Latest advances in the development of dry powder inhalers

Lipid polymer hybrid nanoparticles against lung cancer and their application as inhalable formulation

Lung cancer is a leading cause of global cancer mortality, often treated with chemotherapeutic agents. However, conventional approaches such as oral or intravenous administration of drugs yield low bioavailability and adverse effects. Nanotechnology has unlocked new gateways for delivering medicine to their target sites. Lipid-polymer hybrid nanoparticles (LPHNPs) are one of the nano-scaled delivery platforms that have been studied to exploit advantages of liposomes and polymers, enhancing stability, drug loading, biocompatibility and controlled release. Pulmonary administration of drug-loaded LPHNPs enables direct lung deposition, rapid onset of action and heightened efficacy at low doses of drugs. In this manuscript, we will review the potential of LPHNPs in management of lung cancer through pulmonary administration.

Inhalable tobramycin EEG powder formulation for treating Pseudomonas aeruginosa-induced lung infection

Pulmonary delivery of antibiotics is an effective strategy in treating bacterial lung infection for cystic fibrosis patients, by achieving high local drug concentrations and reducing overall systemic exposure compared to systemic administration. However, the inherent anatomical lung defense mechanisms, formulation characteristics, and drug-device combination determine the treatment efficacy of the aerosol delivery approach. In this study, we prepared a new tobramycin (Tobi) dry powder aerosol using excipient enhanced growth (EEG) technology and evaluated the in vitro and in vivo aerosol performance. We further established a Pseudomonas aeruginosa-induced lung infection rat model using an in-house designed novel liquid aerosolizer device. Notably, novel liquid aerosolizer yields comparable lung infection profiles despite administering 3-times lower P. aeruginosa CFU per rat in comparison to the conventional intratracheal administration. Dry powder insufflator (e.g. Penn-Century DP-4) to administer small powder masses to experimental animals is no longer commercially available. To address this gap, we developed a novel rat air-jet dry powder insufflator (Rat AJ DPI) that can emit 68-70 % of the loaded mass for 2 mg and 5 mg of Tobi-EEG powder formulations, achieving a high rat lung deposition efficiency of 79 % and 86 %, respectively. Rat AJ DPI can achieve homogenous distribution of Tobi EEG powder formulations at both loaded mass (2 mg and 5 mg) over all five lung lobes in rats. We then demonstrated that Tobi EEG formulation delivered by Rat AJ DPI can significantly decrease CFU counts in both trachea and lung lobes at 2 mg (p < 0.05) and 5 mg (p < 0.001) loaded mass compared to the untreated P. aeruginosa-infected group. Tobi EEG powder formulation delivered by the novel Rat AJ DPI showed excellent efficiencies in substantially reducing the P. aeruginosa-induced lung infection in rats.

Nano-Formulations for Pulmonary Delivery: Past, Present, and Future Perspectives

With the development of nanotechnology and confronting the problems of traditional pharmaceutical formulations in treating lung diseases, inhalable nano-formulations have attracted interest. Inhalable nano-formulations for treating lung diseases allow for precise pulmonary drug delivery, overcoming physiological barriers, improving aerosol lung deposition rates, and increasing drug bioavailability. They are expected to solve the difficulties faced in treating lung diseases. However, limited success has been recorded in the industrialization translation of inhalable nano-formulations. Only one relevant product has been approved by the FDA to date, suggesting that there are still many issues to be resolved in the clinical application of inhalable nano-formulations. These systems are characterized by a dependence on inhalation devices, while the adaptability of device formulation is still inconclusive, which is the most important issue impeding translational research. In this review, we categorized various inhalable nano-formulations, summarized the advantages of inhalable nano-formulations over conventional inhalation formulations, and listed the inhalable nano-formulations undergoing clinical studies. We focused on the influence of inhalation devices on nano-formulations and analyzed their adaptability. After extensive analysis of the drug delivery mechanisms, technical processes, and limitations of different inhalation devices, we concluded that vibrating mesh nebulizers might be most suitable for delivering inhalable nano-formulations, and related examples were introduced to validate our view. Finally, we presented the challenges and outlook for future development. We anticipate providing an informative reference for the field.

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.

Dry Powder Inhaler with the technical and practical obstacles, and forthcoming platform strategies

A Dry Powder Inhaler (DPI) is a technique as well as a device used to inhale formulation which is in the form of dry powder, and is inhaled through the nose or mouth. It was developed for the purpose of treating conditions like chronic obstructive pulmonary disease (COPD), Asthma, and even cystic fibrosis etc. The aim of the review is to discuss the different methods of preparation of dry powders along with the characterization of DPI. Here we present the outline of different methods like supercritical fluid extraction (SCF), spray drying, and milling. The review focussed on various devices including single and multi-dose devices used in the DPI. It also highlights on recent advances in the DPI including nano particulate system, siRNA-based medication, liposomes, and pro-liposomes based delivery. In COVID-19 silver nanoparticles-based DPIs provide very prominent results in the infected lungs. Moreover, this review states that the AI-based DPI development provides and improvement in the bioavailability and effectiveness of the drug along with the role of artificial neural networks (ANN). The study also showed that nasally administered drugs (nose to brain) can easily cross the blood-brain barrier (BBB) and enter the central nervous system (CNS) through the olfactory and trigeminal pathway which provides effective CNS concentrations at lower dosage. It is suggested that DPIs not only target respiratory complications but also treat CNS complications too. This review provides support and guides the researcher in the recent development and evaluation of DPI.

Effect of Texture and Surface Chemistry on Deagglomeration and Powder Retention in Capsule-Based Dry Powder Inhaler

Pulmonary delivery systems should administer a high dose of the required formulation with the designated dry powder inhaler (DPI) to achieve therapeutic success. While the effects of device geometry and individual components used on powder dispersion are described in literature, potential effects of DPI surface properties on powder retention within the device and deagglomeration have not been adequately studied, but could impact inhalation therapy by modifying the available dose. For this, inner parts of a model DPI were modified by plasma treatment using various processes. Since both the hydrophilic-hydrophobic and structural properties of the surface were altered, conclusions can be drawn for future optimization of devices. The results show that surface topography has a greater influence on powder deposition and deagglomeration than hydrophilic or hydrophobic surface modification. The most important modification was observed with an increased rough surface texture in the mouth piece, resulting in lower powder deposition in this part (from 5 to 1% quantified amount of powder), without any change in powder deagglomeration compared to an untreated device. In summary, increasing the surface roughness of DPI components in the size range of a few nanometers could be an approach for future optimization of DPIs to increase the delivered dose.

Scientific and regulatory activities initiated by the U.S. food and drug administration to foster approvals of generic dry powder inhalers: Quality perspective

Regulatory science for generic dry powder inhalation products worldwide has evolved over the last decade. The revised draft guidance Metered Dose Inhaler (MDI) and Dry Powder Inhaler (DPI) Products - Quality Considerations [1] (Revision 1, April 2018) that FDA issued summarizes product considerations and potential critical quality attributes (CQAs). This guidance emphasizes the need to apply the principles of quality by design (QbD) and elements of pharmaceutical development discussed in the International Conference for Harmonisation of (ICH) guidelines. Research studies related to quality were used to support guidance recommendations, which preceded the first approval of a generic DPI product in the U.S. This review outlines scientific and regulatory hurdles that need to be surmounted to successfully bring a generic DPI to the market. The goal of this review focuses on relevant issues and various challenges pertaining to CMC topics of the generic DPI quality attributes. Furthermore, this review provides recommendations to abbreviated new drug application (ANDA) applicants to expedite generic approvals.

A review of formulations and preclinical studies of inhaled rifampicin for its clinical translation

Inhaled drug delivery is a promising approach to achieving high lung drug concentrations to facilitate efficient treatment of tuberculosis (TB) and to reduce the overall duration of treatment. Rifampicin is a good candidate for delivery via the pulmonary route. There have been no clinical studies yet at relevant inhaled doses despite the numerous studies investigating its formulation and preclinical properties for pulmonary delivery. This review discusses the clinical implications of pulmonary drug delivery in TB treatment, the drug delivery systems reported for pulmonary delivery of rifampicin, animal models, and the animal studies on inhaled rifampicin formulations, and the research gaps hindering the transition from preclinical development to clinical investigation. A review of reports in the literature suggested there have been minimal attempts to test inhaled formulations of rifampicin in laboratory animals at relevant high doses and there is a lack of appropriate studies in animal models. Published studies have reported testing only low doses (≤ 20 mg/kg) of rifampicin, and none of the studies has investigated the safety of inhaled rifampicin after repeated administration. Preclinical evaluations of inhaled anti-TB drugs, such as rifampicin, should include high-dose formulations in preclinical models, determined based on allometric conversions, for relevant high-dose anti-TB therapy in humans.

Medical Device-related Counseling Practice and Barriers among Sudanese Pharmacists: A Questionnaire-Based Study

Objective:

The aim of the present study was to assess medical devices-related counseling practice and barriers among pharmacists.

Methods:

This was a cross-sectional study conducted using a convenient sample of Sudanese pharmacists. An online-version survey was used to collect data.

Findings:

One hundred and thirty pharmacists responded to the online survey. Most pharmacists in this sample were master or Ph.D. degree holders (62.3% and 12.3%, respectively), having a clinical training experience (70%) and substantial proportion are board-certified (30%). Medical devices reported to be commonly inquired by patients were blood glucose monitors, nebulizers, blood pressure monitors, dry powder inhalers, and insulin pens. Devices most frequently requiring counselling were blood glucose monitors, blood pressure monitors, syringes, thermometers, nebulizers, dry powder inhalers, insulin, and weighing scales. The most frequently supplied devices reported were syringes, blood glucose monitors, insulin pens, blood pressure monitors, thermometers, nebulizers, and dry powder inhalers. Devices least frequently requiring counselling were implanted devices, respirometers, and stethoscopes. The least frequently supplied devices were respirometers, implanted devices, and heart rate monitors.

Conclusion:

Medical devices reported to be commonly inquired by patients were most frequently requiring counseling, and most frequently supplied. Findings reflect the availability of devices in the market and pharmacists' response to the needs of their patients. Pharmacists should maintain adequate knowledge about the proper use of medical devices because this is a common patient inquiry.

Scope and limitations on aerosol drug delivery for the treatment of infectious respiratory diseases

The rise of antimicrobial resistance has created an urgent need for the development of new methods for antibiotics delivery to patients with pulmonary infections in order to mainly increase the effectiveness of the drugs administration, to minimize the risk of emergence of resistant strains, and to prevent patients reinfection. Since bacterial resistance is often related to antibiotic concentration, their pulmonary administration could eradicate strains resistant to the same drug at the concentration achieved through the systemic circulation. Pulmonary administration offers several advantages; it directly targets the site of the infection which allows the inhaled dose of the drug to be reduced compared to that administered orally or parenterally while keeping the same local effect. The review article is made with an objective to compile information about various existing modern technologies developed to provide greater patient compliance and reduce the undesirable side effect of the drugs. In conclusion, aerosol antibiotic delivery appears as one of the best technologies for the treatment of pulmonary infectious diseases and able to limit the systemic adverse effects related to the high drug dose and to make life easier for the patients.

Quality control and testing evaluation of pharmaceutical aerosols

Drug delivery to the respiratory tract locally has become an increasingly effective and important therapeutic method for treating a variety of pulmonary disorders, including chronic abstractive disease, asthma, bronchitis, pneumonia, and cystic fibrosis. Increase in prevalence respiratory disorders is a major factor driving the growth of global respiratory inhaler devices market. The effectiveness of pharmaceutical aerosols therapeutic performance is affected by various factors such as type and characteristics of propellants, whose properties are vapor pressure of propellants, viscosity and density flash point and also other factors such as type and characteristics of active ingredients, containers, valves, and actuators, along with percentage of moisture content and mechanism of emitted dose deposition, spray pattern, efficiency of valve crimping, and measurement of particle size aerosols. The purpose of this book chapter is to discuss the in-process and finished product quality control tests for pharmaceutical aerosols based on pharmacopeia standards and specifications.

Formulation of Dry Powder Inhaler of Anti-tuberculous Drugs Using Spray Drying Technique and Optimization Using 23 Level Factorial Design Approach

Background:

Targeting anti-tubercular therapeutics to alveolar macrophages using microparticles technology mainly focuses on increasing local concentrations of therapeutics and potentially reducing the frequency of dosing requirements. Rifampicin (RIF), Ofloxacin (OFX) and Ethambutol (ETH) combination show synergism.

Objective:

In light of the above facts, the focus of the present study was to develop and characterize novel Dry powder Inhaler formulation incorporating novel drug combination as a pulmonary delivery for the effective eradication of Tuberculosis.

Method:

Biodegradable microparticles containing RIF, OFX and ETH were prepared by a spray drying technique using PLGA polymer through the critical process as well as polymer attributes were screened and optimized using 23 factorial design. The identified critical process parameters (CPP’s) viz. Inlet temperature, Aspiration rate, and feed rate were selected as independent variables while percentage yield, percentage entrapment efficiency, and particle size were selected as a response. The formulated microparticles were evaluated for particle size, drug-polymer compatibility study, aerodynamic behavior, morphology, particle size distribution, crystallinity, residual solvent content, in-vitro drug release study, and stability study.

Results:

By choosing the optimum spray drying conditions maximum yield of 73%, entrapment efficiency of 86% and particle size of 1.4 μm was attained of the optimized batch. Thus the results revealed that spherical microparticles are suitable for inhalation and sustained release for 12 h.

Conclusion:

The successful formulation and evaluation of dry powder could be used as an enhanced therapeutic alternative of the standard oral anti-tubercular regimen, rescuing oral dosing, shortening drug regimen and limiting toxicity. This will ultimately improve patient compliance and diminish the prevalence of MDR resistance.

Delivery of Dry Powders to the Lungs: Influence of Particle Attributes from a Biological and Technological Point of View

Dry powder inhalers are medical devices used to deliver powder formulations of active pharmaceutical ingredients via oral inhalation to the lungs. Drug particles, from a biological perspective, should reach the targeted site, dissolve and permeate through the epithelial cell layer in order to deliver a therapeutic effect. However, drug particle attributes that lead to a biological activity are not always consistent with the technical requirements necessary for formulation design. For example, small cohesive drug particles may interact with neighbouring particles, resulting in large aggregates or even agglomerates that show poor flowability, solubility and permeability. To circumvent these hurdles, most dry powder inhalers currently on the market are carrier-based formulations. These formulations comprise drug particles, which are blended with larger carrier particles that need to detach again from the carrier during inhalation. Apart from blending process parameters, inhaler type used and patient's inspiratory force, drug detachment strongly depends on the drug and carrier particle characteristics such as size, shape, solid-state and morphology as well as their interdependency. This review discusses critical particle characteristics. We consider size of the drug (1-5 µm in order to reach the lung), solid-state (crystalline to guarantee stability versus amorphous to improve dissolution), shape (spherical drug particles to avoid macrophage clearance) and surface morphology of the carrier (regular shaped smooth or nano-rough carrier surfaces for improved drug detachment.) that need to be considered in dry powder inhaler development taking into account the lung as biological barrier.

Inhaled salbutamol from aerolizer and diskus at different inhalation flows, inhalation volume and number of inhalations in both healthy subjects and COPD patients

The aim of the present study was to demonstrate the effect of inhalation-flow, inhalation-volume and number of inhalations on aerosol-delivery of inhaled-salbutamol from two different dry powder inhalers (DPIs) in both healthy-subjects and chronic obstructive pulmonary disease (COPD) patients. Relative pulmonary-bioavailability and systemic-bioavailability of inhaled-salbutamol, delivered by Diskus and Aerolizer, was determined in 24-COPD patients and 24-healthy subjects. The healthy-subjects and the COPD-patients participated in the study for 7 days in which they received 4 study doses of 200 μg salbutamol (one slow-inhalation, two slow-inhalations, one fast-inhalation, and two fast-inhalations) in four alternative days with 24 hr washout period after each dose. Two urine-samples were collected from each study subjects. The first was provided 30 min post inhalation (USAL0.5), as an index of relative pulmonary-bioavailability, and the second was pooled to 24 hr post inhalation (USAL24), as an index of systemic-bioavailability. Fast-inhalation resulted in significantly higher USAL0.5 and USAL24 than slow-inhalation (p˂0.05) after one-inhalation in both healthy-subjects and COPD-patients but there was no significant difference between slow and fast-inhalation after two-inhalations. One-inhalation resulted in significantly higher USAL0.5 and USAL24 in healthy-subjects compared to COPD-patient at both slow and fast-inhalation (p˂0.05) except USAL0.5 with Diskus at slow-inhalation there was no significant difference. Also, two-inhalations resulted in significantly higher USAL0.5 and USAL24 compared to one-inhalation at slow-inhalation only (p˂0.05). No significant difference was found between Aerolizer and Diskus except in USAL0.5 of one slow-inhalation in both health-subjects and COPD-patients (p = 0.048 and 0.047, respectively). Device-formula relation is present at low inhalation-flow since Diskus resulted in significantly higher USAL0.5 and USAL24 in healthy-subjects compared to COPD-patient at slow inhalation than Aerolizer. It is essential to inhale-twice and as hard and deep as possible from each dose when using DPI especially with COPD-patients having poor inspiratory efforts such as elderly patients and children.

Lung delivery of nanoliposomal salbutamol sulfate dry powder inhalation for facilitated asthma therapy

The motive behind present work was to discover a solution for overcoming the problems allied with a deprived oral bioavailability of salbutamol sulfate (SS) due to its first pass hepatic metabolism, shorter half-life, and systemic toxicity at high doses. Pulmonary delivery provides an alternative route of administration to avoid hepatic metabolism of SS, moreover facilitated diffusion and prolonged retention can be achieved by incorporation into liposomes. Liposomes were prepared by thin film hydration technique using 3² full factorial design and formulation was optimized based on the vesicle size and percent drug entrapment (PDE) of liposomes. Optimized liposomal formulation exhibited an average size of about 167.2 ± 0.170 nm, with 80.68 ± 0.74% drug entrapment, and 9.74 ± 1.10 mV zeta potential. The liposomal dispersion was then spray dried and further characterized for in-vitro aerosol performance using Andersen Cascade Impactor. Optimized liposomal formulation revealed prolonged in-vitro drug release of more than 90% up to 14 h following Higuchi's controlled release model. Thus, the proposed new-fangled liposomal formulation would be a propitious alternative to conventional therapy for efficient and methodical treatment of asthma and alike respiratory ailments.

The use of a quartz crystal microbalance as an analytical tool to monitor particle/surface and particle/particle interactions under dry ambient and pressurized conditions: a study using common inhaler components

Metered dose inhalers (MDI) and multidose powder inhalers (MPDI) are commonly used for the treatment of chronic obstructive pulmonary diseases and asthma. Currently, analytical tools to monitor particle/particle and particle/surface interaction within MDI and MPDI at the macro-scale do not exist. A simple tool capable of measuring such interactions would ultimately enable quality control of MDI and MDPI, producing remarkable benefits for the pharmaceutical industry and the users of inhalers. In this paper, we have investigated whether a quartz crystal microbalance (QCM) could become such a tool. A QCM was used to measure particle/particle and particle/surface interactions on the macroscale, by additions of small amounts of MDPI components, in the powder form into a gas stream. The subsequent interactions with materials on the surface of the QCM sensor were analyzed. Following this, the sensor was used to measure fluticasone propionate, a typical MDI active ingredient, in a pressurized gas system to assess its interactions with different surfaces under conditions mimicking the manufacturing process. In both types of experiments the QCM was capable of discriminating interactions of different components and surfaces. The results have demonstrated that the QCM is a suitable platform for monitoring macro-scale interactions and could possibly become a tool for quality control of inhalers.

Simulation of the human airways using virtual topology tools and meshing optimization

A method is proposed to improve the quality of the three-dimensional airway geometric models using a commercial software, checking the number of elements, meshing time, and aspect ratio and skewness parameters. The use of real and virtual topologies combined with patch-conforming and patch-independent meshing algorithms results in four different models being the best solution the combination of virtual topology and patch-independent algorithm, due to an excellent aspect ratio and skewness of the elements, and minimum meshing time. The result is a reduction in the computational time required for both meshing and simulation due to a smaller number of cells. The use of virtual topologies combined with patch-independent meshing algorithms could be extended in bioengineering because the geometries handling is similar to this case. The method is applied to a healthy person using their computed tomography images. The resulting numerical models are able to simulate correctly a forced spirometry.

Inhalation drug delivery devices: technology update

The pulmonary route of administration has proven to be effective in local and systemic delivery of miscellaneous drugs and biopharmaceuticals to treat pulmonary and non-pulmonary diseases. A successful pulmonary administration requires a harmonic interaction between the drug formulation, the inhaler device, and the patient. However, the biggest single problem that accounts for the lack of desired effect or adverse outcomes is the incorrect use of the device due to lack of training in how to use the device or how to coordinate actuation and aerosol inhalation. This review summarizes the structural and mechanical features of aerosol delivery devices with respect to mechanisms of aerosol generation, their use with different formulations, and their advantages and limitations. A technological update of the current state-of-the-art designs proposed to overcome current challenges of existing devices is also provided.

Preparation and Evaluation of Surface Modified Lactose Particles for Improved Performance of Fluticasone Propionate Dry Powder Inhaler

BACKGROUND

Dry powder inhalers (DPI) are generally formulated by mixing micronized drug particles with coarse lactose carrier particles to assist powder handling during the manufacturing and powder aerosol delivery during patient use.

METHODS

In the present study, surface modified lactose (SML) particles were produced using force control agents, and their in vitro performance on dry powder inhaler (DPI) formulation of Fluticasone propionate was studied. With a view to reduce surface passivation of high surface free energy sites on the most commonly used DPI carrier, α- lactose monohydrate, effects of various force control agents such as Pluronic F-68, Cremophor RH 40, glyceryl monostearate, polyethylene glycol 6000, magnesium stearate, and soya lecithin were studied.

RESULTS

DPI formulations prepared with SML showed improved flow properties, and atomic force microscopy (AFM) studies revealed decrease in surface roughness. The DSC and X-ray diffraction patterns of SML showed no change in the crystal structure and thermal behavior under the experimental conditions. The fine particle fraction (FPF) values of lactose modified with Pluronic F-68, Cremophor RH 40, glyceryl monostearate were improved, with increase in concentration up to 0.5%. Soya lecithin and PEG 6000 modified lactose showed decrease in FPF value with increase in concentration. Increase in FPF value was observed with increasing concentration of magnesium stearate. Two different DPI devices, Rotahaler(®) and Diskhaler(®), were compared to evaluate the performance of SML formulations. FPF value of all SML formulations were higher using both devices as compared to the same formulations prepared using untreated lactose. One month stability of SML formulations at 40°C/75% RH, in permeable polystyrene tubes did not reveal any significant changes in FPF values.

CONCLUSION

SML particles can help in reducing product development hindrances and improve inhalational properties of DPI.

Dry powders for oral inhalation free of lactose carrier particles

Dry powder inhaler (DPI) products have traditionally comprised a simple formulation of micronised drug mixed with a carrier excipient, typically lactose monohydrate. The presence of the carrier is aimed at overcoming issues of poor flowability and dispersibility, associated with the cohesive nature of small, micronised active pharmaceutical ingredient (API) particles. Both the powder blend and the DPI device must be carefully designed so as to ensure detachment of the micronised drug from the carrier excipient on inhalation. Over the last two decades there has been a significant body of research undertaken on the design of carrier-free formulations for DPI products. Many of these formulations are based on sophisticated particle engineering techniques; a common aim in formulation design of carrier-free products being to reduce the intrinsic cohesion of the particles, while maximising dispersion and delivery from the inhaler. In tandem with the development of alternative formulations has been the development of devices designed to ensure the efficient delivery and dispersion of carrier-free powder on inhalation. In this review we examine approaches to both the powder formulation and inhaler design for carrier-free DPI products.

Technological and practical challenges of dry powder inhalers and formulations

In the 50 years following the introduction of the first dry powder inhaler to the market, several developments have occurred. Multiple-unit dose and multi-dose devices have been introduced, but first generation capsule inhalers are still widely used for new formulations. Many new particle engineering techniques have been developed and considerable effort has been put in understanding the mechanisms that control particle interaction and powder dispersion during inhalation. Yet, several misconceptions about optimal inhaler performance manage to survive in modern literature. It is, for example still widely believed that a flow rate independent fine particle fraction contributes to an inhalation performance independent therapy, that dry powder inhalers perform best at 4 kPa (or 60 L/min) and that a high resistance device cannot be operated correctly by patients with reduced lung function. Nevertheless, there seems to be a great future for dry powder inhalation. Many new areas of interest for dry powder inhalation are explored and with the assistance of new techniques like computational fluid dynamics and emerging particle engineering technologies, this is likely to result in a new generation of inhaler devices and formulations, that will enable the introduction of new therapies based on inhaled medicines.

Formulation considerations for dry powder inhalers

The market for inhalable dry powder medication has consistently grown over past years. Targeting the lungs has been recognized to offer several advantages compared with oral application of drugs. The successive development of inhalation products has led to advances in local treatment of different respiratory diseases, but has also demonstrated the possibility to utilize the lungs for systemic drug delivery. Since a dry powder inhalation product is always a combination of drug formulation and inhalation device, the requirements for the development of such a system may be particularly complex. Therefore, this review aims to give an overview of the necessary considerations for a successful dry powder inhaler development.

Evaluation and modification of commercial dry powder inhalers for the aerosolization of a submicrometer excipient enhanced growth (EEG) formulation

The aim of this study was to evaluate and modify commercial dry powder inhalers (DPIs) for the aerosolization of a submicrometer excipient enhanced growth (EEG) formulation. The optimized device and formulation combination was then tested in a realistic in vitro mouth-throat - tracheobronchial (MT-TB) model. An optimized EEG submicrometer powder formulation, consisting of albuterol sulfate (drug), mannitol (hygroscopic excipient), l-leucine (dispersion enhancer) and poloxamer 188 (surfactant) in a ratio of 30:48:20:2 was prepared using a Büchi Nano spray dryer. The aerosolization performance of the EEG formulation was evaluated with five conventional DPIs: Aerolizer, Novolizer, HandiHaler, Exubera and Spiros. To improve powder dispersion, the HandiHaler was modified with novel mouth piece (MP) designs. The aerosol performance of each device was assessed using a next generation impactor (NGI) at airflow rates generating a pressure drop of 4 kPa across the DPI. In silico and in vitro deposition and hygroscopic growth of formulations was studied using a MT-TB airway geometry model. Both HandiHaler and Aerolizer produced high emitted doses (EDs) together with a significant submicrometer aerosol fraction. A modified HandiHaler with a MP including a three-dimensional (3D) array of rods (HH-3D) produced a submicrometer particle fraction of 38.8% with a conventional fine particle fraction (%<5 μm) of 97.3%. The mass median diameter (MMD) of the aerosol was reduced below 1 μm using this HH-3D DPI. The aerosol generated from the modified HandiHaler increased to micrometer size (2.8 μm) suitable for pulmonary deposition, when exposed to simulated respiratory conditions, with negligible mouth-throat (MT) deposition (2.6%).

Aerosolization characteristics of dry powder inhaler formulations for the excipient enhanced growth (EEG) application: effect of spray drying process conditions on aerosol performance

The aim of this study was to develop a spray dried submicrometer powder formulation suitable for the excipient enhanced growth (EEG) application. Combination particles were prepared using the Buchi Nano spray dryer B-90. A number of spray drying and formulation variables were investigated with the aims of producing dry powder formulations that were readily dispersed upon aerosolization and maximizing the fraction of submicrometer particles. Albuterol sulfate, mannitol, L-leucine, and poloxamer 188 were selected as a model drug, hygroscopic excipient, dispersibility enhancer and surfactant, respectively. Formulations were assessed by scanning electron microscopy and aerosol performance following aerosolization using an Aerolizer dry powder inhaler (DPI). In vitro drug deposition was studied using a realistic mouth-throat (MT) model. Based on the in vitro aerosolization results, the best performing submicrometer powder formulation consisted of albuterol sulfate, mannitol, L-leucine and poloxamer 188 in a ratio of 30:48:20:2, containing 0.5% solids in a water:ethanol (80:20%, v/v) solution which was spray dried at 70 °C. The submicrometer particle fraction (FPF(1 μm/ED)) of this final formulation was 28.3% with more than 80% of the capsule contents being emitted during aerosolization. This formulation also showed 4.1% MT deposition. The developed combination formulation delivered a powder aerosol developed for the EEG application with high dispersion efficiency and low MT deposition from a convenient DPI device platform.

Respirable dry powder formulation of bleomycin for developing a pulmonary fibrosis animal model

The main purpose of the present study was to develop a respirable powder (RP) formulation of bleomycin (BLM) as a research tool for developing a pulmonary fibrosis animal model. The BLM-RP was prepared with a jet-milling system, the physicochemical properties of which were characterized focusing on morphology, stability, particle size distribution, and inhalation performance. Under an accelerated condition, the BLM-RP was superior to BLM solution in terms of its stability. Cascade impactor analyses demonstrated high inhalation performance with emitted dose and fine particle fraction of approximately 99% and 46%, respectively. Intratracheal administration of the BLM-RP (3 mg BLM/kg) in rats led to significant increases in collagen production and recruitment of inflammatory cells in lung by approximately 1.5- and 29-fold, respectively. The collagen overexpression was consistent with the results from picrosirius red staining of lung tissues in the rats treated with BLM-RP. Inhaled tranilast (TL; 100 μg/rat), an antifibrotic agent, could ameliorate inflammatory/fibrotic responses with reductions of recruited inflammatory cells and collagen content by 32% and 59%, respectively, validating the pulmonary fibrosis animal model. From these findings, the BLM-RP with improved stability could be a beneficial research tool for developing a pulmonary fibrosis model in drug discovery for antifibrotic drug candidates.

Propellant-based inhalers for the non-invasive delivery of genes via oral inhalation

In this work we describe the development of a propellant-based, portable oral inhalation platform for the pulmonary delivery of genes. A core-shell strategy is utilized to efficiently disperse cationic-polymer-DNA nanoparticles in hydrofluoroalkane propellants, and to generate aerosols from the corresponding pressurized metered-dose inhaler formulations (pMDIs) that have excellent aerosol characteristics, suitable for deep lung deposition. The engineered polyplexes and core-shell structures were fully characterized, and their ability to transfect model lung alveolar epithelium cells in vitro was demonstrated. We also show that the propellant does not affect the biological activity of the plasmid DNA, and that the core-shell formulations have no in vitro cytotoxicity. The relevance of this work stems from the fact that pMDIs are the least expensive and most widely used portable oral inhalation devices, and are thus promising platforms for targeting genes to the lungs for the treatment of medically relevant diseases including asthma, cystic fibrosis, chronic obstructive pulmonary disease, and lung cancer.

Investigating the interactions of amino acid components on a mannitol-based spray-dried powder formulation for pulmonary delivery: A design of experiment approach

Combining an amino acid and a sugar is a known strategy in the formulation of spray or freeze dried biomolecule powder formulations. The effect of the amino acid leucine in enhancing performance of spray-dried powders has been previously demonstrated, but interaction effects of several constituents which may provide multiple benefits, are less well-understood. A 3 factor 2 level (2(3)) factorial design was used to study the effects of leucine, glycine and alanine in a mannitol-based dry powder formulation on particle size, aerosolisation, emitted dose and cohesion. Other qualitative tests including scanning electronic microscopy and X-ray powder diffraction were also conducted on the design of experiment (DoE) trials. The results show that the use of glycine and/or alanine, though structurally related to leucine, did not achieve similar aerosol performance enhancing effects, rather the particle formation was hindered. However, when used in appropriate concentrations with leucine, the combination of amino acids produced an enhanced performance regardless of the presence of glycine and/or alanine, yielding significantly modified particle properties. The results from the DoE analyses also revealed the lack of linearity of effects for certain responses with a significant curvature in the model which would otherwise not be discovered using a trial-and-error approach.

The influence of physical properties and morphology of crystallised lactose on delivery of salbutamol sulphate from dry powder inhalers

The aim of this work was to investigate the mechanistic evaluation of physicochemical properties of new engineered lactose on aerosolisation performance of salbutamol sulphate (SS) delivered from dry powder inhaler (DPI). Different crystallised lactose particles were obtained from binary mixtures of butanol:acetone. The sieved fractions (63-90 μm) of crystallised lactose were characterised in terms of size, shape, flowability, true density and aerosolisation performance (using multiple twin stage impinger (MSLI), Aerolizer(®) inhaler device, and salbutamol sulphate as a model drug). Compared to commercial lactose, crystallised lactose particles were less elongated, covered with fine lactose particles, and had a rougher surface morphology. The crystallised lactose powders had a considerably lower bulk and tap density and poorer flow when compared to commercial lactose. Engineered carrier with better flow showed improved drug content homogeneity, reduced amounts of drug "deposited" on the inhaler device and throat, and a smaller drug aerodynamic diameter upon inhalation. Aerodynamic diameter of salbutamol sulphate increased as lactose aerodynamic diameter decreased (linear, R(2)=0.9191) and/or as fine particle lactose content increased (linear, R(2)=0.8653). Improved drug aerosolisation performance in the case of crystallised lactose particles was attributed to lower drug-carrier adhesion forces due to a rougher surface and higher fine particle content. In conclusion, this work proved that using binary combinations of solvents in crystallisation medium is vital in modification of the physicochemical and micromeritic properties of carriers to achieve a desirable aerosolisation performance from DPI formulations. Among all lactose samples, lactose particles crystallised from pure butanol generated the highest overall DPI formulations desirability.

Characteristics of a capsule based dry powder inhaler for the delivery of indacaterol

OBJECTIVE

To report performance characteristics and robustness of the Breezhaler device, a new capsule based dry powder inhaler (DPI) with low resistance (0.07 cm H(2)O(½)/L/min) facilitating high inspiratory flow rates. This device was developed to deliver the novel, inhaled once-daily ultra long-acting β(2)-agonist indacaterol, formulated as an inhalation powder in a capsule, and other investigational drugs including NVA237 and QVA149.

RESEARCH DESIGN AND METHODS

Peak inspiratory flow rates via the DPI device were determined in patients with chronic obstructive pulmonary disease (COPD) using an Inhalation Profile Recorder. The flow-rate dependency of the in vitro performance (delivered dose and fine particle mass) of indacaterol in the DPI device was examined. Data on patient experience were captured throughout the indacaterol phase III registration program, and the robustness of the device was investigated after mechanical stress.

RESULTS

Twenty-six patients with COPD that ranged from mild to very severe were recruited (aged 49-84 years); 25 patients were able to generate flow rates in excess of 60 L/min via the DPI device. The mean delivered dose of indacaterol (150 and 300 µg) remained within 15% of the target dose, with a consistent fine particle mass at flow rates of 50-100 L/min. In the indacaterol registration program, patients with mild to very severe COPD were able to use the device successfully, with a low device complaint rate (<0.03%) and no device failures from approximately 90,000 devices. In mechanical stress tests, drop testing resulted in, at most, only cosmetic damage, with no effect on the delivered dose.

CONCLUSION

The capsule based DPI device is a low resistance device, suitable for use by patients with a wide range of COPD severities, delivering a consistent dose irrespective of disease severity and age. The device provided consistent delivery of indacaterol with no reported device failures in clinical trials.

Recent advances in liposomal dry powder formulations: preparation and evaluation

Liposomal drug dry powder formulations have shown many promising features for pulmonary drug administration, such as selective localization of drug within the lung, controlled drug release, reduced local and systemic toxicities, propellant-free nature, patient compliance, high dose carrying capacity, stability and patent protection. Critical review of the recent developments will provide a balanced view on benefits of liposomal encapsulation while developing dry powder formulations and will help researchers to update themselves and focus their research in more relevant areas. In liposomal dry powder formulations (LDPF), drug encapsulated liposomes are homogenized, dispersed into the carrier and converted into dry powder form by using freeze drying, spray drying and spray freeze drying. Alternatively, LDPF can also be formulated by supercritical fluid technologies. On inhalation with a suitable inhalation device, drug encapsulated liposomes get rehydrated in the lung and release the drug over a period of time. The prepared LDPF are evaluated in vitro and in vivo for lung deposition behavior and drug disposition in the lung using a suitable inhaler device. The most commonly used liposomes are composed of lung surfactants and synthetic lipids. Delivery of anticancer agents for lung cancer, corticosteroids for asthma, immunosuppressants for avoiding lung transplantation rejection, antifungal drugs for lung fungal infections, antibiotics for local pulmonary infections and cystic fibrosis and opioid analgesics for pain management using liposome technology are a few examples. Many liposomal formulations have reached the stage of clinical trials for the treatment of pulmonary distress, cystic fibrosis, lung fungal infection and lung cancer. These formulations have given very promising results in both in vitro and in vivo studies. However, modifications to new therapies for respiratory diseases and systemic delivery will provide new challenges in conducting well-designed inhalation toxicology studies to support these products, especially for chronic diseases.

Chapter 9 - Nanoliposomal dry powder formulations

Liposomal dry powder formulations (DPFs) have proven their superiority over conventional DPFs due to favorably improved pharmacokinetics and pharmacodynamics of entrapped drugs, and thus, reduced local and systemic toxicities. Nanoliposomal DPFs (NLDPFs) provide stable, high aerosolization efficiency to deep lung, prolonged drug release, slow systemic dilution, and avoid macrophage uptake of encapsulated drug by carrier-based delivery of nano-range liposomes. This chapter describes methods of preparation of nanoliposomes (NLs) and NLDPFs, using various techniques, and their characterization with respect to size distribution, flow behavior, in vitro drug release profile, lung deposition, cellular uptake and cytotoxicity, and in vivo pharmacokinetics and pharmacodynamics. Some examples have been detailed for better understanding of the methods of preparation and evaluation of NLDPFs by investigators.