the proportion of misused inhalers at hospital discharge by patients with COPD between a group with standard care and a group receiving an in-hospital intervention. The control group successively included all patients hospitalised between March and June 2022, and the intervention group included patients hospitalised between August and December 2022. The intervention consisted of (a) an evaluation of inhalation technique and PIF at admission, (b) the provision of a written guide to assist in the selection of an inhaler, and (c) therapeutic education. The primary outcome was the proportion of misused inhalers, defined as an inhaler used with a critical error and/or insufficient PIF, at hospital discharge. The primary outcome was assessed by observing inhalation technique and measuring PIF using the In-Check DIAL G16® . RESULTS: The study included 93 patients: 46 in the control group and 47 in the intervention group. Mean age was 70.5 years (SD 10.9 years), 56 patients (60.2%) were men, and 57 patients (62%) were hospitalised for a COPD exacerbation. Patients used an average of 1.9 inhalers at hospital discharge; 98 inhalers were assessed in the control group and 81 in the intervention group. The proportion of misused inhalers at discharge was 61.2% in the control group and 21.0% in the intervention group (absolute risk reduction 40.2% [95% CI 25.5-55.0]; p <0.01). In the intervention group, the proportion of inhalers used with at least one critical error was reduced by 38.6% (95% CI 24.3-52.3%) and that of inhalers used with insufficient PIF by 13.9% (95% CI 4.2-23.6%). CONCLUSIONS: An in-hospital intervention was associated with a reduction in the proportion of misused inhalers at hospital discharge. This intervention should be considered for hospitalised patients with COPD. The trial was registered with ClinicalTrials.gov (NCT05207631).

Overcoming the Low-Stability Bottleneck in the Clinical Translation of Liposomal Pressurized Metered-Dose Inhalers: A Shell Stabilization Strategy Inspired by Biomineralization.

Currently, several types of inhalable liposomes have been developed. Among them, liposomal pressurized metered-dose inhalers (pMDIs) have gained much attention due to their cost-effectiveness, patient compliance, and accurate dosages. However, the clinical application of liposomal pMDIs has been hindered by the low stability, i.e., the tendency of the aggregation of the liposome lipid bilayer in hydrophobic propellant medium and brittleness under high mechanical forces. Biomineralization is an evolutionary mechanism that organisms use to resist harsh external environments in nature, providing mechanical support and protection effects. Inspired by such a concept, this paper proposes a shell stabilization strategy (SSS) to solve the problem of the low stability of liposomal pMDIs. Depending on the shell material used, the SSS can be classified into biomineralization (biomineralized using calcium, silicon, manganese, titanium, gadolinium, etc.) biomineralization-like (composite with protein), and layer-by-layer (LbL) assembly (multiple shells structured with diverse materials). This work evaluated the potential of this strategy by reviewing studies on the formation of shells deposited on liposomes or similar structures. It also covered useful synthesis strategies and active molecules/functional groups for modification. We aimed to put forward new insights to promote the stability of liposomal pMDIs and shed some light on the clinical translation of relevant products.

Novel inhalation therapy in pulmonary fibrosis: principles, applications and prospects.

Pulmonary fibrosis (PF) threatens millions of people worldwide with its irreversible progression. Although the underlying pathogenesis of PF is not fully understood, there is evidence to suggest that the disease can be blocked at various stages. Inhalation therapy has been applied for lung diseases such as asthma and chronic obstructive pulmonary disease, and its application for treating PF is currently under consideration. New techniques in inhalation therapy, such as the application of microparticles and nanoparticles, traditional Chinese medicine monomers, gene therapy, inhibitors, or agonists of signaling pathways, extracellular vesicle interventions, and other specific drugs, are effective in treating PF. However, the safety and effectiveness of these therapeutic techniques are influenced by the properties of inhaled particles, biological and pathological barriers, and the type of inhalation device used. This review provides a comprehensive overview of the pharmacological, pharmaceutical, technical, preclinical, and clinical experimental aspects of novel inhalation therapy for treating PF and focus on therapeutic methods that significantly improve existing technologies or expand the range of drugs that can be administered via inhalation. Although inhalation therapy for PF has some limitations, the advantages are significant, and further research and innovation about new inhalation techniques and drugs are encouraged.

Triple combination dry powder formulation of pretomanid, moxifloxacin, and pyrazinamide for treatment of multidrug-resistant tuberculosis.

Both latent and multidrug-resistant tuberculosis (TB) have been causing significant concern worldwide. A novel drug, pretomanid (PA-824), has shown a potent bactericidal effect against both active and latent forms of Mycobacterium tuberculosis (MTb) and a synergistic effect when combined with pyrazinamide and moxifloxacin. This study aimed to develop triple combination spray dried inhalable formulations composed of antitubercular drugs, pretomanid, moxifloxacin, and pyrazinamide (1:2:8 w/w/w), alone (PaMP) and in combination with an aerosolization enhancer, L-leucine (20 % w/w, PaMPL). The formulation PaMPL consisted of hollow, spherical, dimpled particles (<5 µm) and showed good aerosolization behaviour with a fine particle fraction of 70 %. Solid-state characterization of formulations with and without L-leucine confirmed the amorphous nature of moxifloxacin and pretomanid and the crystalline nature of pyrazinamide with polymorphic transformation after the spray drying process. Further, the X-ray photoelectron spectroscopic analysis revealed the predominant surface composition of L-leucine on PaMPL dry powder particles. The dose-response cytotoxicity results showed pyrazinamide and moxifloxacin were non-toxic in both A549 and Calu-3 cell lines up to 150 µg/mL. However, the cell viability gradually decreased to 50 % when the pretomanid concentration increased to 150 µg/mL. The in vitro efficacy studies demonstrated that the triple combination formulation had more prominent antibacterial activity with a minimum inhibitory concentration (MIC) of 1 µg/mL against the MTb H37Rv strain as compared to individual drugs. In conclusion, the triple combination of pretomanid, moxifloxacin, and pyrazinamide as an inhalable dry powder formulation will potentially improve treatment efficacy with fewer systemic side effects in patients suffering from latent and multidrug-resistant TB.

Formulation and evaluation of inhaled Sildenafil-loaded PLGA microparticles for treatment of pulmonary arterial hypertension (PAH): A novel high drug loaded formulation and scalable process via hot melt extrusion technology (Part â ).

In recent years, several techniques were employed to develop a local sustained pulmonary delivery of sildenafil citrate (SC) as an alternative for the intravenous and oral treatment of pulmonary arterial hypertension (PAH). Most of these methods, however, need to be improved due to limitations of scalability, low yield production, low drug loading, and stability issues. In this study, we report the use of hot-melt extrusion (HME) as a scalable process for making Poly (lactic-co-glycolic acid) (PLGA) microparticles with high SC load. The prepared particles were tested in vitro for local drug delivery to the lungs by inhalation. Sodium bicarbonate was included as a porogen in the formulation to make the particles more brittle and to impart favorable aerodynamic properties. Six formulations were prepared with different formulation compositions. Laser diffraction analysis was used to estimate the geometric particle size distribution of the microparticles. In-vitro aerodynamic performance was evaluated by the next-generation cascade impactor (NGI). It was reported in terms of an emitted dose (ED), an emitted fraction (EF%), a respirable fraction (RF%), a fine particle fraction (FPF%), a mass median aerodynamic diameter (MMAD), and geometric standard deviation (GSD). The formulations have also been characterized for surface morphology, entrapment efficiency, drug load, and in-vitro drug release. The results demonstrated that PLGA microparticles have a mean geometric particle size between 6 and 14 µm, entrapment efficiency of 77 to 89 %, and SC load between 17 and 33 % w/w. Fifteen percent of entrapped sildenafil was released over 24 h from the PLGA microparticles, and seventy percent over 7 days. The aerodynamic properties included fine particle fraction ranging between 19 and 33 % and an average mass median aerodynamic diameter of 6-13 µm.

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.