Design of fine particles for pulmonary drug delivery

Use of a fundamental approach to spray-drying formulation design to facilitate the development of multi-component dry powder aerosols for respiratory drug delivery

PURPOSE

A fundamental approach incorporating current theoretical models into aerosol formulation design potentially reduces experimental work for complex formulations. A D-amino acid mixture containing D-Leucine (D-Leu), D-Methionine, D-Tryptophan, and D-Tyrosine was selected as a model formulation for this approach.

METHODS

Formulation design targets were set, with the aim of producing a highly dispersible D-amino acid aerosol. Particle formation theory and a spray dryer process model were applied with boundary conditions to the design targets, resulting in a priori predictions of particle morphology and necessary spray dryer process parameters. Two formulations containing 60% w/w trehalose, 30% w/w D-Leu, and 10% w/w remaining D-amino acids were manufactured.

RESULTS

The design targets were met. The formulations had rugose and hollow particles, caused by deformation of a crystalline D-Leu shell while trehalose remained amorphous, as predicted by particle formation theory. D-Leu acts as a dispersibility enhancer, ensuring that both formulations: 1) delivered over 40% of the loaded dose into the in vitro lung region, and 2) achieved desired values of lung airway surface liquid concentrations based on lung deposition simulations.

CONCLUSIONS

Theoretical models were applied to successfully achieve complex formulations with design challenges a priori. No further iterations to the design process were required.

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.

Pretreatment with inhaled procaterol improves symptoms of dyspnea and quality of life in patients with severe COPD

BACKGROUND

The clinical efficacy of short-acting β(2)-agonists administered before performing daily activities in chronic obstructive pulmonary disease (COPD) is unclear. The aim of this study was to investigate the clinical effect of supplementary inhaled procaterol hydrochloride in patients with COPD.

METHODS

Thirty outpatients with moderate to severe COPD (Stage II-IV) regularly using inhaled tiotropium bromide alone and with dyspnea during daily activities were enrolled. Subjects self-administered 20 μg of inhaled procaterol before daily activities no more than four times daily. Dyspnea symptom scores, St George's Respiratory Questionnaire (SGRQ) activity domains, impulse oscillometry system parameters, and pulmonary function tests were recorded at the beginning and end of the 2-week study.

RESULTS

At baseline, more than 80% of subjects reported dyspnea when walking up a slope (100.0%), climbing stairs (100.0%), gardening (93.3%), walking on flat ground (90.0%), bathing (86.7%), getting on a bus or train (83.3%), and changing clothes (80.0%). After 2 weeks, subjects with Stage III symptoms had significantly improved dyspnea scores on walking up a slope (P = 0.047), climbing stairs (P = 0.014), gardening (P = 0.034), walking on flat ground (P = 0.006), getting on a bus or train (P = 0.039), and changing clothes (P = 0.045). Both symptom and activity SGRQ domains improved significantly in subjects with Stage III symptoms (P = 0.036 and P = 0.028, respectively). Resistance of small airways and low-frequency reactance area values improved significantly in subjects with Stage III symptoms (P = 0.003 and P = 0.004, respectively). No significant changes were found in pulmonary function tests.

CONCLUSION

Use of supplementary inhaled procaterol before performing daily activities improved dyspnea symptoms in subjects with Stage III COPD.

Dose emission characteristics of placebo PulmoSphere® particles are unaffected by a subject's inhalation maneuver

BACKGROUND

Good compliance to the prescribed dosing regimen and inhaler instructions for use are critical for asthma/chronic obstructive pulmonary disease (COPD) patients to achieve good control of their disease. We investigated the extent to which a system comprising porous particles delivered with a passive dry powder inhaler could be designed to achieve significant reductions in dose inhalation errors.

METHODS

Porous placebo particles were prepared by an emulsion-based spray-drying method (PulmoSphere® technology). The formulations were administered as dry powders with a portable, blister-based dry powder inhaler (Simoon Inhaler). The inhalation profiles of 69 asthma/COPD subjects were determined with an inhaler simulator with resistance comparable to that of the Simoon Inhaler. Powder emptying from the device was assessed by laser photometry. Aerosol performance was assessed on a Next Generation Impactor, and with the idealized Alberta mouth-throat model using both square-wave and subject-inhalation profiles generated in the breathing study.

RESULTS

Virtually all subjects could achieve a pressure drop of at least 1 kPa and an inhaled volume of at least 500 mL with the Simoon Inhaler. In vitro measures of particle deposition were found to be largely independent of the inhalation maneuver (flow rate, inhaled volume, ramp time) across the broad range of inhalation profiles observed in the breathing study. The rapid emptying of powder from the Simoon Inhaler minimizes the impact of dose-related errors, such as failure to exhale before inhalation and failure to breath-hold post inhalation.

CONCLUSIONS

Inertial impaction that is largely independent of a subject's inhalation maneuver can be achieved with a drug/device combination product comprising a porous particle formulation and blister-based inhaler.

Drug-lactose binding aspects in adhesive mixtures: controlling performance in dry powder inhaler formulations by altering lactose carrier surfaces

For dry powder inhaler formulations, micronized drug powders are commonly mixed with coarse lactose carriers to facilitate powder handling during the manufacturing and powder aerosol delivery during patient use. The performance of such dry powder inhaler formulations strongly depends on the balance of cohesive and adhesive forces experienced by the drug particles under stresses induced in the flow environment during aerosolization. Surface modification with appropriate additives has been proposed as a practical and efficient way to alter the inter-particulate forces, thus potentially controlling the formulation performance, and this strategy has been employed in a number of different ways with varying degrees of success. This paper reviews the main strategies and methodologies published on surface coating of lactose carriers, and considers their effectiveness and impact on the performance of dry powder inhaler formulations.

Novel cosuspension metered-dose inhalers for the combination therapy of chronic obstructive pulmonary disease and asthma

Pressurized metered dose inhaler is the most common inhaled dosage form, ideally suited for delivering the highly potent compounds that medicinal chemists typically discover for respiratory therapeutic targets. The clinical benefit of combination therapy for asthma and chronic obstructive pulmonary disease has been well established, and many of the new discovery candidates are likely to be studied in the clinic as combination drugs even at early stages of development. We present a novel pressurized metered dose inhaler formulation approach to enable consistent aerosol performance of a respiratory therapeutic whether it is emitted from a single-, double- or triple-therapy product. This should enable rapid nonclinical and clinical assessment whether alone or in combination with other drugs, without the challenge of in vitro performance dissimilarity across product types.

Novel dry powder inhaler particle-dispersion systems

Dry powder inhalers are a diverse family of devices that have emerged as a rapidly growing segment of the respiratory therapeutics area. The forces that these devices must impart into dry powder formulations for effective dispersion performance and reproducibility of delivery are relatively large, and multiple mechanisms have been developed in attempts to improve the efficiency of these systems. In this review, we address the reasons for the proliferation of dry powder inhalers, beginning with an abbreviated introduction on the basic inter-particulate forces that need to be disrupted to achieve successful powder dispersion and effective lung delivery. From this background, we survey the diversity of inhaler designs, starting from marketed devices, before introducing some of the novel device designs under development, both patient driven (passive) and device driven (active), as we attempt to link the themes of the device design features to the present understanding of the dynamics governing powder dispersion. Finally, we conclude by providing some assessment on the future of the wide range of device designs and mechanisms that have evolved by considering technical, regulatory and market forces.

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.

Nanoparticle-stabilized colloids in compressible hydrofluoroalkanes

In this work, we show that nanoparticles (NPs) dispersed in compressible hydrofluoroalkanes (HFAs) at small volume fractions are capable of stabilizing micrometer-sized particle colloids, which otherwise flocculate due to strong van der Waals forces. Water-soluble, biodegradable NPs with a chitosan (CS) core, grafted with highly HFA-philic moieties, can be readily dispersed in the low dielectric HFAs and are capable of imparting stability to a wide range of therapeutic particles having different chemistries (polar or hydrophobic; small and large molecular weight, including peptides and proteins) and morphologies (micronized crystals or amorphous). These NP systems thus serve as a broadly applicable platform for the noninvasive delivery of therapeutics to and through the lungs using propellant-based, portable inhalers, and are also of potential relevance in other industries where HFAs are employed as solvents or propellants. This concept may also be applicable to other compressible solvents.

Spray-dried respirable powders containing bacteriophages for the treatment of pulmonary infections

Myoviridae bacteriophages were processed into a dry powder inhalable dosage form using a low-temperature spray-drying process. The phages were incorporated into microparticles consisting of trehalose, leucine, and optionally a third excipient (either a surfactant or casein sodium salt). The particles were designed to have high dispersibility and a respirable particle size, and to preserve the phages during processing. Bacteriophages KS4- M, KS14, and cocktails of phages ΦKZ/D3 and ΦKZ/D3/KS4-M were spray-dried with a processing loss ranging from 0.4 to 0.8 log pfu. The aerosol performance of the resulting dry powders as delivered from an Aerolizer® dry powder inhaler (DPI) exceeded the performance of commercially available DPIs; the emitted mass and the in vitro total lung mass of the lead formulation were 82.7% and 69.7% of filled capsule mass, respectively. The total lung mass had a mass median aerodynamic diameter of 2.5-2.8 µm. The total in vitro lung doses of the phages, delivered from a single actuation of the inhaler, ranged from 10(7) to 10(8) pfu, levels that are expected to be efficacious in vivo. Spray drying of bacteriophages into a respirable dry powder was found to be feasible.

Development of an inhaled dry-powder formulation of tobramycin using PulmoSphere™ technology

Abstract At present, the only approved inhaled antipseudomonal antibiotics for chronic pulmonary infections in patients with cystic fibrosis (CF) are nebulized solutions. However, prolonged administration and cleaning times, high administration frequency, and cumbersome delivery technologies with nebulizers add to the high treatment burden in this patient population. PulmoSphere™ technology is an emulsion-based spray-drying process that enables the production of light porous particle, dry-powder formulations, which exhibit improved flow and dispersion from passive dry powder inhalers. This review explores the fundamental characteristics of PulmoSphere technology, focusing on the development of a dry powder formulation of tobramycin for the treatment of chronic pulmonary Pseudomonas aeruginosa (Pa) infection in CF patients. This dry powder formulation provides substantially improved intrapulmonary deposition efficiency, faster delivery, and more convenient administration over nebulized formulations. The availability of more efficient and convenient treatment options may improve treatment compliance, and thereby therapeutic outcomes in CF.

Formation, characterization, and fate of inhaled drug nanoparticles

Nanoparticles bring many benefits to pulmonary drug delivery applications, especially for systemic delivery and drugs with poor solubility. They have recently been explored in pressurized metered dose inhaler, nebulizer, and dry powder inhaler applications, mostly in polymeric forms. This article presents a review of processes that have been used to generate pure (non polymeric) drug nanoparticles, methods for characterizing the particles/formulations, their in-vitro and in-vivo performances, and the fate of inhaled nanoparticles.

Dry powder vaccines for mucosal administration: critical factors in manufacture and delivery

Dry powder vaccine formulations have proved effective for induction of systemic and mucosal immune responses. Here we review the use of dry vaccines for immunization in the respiratory tract. We discuss techniques for powder formulation, manufacture, characterization and delivery in addition to methods used for evaluation of stability and safety. We review the immunogenicity and protective efficacy of dry powder vaccines as compared to liquid vaccines delivered by mucosal or parenteral routes. Included is information on mucosal adjuvants and mucoadhesives that can be used to enhance nasal or pulmonary dry vaccines. Mucosal immunization with dry powder vaccines offers the potential to provide a needle-free and cold chain-independent vaccination strategy for the induction of protective immunity against either systemic or mucosal pathogens.

Personalizing aerosol medicine: development of delivery systems tailored to the individual

Inhalation of drugs for therapeutic effects is not a recent innovation as illicit drugs have been ‘smoked’ for millennia. Nicotine delivery ‘devices’ in convenient packaged cartons of cigarettes are simple to use, inexpensive per dose and accessible to people of most ages and lung function, but of course their use leads to increased cancer, emphysema, heart disease and other medical and societal problems. In contrast, many inhalation pharmaceutical medical devices are expensive, nonportable, inconvenient, and/or are used improperly thus leading to poor therapeutic benefit. We review the current state of the art with respect to aerosol delivery, inhalation devices and the ability to personalize the treatment and management of lung disease. The confluence of many drivers will lead to more programmable and flexible devices in the future: the transition from the blockbuster model to customized therapy, technological advancements (e.g., smartphones) and cultural changes including social networking.

Study of the RESS process for producing beclomethasone-17,21-dipropionate particles suitable for pulmonary delivery

The purpose of this research was to micronize beclomethasone-17,21-dipropionate (BDP), an anti-inflammatory inhaled corticosteroid commonly used to treat asthma, using the rapid expansion of supercritical solution (RESS) technique. The RESS technique was chosen for its ability to produce both micron particles of high purity for inhalation, and submicron/nano particles as a powder handling aid for use in next generation dry powder inhalers (DPIs). Particle formation experiments were carried out with a capillary RESS system to determine the effect of experimental conditions on the particle size distribution (PSD). The results indicated that the RESS process conditions strongly influenced the particle size and morphology; with the BDP mean particle size decreasing to sub-micron and nanometer dimensions. An increase in the following parameters, i.e. nozzle diameter, BDP mol fraction, system pressure, and system temperature; led to larger particle sizes. Aerodynamic diameters were estimated from the SEM data using three separate relations, which showed that the RESS technique is promising to produce particles suitable for pulmonary delivery.

Pharmaceutical particle engineering via spray drying

This review covers recent developments in the area of particle engineering via spray drying. The last decade has seen a shift from empirical formulation efforts to an engineering approach based on a better understanding of particle formation in the spray drying process. Microparticles with nanoscale substructures can now be designed and their functionality has contributed significantly to stability and efficacy of the particulate dosage form. The review provides concepts and a theoretical framework for particle design calculations. It reviews experimental research into parameters that influence particle formation. A classification based on dimensionless numbers is presented that can be used to estimate how excipient properties in combination with process parameters influence the morphology of the engineered particles. A wide range of pharmaceutical application examples—low density particles, composite particles, microencapsulation, and glass stabilization—is discussed, with specific emphasis on the underlying particle formation mechanisms and design concepts.