Transition to CFC-free metered dose inhalers--into the new millennium

Pulmonary inhalation for disease treatment: Basic research and clinical translations

Pulmonary drug delivery has the advantages of being rapid, efficient, and well-targeted, with few systemic side effects. In addition, it is non-invasive and has good patient compliance, making it a highly promising drug delivery mode. However, there have been limited studies on drug delivery via pulmonary inhalation compared with oral and intravenous modes. This paper summarizes the basic research and clinical translation of pulmonary inhalation drug delivery for the treatment of diseases and provides insights into the latest advances in pulmonary drug delivery. The paper discusses the processing methods for pulmonary drug delivery, drug carriers (with a focus on various types of nanoparticles), delivery devices, and applications in pulmonary diseases and treatment of systemic diseases (e.g., COVID-19, inhaled vaccines, diagnosis of the diseases, and diabetes mellitus) with an updated summary of recent research advances. Furthermore, this paper describes the applications and recent progress in pulmonary drug delivery for lung diseases and expands the use of pulmonary drugs for other systemic diseases.

A CFD Investigation on the Aerosol Drug Delivery in the Mouth–Throat Airway Using a Pressurized Metered-Dose Inhaler Device

Inhalation therapy involving a pressurized metered-dose inhaler (pMDI) is one of the most commonly used and effective treatment methods for patients with asthma. The purpose of this study was to develop a computational fluid dynamics (CFD) model to characterize aerosol flow issued from a pMDI into a simulated mouth–throat geometry. The effects of air flow rate and cone angle were analyzed in detail. The behaviour of the multiphase flow initiated at the inhaler actuation nozzle and extended through the mouth–throat airway was simulated based on the Eulerian-Lagrangian discrete phase model, with the k-ω model applied for turbulency. We validated our model against published experimental measurements and cover the hydrodynamic aspect of the study. The recirculation we observed at the 90° bend inside the mouth–throat airway resulted in the selective retention of larger diameter particles, and the fluid flow patterns were correlated with drug deposition behaviour. Enhancing air flow rates up to three times reduced the aerodynamic particle diameters to 20%. We also observed that, as cone angle increased, mouth deposition increased; an 8° cone angle was the best angle for the lowest mouth–throat deposition.

The history, current state and perspectives of aerosol therapy

Nebulization is a very effective method of drug administration. This technique has been popular since ancient times when inhalation of plants rich in tropane alkaloids with spasmolytic and analgesic effects was widely used. Undoubtedly, the invention of anasthesia in the 19th century had an influence on the development of this technique. It resulted in the search for devices that facilitated anasthesia such as pulveriser or hydronium. From the second half of the 21st century, when the first DPI and MDI inhalers were launched, the constant development of aerosol therapy has been noticed. This is due to the fact that nebulization, compared with other means of medicinal substance application (such as oral and intravenous routes of administration), is safer and it exhibits a positive dose/efficacy ratio connected to the reduction of the dose. It enables drugs administration through the lung and possesses very fast onset action. Therefore, various drugs prescribed in respiratory diseases (such as corticosteroids, β-agonists, anticholinergics) are present on the market in a form of an aerosol.

Low Drug Loading Hampers the Clinical Translation of Peptide Drugs-Containing Metered-Dose Inhalers

Peptide-based drugs have attracted extensive attention from the medical and pharmaceutical industry because of their relatively high safety and efficacy. However, most of the peptide drugs approved are administrated by injection, which can easily cause poor patient compliance. In this circumstance, pulmonary administration as an alternative to injection administration can not only avoid the above issue but also accelerate the absorption rate of peptide drugs and improve bioavailability. Among the pulmonary delivery systems available on the market, metered-dose inhalers (MDIs) have emerged as appealing candidates for pulmonary delivery systems with clinical translational value, owing to their many merits, including portable, easy-to-operate, and cost-effective properties. Nevertheless, the industrialization of peptide drugs-containing MDIs encounters a bottleneck of low drug loading, owing to the incompatibility between the propellant and the peptide drugs, which cannot be effectively overcome by the current carrier particle encapsulation strategy. Herein, we put forward the following strategies: (1) To screen amphiphilic materials with high surface activity and strong interaction with peptide drugs; (2) To construct a chemical connection between peptide drugs and amphiphilic substances; (3) To optimize the cosolvent for dispersing peptide drugs. We suppose these strategies have the potential to defeat the bottleneck problem and provide a new idea for the industrialization of peptide drugs-containing MDIs.

Cascade Impactor Performance of Commercial pMDI Formulations Using Modified Induction Ports

The induction port (IP) for aerosol analysis with the Next Generation Pharmaceutical Impactor as monographed in the United States and European pharmacopoeia (USPIP) lacks physiological relevance, which, amongst other reasons, has been identified as critical for the predictability of in vitro aerosol data to lung deposition observed in vivo. In this publication, we report the impact of replacing the USPIP with two modified induction ports, which were designed based around geometries derived from a computer tomographic scan of a human trachea and the distal section of the USPIP. Test formulations were selected on the basis of availability of in vivo lung deposition data so that results obtained in vitro could be evaluated for their predictability. All formulations assessed showed increased deposition in the modified induction ports, and different mechanisms of particle deposition have been identified. In vitro predictions of the lung deposition were found to correlate well with the in vivo observations reported using the modified induction ports. Furthermore, the quality of the correlation was found superior to the one achieved with the USPIP with an average deviation of the predicted from observed values (n = 10) of 6 ± 4, 12 ± 6, and 16 ± 6% for the modified induction ports (mIP and mIPext) and the USPIP, respectively, when using a fine particle fraction (FPF) cutoff value of 5 μm. Using a FPF cutoff value of 3 μm yielded a more accurate in vitro-in vivo correlation with an average deviation of the predicted from observed values of 5 ± 4, 7 ± 5, and 8 ± 4% for the mIP, mIPext, and USPIP, respectively. For both FPF size cutoff values, the mIP yielded the most accurate in vitro-in vivo correlation.

Emerging trends in inhaled drug delivery

Ideally, inhaled therapy is driven by the needs of specific disease management. Lung biology interfaces with inhaler performance to allow optimal delivery of therapeutic agent for disease treatment. Inhalation aerosol products consist of the therapeutic agent, formulation, and device. The manufacturing specifications on each of the components, and their combination, allow accurate and reproducible control of measures of quality and in-vitro performance. These product variables in combination with patient variables, including co-ordination skill during inhaler use, intrinsic lung biology, disease and consequent pulmonary function, contribute to drug safety and efficacy outcomes. Due to the complexity of pulmonary drug delivery, predicting biological outcomes from first principles has been challenging. Ongoing research appears to offer new insights that may allow accurate prediction of drug behavior in the lungs. Disruptive innovations were characteristic of research and development in inhaled drug delivery at the end of the last century. Although there were relatively few new inhaled products launched in the first decade of the new millennium it was evident that the earlier years of exploration resulted in maturation of commercially successful technologies. A significant increase in new and generic products has occurred in the last decade and technical, regulatory and disease management trends are emerging. Some of these developments can trace their origins to earlier periods of creativity in the field while others are a reflection of advances in other areas of basic and computer, sciences and engineering. Select biological and technical advances are highlighted with reflections on the potential to impact future clinical and regulatory considerations.

Medicated Foams and Film Forming Dosage Forms as Tools to Improve the Thermodynamic Activity of Drugs to be Administered Through the Skin

Medicated foams and film forming systems are dosage forms formulated to undergo a con-trolled metamorphosis when applied on the skin. Indeed, due to the presence of propellant or a particular air-spray foam pump, a liquid can generate foam when applied on the stratum corneum, or a liquid or conventional dosage form can form on the skin a continuous film as a consequence of the solvent evapora-tion. Thanks to these controlled modifications, the drug thermodynamic activity increases favoring the skin penetration and, therefore, the bioavailability with respect to conventional semi-solid and liquid dosage forms. Furthermore, the available clinical data also evidence that these dosage forms improve the patient’s compliance. The main formulative aspects of medicated foams and film forming systems are reviewed with the aim to underline the possible advantages in terms of biopharmaceutical performances and pa-tient’s adherence.

Drug Delivery from an Innovative LAMA/LABA Co-suspension Delivery Technology Fixed-Dose Combination MDI: Evidence of Consistency, Robustness, and Reliability

To ensure consistency of clinical outcomes, orally inhaled therapies must exhibit consistent delivered dose and aerosol properties at the time of manufacturing, throughout storage, and during various patient-use conditions. Achieving consistency across these scenarios has presented a significant challenge, especially for combination products that contain more than one drug. This study characterized the delivered dose and aerosol properties of glycopyrrolate/formoterol fumarate metered dose inhaler (GFF MDI; Bevespi Aerosphere™). GFF MDI, a fixed-dose combination (FDC) of a long-acting muscarinic antagonist, glycopyrrolate (18 μg, equivalent to glycopyrronium 14.4 μg), and a long-acting β₂-agonist, formoterol fumarate (9.6 μg; equivalent to formoterol fumarate dihydrate 10 μg), is formulated using innovative co-suspension delivery technology, which suspends micronized drug crystals with spray-dried phospholipid porous particles in hydrofluoroalkane propellant. In this study, delivered dose uniformity was assessed through the labeled number of doses, and aerosol properties, such as percent fine particle fraction (FPF) and mass median aerodynamic diameter, were determined by cascade impaction. GFF MDI achieved reproducible dose delivery and an FPF greater than 55%, whether formulated and delivered as a monocomponent or dual FDC. The performance of GFF MDI was maintained across various manufacturing batches, under extended storage, and with variations in flow rate. Furthermore, unlike a GFF drug crystal-only suspension, drug delivery remained consistent for GFF MDI when simulated patient-handling errors were applied, such as reduced shake energy and delays between shaking and actuation. These results demonstrate that co-suspension delivery technology overcomes well-known sources of variability in MDI drug delivery.

Devices for dry powder drug delivery to the lung

Dry powder inhalers (DPIs) are an important and increasingly investigated method of modern therapy for a growing number of respiratory diseases. DPIs are a promising option for certain patient populations, and may help to overcome several limitations that are associated with other types of inhalation delivery systems (e.g., accuracy and reproducibility of the dose delivered, compliance and adherence issues, or environmental aspects). Today, more than 20 different dry powder inhalers are on the market to deliver active pharmaceutical ingredients (APIs) for local and/or systemic therapy. Depending on the mechanism of deagglomeration, aerosolization, dose metering accuracy, and the interpatient variability, dry powder inhalers demonstrate varying performance levels. During development, manufacturers focus on improving aspects characteristic of their specific DPI devices, depending on the intended type of application and any particular requirements associated with it. With the wide variety of applications related to specific APIs, there exists a range of different devices with distinct features. In addition to the routinely used multi-use DPIs, several single-use disposable devices are under development or already approved. The recent introduction of disposable devices will expand the range of possible applications for use by including agents such as vaccines, analgesics, or even rescue medications. This review article discusses the performance and advantages of recently approved dry powder inhalers as well as disposable single-use inhalers that are currently under development.

Advances in metered dose inhaler technology: formulation development

Pressurized metered dose inhalers (MDIs) are a long-standing method to treat diseases of the lung, such as asthma and chronic obstructive pulmonary disease. MDIs rely on the driving force of the propellant, which comprises the bulk of the MDI formulation, to atomize droplets containing drug and excipients, which ideally should deposit in the lungs. During the phase out of chlorofluorocarbon propellants and the introduction of more environmentally friendly hydrofluoroalkane propellants, many improvements were made to the methods of formulating for MDI drug delivery along with a greater understanding of formulation variables on product performance. This review presents a survey of challenges associated with formulating MDIs as solution or suspension products with one or more drugs, while considering the physicochemical properties of various excipients and how the addition of these excipients may impact overall product performance of the MDI. Propellants, volatile and nonvolatile cosolvents, surfactants, polymers, suspension stabilizers, and bulking agents are among the variety of excipients discussed in this review article. Furthermore, other formulation approaches, such as engineered excipient and drug-excipient particles, to deliver multiple drugs from a single MDI are also evaluated.

Advances in metered dose inhaler technology: formulation development

Pressurized metered dose inhalers (MDIs) are a long-standing method to treat diseases of the lung, such as asthma and chronic obstructive pulmonary disease. MDIs rely on the driving force of the propellant, which comprises the bulk of the MDI formulation, to atomize droplets containing drug and excipients, which ideally should deposit in the lungs. During the phase out of chlorofluorocarbon propellants and the introduction of more environmentally friendly hydrofluoroalkane propellants, many improvements were made to the methods of formulating for MDI drug delivery along with a greater understanding of formulation variables on product performance. This review presents a survey of challenges associated with formulating MDIs as solution or suspension products with one or more drugs, while considering the physicochemical properties of various excipients and how the addition of these excipients may impact overall product performance of the MDI. Propellants, volatile and nonvolatile cosolvents, surfactants, polymers, suspension stabilizers, and bulking agents are among the variety of excipients discussed in this review article. Furthermore, other formulation approaches, such as engineered excipient and drug-excipient particles, to deliver multiple drugs from a single MDI are also evaluated.

The availability, pricing and affordability of three essential asthma medicines in 52 low- and middle-income countries

BACKGROUND

Almost 300 million people suffer from asthma, yet many in low- and middle-income countries have difficulty accessing essential asthma medicines. Availability, price and affordability of medicines are likely to affect access. Very few studies have included asthma medicines, particularly inhaled corticosteroids, in these countries. Reflections about international reference prices (IRPs) are generally absent from pricing studies, yet some IRPs may be masking the extent of access problems.

OBJECTIVES

Our objective was to determine the availability, pricing and affordability of beclometasone, budesonide and salbutamol, the three asthma medicines on the World Health Organization's Model List of Essential Medicines (EML) in selected low- and middle-income countries and to reflect on the appropriateness of using IRPs.

METHODS

A cross-sectional pricing survey was conducted in 52 countries. Data were collected on country demographics including national currency, $US exchange rate and daily wage of the lowest-paid unskilled government worker. Pricing and availability data were collected for salbutamol, beclometasone and budesonide in two private retail pharmacies, the national procurement centre and a main public hospital.

RESULTS

Availability was particularly poor for corticosteroids, and worse in national procurement centres and main hospitals. The surveyed strength of beclometasone was only on the EML of ten countries. Considerable variability was found in pricing and affordability across countries. Procurement systems appeared largely inefficient when Asthma Drug Facility prices were applied as references. Some countries appear to be subsidising asthma medicines, making them free or less expensive for patients, while other countries are applying very high margins, which can significantly increase the price for patients unless a reimbursement system exists.

CONCLUSIONS

Findings raise important policy concerns. Availability of inhaled corticosteroids is poor; many EMLs are not updated; IRPs can be misleading; health systems and patients are paying more than necessary for asthma medicines, which are unaffordable for many patients in many countries.

The influence of initial atomized droplet size on residual particle size from pressurized metered dose inhalers

Pressurized metered dose inhalers (pMDIs) are widely used for the treatment of diseases of the lung, including asthma and chronic obstructive pulmonary disease. The mass median aerodynamic diameter of the residual particles (MMADR) delivered from a pMDI plays a key role in determining the amount and location of drug deposition in the lung and thereby the efficacy of the inhaler. The mass median diameter of the initial droplets (MMDI), upon atomization of a formulation, is a significant factor influencing the final particle size. The purpose of this study was to evaluate the extent that MMDI and initial droplet geometric standard deviation (GSD) influence the residual aerodynamic particle size distribution (APSDR) of solution and suspension formulations. From 48 solution pMDI configurations with varying ethanol concentrations, valve sizes and actuator orifice diameters, it was experimentally found that the effective MMDI ranged from 7.8 to 13.3 μm. Subsequently, computational methods were utilized to determine the influence of MMDI on MMADR, by modulating the MMDI for solution and suspension pMDIs. For solution HFA-134a formulations of 0.5% drug in 10% ethanol, varying the MMDI from 7.5 to 13.5 μm increased the MMADR from 1.4 to 2.5 μm. For a suspension formulation with a representative particle size distribution of micronized drug (MMAD=2.5 μm, GSD=1.8), the same increase in MMDI resulted in an increase in the MMADR from 2.7 to only 3.3 μm. Hence, the same increase in MMDI resulted in a 79% increase in MMADR for the solution formulation compared to only a 22% increase for the suspension formulation. Similar trends were obtained for a range of drug concentrations and input micronized drug sizes. Thus, APSDR is more sensitive to changes in MMDI for solution formulations than suspension formulations; however, there are situations in which hypothetically small micronized drug in suspension (e.g. 500 nm MMAD) could resemble trends observed for solution formulations. Furthermore, the relationship between APSDR and drug concentration and MMDI is predictable for solution pMDIs, but this is not as straightforward for suspension formulations. In addition, the MMADR was relatively insensitive to changes in initial droplet GSD (from 1.6 to 2.0) and the solution and suspension pMDI residual particle GSDs were essentially identical to the initial droplet GSDs.

Tuning aerosol particle size distribution of metered dose inhalers using cosolvents and surfactants

OBJECTIVES

The purpose of these studies was to understand the influence of cosolvent and surfactant contributions to particle size distributions emitted from solution metered dose inhalers (pMDIs) based on the propellant HFA 227.

METHODS

Two sets of formulations were prepared: (a) pMDIs-HFA 227 containing cosolvent (5-15% w/w ethanol) with constant surfactant (pluronic) concentration and (b) pMDIs-HFA 227 containing surfactant (0-5.45% w/w pluronic) with constant cosolvent concentration. Particle size distributions emitted from these pMDIs were analyzed using aerodynamic characterization (inertial impaction) and laser diffraction methods.

RESULTS

Both cosolvent and surfactant concentrations were positively correlated with median particle sizes; that is, drug particle size increased with increasing ethanol and pluronic concentrations. However, evaluation of particle size distributions showed that cosolvent caused reduction in the fine particle mode magnitude while the surfactant caused a shift in the mode position. These findings highlight the different mechanisms by which these components influence droplet formation and demonstrate the ability to utilize the different effects in formulations of pMDI-HFA 227 for independently modulating particle sizes in the respirable region.

CONCLUSION

Potentially, the formulation design window generated using these excipients in combination could be used to match the particle size output of reformulated products to preexisting pMDI products.

Formulation and evaluation of CFC free inhalers for beclomethasone dipropionate

Beclomethasone dipropionate CFC free inhalation formulations were developed with a view to treat asthma prophylactically. Dry powder inhalers (DPI) for beclomethasone dipropionate were prepared with different grades of lactose monohydrate. The influence of carrier and overages on performance of DPI was studied. Metered dose inhalers (MDI) with HFA based propellants were formulated with various doses, overages and different concentrations of alcohol. Formulated DPI and MDI were evaluated for various official and unofficial quality control tests. The influence of over doses on valve delivery, effect of overages on emitted dose and influence of alcohol on spray pattern from MDI were studied. The better fine particle fraction and emitted dose were obtained from the DPI formulated with 10:90 ratio of fine lactose: coarse lactose and with 20% w/w overages. The studies on MDI revealed that the 15% of overdoses are required for effective valve delivery and 20% overages are required for 100% drug delivery. 5-10%v/v alcohol was found to be preferable to get optimum emitted dose and fine particle fraction.

The paucity of ethical analysis in allergology

While a growing body of research is uncovering the aetiology and effective treatments for allergy, research that assess the broader ethical implications of this disease is lacking significantly. This article will demonstrate both the paucity of academic research concerning ethical implications in allergy and explain why ethical analysis is integral to formulating effective health strategies for allergic disease. An exhaustive literature search of publications in French and English identified less than 35 academic articles focussed on the topic of ethics and allergy; this is a miniscule number when compared to the amount of articles published on ethical issues related to other chronic illnesses, such as obesity. It is important to demonstrate to allergy specialists the need for, and utility of, further incorporating ethical analyses in allergology; the current success of Ethical, Legal, Social Implications (ELSI) research programmes in human genetics and nanotechnology will serve as notable examples. Indeed, future research and innovation in allergy will undoubtedly encounter ethical dilemmas and the allergology community should play a significant role in helping to address these issues. However, incorporating ethical analyses in allergology does not imply that the allergology community must acquire extensive knowledge in bioethics; instead, interdisciplinary research that incorporates expertise from allergology and bioethics would enable allergy specialists to advance critical knowledge development in this largely overlooked domain of study.

Pulmonary dispersion formulations: the impact of dispersed powder properties on pressurized metered dose inhaler stability

Suspension-type metered dose inhaler formulations characteristically have a high degree of dispersion instability. This may occur as the result of any of a large number of formulation issues including phase separation, particle growth, agglomeration/flocculation, moisture ingress, and particle interactions with both the canister material and other particles. Many of these undesirable instabilities may arise as a result of the physical and chemical properties of the dispersed powder in the liquid propellant system. As such, this review provides a detailed understanding of the characteristics of the dispersed phase in the liquid propellant system necessary to ensure stability of the final formulation.

Surfactants: their critical role in enhancing drug delivery to the lungs

For local lung conditions and diseases, pulmonary drug delivery has been widely used for more than 50 years now. A more recent trend involves the pulmonary route as a systemic drug-delivery target. Advantages such as avoidance of the gastrointestinal environment, different enzyme content compared with the intestine, and avoidance of first-pass metabolism make the lung an alternative route for the systemic delivery of actives. However, the lung offers barriers to absorption such as a surfactant layer, epithelial surface lining fluid, epithelial monolayer, interstitium and basement membrane, and capillary endothelium. Many delivery strategies have been developed in order to overcome these limitations. The use of surfactants is one of these approaches and their role in enhancing pulmonary drug delivery is reviewed in this article. A systematic review of the literature relating to the effect of surfactants on formulations for pulmonary delivery was conducted. Specifically, research reporting enhancement of in vivo performance was focused on. The effect of the addition of surfactants such as phospholipids, bile salts, non-ionic, fatty acids, and liposomes as phospholipid-containing carriers on the enhancement of therapeutic outcomes of drugs for pulmonary delivery was compiled. The main use attributed to surfactants in pulmonary drug delivery is as absorption enhancers by mechanisms of action not yet fully understood. Furthermore, surfactants have been used to improve the delivery of inhaled drugs in various additional strategies discussed herein.

Advanced microscopy techniques to assess solid-state properties of inhalation medicines

Efficient control and characterisation of the physico-chemical properties of active pharmaceutical ingredients (APIs) and excipients for orally inhaled drug products (OIDPs) are critical to successful product development. Control and reduction of risk require the introduction of a material science based approach to product development and the use of advanced analytical tools in understanding how the solid-state properties of the input materials influence structure and product functionality. The key issues to be addressed, at a microscopic scale, are understanding how the critical quality attributes of input materials influence surface, interfacial and particulate interactions within OIDPs. This review offers an in-depth discussion on the use of advanced microscopy techniques in characterising of the solid-state properties of particulate materials for OIDPs. The review covers the fundamental principles of the techniques, instrumentation types, data interpretation and specific applications in relation to the product development of OIDPs.

Forced degradation studies of corticosteroids with an alumina-steroid-ethanol model for predicting chemical stability and degradation products of pressurized metered-dose inhaler formulations

An alumina (Al(2)O(3))-steroid-ethanol model is used for forced degradation testing of corticosteroids to predict chemical stability and degradation products in pressurized metered-dose inhaler (pMDI) solution formulations. The model involves an ethanolic solution of a test steroid with Al(2)O(3), stressed at elevated temperatures to mimic the chemical interaction of drug, excipient, and packaging (an aluminum aerosol canister). The reactivity order of eight synthetic corticosteroids toward Al(2)O(3)-induced reactions is ranked with the stress model. The corticosteroids containing a C21-OH group possess the highest reactivity, suggesting that aluminum canisters with an inert interior coating are needed to stabilize their solution pMDIs. The Al(2)O(3)-induced degradation products and degradation pathways of a steroid containing C21-OH and triamcinolone acetonide are presented, and the role of Al(2)O(3) in the degradation pathways is briefly discussed. A potential degradation profile of beclomethasone dipropionate (BDP) established with an Al(2)O(3)-BDP-ethanol stress model is the same as the actual degradation profile of the BDP pMDI product, indicating that the model indeed predicts the degradation products.

Investigation of solute permeation across hydrogels composed of poly(methyl vinyl ether-co-maleic acid) and poly(ethylene glycol)

OBJECTIVES

Swelling kinetics and solute permeation (theophylline, vitamin B(12) and fluorescein sodium) of hydrogels composed of poly(methyl vinyl ether-co-maleic acid) (PMVE/MA) and poly(ethylene glycol) (PEG) are presented.

METHODS

The effects of PMVE/MA and PEG 10 000 content on swelling behaviour (percentage swelling, the type of diffusion and swelling rate constant) were investigated in 0.1 m phosphate buffer. Network parameters, such as average molecular weight between crosslinks (M(c)) and crosslink density, were evaluated.

KEY FINDINGS

The percentage swelling and M(c) of hydrogels increased with decrease in PMVE/MA content, where the water diffusion mechanism into the hydrogels was Class-II type. In contrast, increase in PMVE/MA content caused an increase in the crosslink density. Permeation of theophylline, vitamin B(12) and fluorescein sodium, with increasing hydrodynamic radii, was studied through the equilibrium swollen hydrogels composed of PMVE/MA and PEG. In general, the permeability and diffusion coefficients of all three solutes decreased with increase in the PMVE/MA content. In addition, permeability and diffusion coefficient values increased with decreases in the hydrodynamic radii of the solute molecules.

CONCLUSIONS

The hydrogels have shown a change in swelling behaviour, crosslink density, M(c) and solute permeation with change in PMVE/MA content, thus suggesting a potential application in controlled drug-delivery systems.

Swellable hydrogel particles for controlled release pulmonary administration using propellant-driven metered dose inhalers

BACKGROUND

Swellable hydrogel microparticle-based pressurized metered dose inhaler (pMDI) formulations allow delivery of small respirable sized particles (1-5 microns), which swell upon the deposition in the deep lung and therefore can elude alveolar macrophage uptake via their larger geometric sizes. In addition, optimized surface chemistry may allow for sustained release of drug for multiple days.

METHODS

Drug-loaded PLGA nanoparticles encapsulated in PEG/chitosan (Cs) graft copolymer-based hydrogel microparticles were synthesized and characterized. Physical stability of dispersions within Hydrofluoroalkane propellant systems was assessed. The formulations were evaluated for aerosolization performance using a Next Generation Impactor.

RESULTS

Low density PEG/chitosan (Cs) graft copolymer-based hydrogel microparticles containing drug-loaded PLGA nanoparticles has an average diameter of 1-2 μm. These dispersions showed good compatibility with HFA227ea. Suspension stability was found to vary with the concentration of hydrogel particles. It was typically between 1 to 5 min and was found to be easily redispersible. Aerosolization studies showed fine particle fraction as high as 65% could be achieved.

CONCLUSIONS

These swellable hydrogel-based microparticle pMDI formulations could be used as potential delivery vehicles for nanoparticle therapeutics.

Ultrasonic nebulization platforms for pulmonary drug delivery

IMPORTANCE OF THE FIELD

Since the 1950s, ultrasonic nebulizers have played an important role in pulmonary drug delivery. As the process in which aerosol droplets are generated is independent and does not require breath-actuation, ultrasonic nebulizers, in principle, offer the potential for instantaneously fine-tuning the dose administered to the specific requirements of a patient, taking into account the patient's breathing pattern, physiological profile and disease state. Nevertheless, owing to the difficulties and limitations associated with conventional designs and technologies, ultrasonic nebulizers have never been widely adopted, and have in recent years been in a state of decline.

AREAS COVERED IN THIS REVIEW

An overview is provided on the advances in new miniature ultrasonic nebulization platforms in which large increases in lung dose efficiency have been reported.

WHAT THE READER WILL GAIN

In addition to a discussion of the underlying mechanisms governing ultrasonic nebulization, in which there appears to be widely differing views, the advantages and shortcomings of conventional ultrasonic nebulization technology are reviewed and advanced state-of-the-art technologies that have been developed recently are discussed.

TAKE HOME MESSAGE

Recent advances in ultrasonic nebulization technology demonstrate significant potential for the development of smart, portable inhalation therapy platforms for the future. Nevertheless, there remain considerable challenges that need to be addressed before such personalized delivery systems can be realized. These have to be addressed across the spectrum from fundamental physics through to in vivo device testing and dealing with the relevant regulatory framework.

Hydrofluoroalkane preparations of fluticasone propionate

Fluticasone propionate is approved for the long-term maintenance therapy of persistent asthma of all severities, and its safety and efficacy has been well established in clinical trials and practice. With the need to phase out chlorofluorocarbons (CFCs) as propellants in pressurized metered-dose inhalers (pMDIs), hydrofluoroalkane (HFA) propellants have been introduced as a safer, environmentally friendly alternative. A HFA formulation of fluticasone propionate has been developed as a microgram-equivalent replacement for the traditional CFC pMDI. Clinical trials have demonstrated that the fluticasone propionate HFA pMDI is an acceptable clinical alternative for the CFC pMDI with similar safety and efficacy.

Advancements in dry powder delivery to the lung

The dry powder inhaler (DPI) has become widely known as a very attractive platform for drug delivery. Many patients have traditionally used DPIs to treat asthma and chronic obstructive pulmonary disease. Recently, the development of new DPIs for delivering therapeutic proteins such as insulin has been accelerated by patient demands, and innovative research. The current market for DPIs has over 20 devices presently in use, and many devices under development for delivering a variety of therapeutic agents. DPIs are recognized as suitable alternatives to pressurized metered dose inhalers for some patients, but the performance of DPI devices may vary according to a given patient's physiological condition. This variation can be associated with the necessary powder dispersion mechanism of each device. As such, much interest has focused on the development of efficient powder dispersion mechanisms, as this effectively minimizes the influence of interpatient variability. This article reviews DPI devices currently available, advantages of newly developed devices, outlines some requirements for future device design.

Reverse aqueous emulsions and microemulsions in HFA227 propellant stabilized by non-ionic ethoxylated amphiphiles

In this work we use in situ high-pressure tensiometry to screen non-ionic ethoxylated surfactants at the 1,1,1,2,3,3,3-heptafluoropropane (HFA227) propellant|Water (HFA227|W) interface. The EO(n)PO( approximately )(30)EO(n) series, where EO stands for ethylene oxide and PO for propylene oxide, and n the number of repeat EO units, was selected for this study based on the favorable interactions reported between HFA propellants and the PO moiety. The surfactants used in FDA-approved pressurized metered-dose inhaler formulations were also investigated. Tension measurements provide not only information on the relative activity of the different surfactants in the series, but they also serve as a guide for selecting an appropriate candidate for the formation of reverse aggregates based on the surfactant natural curvature. Moreover, the effect of ethanol and the chemistry of the surfactant tail group on the surfactant activity were also investigated. Surfactants with hydrogenated tails are not capable of forming stable water-in-HFA227 microemulsions. This is true even at very low tensions observed when in the presence of ethanol, indicating the lack of affinity between HFA227 and hydrogenated moieties-the surfactant does not tend to curve about water. On the other hand, PO-based amphiphiles can significantly reduce the tension of the HFA227|W interface. Small angle neutron scattering (SANS) and UV-vis spectroscopy results also reveal that a selected ethoxylated amphiphile (EO(13)PO(30)EO(13) at 1mM concentration), when in the presence of ethanol, is capable of forming stable cylindrical reverse aqueous microemulsions. EO(13)PO(30)EO(13) is also capable of forming emulsions of water-in-HFA227 that are fairly stable against coalescence. Such dispersions are potential candidates for the delivery of small polar solutes and larger therapeutic biomolecules to and through the lungs in the form of pMDI formulations, and in other medical sprays.

Ethoxylated copolymersurfactants for the HFA134a- interface: interfacial activity, aggregate microstructure and biomolecule uptake

In this work we examine the aggregation behavior of ethoxylated copolymer surfactants in 1,1,1,2-tetrafluoroethane in the presence of water, and the ability of such aggregates to uptake a model biomolecule. Our approach consists of developing a rational framework for understanding the behavior of interfacially active species at the HFA134a-water (HFA134a|W) interface using a combination of in situ high-pressure tensiometry, spectroscopy, and small-angle neutron scattering (SANS). The optimum hydrophilic-to-HFA-philic balance (HFB) for the ethylene oxide-propylene oxide-ethylene oxide (EOnPO∼43EOn, where subscripts indicate the number of repeat units) surfactant series at the HFA134a|W interface was determined at 298 K and saturation pressure of the propellant (under pressure). The selection of promising candidates for the reverse aggregate formation studies was based on the tension vs. HFB scan. Tensiometric information revealed that EO3PO43EO3 occupies a very large area per molecule at the HFA134a|W interface, which represents a general trend for compressible solvents that are small and also able to interact with water more favorably than alkane solvents. The water solubilization capacity of the EO3PO43EO3 surfactant was investigated in situ by UV-vis spectroscopy, with a suitable solvatochromic probe. At a surfactant concentration above the determined critical aggregation concentration, a shift in the absorption maximum of the probe towards that of pure water was observed as the water-to-surfactant ratio increases. A similar but more pronounced shift was observed in the presence of a co-solvent. The nature of the aqueous environment associated with the aggregates is discussed based on the spectroscopic results. The microstructure of the aggregates is investigated by SANS. Scattering curves were also used to confirm the uptake of a model protein in the reverse aggregates. The relevance of this work stems from the fact that reverse aggregates of water in HFA134a are potential candidate formulations for the delivery of hydrophilic drugs, including biomolecules, to and through the lungs.

Biocompatible and biodegradable copolymer stabilizers for hydrofluoroalkane dispersions: a colloidal probe microscopy investigation

In this work we investigate the ability of biodegradable and biocompatible lactide-based nonionic amphiphiles to stabilize a model drug (salbutamol base) dispersion in hydrofluoroalkane (HFA) propellant. A series of triblock copolymers of the type poly(lactide)-poly(ethylene glycol)-poly(lactide) (LA(m)EO(n)LA(m)) with varying molecular weight (MW) and % EO were synthesized. The cohesive forces between drug particles in liquid HFA in the presence of the amphiphiles were quantitatively determined by colloidal probe microscopy (CPM). The effect of cosolvent, oleic acid, and a nonionic triblock copolymer with the propylene oxide moiety as the HFA-phile was also investigated. CPM results show that the overall concentration, MW, surfactant tail (LA) length, and the ratio between the stabilizing LA moiety and the anchor EO group have a great impact on the drug cohesive forces. The CPM results in liquid HFA were correlated to the bulk physical stability of the drug suspensions in the propellant 1,1,1,2,3,3,3-heptafluoropropane (HFA227). The dispersions in HFA227 were significantly improved in the presence of LA(m)EO(n)LA(m), correlating well with the low cohesive forces determined by CPM. The applicability of LA-based amphiphiles might be extended to other suspension-based formulations provided a suitable headgroup is found. This study is relevant for the development of HFA-based dispersion pressurized metered-dose inhaler formulations.

Novel propellant-driven inhalation formulations: engineering polar drug particles with surface-trapped hydrofluoroalkane-philes

Challenges in reformulating pressurized metered-dose inhalers (pMDIs) with hydrofluoroalkane (HFA) propellants, and the potential of inhalation formulations for the delivery of drugs to and through the lungs have encouraged the development of novel suspension-based pMDI formulations. In this work we propose a new methodology for engineering polar drug particles with enhanced stability and aerosol characteristics in propellant HFAs. The approach consists in 'trapping' HFA-philic moieties at the surface of particles, which are formed using a modified emulsification-diffusion method. The trapped moieties act as stabilizing agents, thus preventing flocculation of the otherwise unstable colloidal drug particles. This approach has advantages compared to surfactant-stabilized colloids in that no free stabilizers remain in solution (reduced toxicity), and the challenges associated with the synthesis of well-balanced amphiphiles are circumvented. The methodology was tested by trapping polyethylene glycol (PEG) at the surface of particles of a model polar drug-salbutamol sulfate. Colloidal probe microscopy is used to quantitatively demonstrate the trapping of the HFA-phile at the surface, and the ability of PEG in screening particle-particle cohesive interactions. Both physical stability and the corresponding aerosol characteristics are significantly improved compared to those of a commercial formulation. The fine particle fraction of PEG-coated salbutamol sulfate was observed to be 42% higher than that of Ventolin HFA. The formation of stable dispersions of terbutaline hemisulfate using the same approach, suggests this to be a generally applicable methodology to polar drugs.

Core-shell particles for the dispersion of small polar drugs and biomolecules in hydrofluoroalkane propellants

PURPOSE

Demonstrate the applicability of a novel particle-based technology for the development of suspensions of small polar drugs and biomolecules in hydrofluoroalkane (HFA) propellants for pressurized metered-dose inhalers (pMDIs).

MATERIALS AND METHODS

Emulsification diffusion was used to prepare core-shell particles. The shell consisted of oligo(lactide) grafts attached onto a short chitosan backbone. The active drug was arrested within the particle core. Colloidal Probe Microscopy (CPM) was used to determine the cohesive forces between particles in a model HFA propellant. The aerosol characteristics of the formulations were determined using an Anderson Cascade Impactor (ACI). Cytotoxicity studies were performed on lung epithelial and alveolar type II cells.

RESULTS

CPM results indicate that particle cohesive forces in liquid HFA are significantly screened in the presence of the polymeric shell and correlate well with the physical stability of suspensions in propellant HFA. The proposed formulation showed little or no cytotoxic effects on both Calu-3 and A549 cells.

CONCLUSIONS

Core-shell particles with a shell containing the lactide moiety as the HFA-phile showed excellent dispersion stability and aerosol characteristics in HFA-based pMDIs. This is a general strategy that can be used for developing novel suspension pMDIs of both small polar drugs and large therapeutic molecules.

Inhalation devices for long-acting beta2-agonists: efficiency and ease of use of dry powder formoterol inhalers for use by patients with asthma and COPD

BACKGROUND

Since the long-acting beta(2)-agonist bronchodilator, formoterol, first became available for the treatment of subjects with asthma or chronic obstructive pulmonary disease (COPD), generic forms of this agent have been launched in a variety of devices. It is timely to review the characteristics of the original dry powder delivery device, the single-dose Aerolizer, its in vitro performance and its comparability with other inhaler devices that are now available for delivery of formoterol.

SCOPE

This review focuses on the performance of the formoterol Aerolizer inhaler in comparison with other inhalers. Publically available data (PubMed) on the device performance characteristics of the Aerolizer were reviewed and summarized, together with the results of comparative studies performed by the authors. Published studies (PubMed) on patient handling and inhaler technique that include the Aerolizer are described and studies comparing the clinical effect of formoterol in the Aerolizer with formoterol delivered via other devices were reviewed and are summarized.

FINDINGS

The Aerolizer performs consistently in dosing efficiency across a range of inspiratory flow rates, suggesting its suitability for use by patients with differing inspiratory flow abilities. The single-dose, capsule-based nature of the device provides patients with obvious feedback on whether the drug has been taken successfully and the Aerolizer has been shown to be one of the more easily used devices in comparative patient handling studies. Studies comparing the clinical effect of formoterol delivered by different inhalation devices show that formoterol via Aerolizer has an equivalent therapeutic effect.

CONCLUSION

Judged on the basis of dosing efficiency, ease of use and clinical equivalence, formoterol Aerolizer remains a useful option in the management of patients with asthma or COPD.

Advances in asthma and COPD management: delivering CFC-free inhaled therapy using Modulite technology

Inhaled corticosteroids (ICS) and long-acting beta-agonists (LABA) are currently used in the management of asthma and chronic obstructive pulmonary disease (COPD). Localized targeted delivery of these drugs into the lungs is achieved by means of two types of inhalation devices; pressurized metered-dose inhalers (pMDIs) and dry powder-inhalers (DPIs). For environmental reasons, the chlorofluorocarbon (CFC) propellants used in pMDIs are now being replaced by ozone friendly hydrofluoroalkanes (HFAs). These new generation HFA-based pMDIs, developed to provide effective lung deposition of the active moiety, have a favorable safety and tolerability profile. However, HFA-based re-formulation of LABAs and ICS for pMDIs presents particular technical difficulties, especially in terms of ensuring dose content uniformity. This review focuses on the technology and clinical efficacy of the HFA solution pMDIs using Modulite platform technology (Chiesi Farmaceutici S.p.A). Modulite technology allows the development of HFA solution formulations that can mimic the established CFC-based drug formulations on a microgram to microgram basis and provides formulations with novel particle size distributions that improve on existing delivery systems; by manipulation of aerosol clouds and particle size, the delivery of HFA-formulated drugs can be optimized to either achieve fine particle fractions and deposition patterns similar to established CFC-based drug formulations, thus facilitating the transition to new environment-friendly pMDIs in the clinical setting, or achieve finer drug particles able to penetrate deeper into the bronchi for targeted drug delivery as medical need may dictate. Long-term, multiple-dose clinical studies of Modulite formulations of beclomethasone dipropionate (BDP), budesonide and formoterol have been demonstrated to be therapeutically equivalent to their respective previously established CFC or DPI formulations. As a result, a number of Modulite pMDIs have either recently gained regulatory approval in several European countries, or have completed clinical trials and are in the regulatory submission phase. Availability, in pMDI form, of drugs like formoterol, ICSs, and ICS/LABA combinations, all central to the effective management of asthma and COPD, is therefore expected to impact positively in assuring the continued availability of vital treatment options to patients and physicians.

Aerosol delivery devices and obstructive airway disease

Two obstructive lung diseases, asthma and chronic obstructive pulmonary disease, account for the vast majority of prescriptions for aerosolized medications and devices . Asthma is an immunologically mediated condition characterized by episodic reversible airway obstructions that occur in all age groups. In contrast, chronic obstructive pulmonary disease is a condition characterized by relatively irreversible obstruction that is seen in middle-aged and elderly cigarette smokers. Nevertheless, there is sufficient overlap in terms of airway physiology and therapeutics to allow a review of the challenge of aerosol delivery in both conditions in the same article. This review will concentrate on issues related to aerosol delivery.

The use of amino acids to enhance the aerosolisation of spray-dried powders for pulmonary gene therapy

BACKGROUND

Pulmonary delivery of gene therapy offers the potential for the treatment of a range of lung conditions, including cystic fibrosis, asthma and lung cancer. Spray-drying may be used to prepare dry powders for inhalation; however, aerosolisation of such powders is limited, resulting in poor lung deposition and biological functionality. In this study, we examine the use of amino acids (arginine, aspartic acid, threonine, phenylalanine) to enhance the aerosolisation of spray-dried powders containing model non-viral gene vectors.

METHODS

Lipid/polycation/pDNA (LPD) vectors, in the presence or absence of amino acids, were dispersed in lactose solutions, and spray-dried to produce appropriately sized dry powders. Scanning electron microscopy and laser diffraction were used to determine particle morphology and diameter, respectively. Gel electrophoresis was used to examine the influence of amino acids on the structural integrity of the LPD complex. In vitro cell (A549) transfection was used to determine the biological functionality of the dry powders, and the in vitro aerosolisation performance was assessed using a multistage liquid impinger (MSLI).

RESULTS

Both gel electrophoresis and in vitro cell transfection indicated that certain amino acids (aspartic acid, threonine) can adversely affect the integrity and biological functionality of the LPD complex. All amino acids significantly increased the aerosolisation of the powder, with the arginine and phenylalanine powders showing optimal deposition in the lower stages of the MSLI.

CONCLUSIONS

Amino acids can be used to enhance the aerosolisation of spray-dried powders for respiratory gene delivery, allowing the development of stable and viable formulations for pulmonary gene therapy.

Deposition of corticosteroid aerosol in the human lung by Respimat Soft Mist inhaler compared to deposition by metered dose inhaler or by Turbuhaler dry powder inhaler

Fourteen mild-to-moderate asthmatic patients completed a randomized four-way crossover scintigraphic study to determine the lung deposition of 200 microg budesonide inhaled from a Respimat Soft Mist Inhaler (Respimat SMI), 200 microg budesonide inhaled from a Turbuhaler dry powder inhaler (Turbuhaler DPI, used with fast and slow peak inhaled flow rates), and 250 microg beclomethasone dipropionate inhaled from a pressurized metered dose inhaler (Becloforte pMDI). Mean (range) whole lung deposition of drug from the Respimat SMI (51.6 [46-57]% of the metered dose) was significantly (p < 0.001) greater than that from the Turbuhaler DPI used with both fast and slow inhaled flow rates (28.5 [24-33]% and 17.8 [14-22]%, respectively) or from the Becloforte pMDI (8.9 [6-12]%). The deposition pattern within the lungs was more peripheral for Respimat SMI than for Turbuhaler DPI. The results of this study showed that Respimat SMI deposited corticosteroid more efficiently in the lungs than either of two widely used inhaler devices, Turbuhaler DPI or Becloforte pMDI.

High-pressure aerosol suspensions—A novel laser diffraction particle sizing system for hydrofluoroalkane pressurised metered dose inhalers

In this study, a novel laser diffraction particle size analysis dispersion system, capable of sizing particles in situ within suspension hydrofluoroalkane (HFA) pressurised metered dose inhalers (pMDIs), was developed and tested. The technique was compared to four indirect particle sizing methods commonly used to determine the size of particles suspended in HFA pMDIs. The median volume diameter obtained using laser diffraction of both the salbutamol sulphate and fluticasone propionate suspended either in 2H, 3H-decafluoropentane or perfluoropentane (employed as surrogate propellants) was over one-order of magnitude larger than the particle sizes of the drugs suspended in HFA 134a. In contrast, the "in-flight" particle size using the Sympatec inhaler 2000 laser diffraction equipment undersized the particles, predicting higher delivery efficacy compared to the other sizing methods. However, the size of particles suspended in HFAs derived using the novel pressurised dispersion system, showed a linear correlation with the impaction results, r2=0.8894 (n=10). The novel pressure cell sizing technique proved to be simple to use, has the ability to be automated and was accurate, suggesting it could be an essential tool in the development of new suspension-based pMDI formulations.

Modulite: a simple solution to a difficult problem

The development of HFA-based pMDIs has proved difficult due to differences in the physico-chemical properties of CFC and HFA propellants. However, the development of solution formulations instead of suspensions has provided a way to formulate products whose cloud characteristics can be modulated in a controlled manner by permitting different formulation and device hardware variables. The new approach has proved successful in formulating several different drugs including steroids and has now been applied to developing a formoterol Modulite solution formulation characterized by good chemical stability, delivery performance, and clinical results.

Surfactant solubility and aggregate orientation in hydrofluoroalkanes

PURPOSE

To find surfactants soluble in the two hydrofluoroalkane (HFA) propellants, HFA-134a and HFA-227ea; to compare surfactant solubility in the two propellants with those in 2H,3H-decafluoropentane (DFP) in order to assess latter's suitability as a liquid model propellant and to investigate surfactant aggregation and aggregate orientation in HFAs.

METHODS

To assess surfactant solubility, HFA was added to a known amount of surfactant until dissolution was visibly apparent. An iodine solubilization method was used to determine surfactant aggregation behaviour in DFP. Fluorescence spectroscopic investigations on the surfactant orientation in aggregates were carried out in HFAs using a microviscosity sensitive fluorescent probe (1,3-dipyrenylpropane). The aim was to assess viscosity changes in the microenvironment of this lipophilic probe upon incorporation into surfactant aggregates.

RESULTS

Soluble surfactants could be found among the polyoxyethylene-ethers and POE-PPO-block copolymer surfactants. Solubility in DFP appears to correlate with solubility in HFA-134a, but not HFA-227ea. Iodine solubilization indicates micellization of Brij 30 in DFP at a cmc (type II association behaviour). L-44 in DFP, on the other hand, does not exhibit a well defined cmc, but shows continuous surfactant aggregation (type I association behaviour). The fluorescence spectroscopic studies showed evidence for probe incorporation into surfactant aggregates in HFAs.

CONCLUSIONS

DFP proved to be a good model for HFA-134a only. An L1-aggregate orientation was shown for surfactants in HFAs and is in marked contrast to the chlorofluorocarbon propellant where a L2-aggregate orientation exists.