Formulation and physical characterization of large porous particles for inhalation

Inhaled sildenafil as an alternative to oral sildenafil in the treatment of pulmonary arterial hypertension (PAH)

The practice of treating PAH patients with oral or intravenous sildenafil suffers from the limitations of short dosing intervals, peripheral vasodilation, unwanted side effects, and restricted use in pediatric patients. In this study, we sought to test the hypothesis that inhalable poly(lactic-co-glycolic acid) (PLGA) particles of sildenafil prolong the release of the drug, produce pulmonary specific vasodilation, reduce the systemic exposure of the drug, and may be used as an alternative to oral sildenafil in the treatment of PAH. Thus, we prepared porous PLGA particles of sildenafil using a water-in-oil-in-water double emulsion solvent evaporation method with polyethyleneimine (PEI) as a porosigen and characterized the formulations for surface morphology, respirability, in-vitro drug release, and evaluated for in vivo absorption, alveolar macrophage uptake, and safety. PEI increased the particle porosity, drug entrapment, and produced drug release for 36h. Fluorescent particles showed reduced uptake by alveolar macrophages. The polymeric particles were safe to rat pulmonary arterial smooth muscle cell and to the lungs, as evidenced by the cytotoxicity assay and analyses of the injury markers in the bronchoalveolar lavage fluid, respectively. Intratracheally administered sildenafil particles elicited more pulmonary specific and sustained vasodilation in SUGEN-5416/hypoxia-induced PAH rats than oral, intravenous, or intratracheal plain sildenafil did, when administered at the same dose. Overall, true to the hypothesis, this study shows that inhaled PLGA particles of sildenafil can be administered, as a substitute for oral form of sildenafil, at a reduced dose and longer dosing interval.

Pharmacokinetics of Ethionamide Delivered in Spray-Dried Microparticles to the Lungs of Guinea Pigs

The use of ethionamide (ETH) in treating multidrug-resistant tuberculosis is limited by severe side effects. ETH disposition after pulmonary administration in spray-dried particles might minimize systemic exposure and side effects. To explore this hypothesis, spray-dried ETH particles were optimized for performance in a dry powder aerosol generator and exposure chamber. ETH particles were administered by the intravenous (IV), oral, or pulmonary routes to guinea pigs. ETH appearance in plasma, bronchoalveolar lavage, and lung tissues was measured and subjected to noncompartmental pharmacokinetic analysis. Dry powder aerosol generator dispersion of 20% ETH particles gave the highest dose at the exposure chamber ports and fine particle fraction of 72.3%. Pulmonary ETH was absorbed more rapidly and to a greater extent than orally administered drug. At T_max, ETH concentrations were significantly higher in plasma than lungs from IV dosing, whereas insufflation lung concentrations were 5-fold higher than in plasma. AUC_(0-t) (area under the curve) and apparent total body clearance (CL) were similar after IV administration and insufflation. AUC_(0-t) after oral administration was 6- to 7-fold smaller and CL was 6-fold faster. Notably, ETH bioavailability after pulmonary administration was significantly higher (85%) than after oral administration (17%). These results suggest that pulmonary ETH delivery would potentially enhance efficacy for tuberculosis treatment given the high lung concentrations and bioavailability.

Aerosolizable modified-release particles of montelukast improve retention and availability of the drug in the lungs

Montelukast, a cysteinyl leukotriene receptor antagonist available as oral tablets, is used as a second-line therapy in asthma. In this study, we sought to enhance the availability of montelukast in the lungs by encapsulating the drug in poly (lactide-co-glycolic acid)-based (PLGA) respirable large porous particles. We determined the oral and lung specific availability of montelukast by assessing metabolic stability of the drug in the lung and liver homogenates, respectively. We similarly measured the oral and inhalational bioavailability by monitoring the pharmacokinetics and disposition of the drug in live animals. After preparing montelukast-loaded particles with various polymers, in the absence or presence of polyethylenimine (PEI-1), we characterized the particles for physical-chemical properties, entrapment efficiency, in vitro release, uptake by alveolar macrophages, deposition in the lungs, and safety after pulmonary administration. When incubated in lung or liver homogenates, the amount of intact drug in the lung homogenates was greater than that in the liver homogenates. Likewise, the extent of montelukast absorption via the lungs was greater than that via the oral route. Compared with smaller non-porous particles, large porous particles (PEI-1) were taken up by the alveolar macrophages at a lesser extent but deposited in the lungs at a greater extent. The levels of injury markers in the bronchoalveolar lavage fluid (BALF), collected from rat lungs treated with PEI-1, were no different from that in BALF collected from saline treated rats. Overall, the retention time and concentration of montelukast in the lungs can be increased by formulating the drug in large porous particles of PLGA.

Synthesis and biomedical applications of aerogels: Possibilities and challenges

Aerogels are an exceptional group of nanoporous materials with outstanding physicochemical properties. Due to their unique physical, chemical, and mechanical properties, aerogels are recognized as promising candidates for diverse applications including, thermal insulation, catalysis, environmental cleaning up, chemical sensors, acoustic transducers, energy storage devices, metal casting molds and water repellant coatings. Here, we have provided a comprehensive overview on the synthesis, processing and drying methods of the mostly investigated types of aerogels used in the biological and biomedical contexts, including silica aerogels, silica-polymer composites, polymeric and biopolymer aerogels. In addition, the very recent challenges on these aerogels with regard to their applicability in biomedical field as well as for personalized medicine applications are considered and explained in detail.

The Delivery of High-Dose Dry Powder Antibiotics by a Low-Cost Generic Inhaler

The routine of loading multiple capsules for delivery of high-dose antibiotics is time consuming, which may reduce patient adherence to inhaled treatment. To overcome this limitation, an investigation was carried out using four modified versions of the Aerolizer® that accommodate a size 0 capsule for delivery of high payload formulations. In some prototypes, four piercing pins of 0.6 mm each were replaced with a single centrally located 1.2-mm pin and one-third reduced air inlet of the original design. The performance of these inhalers was evaluated using spray-dried antibiotic powders with distinct morphologies: spherical particles with a highly corrugated surface (colistin and tobramycin) and needle-like particles (rifapentine). The inhalers were tested at capsule loadings of 50 mg (colistin), 30 mg (rifapentine) and 100 mg (tobramycin) using a multistage liquid impinger (MSLI) operating at 60 L/min. The device with a single pin and reduced air inlet showed a superior performance than the other prototypes in dispersing colistin and rifapentine powders, with a fine particle fraction (FPF wt% <5 μm in the aerosol) between 62 and 68%. Subsequently, an Aerolizer® with the same configuration (single pin and one-third air inlet) that accommodates a size 00 capsule was designed to increase the payload of colistin and rifapentine. The performance of the device at various inspiratory flow rates and air volumes achievable by most cystic fibrosis (CF) patients was examined at the maximum capsule loading of 100 mg. The device showed optimal performance at 45 L/min with an air volume of 1.5-2.0 L for colistin and 60 L/min with an air volume of 2.0 L for rifapentine. In conclusion, the modified size 00 Aerolizer® inhaler as a low-cost generic device demonstrated promising results for delivery of various high-dose formulations for treatment of lung infections.

Pulmonary Anti-inflammatory Effects of Chitosan Microparticles Containing Betamethasone

Chitosan microparticles (CMs) are of potential interest for controlled delivery of therapeutic agents to cells and tissues, especially to mucosal-epithelial surfaces in the body. CM incorporation efficiency and release kinetics for betamethasone (B), an epimeric synthetic glucocorticoid, were investigated. Evidence for mild but significant inflammatory reactions in rat lung exposed to high CM concentrations was observed. Inflammation in the rat lung was significantly decreased by inhalation of B-loaded CMs (BCMs). Decreases in bronchoalveolar lavage fluid protein, content of polymorphonuclear neutrophils, lactate dehydrogenase (LDH) activity, lung tissue myeloperoxidase (MPO) activity, and leukocyte infiltration were observed. For all biochemical parameters tested, CMs loaded with 1.0-1.2mg/kg B decrease the inflammation by 1.63±0.14 fold, to near air-inhalation control levels. Thus, the drug was efficiently delivered and active in the pulmonary tissues by this technique.

One-Step Method to Prepare PLLA Porous Microspheres in a High-Voltage Electrostatic Anti-Solvent Process

A one-step method using a high-voltage electrostatic anti-solvent process was employed to fabricate poly-l-lactide (PLLA) porous microspheres (PMs). To address the simplification and control of the preparation process, a 2⁴ full factorial experiment was performed to optimize the operating process and analyze the effect of the factors on the morphology and aerodynamic properties of the PLLA PMs, and various characterization tests were also performed. The resulting PLLA PMs exhibited an even and porous morphology with a density less than 0.4 g/cm³, a geometric mean diameter (Dg) of 10-30 μm, an aerodynamic diameter (Da) of 1-5 μm, a fine particle fraction (FPF) of 56.3%, and a porosity of 76.2%, meeting the requirements for pulmonary drug delivery. The physicochemical characterizations reveal that no significant chemical change occurred in the PLLA during the process. An investigation of its in vitro cytotoxicity and pulmonary toxicity shows no obvious toxic response, indicating good biosafety. This study indicates that the one-step method using a high-voltage electrostatic anti-solvent process has great potential in developing an inhalable drug carrier for pulmonary drug delivery.

Preparation of large porous deslorelin-PLGA microparticles with reduced residual solvent and cellular uptake using a supercritical carbon dioxide process

PURPOSE

The purpose of this study was to prepare large-porous peptide-encapsulating polymeric particles with low residual solvent that retain deslorelin integrity, sustain drug release, and exhibit reduced epithelial and macrophage uptake. We hypothesized that supercritical carbon dioxide (SC CO2) pressure-quench treatment of microparticles prepared using conventional approach expands these particles and extracts the residual organic solvent.

METHODS

Initial studies with crystalline L-lactide (L-PLA) and amorphous copolymers of lactide-co-glycolide (PLGA) 50:50, 65:35, and 75:25 indicated that PLGA 50:50 was the most amenable to morphological changes upon SC CO2 treatment. Therefore, we prepared deslorelin-PLGA (50:50) microparticles using the conventional emulsion-solvent evaporation method, and in a second step equilibrated with SC CO2 at various temperatures (33-37 degrees C) and pressures (1200-2000 psi) for discrete intervals followed by rapid isothermal depressurization. The particles were then characterized for morphology, polymer thermal properties, particle size, porosity, bulk density, and residual solvent content. Also, deslorelin integrity, conformation, release, and cellular uptake before and after SC CO2 treatment was determined.

RESULTS

Upon SC CO2 treatment (1200 psi, 33 degrees C for 30 min), the mean particle size of the deslorelin PLGA microparticles increased from 2.2 to 13.8 microm, the mean porosity increased from 39 to 92.38% the mean pore diameter increased from 90 to 190 nm, the mean bulk density reduced from 0.7 to 0.082 g/cc, mass spectrometry indicated structural integrity of released deslorelin, the circular dichroism spectrum indicated stabilization of beta-turn conformation, and the scanning electron microscopy confirmed increased particle size and pore formation. The deslorelin release was sustained during the 7-day study period. Also, the peak Tg of PLGA decreased from 51 to 45 degrees C, and the residual solvent content was reduced from 4500 ppm to below detection limit (< 25 ppm). The accumulation of drug from SC CO2 treated particles in cell layers of Calu-3, A549, and rat alveolar macrophages was reduced by 87, 91 and 50%, respectively, compared to untreated particles.

CONCLUSION

An SCF-derived process could be successfully applied to prepare large porous deslorelin-PLGA particles with reduced residual solvent content, which retained deslorelin integrity, sustained deslorelin release, and reduced cellular uptake.

Edge activators and a polycationic polymer enhance the formulation of porous voriconazole nanoagglomerate for the use as a dry powder inhaler

PURPOSE

Voriconazole has both low aqueous solubility and stability. We hypothesize that designing voriconazole in the form of a nano powder inhaler at a geometric diameter within 1-5 μm will enhance its stability and solubility. Therefore, we prepared nanoagglomerates of voriconazole which will collapse in the lungs to reform the nanoparticles.

METHOD

The nanoparticles were formulated using both stearic acid and sodium deoxycholate as edge activators. Osmogenic polycation polyethyleneimine (PEI) was used to form agglomerates of controllable size.

RESULTS

Voriconazole nanoparticles and agglomerates showed a significant higher cumulative drug release than the pure powder (p < 0.05) with R(2 )=( )0.95. Small-sized particles were formed (353 nm), while their zeta potential was -30.7 mV. The agglomerates were 2.7 μm in size and their zeta potential was -20.9 mV. The formation of porous agglomerates was confirmed using a transmission electron microscope. Cascade impactor was used to evaluate the aerodynamic properties of the nanoparticles and the agglomerates. The aerodynamic characterization of the nanoparticles and the agglomerates resulted in a significant smaller mass median aerodynamic diameter (MMAD) (p < 0.05) and higher fine particle dose (FPD) (p < 0.01), fine particle fraction (FPF) (p < 0.01), and total emitted dose (TED) (p < 0.01) than the pure powder.

CONCLUSION

The results suggest that using the combination of edge activators and diluted polycationic polymer solution provides porous voriconazole nanoagglomerates in a respirable range, which is proved successful in enhancing both the deposition and the dissolution of water insoluble-drugs in the lung.

Development of low density azithromycin-loaded polycaprolactone microparticles for pulmonary delivery

CONTEXT

The development of low-density polymeric microparticles may be a useful approach to deliver antibiotics such as azithromycin into the lung.

OBJECTIVE

The aim of this study was to develop azithromycin-loaded low density polycaprolactone microparticles by the double emulsion/solvent evaporation method.

MATERIALS AND METHODS

Microparticles were prepared and characterized according to their physicochemical properties, drug loading, and drug release profiles. A full 2(3) factorial design was used to evaluate the effect of some independent variables on the drug loading and aerodynamic diameter of the particles. An in silico pulmonary deposition model was used to predict the lung deposition profiles for the formulations.

RESULTS AND DISCUSSION

The resulting particles presented drug loading up to 23.1% (wt%) and mean geometric diameters varying from 4.0 µm to 15.4 µm. Bulk and tapped densities were low, resulting in good or excellent flow properties. SEM images showed spherical particles with a smooth surface. However, hollow inner structures were observed, which may explain the low values of bulk density. The estimated aerodynamic diameters ranged from 2.3 µm to 8.9 µm. The in silico pulmonary deposition profiles indicated, for some formulations, that a significant fraction of the particles would be deposited in the deeper lung regions.

CONCLUSIONS

Statistical analysis demonstrated that not only drug loading but also the aerodynamic diameter of the microparticles is greatly affected by the preparation conditions. Overall, the results indicated that the low-density azithromycin-loaded microparticles with a relatively high respirable fraction may be obtained for the local treatment of lung infections.

Novel drug delivery systems for actinides (uranium and plutonium) decontamination agents

The possibility of accidents in the nuclear industry or of nuclear terrorist attacks makes the development of new decontamination strategies crucial. Among radionuclides, actinides such as uranium and plutonium and their different isotopes are considered as the most dangerous contaminants, plutonium displaying mostly a radiological toxicity whereas uranium exhibits mainly a chemical toxicity. Contamination occurs through ingestion, skin or lung exposure with subsequent absorption and distribution of the radionuclides to different tissues where they induce damaging effects. Different chelating agents have been synthesized but their efficacy is limited by their low tissue specificity and high toxicity. For these reasons, several groups have developed smart delivery systems to increase the local concentration of the chelating agent or to improve its biodistribution. The aim of this review is to highlight these strategies.

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.

Pulmonary drug delivery systems for tuberculosis treatment

Tuberculosis (TB) remains a major global health problem as it is the second leading cause of death from an infectious disease worldwide, after the human immunodeficiency virus (HIV). Conventional treatments fail either because of poor patient compliance to the drug regimen or due to the emergence of multidrug-resistant tuberculosis. The aim of this review is to give an update on the information available on tuberculosis, its pathogenesis and current antitubercular chemotherapies. Direct lung delivery of anti-TB drugs using pulmonary delivery systems is then reviewed since it appears as an interesting strategy to improve first and second line drugs. A particular focus is place on research performed on inhalable dry powder formulations of antitubercular drugs to target alveolar macrophages where the bacteria develop. Numerous studies show that anti-TB drugs can be incorporated into liposomes, microparticles or nanoparticles which can be delivered as dry powders to the deep lungs for instantaneous, targeted and/or controlled release. Treatments of infected animals show a significant reduction of the number of viable bacteria as well as a decrease in tissue damage. These new formulations appear as interesting alternatives to deliver directly drugs to the lungs and favor efficient TB treatment.

Development and application of an inhalation bioaccessibility method (IBM) for lead in the PM10 size fraction of soil

An approach for assessing the inhalation bioaccessibility of Pb in the PM10 size fraction is presented, using an in vitro simulated epithelial lung fluid to represent the extracellular environment of the lung. The developed inhalation bioaccessibility method (IBM) is applied to a range of urban surface soils and mining wastes obtained from Mitrovica, Kosovo, a site where impacts upon human health following exposure to Pb have been internationally publicised. All Pb determinations were undertaken by inductively coupled plasma mass spectrometry (ICP-MS). The pseudo-total concentration of Pb (microwave acid digestion using aqua-regia) varied between matrices: smelter (20,900-72,800mgkg(-1)), topsoil (274-13,700mgkg(-1)), and tailings (2990mgkg(-1)-25,300mgkg(-1)). The in vitro inhalation bioaccessibility was typically several orders of magnitude lower: smelter (7.0-965mgkg(-1)), topsoil (9.8-1060mgkg(-1)), and tailings (0.7mgkg(-1)-49.2mgkg(-1)). The % inhalation bioaccessibility ranged from 0.02 to 11.0%, with the higher inhalation bioaccessible Pb concentrations being observed for samples from the Bosniak Mahalla area of Mitrovica (an area proposed for the relocation of internally displaced peoples). The estimated inhalation dose (for adults) calculated from the PM10 pseudo-total Pb concentration ranged from 0.369 to 1.284μgkg(-1)BWday(-1) (smelter), 0.005-0.242μgkg(-1)BWday(-1) (topsoil), and 0.053-0.446μgkg(-1)BWday(-1) (tailings). When daily inhalation doses were calculated using the bioaccessible Pb concentration the modelled exposure doses were much lower: smelter (0.0001-0.0170μgkg(-1)BWday(-1)), topsoil (0.0002-0.0187μgkg(-1)BWday(-1)) and tailings (0.0001-0.0009μgkg(-1)BWday(-1)). Modelled for the neutral pH conditions of the interstitial lung environment, the results indicate a low potential inhalation bioaccessibility for Pb in these samples. Given the already elevated environmental Pb burden experienced by the local population, where significant prolonged dust or particulate generating activities are taking place, or where the inhaled particles are phagocytized, then inhalation exposure has the potential to significantly add to the overall Pb burden. Such data are important for local policy makers to better enable them to assess risk, especially in areas where soils/dusts have elevated levels of contamination.

Delivery strategies for sustained drug release in the lungs

Drug delivery to the lungs by inhalation offers a targeted drug therapy for respiratory diseases. However, the therapeutic efficacy of inhaled drugs is limited by their rapid clearance in the lungs. Carriers providing sustained drug release in the lungs can improve therapeutic outcomes of inhaled medicines because they can retain the drug load within the lungs and progressively release the drug locally at therapeutic levels. This review presents the different formulation strategies developed to control drug release in the lungs including microparticles and the wide array of nanomedicines. Large and porous microparticles offer excellent aerodynamic properties. Their large geometric size reduces their uptake by alveolar macrophages, making them a suitable carrier for sustained drug release in the lungs. Similarly, nanocarriers present significant potential for prolonged drug release in the lungs because they largely escape uptake by lung-surface macrophages and can remain in the pulmonary tissue for weeks. They can be embedded in large and porous microparticles in order to facilitate their delivery to the lungs. Conjugation of drugs to polymers as polyethylene glycol can be particularly beneficial to sustain the release of proteins in the lungs as it allows high protein loading. Drug conjugates can be readily delivered to respiratory airways by any current nebulizer device. Nonetheless, liposomes represent the formulation most advanced in clinical development. Liposomes can be prepared with lipids endogenous to the lungs and are particularly safe. Their composition can be adjusted to modulate drug release and they can encapsulate both hydrophilic and lipophilic compounds with high drug loading.

Lipid-based carriers for pulmonary products: preclinical development and case studies in humans

A number of lipid-based technologies have been applied to pharmaceuticals to modify their drug release characteristics, and additionally, to improve the drug loading for poorly soluble drugs. These technologies, including solid-state lipid microparticles, many of which are porous in nature, liposomes, solid lipid nanoparticles and nanostructured lipid carriers, are increasingly being developed for inhalation applications. This article provides a review of the rationale for the use of these technologies in the pulmonary delivery of drugs, and summarizes the manufacturing processes and their limitations, the in vitro and in vivo performance of these systems, the safety of these lipid-based systems in the lung, and their promise for commercialization.

Dry powders for oral inhalation free of lactose carrier particles

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

In vitro and in vivo performance of dry powder inhalation formulations: comparison of particles prepared by thin film freezing and micronization

Recently, inhaled immunosuppressive agents have attracted increasing attention for maintenance therapy following lung transplantation. The rationale for this delivery approach includes a more targeted and localized delivery to the diseased site with reduced systemic exposure, potentially leading to decreased adverse side effects. In this study, the in vitro and in vivo performance of an amorphous formulation prepared by thin film freezing (TFF) and a crystalline micronized formulation produced by milling was compared for tacrolimus (TAC). Despite the relatively large geometric size, the TFF-processed formulation was capable of achieving deep lung delivery due to its low-density, highly porous, and brittle characteristics. When emitted from a Miat® monodose inhaler, TFF-processed TAC formulations exhibited a fine particle fraction (FPF) of 83.3% and a mass median aerodynamic diameter (MMAD) of 2.26 μm. Single-dose 24-h pharmacokinetic studies in rats demonstrated that the TAC formulation prepared by TFF exhibited higher pulmonary bioavailability with a prolonged retention time in the lung, possibly due to decreased clearance (e.g., macrophage phagocytosis), compared to the micronized TAC formulation. Additionally, TFF formulation generated a lower systemic TAC concentration with smaller variability than the micronized formulation following inhalation, potentially leading to reduced side effects related to the drug in systemic circulation.

Technological and practical challenges of dry powder inhalers and formulations

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

Aerosolized montelukast polymeric particles-an alternative to oral montelukast-alleviate symptoms of asthma in a rodent model

PURPOSE

Cysteinyl leukotrienes (CysLTs) propagate inflammatory reactions that result from allergen exposure in asthma. Montelukast, a CysLT type-1 receptor antagonist, disrupts mediator-receptor interactions and minimizes inflammatory response. In this study, we have evaluated anti-asthmatic efficacy of inhalable montelukast-loaded large porous particulate formulations in ovalbumin-induced rat airway inflammation model that mimics asthma.

METHODS

The anti-inflammatory effects of a montelukast-loaded formulation were investigated in rats by measuring the total protein content, levels of injury markers and number of inflammatory cells in the bronchoalveolar lavage fluid (BALF). The histopathological studies assessed the morphological and structural changes that occur in asthmatic lungs. Animals were also challenged with methacholine to examine the airway hyper-reactivity.

RESULTS

Compared with healthy animals, asthmatic animals showed a 3.8- and 4.77-fold increase in the protein content and number of inflammatory cells in BALF, respectively. Intratracheal montelukast particles reduced the protein content by 3.3-fold and the number of inflammatory cells by 2.62-fold. Also, montelukast particles reduced the lactate dehydrogenase (LDH) and myeloperoxidase (MPO) levels by a 4.87- and 6.8-fold in BALF, respectively. Montelukast particles reduced the airway wall thickness by 2.5-fold compared with untreated asthmatic lungs. Further, particulate formulation protected the lungs against methacholine-induced bronchial provocation (p < 0.05).

CONCLUSIONS

Respirable large porous particles containing montelukast alleviated allergen-induced inflammatory response in an animal model and prevented histological changes associated with asthma. Thus montelukast-loaded large porous polylactic acid (PLA) particles could be an aerosolized delivery approach for administration of currently available oral montelukast.

How can we bring high drug doses to the lung?

In the last decades, dry powder inhalation has become a very attractive option for pulmonary drug delivery to treat lung diseases like cystic fibroses and lung infections. In contrast to the traditional pulmonary application of drugs for asthma and chronic obstructive pulmonary disease, these therapies require higher lung doses to be administered. The developments and improvements toward high dose powder pulmonary drug delivery are summarized and discussed in this chapter. These include the invention and improvement of novel inhaler devices as well as the further development of formulation principles and new powder engineering methods. The implementation of these strategies is subsequently described for some prototypes and formulations in research and development stage as well as for already marketed dry powder products. Finally, possible adverse effects that can occur after inhalation of high powder doses are shortly addressed.

Alternative carriers in dry powder inhaler formulations

The aerosolization efficiency of a powder is highly dependent on carrier characteristics, such as particle size distribution, shape and surface properties. The main objective in the inhalation field is to achieve a high and reproducible pulmonary deposition. This can be provided by successful carrier selection and careful process optimization for carrier modification. Lactose is the most common and frequently used carrier in dry powder inhaler (DPI) formulations. But lactose shows some limitations in formulation with certain drugs and peptides that prohibit its usage as a carrier in DPI formulations. Here, we criticality review the most important alternative carriers to lactose with merits, demerits and applications in DPI formulations.

Aerosol generation using nanometer liposome suspensions for pulmonary drug delivery applications

Pulmonary lung targeting finds applications in drug delivery to the lung itself and to other body organs, via blood circulation following transfer across alveolar membranes. Understanding pulmonary drug delivery systems towards improving their efficacy needs identification of particle sizes of relevance and elucidation of links between suspension properties, techniques of atomisation and properties of the generated aerosols. This review article is focussed on understanding the elements of pulmonary drug delivery, specifically related to suspensions of small liposomes. Specific objectives of this review include (a) understanding aerosol particle deposition and absorption on pulmonary surface, (b) links between properties of aerosol generation and colloidal drug carriers used for drug encapsulation, and (c) investigation on the controlled properties of liposome aerosols generated using different atomisation techniques for efficacious aerosol therapy.

Optimization of the fine particle fraction of a lyophilized lysozyme formulation for dry powder inhalation

PURPOSE

A new dry powder inhalation technology creates inhalable particles from a coherent lyophilized bulk at the time of inhalation. The aim of this study was to evaluate several approaches to improve the fine particle fraction (FPF) and to understand underlying mechanisms.

METHODS

Lysozyme was chosen as model drug. Phenylalanine and valine were added, and the freezing process was varied. Lyophilisate characteristics as well as aerosolization behavior was analyzed.

RESULTS

The addition of the crystalline amino acids rendered a dose independent three-fold increase of the FPF. This is possibly due to enhanced fracture properties of the lyophilisates upon impact of the air stream and reduced particle agglomeration/cohesion caused by a rougher surface. This positive effect was well preserved over 3 months of storage. The structure of the lyophilisate was influenced by the freezing process which in turn affected the aerosolization behavior. Liquid nitrogen and vacuum-induced freezing performed best, doubling the FPF. The special cake morphology with elongated channels enabled easy disintegration. The resulting large porous particles comprise a low density being advantageous for a high FPF.

CONCLUSION

The variation of the lyophilization process and formulation utilizing excipients enabled an optimization of the FPF of the novel lyophilisate based DPI system.