Design of dry powder inhalers to improve patient outcomes: it's not just about the device.

INTRODUCTION: Up to 50% of asthma/COPD patients make critical errors in dose preparation and dose inhalation with current marketed DPIs which negatively impact clinical outcomes. Others fail to adhere to their chronic treatment regimen. AREAS COVERED: For this review, we describe how a human-factors approach to design of a dry powder inhaler can be used to improve usability, proficiency, and functionality of DPIs, while effectively mitigating critical errors associated with DPIs. The review highlights the critical importance of utilizing improved formulations with monomodal aerodynamic particle size distributions to reduce variability associated with oropharyngeal filtering of particles, flow rate dependence, and co-formulation effects. EXPERT OPINION: Much of the variability in dose delivery with DPIs is associated with limitations of the bimodal APSDs inherent in current lactose blend formulations. Evidence supports that improved lung targeting and dose consistency can be achieved with drug-device combination products comprising spray-dried powders. Unfortunately, no data exists to assess whether these advances observed in in vitro and in vivo dose delivery studies will translate into improved clinical outcomes. Given the significant percentage of patients that receive suboptimal drug delivery with current DPIs it would behoove the industry to assess the efficacy of new approaches.

Targeting of Inhaled Therapeutics to the Small Airways: Nanoleucine Carrier Formulations.

Current dry powder formulations for inhalation deposit a large fraction of their emitted dose in the upper respiratory tract where they contribute to off-target adverse effects and variability in lung delivery. The purpose of the current study is to design a new formulation concept that more effectively targets inhaled dry powders to the large and small airways. The formulations are based on adhesive mixtures of drug nanoparticles and nanoleucine carrier particles prepared by spray drying of a co-suspension of leucine and drug particles from a nonsolvent. The physicochemical and aerosol properties of the resulting formulations are presented. The formulations achieve 93% lung delivery in the Alberta Idealized Throat model that is independent of inspiratory flow rate and relative humidity. Largely eliminating URT deposition with a particle size larger than solution pMDIs is expected to improve delivery to the large and small airways, while minimizing alveolar deposition and particle exhalation.

Optimizing Spray-Dried Porous Particles for High Dose Delivery with a Portable Dry Powder Inhaler.

This manuscript critically reviews the design and delivery of spray-dried particles for the achievement of high total lung doses (TLD) with a portable dry powder inhaler. We introduce a new metric termed the product density, which is simply the TLD of a drug divided by the volume of the receptacle it is contained within. The product density is given by the product of three terms: the packing density (the mass of powder divided by the volume of the receptacle), the drug loading (the mass of drug divided by the mass of powder), and the aerosol performance (the TLD divided by the mass of drug). This manuscript discusses strategies for maximizing each of these terms. Spray drying at low drying rates with small amounts of a shell-forming excipient (low Peclet number) leads to the formation of higher density particles with high packing densities. This enables ultrahigh TLD (>100 mg of drug) to be achieved from a single receptacle. The emptying of powder from capsules is directly proportional to the mass of powder in the receptacle, requiring an inhaled volume of about 1 L for fill masses between 40 and 50 mg and up to 3.2 L for a fill mass of 150 mg.

Safety, Tolerability, and Pharmacokinetics of RT234 (Vardenafil Inhalation Powder): A First-in-Human, Ascending Single- and Multiple-Dose Study in Healthy Subjects.

Background: RT234 (vardenafil inhalation powder) is being developed for pulmonary administration "as needed", to acutely improve exercise tolerance and symptoms in patients with pulmonary arterial hypertension (PAH). Methods: This single-center, open-label, randomized study in 32 healthy adult subjects evaluated single and multiple inhalation doses of RT234, for safety, tolerability, and pharmacokinetics (PKs). Results: RT234 was generally safe and well tolerated at single doses of 0.2-2.4 mg and after repeated dose administration of up to 2.4 mg q4h for four doses daily for 9 days. The most common treatment-emergent adverse events were mild-to-moderate headaches. There was no evidence of pulmonary irritation or inflammation. Vardenafil was absorbed very rapidly after inhalation as RT234, independent of dose level and number of doses administered. The tmax occurred at the time that the first blood sample following completion of dosing. After Cmax was achieved, plasma vardenafil concentrations declined rapidly in an exponential fashion that appeared to be parallel among dose levels. Vardenafil plasma concentrations and PK parameters increased in a dose-proportional manner. Vardenafil systemic exposure was notably greater after oral administration of 20 mg vardenafil tablets (Levitra®) than after administration of any dose level of RT234. During repeated dose administration of RT234, Cmax was attained rapidly following each dose and in a pattern similar to that observed after single-dose administration. Minor accumulation, characterized by very low mean morning predose vardenafil concentrations (<0.5 ng/mL), occurred after q4h dosing of up to four doses per day for 9 days. Taken together, these findings show that no clinically important vardenafil accumulation is likely after repeated-dose administration of RT234. Mean vardenafil t1/2 values were comparable after single- and repeated-dose administration. Conclusions: Comparative plasma vardenafil bioavailability data from this study provide scientific justification for reliance on Food and Drug Administration findings for Levitra tablets. These findings support further evaluation of RT234 for as-needed treatment of patients with PAH. The Clinical Trials Registration number is ACTRN12618001077257.

Post-inhalation cough with therapeutic aerosols: Formulation considerations.

This review provides an assessment of post-inhalation cough with therapeutic aerosols. Factors that increase cough may be mitigated through design of the drug, formulation, and device. The incidence of cough is typically less than 5% for drugs with a nominal dose less than 1 mg, including asthma and COPD therapeutics. Cough increases markedly as the dose approaches 100 mg. This is due to changes in the composition of epithelial lining fluid (e.g., increases in osmolality, proton concentration). Whether an individual exhibits cough depends on their degree of sensitization to mechanical and chemical stimuli. Hypersensitivity is increased when the drug, formulation or disease result in increases in lung inflammation. Cough related to changes in epithelial lining fluid composition can be limited by using insoluble neutral forms of drugs and excipients.

The Confusing World of Dry Powder Inhalers: It Is All About Inspiratory Pressures, Not Inspiratory Flow Rates.

Dry powder inhalers (DPIs) all have the ability to aerosolize dry powders, but they each offer different operating mechanisms and resistances to inhaled airflow. This variety has resulted in both clinician and patient confusion concerning DPI performance, use, and effectiveness. Particularly, there is a growing misconception that a single peak inspiratory flow rate (PIFR) can determine a patient's ability to use a DPI effectively, regardless of its design or airflow resistance. For this review article, we have sifted through the relevant literature concerning DPIs, inspiratory pressures, and inspiratory flow rates to provide a comprehensive and concise discussion and recommendations for DPI use. We ultimately clarify that the controlling parameter for DPI performance is not the PIFR but the negative pressure generated by the patient's inspiratory effort. A pressure drop ∼≥1 kPa (∼10 cm H2O) with any DPI is a reasonable threshold above which a patient should receive an adequate lung dose. Overall, we explore the underlying factors controlling inspiratory pressures, flow rates and dispensing, and dispersion characteristics of the various DPIs to clarify that inspiratory pressures, not flow rates, limit and control a patient's ability to generate sufficient flow for effective DPI use.

Spray-Dried PulmoSphere™ Formulations for Inhalation Comprising Crystalline Drug Particles.

Over the past 20 years, solution-based spray dried powders have transformed inhaled product development, enabling aerosol delivery of a wider variety of molecules as dry powders. These include inhaled proteins for systemic action (e.g., Exubera®) and high-dose inhaled antibiotics (e.g., TOBI® Podhaler™). Although engineered particles provide several key advantages over traditional powder processing technologies (e.g., spheronized particles and lactose blends), the physicochemical stability of the amorphous drug present in these formulations brings along its own unique set of constraints. To this end, a number of approaches have been developed to maintain the crystallinity of drugs throughout the spray drying process. One approach is to spray dry suspensions of micronized drug(s) from a liquid feed. In this method, minimization of drug particle dissolution in the liquid feed is critical, as dissolved drug is converted into amorphous domains in the spray-dried drug product. The review explores multiple formulation and engineering strategies for decreasing drug dissolution independent of the physicochemical properties of the drug(s). Strategies to minimize particle dissolution include spray blending of particles of different compositions, formation of respirable agglomerates of micronized drug with small porous carrier particles, and use of common ions. The formulations extend the range of doses that can be delivered with a portable inhaler from about 100 ng to 100 mg. The spray-dried particles exhibit significant advantages in terms of lung targeting and dose consistency relative to conventional lactose blends, while still maintaining the crystallinity of drug(s) in the formulated drug product.

Idealhalers Versus Realhalers: Is It Possible to Bypass Deposition in the Upper Respiratory Tract?

This review discusses how advances in formulation and device design can be utilized to dramatically improve lung targeting and dose consistency relative to current marketed dry powder inhalers (DPIs). Central to the review is the development of engineered particles that effectively bypass deposition in the upper respiratory tract (URT). This not only reduces the potential for off-target effects but it also reduces variability in dose delivery to the lungs resulting from anatomical differences in the soft tissue in the mouth and throat. Low-density porous particles are able to largely bypass URT deposition due to the fact that both the primary particles and their agglomerates are respirable. The low-density particles also exhibit dose delivery to the lungs that is largely independent of inspiratory flow rate across a range of flow rates that most subjects achieve with portable DPIs. Coupling this with delivery devices that are breath actuated, simple to operate (open-inhale-close), and have adherence-tracking capability enables drug delivery that is largely independent of how a subject inhales, with a user experience that is close to that of an "idealhaler."

Ciprofloxacin Dry Powder for Inhalation (ciprofloxacin DPI): Technical design and features of an efficient drug-device combination.

Bronchiectasis is a chronic respiratory disease with heterogeneous etiology, characterized by a cycle of bacterial infection and inflammation, resulting in increasing airway damage. Exacerbations are an important cause of morbidity and are strongly associated with disease progression. Many patients with bronchiectasis suffer from two or more exacerbations per year. However, there are no approved therapies to reduce or delay exacerbations in this patient population. Ciprofloxacin DPI is in development as a long-term, intermittent therapy to reduce exacerbations in patients with non-cystic fibrosis (CF) bronchiectasis and evidence of respiratory pathogens. Ciprofloxacin DPI combines drug substance, dry powder manufacturing technology, and an efficient, pocket-sized, dry powder inhaler to deliver an effective antibiotic directly to the site of infection, with minimal systemic exposure and treatment burden. Here we review the drug substance and particle engineering (PulmoSphere™) technology used, and key physical properties of Ciprofloxacin Inhalation Powder, including deposition, delivered dose uniformity, consistency, and stability. Design features of the T-326 Inhaler are described in relation to lung targeting, safety and tolerability of inhalation powders, as well as treatment burden and adherence. If approved, Ciprofloxacin DPI may provide a valuable treatment option for those with frequent exacerbations and respiratory pathogens.

Physical Characterization of Tobramycin Inhalation Powder: II. State Diagram of an Amorphous Engineered Particle Formulation.

Tobramycin Inhalation Powder (TIP) is a spray-dried engineered particle formulation used in TOBI Podhaler, a drug-device combination for treatment of cystic fibrosis (CF). A TIP particle consists of two phases: amorphous, glassy tobramycin sulfate and a gel-phase phospholipid (DSPC). The objective of this work was to characterize both the amorphous and gel phases following exposure of TIP to a broad range of RH and temperature. Because, in principle, changes in either particle morphology or the solid-state form of the drug could affect drug delivery or biopharmaceutical properties, understanding physical stability was critical to development and registration of this product. Studies included morphological assessments of particles, thermal analysis to measure the gel-to-liquid crystalline phase transition (Tm) of the phospholipid and the glass transition temperature (Tg) of tobramycin sulfate, enthalpy relaxation measurements to estimate structural relaxation times, and gravimetric vapor sorption to measure moisture sorption isotherms of TIP and its components. Collectively, these data enabled development of a state diagram for TIP-a map of the environmental conditions under which physical stability can be expected. This diagram shows that, at long-term storage conditions, TIP is at least 50 °C below the Tg of the amorphous phase and at least 40 °C below the Tm of the gel phase. Enthalpy relaxation measurements demonstrate that the characteristic structural relaxation times under these storage conditions are many orders of magnitude greater than that at Tg. These data, along with long-term physicochemical stability studies conducted during product development, demonstrate that TIP is physically stable, remaining as a mechanical solid over time scales and conditions relevant to a pharmaceutical product. This met a key design goal in the development of TIP: a room-temperature-stable formulation (3-year shelf life) that obviates the need for refrigeration for long-term storage. This has enabled development of TOBI Podhaler-an approved inhaled drug product that meaningfully reduces the treatment burden of CF patients worldwide.

Design of spray dried insulin microparticles to bypass deposition in the extrathoracic region and maximize total lung dose.

Inhaled drugs all too often deliver only a fraction of the emitted dose to the target lung site due to deposition in the extrathoracic region (i.e., mouth and throat), which can lead to increased variation in lung exposure, and in some instances increases in local and systemic side effects. For aerosol medications, improved targeting to the lungs may be achieved by tailoring the micromeritic properties of the particles (e.g., size, density, rugosity) to minimize deposition in the mouth-throat and maximize the total lung dose. This study evaluated a co-solvent spray drying approach to modulate particle morphology and dose delivery characteristics of engineered powder formulations of insulin microparticles. The binary co-solvent system studied included water as the primary solvent mixed with an organic co-solvent, e.g., ethanol. Factors such as the relative rate of evaporation of each component of a binary co-solvent mixture, and insulin solubility in each component were considered in selecting feedstock compositions. A water-ethanol co-solvent mixture with a composition range considered suitable for modulating particle shell formation during drying was selected for experimental investigation. An Alberta Idealized Throat model was used to evaluate the in vitro total lung dose of a series of spray dried insulin formulations engineered with different bulk powder properties and delivered with two prototype inhalers that fluidize and disperse powder using different principles. The in vitro total lung dose of insulin microparticles was improved and favored for powders with low bulk density and small primary particle size, with reduction of deposition in the extrathoracic region. The results demonstrated that a total lung dose >95% of the delivered dose can be achieved with engineered particles, indicating a high degree of lung targeting, almost completely bypassing deposition in the mouth-throat.

Formulation Design of Dry Powders for Inhalation.

Drugs for inhalation are no longer exclusively highly crystalline small molecules. They may also be amorphous small molecules, peptides, antibodies, and myriad types of engineered proteins. The evolution of respiratory therapeutics has created a need for flexible formulation technologies to engineer respirable particles. These technologies have enabled medicinal chemists to focus on molecular design without concern regarding compatibility of physicochemical properties with traditional, blend-based technologies. Therapeutics with diverse physicochemical properties can now be formulated as stable and respirable dry powders. Particle engineering technologies have also driven the deployment of new excipients, giving formulators greater control over particle and powder properties. This plays a key role in enabling efficient delivery of drugs to the lungs. Engineered powder and device combinations enable aerosols that largely bypass the mouth and throat, minimizing the inherent variability among patients that arises from differences in oropharyngeal and airway anatomies and in breathing profiles. This review explores how advances among molecules, particles, and powders have transformed inhaled drug product development. Ultimately, this scientific progress will benefit patients, enabling new classes of therapeutics to be formulated as dry powder aerosols with improved efficacy, reduced variability and side effects, and improved patient adherence.

Physical Characterization of Tobramycin Inhalation Powder: I. Rational Design of a Stable Engineered-Particle Formulation for Delivery to the Lungs.

A spray-dried engineered particle formulation, Tobramycin Inhalation Powder (TIP), was designed through rational selection of formulation composition and process parameters. This PulmoSphere powder comprises small, porous particles with a high drug load. As a drug/device combination, TOBI Podhaler enables delivery of high doses of drug per inhalation, a feature critical for dry powder delivery of anti-infectives for treatment of cystic fibrosis. The objective of this work was to characterize TIP on both the particle and molecular levels using multiple orthogonal physical characterization techniques. Differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), electron spectroscopy for chemical analysis (ESCA), and Raman measurements show that a TIP particle consists of two phases: amorphous, glassy tobramycin sulfate with a glass transition temperature of about 100 °C and a gel-phase phospholipid (DSPC) with a gel-to-liquid-crystal transition temperature of about 80 °C. This was by design and constituted a rational formulation approach to provide Tg and Tm values that are well above the temperatures used for long-term storage of TIP. Raman and ESCA data provide support for a core/shell particle architecture of TIP. Particle surfaces are enriched with a porous, hydrophobic coating that reduces cohesive forces, improving powder fluidization and dispersibility. The excellent aerosol dispersibility of TIP enables highly efficient delivery of fine particles to the respiratory tract. Collectively, particle engineering has enabled development of TOBI Podhaler, an approved inhaled drug product that meaningfully reduces the treatment burden to cystic fibrosis patients worldwide.

In Vitro-In Vivo Correlations Observed With Indacaterol-Based Formulations Delivered with the Breezhaler®.

BACKGROUND: Establishing robust in vitro-in vivo correlations (IVIVC) between aerosol performance, pharmacokinetics, and clinical efficacy is critical in developing bioequivalent drug-device combination products. Recent studies have demonstrated that realistic throat models tested under realistic test conditions may provide good IVIVC with respect to total lung deposition. METHODS: The Alberta idealized throat (AIT) model was utilized with mean peak inspiratory flow rates determined from patient breathing studies. Various formulations of indacaterol (e.g., lactose blends, fixed dose combinations, engineered PulmoSphere™ particles) were tested in the AIT model and in clinical pharmacokinetic studies. RESULTS: Good IVIVC were observed with respect to total lung deposition, systemic delivery, and the contribution of oral absorption to systemic delivery, with percentage differences from the mean in vivo measurements <15%, with most comparisons <5%. CONCLUSIONS: Anatomical throat models represent an exciting tool to aid in formulation development of pharmaceutical aerosols.

Inhaler devices: what remains to be done?

The 1000 Years of Pharmaceutical Aerosols Conference convened posing the question; "what remains to be done?" When applying this question to the topic of inhaler devices, two hugely different perspectives could be taken. On the one hand, it could be argued that because there is an array of delivery systems available and the industry, prescribing physicians and patients alike have considerable choice, why would we believe it necessary to do anything further? On the other hand, as an industry, we are constantly reminded by our "customers" that the inhaler devices available are less than adequate, and in some cases woefully inadequate, that they are not "patient" friendly, not intuitive to use and importantly do nothing to encourage the patient to take the medication as intended and as prescribed. So, taking the second point of view as more reflective of reality--the Voice of the Customer--our starting point must be that there is still much to do in the field of inhaler devices. The purpose of this article is to outline some key basic requirements for inhaler design and perhaps to question some of the entrenched thinking that has pervaded inhaler product design for too many years.

Pulmonary formulations: what remains to be done?

Significant advances have been made in the last 50 years in developing safe and efficacious aerosol formulations for pulmonary delivery. The key to future innovation may lie at the interface between biology and particle engineering. Improved understanding of biological processes including particle clearance, cellular targeting, intracellular trafficking, and drug absorption are needed to better design formulations that deliver to the "target" with the optimal balance of pharmacodynamic, pharmacokinetic, and safety profiles. More specifically, continued advances are needed in the development of: (1) controlled release formulations; (2) formulations with improved regional targeting within the lungs (e.g., airway versus alveoli and vice versa); (3) formulations containing active targeting moieties; (4) formulation strategies for improving the systemic bioavailability of inhaled macromolecules; (5) formulation strategies for delivering macromolecules, including siRNA and DNA into cells; and (f) formulations with improved dose consistency. It is likely that such innovation will require the development of novel excipients and particle engineering strategies. Future innovation must also take into the account the changing marketplace and the diverse set of customers (patient, healthcare professional, heath authorities, payers, and politicians) who must be satisfied. The pharmacoeconomics of new delivery systems will be closely scrutinized, so it is imperative that cost factors be taken into account. Otherwise, the new technology option may overshoot the evolving inhalation marketplace.

Design of fine particles for pulmonary drug delivery.

Particle design for inhalation is characterized by advances in particle processing methods and the utilization of new excipients. Processing methods such as spray drying allow control over critical particle design features, such as particle size and distribution, surface energy, surface rugosity, particle density, surface area, porosity and microviscosity. Control of these features has enabled new classes of therapeutics to be delivered by inhalation. These include therapeutics that have a narrow therapeutic index, require a high delivered dose, and/or elicit their action systemically. Engineered particles are also being utilized for immune modulation, with exciting advances being made in the delivery of antibodies and inhaled vaccines. Continued advances are expected to result in 'smart' therapeutics capable of active targeting and intracellular trafficking.

Characterization of suspension-based metered dose inhaler formulations composed of spray-dried budesonide microcrystals dispersed in HFA-134a.

PURPOSE: To assess the physicochemical characteristics and aerosol properties of suspensions of lipid-coated budesonide microcrystals dispersed in HFA-134a. METHODS: Lipid-coated budesonide microcrystals were prepared by spray-drying an emulsion-based feedstock. Physicochemical characteristics of spray-dried particles were assessed by electron microscopy, laser diffraction, and differential scanning calorimetry. Purity and content were determined by reverse-phase HPLC. Particle aggregation and suspension stability were assessed visually, and aerosol performance was assessed by Andersen cascade impaction and dose content uniformity. RESULTS: Spray-drying of micronized budesonide microcrystals in the presence of phospholipid-coated emulsion droplets results in the production of low-density lipid-coated microcrystals with low surface energy. These spray-dried particles form stable suspensions in HFA-134a. This translates into good uniformity in the metered dose across the contents of the inhaler and acceptable aerodynamic particle size distributions (MMAD = 3.2 to 3.4 microm). The formulation was observed to maintain its performance over 6 months at 40 degrees C/75% RH and 16 months at 25 degrees C/60% RH. No effect of storage orientation was observed on the content of first sprays following storage (i.e., no Cyr effect). The fine particle dose was found to be linear out to suspension concentrations of about 2% wt/vol, and FPD(4.7 microm) values approaching 400 microg can be delivered in a single inhalation. CONCLUSIONS: Engineered particles comprised of lipid-coated microcrystals may provide an acceptable alternative formulation technology for metered dose inhalers in the new hydrofluoroalkane propellants.

Characterization of fluorocarbon-in-water emulsions with added triglyceride.

Fluorocarbon-in-water emulsions are being explored clinically as synthetic oxygen carriers in general surgery. Stabilizing fluorocarbon emulsions against coarsening is critical in maintaining the biocompatibility of the formulation following intravenous administration. It has been purported that the addition of a small percentage of long-chain triglyceride results in stabilization of fluorocarbon emulsions via formation of a three-phase emulsion. In a three-phase emulsion, the triglyceride forms a layer around the dispersed fluorocarbon, thereby improving the adhesion of the phospholipid surfactant to the dispersed phase. In the present study, we examined the effect of triglyceride addition on the physicochemical characteristics of the resulting complex dispersion. In particular, we examined the particle composition and stability of the dispersed particles using a method which first fractionates (classifies) the different particles prior to sizing (i.e., sedimentation field-flow fractionation). It was determined that the addition of a long-chain triglyceride (soybean oil) results in oil demixing and two distinct populations of emulsion droplets. The presence of the two types of emulsion droplets is not observed via light scattering techniques, since the triglyceride droplets dominate the scattering due to a large difference in the refractive index between the particles and the medium as compared to fluorocarbon droplets. The growth of the fractionated fluorocarbon emulsion droplets was followed over time, and it was found that there was no difference in growth rates with and without added triglyceride. In contrast, addition of medium-chain-triglyceride (MCT) oils results in a single population of emulsion droplets (i.e., a three-phase emulsion). These emulsions are not stable to droplet coalescence, however, as significant penetration of MCT into the phospholipid lipid interfacial layer results in a negative increment in the monolayer spontaneous curvature, thereby favoring water-in-oil emulsions and resulting in destabilization of the emulsion to the effects of terminal heat sterilization or mechanical stress.