Formation of particles for dry powder inhalers

Modern trends in the formulation of microparticles for lung delivery using porogens: methods, principles and examples

Inhalation drug administration is increasingly used for local pharmacotherapy of lung disorders and as an alternative route for systemic drug delivery. Modern inhalation powder systems aim to target drug deposition in the required site of action. Large porous particles (LPP), characterized by an aerodynamic diameter over 5 μm, density below 0.4 g/cm3, and the ability to avoid protective lung mechanisms, come to the forefront of the research. They are mostly prepared by spray techniques such as spray drying or lyophilization using pore-forming substances (porogens). These substances could be gaseous, solid, or liquid, and their selection depends on their polarity, solubility, and mutual compatibility with the carrier material and the drug. According to the pores-forming mechanism, porogens can be divided into groups, such as osmogens, extractable porogens, and porogens developing gases during decomposition. This review characterizes modern trends in the formulation of solid microparticles for lung delivery; describes the mechanisms of action of the most often used porogens, discusses their applicability in various formulation methods, emphasizes spray techniques; and documents discussed topics by examples from experimental studies.

Novel Dry Hyaluronic Acid-Vancomycin Complex Powder for Inhalation, Useful in Pulmonary Infections Associated with Cystic Fibrosis

Polyelectrolyte-drug complexes are interesting alternatives to improve unfavorable drug properties. Vancomycin (VAN) is an antimicrobial used in the treatment of methicillin-resistant Staphylococcus aureus pulmonary infections in patients with cystic fibrosis. It is generally administered intravenously with a high incidence of adverse side effects, which could be reduced by intrapulmonary administration. Currently, there are no commercially available inhalable formulations containing VAN. Thus, the present work focuses on the preparation and characterization of an ionic complex between hyaluronic acid (HA) and VAN with potential use in inhalable formulations. A particulate-solid HA-VAN25 complex was obtained by spray drying from an aqueous dispersion. FTIR spectroscopy and thermal analysis confirmed the ionic interaction between HA and VAN, while an amorphous diffraction pattern was observed by X-ray. The powder density, geometric size and morphology showed the suitable aerosolization and aerodynamic performance of the powder, indicating its capability of reaching the deep lung. An in vitro extended-release profile of VAN from the complex was obtained, exceeding 24 h. Microbiological assays against methicillin-resistant and -sensitive reference strains of Staphylococcus aureus showed that VAN preserves its antibacterial efficacy. In conclusion, HA-VAN25 exhibited interesting properties for the development of inhalable formulations with potential efficacy and safety advantages over conventional treatment.

Towards More Precise Targeting of Inhaled Aerosols to Different Areas of the Respiratory System

Pharmaceutical aerosols play a key role in the treatment of lung disorders, but also systemic diseases, due to their ability to target specific areas of the respiratory system (RS). This article focuses on identifying and clarifying the influence of various factors involved in the generation of aerosol micro- and nanoparticles on their regional distribution and deposition in the RS. Attention is given to the importance of process parameters during the aerosolization of liquids or powders and the role of aerosol flow dynamics in the RS. The interaction of deposited particles with the fluid environment of the lung is also pointed out as an important step in the mass transfer of the drug to the RS surface. The analysis presented highlights the technical aspects of preparing the precursors to ensure that the properties of the aerosol are suitable for a given therapeutic target. Through an analysis of existing technical limitations, selected strategies aimed at enhancing the effectiveness of targeted aerosol delivery to the RS have been identified and presented. These strategies also include the use of smart inhaling devices and systems with built-in AI algorithms.

Inhalation Dosage Forms: A Focus on Dry Powder Inhalers and Their Advancements

In this review, an extensive analysis of dry powder inhalers (DPIs) is offered, focusing on their characteristics, formulation, stability, and manufacturing. The advantages of pulmonary delivery were investigated, as well as the significance of the particle size in drug deposition. The preparation of DPI formulations was also comprehensively explored, including physico-chemical characterization of powders, powder processing techniques, and formulation considerations. In addition to manufacturing procedures, testing methods were also discussed, providing insights into the development and evaluation of DPI formulations. This review also explores the design basics and critical attributes specific to DPIs, highlighting the significance of their optimization to achieve an effective inhalation therapy. Additionally, the morphology and stability of 3 DPI capsules (Spiriva, Braltus, and Onbrez) were investigated, offering valuable insights into the properties of these formulations. Altogether, these findings contribute to a deeper understanding of DPIs and their development, performance, and optimization of inhalation dosage forms.

Spray-dried microparticles of encapsulated gefitinib for slow-release localized treatment of periodontal disease

Periodontal disease (PD) can be prevented by local or systemic application of epidermal growth factor receptor inhibitors (EGFRIs) that stabilize αvβ6 integrin levels in the periodontal tissue, leading to an increase in the expression of anti-inflammatory cytokines, such as transforming growth factor-β1. Systemic EGFRIs have side effects and, therefore, local treatment of PD applied into the periodontal pockets would be preferrable. Thus, we have developed slow-release three-layered microparticles of gefitinib, a commercially available EGFRI. A combination of different polymers [cellulose acetate butyrate (CAB), Poly (D, L-lactide-co-glycolide) (PLGA) and ethyl cellulose (EC)] and sugars [D-mannose, D-mannitol and D-(+)-trehalose dihydrate] were used for the encapsulation. The optimal formulation was composed of CAB, EC, PLGA, mannose and gefitinib (0.59, 0.24, 0.09, 1, and 0.005 mg/ml, respectively; labeled CEP-gef), and created microparticles of 5.7 ± 2.3 µm in diameter, encapsulation efficiency of 99.98%, and a release rate of more than 300 hours. A suspension of this microparticle formulation blocked EGFR phosphorylation and restored αvβ6 integrin levels in oral epithelial cells, while the respective control microparticles showed no effect.

Dry Powder Inhalation for Lung Delivery in Cystic Fibrosis

Pulmonary drug delivery has long been used for local and systemic administration of different medications used in acute and chronic respiratory diseases. Certain lung diseases, such as cystic fibrosis, rely heavily on chronic treatments, including targeted lung delivery. Pulmonary drug delivery possesses various physiological advantages compared to other delivery methods and is also convenient for the patient to use. However, the formulation of dry powder for pulmonary delivery proves challenging due to aerodynamic restrictions and the lower tolerance of the lung. The aim of this review is to provide an overview of the respiratory tract structure in patients with cystic fibrosis, including during acute and chronic lung infections and exacerbations. Furthermore, this review discusses the advantages of targeted lung delivery, including the physicochemical properties of dry powder and factors affecting clinical efficacy. Current inhalable drug treatments and drugs currently under development will also be discussed.

Segregation in inhalable powders: Quantification of the effect of vibration on adhesive mixtures

The objective of this investigation was to study the effect of induced vibrations on adhesive mixtures containing budesonide and salbutamol sulphate as active pharmaceutical ingredients (APIs) and InhaLac 70 as carrier. A series of adhesive mixtures with varied API concentration (1-4%) was prepared for each API. Half of the adhesive mixture was stressed on a vibrating sieve under conditions resembling hopper flow. Based on scanning electron micrographs, it was concluded that InhaLac 70 contains particles of two distinct shapes, one irregular with groves and valleys and the other more regular with well defined edges. The dispersibility of the control and stressed mixtures was studied using a next generation impactor. The stressed mixtures containing 1 and 1.5% API displayed a significant reduction in fine particle dose (FPD) compared to the control. The reduction in FPD resulted from a loss of API from the adhesive mixture during vibration and as a consequence of restructuring and self agglomeration resulting in reduced dispersibility. However, no significant difference was observed for mixtures with larger weight fractions of API (2 and 4% API) but these have a drawback of reduced fine particle fraction (FPF). It is concluded that vibrations induced on the adhesive mixtures during handling potentially have a significant effect on the dispersibility of the API and the total amount of drug delivered to the lungs.

Inhalable Nanoparticle-based Dry Powder Formulations for Respiratory Diseases: Challenges and Strategies for Translational Research

The emergence of novel respiratory infections (e.g., COVID-19) and expeditious development of nanoparticle-based COVID-19 vaccines have recently reignited considerable interest in designing inhalable nanoparticle-based drug delivery systems as next-generation respiratory therapeutics. Among various available devices in aerosol delivery, dry powder inhalers (DPIs) are preferable for delivery of nanoparticles due to their simplicity of use, high portability, and superior long-term stability. Despite research efforts devoted to developing inhaled nanoparticle-based DPI formulations, no such formulations have been approved to date, implying a research gap between bench and bedside. This review aims to address this gap by highlighting important yet often overlooked issues during pre-clinical development. We start with an overview and update on formulation and particle engineering strategies for fabricating inhalable nanoparticle-based dry powder formulations. An important but neglected aspect in in vitro characterization methodologies for linking the powder performance with their bio-fate is then discussed. Finally, the major challenges and strategies in their clinical translation are highlighted. We anticipate that focused research onto the existing knowledge gaps presented in this review would accelerate clinical applications of inhalable nanoparticle-based dry powders from a far-fetched fantasy to a reality.

Optimization of Spray Drying Process Parameters for the Preparation of Inhalable Mannitol-Based Microparticles Using a Box-Behnken Experimental Design

Inhalation is used for local therapy of the lungs and as an alternative route for systemic drug delivery. Modern powder inhalation systems try to target the required site of action/absorption in the respiratory tract. Large porous particles (LPPs) with a size >5 μm and a low mass density (usually measured as bulk or tapped) of <0.4 g/cm³ can avoid protective lung mechanisms. Their suitable aerodynamic properties make them perspective formulations for deep lung deposition. This experiment studied the effect of spray-drying process parameters on LPP properties. An experimental design of twelve experiments with a central point was realized using the Box-Behnken method. Three process parameters (drying temperature, pump speed, and air speed) were combined on three levels. Particles were formed from a D-mannitol solution, representing a perspective material for lung microparticles. The microparticles were characterized in terms of physical size (laser diffraction), aerodynamic diameter (aerodynamic particle sizer), morphology (SEM), and densities. The novelty and main goal of this research were to describe how the complex parameters of the spray-drying process affect the properties of mannitol LPPs. New findings can provide valuable data to other researchers, leading to the easy tuning of the properties of spray-dried particles by changing the process setup.

Particle Design and Inhalation Delivery of Iodine for Upper Respiratory Tract Infection Therapy

Diseases caused by upper respiratory tract (URT) and pulmonary infections have been a serious threat to human health for millennia and lack of targeted effective therapeutic techniques. In this study, two kinds of cyclodextrin particles with typical particle shapes of nanocubes and microbars were synthesized through a facile process. Subsequently, the particles were used as carriers for loading and stabilizing iodine and characterizations were performed to demonstrate the loading mechanism. Next-generation impactor (NGI) experiments showed that iodine-loaded microbars (I₂@microbars) had a deposition rate of 79.75% in URT, while iodine-loaded nanocubes (I₂@nanocubes) were delivered to the deep lungs with a fine particle fraction (FPF) of 46.30%. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) indicated that the iodine-loaded nanocubes and microbars had similar bactericidal effect to povidone iodine solution. Cell viability studies and extracellular pro-inflammatory factor (TNF-α, IL-1β, IL-6) evaluations demonstrate noncytotoxic effects of the blank carriers and anti-inflammatory effects of iodine-loaded samples. The irritation of the rat pharynx by I₂@microbars was evaluated for the behavioral observations, body weight changes, histopathological studies, and TNF-α, IL-1β, and IL-6 levels in pharyngeal tissues. The results showed that I₂@microbars had no irritation to rat pharyngeal tissues at therapeutic doses. In conclusion, the present study provides novel treatment of URT infections via supramolecular cyclodextrin carriers for URT local therapy with iodine loading by a solvent-free method, which enhances the stability and reduces the inherent irritation without inhibiting their antimicrobial effects.

CFD Study of Dry Pulmonary Surfactant Aerosols Deposition in Upper 17 Generations of Human Respiratory Tract

The efficient generation of high concentrations of fine-particle, pure surfactant aerosols provides the possibility of new, rapid, and effective treatment modalities for Acute Respiratory Distress Syndrome (ARDS). SUPRAER-CATM is a patented technology by Kaer BiotherapeuticsTM, which is a new class of efficient aerosol drug generation and delivery system using Compressor Air (CA). SUPRAER-CA is capable of aerosolizing relatively viscous solutions or suspensions of proteins and surfactants and of delivering them as pure fine particle dry aerosols. In this Computational Fluid Dynamics (CFD) study, we select a number of sites within the upper 17 generations of the human respiratory tract for calculation of the deposition of dry pulmonary surfactant aerosol particles. We predict the percentage of inhaled dry pulmonary surfactant aerosol arriving from the respiratory bronchioles to the terminal alveolar sacs. The dry pulmonary surfactant aerosols, with a Mass Median Aerodynamic Diameter (MMAD) of 2.6 µm and standard deviation of 1.9 µm, are injected into the respiratory tract at a dry surfactant aerosol flow rate of 163 mg/min to be used in the CFD study at an air inhalation flow rate of 44 L/min. This CFD study in the upper 17th generation of a male adult lung has shown computationally that the penetration fraction (PF) is approximately 25% for the inhaled surfactant aerosols. In conclusion, an ARDS patient might receive approximately one gram of inspired dry surfactant aerosol during an administration period of one hour as a possible means of further inflating partly collapsed alveoli.

Engineered nasal dry powder for the encapsulation of bioactive compounds

In this review, we present the potential of nasal dry powders to deliver stable bioactive compounds and their manufacture using spray-drying (SD) techniques to achieve encapsulation. We also review currently approved and experimental excipients used for powder manufacturing for specific target drugs. Polymers, sugars, and amino acids are recommended for specific actions, such as mucoadhesive interactions, to increase residence time on the nasal mucosa; for example, high-molecular weight polymers, such as hydroxypropyl methylcellulose, or mannitol, which protect the bioactive compounds, increase their stability, and enhance drug absorption in the nasal mucosa; and leucine, which promotes particle formation and improves aerosol performance. Teaser: XXXX.

Novel Fluticasone Propionate and Salmeterol Fixed-Dose Combination Nano-Encapsulated Particles Using Polyamide Based on L-Lysine

One of the key challenges in developing a dry powder inhaler (DPI) of an inhalable potent fixed-dose combination (FDC) is the ability of the formulation to generate an effective and reproducible aerosol able to reach the lower parts of the lungs. Herein, a one-step approach is presented to expedite the synthesis of nanoaggregates made from a biocompatible and biodegradable polyamide based on L-lysine amino acid employing market-leading active pharmaceutical ingredients (fluticasone propionate (FP) and salmeterol xinafoate (SAL)) for the management of asthma. The nanoaggregates were synthesized using interfacial polycondensation that produced nanocapsules with an average particle size of 226.7 ± 35.3 nm and zeta potential of −30.6 ± 4.2 mV. Differential scanning calorimetric analysis and x-ray diffraction, as well as scanning electron microscopy of the produced FDC, revealed the ability of the produced nanocapsules to encapsulate the two actives and display the best aerodynamic performance. The FDC nanocapsules displayed 88.5% and 98.5% of the emitted dose for FP and SAL, respectively. The fine particle fraction of the nominated dose was superior to the marketed product (Seretide Diskus®, Brentford, United Kingdom). The in-vitro release study showed an extended drug release profile. Our findings suggest that nanoaggregates using polyamides based on L-lysine and interfacial polycondensation can serve as a good platform for pulmonary drug delivery of FDC systems.

Spray Freeze-Drying for inhalation application: Process and Formulation Variables

High porous particles with specific aerodynamic properties were processed by the spray freeze-drying (SFD) method. Comprehensive knowledge about all aspects of the SFD method is required for particle engineering of various pharmaceutical products with good flow properties. In this review, different types of the SFD method, the most frequently employed excipients, properties of particles prepared by this method, and most recent approaches concerning SFD are summarized. Generally, this technique can prepare spherical-shaped particles with a highly porous interior structure, responsible for the very low density of powders. Increasing the solubility of spray freeze-dried formulations achieves the desired efficacy. Also, due to the high efficiency of SFD, by determining the different features of this method and optimizing the process by model-based studies, desirable results for various inhaled products can be achieved and significant progress can be made in the field of pulmonary drug delivery.

Porous particles and novel carrier particles with enhanced penetration for efficient pulmonary delivery of antitubercular drugs

This study aimed to design dry powder inhaler formulations using a hydrophilic polymeric polysaccharide, phytoglycogen (PyG), as a multi-functional additive that increases the phagocytic activity of macrophage-like cells and enhances pulmonary delivery of drugs. The safety and usefulness of PyG were determined using in vitro cell-based studies. Dry powder inhaler formulations of an antitubercular drug, rifampicin, were fabricated by spray drying with PyG. The cytotoxicity, effects on phagocytosis, particle size, and morphology were evaluated. The aerosolization properties of the powder formulations were evaluated using an Andersen cascade impactor (ACI). Scanning electron microscope images of the particles on each ACI stage were captured to observe the deposition behavior. PyG showed no toxicity in A549, Calu-3, or RAW264.7 cell lines. At concentrations of 0.5 and 1 g/L, PyG facilitated the cellular uptake of latex beads and the expression of pro-inflammatory cytokine genes in RAW264.7 cells. Formulations with outstanding inhalation potential were produced. The fine particle fraction (aerodynamic size 2-7 µm) of the porous particle batch reached nearly 60%, whereas in the formulation containing wrinkled carrier particles, the extra-fine particle fraction (aerodynamic particle size < 2 μm) was 25.0% ± 1.7%. The deposition of porous and wrinkled particles on individual ACI stages was distinct. The inclusion of PyG dramatically improved the inhalation performance of porous and wrinkled powder formulations. These easily inhaled immunostimulatory carrier particles may advance the state of research by enhancing the therapeutic effect and alveolar delivery of antitubercular drugs.

A quantitative approach to predicting lung deposition profiles of pharmaceutical powder aerosols

Dry powder inhalers (DPI) are widely used systems for pulmonary delivery of therapeutics. The inhalation performance of DPIs is influenced by formulation features, inhaler device and inhalation pattern. The current review presents the affecting factors with great focus on powder characteristics which include particle size, shape, surface, density, hygroscopicity and crystallinity. The properties of a formulation are greatly influenced by a number of physicochemical factors of drug and added excipients. Since available particle engineering techniques result in particles with a set of modifications, it is difficult to distinguish the effect of an individual feature on powder deposition behavior. This necessitates developing a predictive model capable of describing all influential factors on dry powder inhaler delivery. Therefore, in the current study, a model was constructed to correlate the inhaler device properties, inhalation flow rate, particle characteristics and drug/excipient physicochemical properties with the resultant fine particle fraction. The r² value of established correlation was 0.74 indicating 86% variability in FPF values is explained by the model with the mean absolute errors of 0.22 for the predicted values. The authors believe that this model is capable of predicting the lung deposition pattern of a formulation with an acceptable precision when the type of inhaler device, inhalation flow rate, physicochemical behavior of active and inactive ingredients and the particle characteristics of DPI formulations are considered.

Inhaled aerosols: Their role in COVID-19 transmission, including biophysical interactions in the lungs

The high rate of spreading of COVID-19 is attributed to airborne particles exhaled by infected but often asymptomatic individuals. In this review, the role of aerosols in SARS-CoV-2 coronavirus transmission is discussed from the biophysical perspective. The essential properties of the coronavirus virus transported inside aerosol droplets, their successive inhalation, and size-dependent deposition in the respiratory system are highlighted. The importance of face covers (respirators and masks) in the reduction of aerosol spreading is analyzed. Finally, the discussion of the physicochemical phenomena of the coronavirus entering the surface of lung liquids (bronchial mucus and pulmonary surfactant) is presented with a focus on a possible role of interfacial phenomena in pulmonary alveoli. Information given in this review should be important in understanding the essential biophysical conditions of COVID-19 infection via aerosol route as a prerequisite for effective strategies of respiratory tract protection, and possibly, indications for future treatments of the disease.

Dry Powder for Pulmonary Delivery: A Comprehensive Review

The pulmonary route has long been used for drug administration for both local and systemic treatment. It possesses several advantages, which can be categorized into physiological, i.e., large surface area, thin epithelial membrane, highly vascularized, limited enzymatic activity, and patient convenience, i.e., non-invasive, self-administration over oral and systemic routes of drug administration. However, the formulation of dry powder for pulmonary delivery is often challenging due to restrictions on aerodynamic size and the lung’s lower tolerance capacity in comparison with an oral route of drug administration. Various physicochemical properties of dry powder play a major role in the aerosolization, deposition, and clearance along the respiratory tract. To prepare suitable particles with optimal physicochemical properties for inhalation, various manufacturing methods have been established. The most frequently used industrial methods are milling and spray-drying, while several other alternative methods such as spray-freeze-drying, supercritical fluid, non-wetting templates, inkjet-printing, thin-film freezing, and hot-melt extrusion methods are also utilized. The aim of this review is to provide an overview of the respiratory tract structure, particle deposition patterns, and possible drug-clearance mechanisms from the lungs. This review also includes the physicochemical properties of dry powder, various techniques used for the preparation of dry powders, and factors affecting the clinical efficacy, as well as various challenges that need to be addressed in the future.

Development of High Dose Oseltamivir Phosphate Dry Powder for Inhalation Therapy in Viral Pneumonia

Oseltamivir phosphate (OP) is an antiviral drug available only as oral therapy for the treatment of influenza and as a potential treatment option when in combination with other medication in the fight against the corona virus disease (COVID-19) pneumonia. In this study, OP was formulated as a dry powder for inhalation, which allows drug targeting to the site of action and potentially reduces the dose, aiming a more efficient therapy. Binary formulations were based on micronized excipient particles acting like diluents, which were blended with the drug OP. Different excipient types, excipient ratios, and excipient size distributions were prepared and examined. To investigate the feasibility of delivering high doses of OP in a single dose, 1:1, 1:3, and 3:1 drug/diluent blending ratios have been prepared. Subsequently, the aerosolization performance was evaluated for all prepared formulations by cascade impaction using a novel medium-resistance capsule-based inhaler (UNI-Haler). Formulations with micronized trehalose showed relatively excellent aerosolization performance with highest fine-particle doses in comparison to examined lactose, mannitol, and glucose under similar conditions. Focusing on the trehalose-based dry-powder inhalers' (DPIs) formulations, a physicochemical characterization of extra micronized grade trehalose in relation to the achieved performance in dispersing OP was performed. Additionally, an early indication of inhaled OP safety on lung cells was noted by the viability MTT assay utilizing Calu-3 cells.

The Use of a Three-Fluid Atomising Nozzle in the Production of Spray-Dried Theophylline/Salbutamol Sulphate Powders Intended for Pulmonary Delivery

The aim of this study was to investigate the use of a three-fluid atomising nozzle in a lab-scale spray dryer for the production of dry powders intended for pulmonary delivery. Powders were composed of salbutamol sulphate and theophylline in different weight ratios. The three-fluid nozzle technology enabled powders containing a high theophylline content to be obtained, overcoming the problems associated with its relatively low solubility, by pumping two separate feed solutions (containing the two different active pharmaceutical ingredients (APIs)) into the spray dryer via two separate nozzle channels at different feed rates. The final spray-dried products were characterized in terms of morphology, solid-state properties and aerosolization performance, and were compared with an equivalent formulation prepared using a standard two-fluid atomising nozzle. Results confirmed that most of the powders made using the three-fluid atomising nozzle met the required standards for a dry powder inhaler formulation in terms of physical characteristics; however, aerosolization characteristics require improvement if the powders are to be considered suitable for pulmonary delivery.

Respiratory Tract: Structure and Attractions for Drug Delivery Using Dry Powder Inhalers

Respiratory tract is one of the oldest routes for drug delivery. It can be used for local and systemic drug deliveries. Inhalation therapy has several advantages over oral. It delivers the drug efficiently to the lung with minimal systemic exposure, thus avoiding systemic side effects common with oral route. In this review, different types of inhaler devices are illustrated like metered dose inhalers (MDIs), dry powder inhalers (DPIs), nebulizers, and the new soft mist inhalers (SMIs). Since dry powder is more stable than when in liquid form, we will discuss in detail DPIs highlighting different techniques utilized in preparation of dry powders with or without carrier to improve flowability and drug delivery to deep lungs. Types of DPIs are briefly discussed with examples from the market. Several mechanisms for particle deposition are mentioned with factors governing the process. Pharmacokinetic profile of the inhaled particles is detailed starting from the dissolution, followed by the rapid absorption and ending with systemic clearance. New technologies like 3D printing in pulmonary field are also highlighted.

Spray Drying for the Preparation of Nanoparticle-Based Drug Formulations as Dry Powders for Inhalation

Nanoparticle-based therapeutics have been used in pulmonary formulations to enhance delivery of poorly water-soluble drugs, protect drugs against degradation and achieve modified release and drug targeting. This review focuses on the use of spray drying as a solidification technique to produce microparticles containing nanoparticles (i.e., nanoparticle (NP) agglomerates) with suitable properties as dry powders for inhalation. The review covers the general aspects of pulmonary drug delivery with emphasis on nanoparticle-based dry powders for inhalation and the principles of spray drying as a method for the conversion of nanosuspensions to microparticles. The production and therapeutic applications of the following types of NP agglomerates are presented: nanoporous microparticles, nanocrystalline agglomerates, lipid-based and polymeric formulations. The use of alternative spray-drying techniques, namely nano spray drying, and supercritical CO2-assisted spray drying is also discussed as a way to produce inhalable NP agglomerates.

Medication Tracking: Design and Fabrication of a Dry Powder Inhaler with Integrated Acoustic Element by 3D Printing

PURPOSE

Asthma is a prevalent lung disorder that cause heavy burdens globally. Inhalation medicaments can relieve symptoms, improve lung function and, thus, the quality of life. However, it is well-documented that patients often do not get the prescribed dose out of an inhaler and the deposition of drug is suboptimal, due to incorrect handling of the device and wrong inhalation technique. This study aims to design and fabricate an acoustic dry powder inhaler (ADPI) for monitoring inhalation flow and related drug administration in order to evaluate whether the patient receives the complete dose out of the inhaler.

METHODS

The devices were fabricated using 3D printing and the impact of the acoustic element geometry and printing resolution on the acoustic signal was investigated. Commercial Foradil (formoterol fumarate) capsules were used to validate the availability of the ADPI for medication dose tracking. The acoustic signal was analysed with Partial-Least-Squares (PLS) regression.

RESULTS

Indicate that specific acoustic signals could be generated at different air flow rates using a passive acoustic element with specific design features. This acoustic signal could be correlated with the PLS model to the air flow rate. A more distinct sound spectra could be acquired at higher printing resolution. The sound spectra from the ADPI with no capsule, a full capsule and an empty capsule are different which could be used for medication tracking.

CONCLUSIONS

This study shows that it is possible to evaluate the medication quality of inhaled medicaments by monitoring the acoustic signal generated during the inhalation process.

Physical stability of dry powder inhaler formulations

Introduction: Dry powder inhalers (DPIs) are popular for pulmonary drug delivery. Various techniques have been employed to produce inhalation drug particles and improve the delivery efficiency of DPI formulations. Physical stability of these DPI formulations is critical to ensure the delivery of a reproducible dose to the airways over the shelf-life.Areas covered: This review focuses on the impact of solid-state stability on aerosolization performance of DPI drug particles manufactured by powder production approaches and particle-engineering techniques. It also highlights the different analytical tools that can be used to characterize the physical instability originating from production and storage.Expert opinion: A majority of the DPI literature focuses on the effects of physico-chemical properties such as size, morphology, and density on aerosolization. While little has been reported on the physical stability, particularly the stability of engineered drug particles for use in DPIs. Literature data have shown that different particle-engineering methods and storage conditions may cause physical instability of dry powders for inhalation and can significantly change the aerosol performance. A systematic examination of physical instability mechanisms in DPI formulations is necessary during formulation development in order to select the optimum formulation with satisfactory stability. In addition, the use of appropriate characterization tools is critical to detect and understand physical instability during the development of DPI formulations.

Formulation and evaluation of carrier-free dry powder inhaler containing sildenafil

Pulmonary delivery of sildenafil for the treatment of pulmonary arterial hypertension could overcome the limitations of intravenous and oral administration routes, such as poor patient compliance and systemic side effects. In this study, a carrier-free dry powder inhaler (DPI) formulation was developed, using spray drying technique and L-leucine as a dispersibility enhancer. Sildenafil citrate salt and sildenafil free base were evaluated for drug transport using a Calu-3 cell model, and their suitability for DPI production by spray drying was tested. Characteristics of the resultant carrier-free DPI powders were examined, namely crystallinity, morphology, size distribution, density, zeta potential, and aerodynamic performance. A Box-Behnken design was adopted to optimize the formulation and process conditions, including leucine amount, fraction of methanol in spraying solvent, and inlet temperature. While both sildenafil forms exhibited sufficient permeability for lung absorption, only sildenafil base resulted in DPI powders which were stable for 6 months. The introduction of leucine into the formulations effectively enhanced aerodynamic performance of the powders and particles with favorable size, shape, and density were produced. The optimal DPI formulation determined from experimental design possesses excellent aerodynamic performance with 89.39% emitted dose and 80.08% fine particle fraction, indicating the possibility of incorporating sildenafil into carrier-free DPIs for pulmonary delivery.

Moisture-Resistant Co-Spray-Dried Netilmicin with l-Leucine as Dry Powder Inhalation for the Treatment of Respiratory Infections

Netilmicin (NTM) is one of the first-line drugs for lower respiratory tract infections (LRTI) therapy, but its nephrotoxicity and ototoxicity caused by intravenous injection restrict its clinical application. Dry powder inhalation (DPI) is a popular local drug delivery system that is introduced as a solution. Due to the nature of NTM hygroscopicity that hinders its direct use through DPI, in this study, L-leucine (LL) was added into NTM dry powder to reduce its moisture absorption rate and improve its aerosolization performance. NTM DPIs were prepared using spray-drying with different LL proportions. The particle size, density, morphology, crystallinity, water content, hygroscopicity, antibacterial activity, in vitro aerosolization performance, and stability of each formulation were characterized. NTM DPIs were suitable for inhalation and amorphous with a corrugated surface. The analysis indicated that the water content and hygroscopicity were decreased with the addition of LL, whilst the antibacterial activity of NTM was maintained. The optimal formulation ND₂ (NTM:LL = 30:1) showed high fine particle fraction values (85.14 ± 8.97%), which was 2.78-fold those of ND₀ (100% NTM). It was stable after storage at 40 ± 2 °C, 75 ± 5% relative humidity (RH). The additional LL in NTM DPI successfully reduced the hygroscopicity and improved the aerosolization performance. NTM DPIs were proved to be a feasible and desirable approach for the treatment of LRTI.

Fragmented particles containing octreotide acetate prepared by spray drying technique for dry powder inhalation

Dry powder inhalers (DPIs) have been proposed as an alternative administration route for protein and peptide drugs. However, DPI particles are easy to aggregate due to the strong interactions between the particles, leading to poor aerosolization performance. In this study, fragmented particles containing octreotide acetate (OA) were prepared by spray drying technique for dry powder inhalation, which were expected to decrease the particle-particle interaction by reducing the contact sites. Mannitol and ammonium carbonate were used as protein stabilizer and fragment-forming agent, respectively. The obtained fragmented particles presented larger particle size, lower density, better dispersibility, and well in vitro aerodynamic behavior (emitted dose > 97%, fine particle fraction ≈ 40%). The circular dichroism spectrum results indicated that OA maintained the stability throughout the spray drying process. The relative bioavailability of dry powder inhalation (DPI) compared with subcutaneous injection of commercial product was up to 88.0%, demonstrating the feasibility of DPI for OA delivery. These results confirmed that the proposed fragmented particles had great potential for pulmonary delivery of protein and peptide drugs in a painless, rapid, and convenient manner.