In vitro and in vivo dose delivery characteristics of large porous particles for inhalation

A Review on Micro and Nanoengineering in Powder-Based Pulmonary Drug Delivery

Pulmonary delivery of drugs has emerged as a promising approach for the treatment of both lung and systemic diseases. Compared to other drug delivery routes, inhalation offers numerous advantages including high targeting, fewer side effects, and a huge surface area for drug absorption. However, the deposition of drugs in the lungs can be limited by lung defence mechanisms such as mucociliary and macrophages' clearance. Among the delivery devices, dry powder inhalers represent the optimal choice due to their stability, ease of use, and absence of propellants. In the last decades, several bottom-up techniques have emerged over traditional milling to produce inhalable powders. Among these techniques, the most employed ones are spray drying, supercritical fluid technology, spray freeze-drying, and thin film freezing. Inhalable dry powders can be constituted by micronized drugs attached to a coarse carrier (e.g., lactose) or drugs embedded into a micro- or nanoparticle. Particulate-based formulations are commonly composed of polymeric micro- and nanoparticles, liposomes, solid lipid nanoparticles, dendrimers, nanocrystals, extracellular vesicles, and inorganic nanoparticles. Moreover, engineered formulations including large porous particles, swellable microparticles, nano-in-microparticles, and effervescent nanoparticles have been developed. Particle engineering has also a crucial role in tuning the physical-chemical properties of both carrier-based and carrier-free inhalable powders. This approach can increase powder flowability, deposition, and targeting by customising particle surface features.

Bioactive Betulin and PEG Based Polyanhydrides for Use in Drug Delivery Systems

In the course of this study, a series of novel, biodegradable polyanhydrides based on betulin disuccinate and dicarboxylic derivatives of poly(ethylene glycol) were prepared by two-step polycondensation. These copolymers can be used as carriers in drug delivery systems, in the form of microspheres. Betulin and its derivatives exhibit a broad spectrum of biological activity, including cytotoxic activity, which makes them promising substances for use as therapeutic agents. Microspheres that were prepared from betulin based polyanhydrides show promising properties for use in application in drug delivery systems, including inhalation systems. The obtained copolymers release the active substance-betulin disuccinate-as a result of hydrolysis under physiological conditions. The use of a poly(ethylene glycol) derivative as a co-monomer increases the solubility and bioavailability of the obtained compounds. Microspheres with diameters in the range of 0.5-25 µm were prepared by emulsion solvent evaporation method and their physicochemical and aerodynamic properties were analyzed. The morphological characteristics of the microspheres depended on the presence of poly(ethylene glycol) (PEG) segment within the structure of polyanhydrides. The porosity of the particles depended on the amount and molecular weight of the PEG used and also on the speed of homogenization. The most porous particles were obtained from polyanhydrides containing 20% wt. of PEG 600 by using a homogenization speed of 18,000 rpm.

Profile of inhaled levodopa and its potential in the treatment of Parkinson's disease: evidence to date

Inhaled levodopa is a newly emerging therapeutic option in the treatment of "off " symptoms associated with Parkinson's disease (PD). Its mode of delivery offers more rapid absorption of levodopa and shorter onset of clinical benefit compared to oral formulations, and has been shown to be feasible for use in patients with PD experiencing worse motor function due to declining plasma levodopa levels. Clinical development of this compound is supported by preclinical, Phase I-III, long-term-safety studies and studies in special populations, including otherwise-healthy asthmatics and smokers. These investigations demonstrated that the drug is well tolerated without risk of long-term (up to 1 year) changes in pulmonary function or spirometry measures. The most common side effects among PD patients were a mild cough, upper respiratory tract infection, nausea, sputum discoloration, and dyskinesia. Inhaled levodopa offers a different administration method and side-effect profile from the currently available options for rescue therapy for Off periods in PD, though comparative studies have not been performed. The drug is presently under review by the US Food and Drug Administration.

Large porous particles for respiratory drug delivery. Glycine-based formulations

Large porous particles are becoming increasingly popular as carriers for pulmonary drug delivery with both local and systemic applications. These particles have high geometric diameters (5-30μm) but low bulk density (~0.1g/cm³ or less) such that the aerodynamic diameter remains low (1-5μm). In this study salbutamol and budesonide serve as model inhalable drugs with poor water solubility. A novel method is proposed for the production of dry powder inhaler formulations with enhanced aerosol performance (e.g. for salbutamol-glycine formulation the fine particle fraction (FPF≤4.7μm) value is 67.0±1.3%) from substances that are poorly soluble in water. To overcome the problems related to extremely poor aqueous solubility of the APIs, not individual solvents are used for spray freeze-drying of API solutions, but organic-water mixtures, which can form clathrate hydrates at low temperatures and release APIs or their complexes as fine powders, which form large porous particles after the clathrates are removed by sublimation. Zwitterionic glycine has been used as an additive to API directly in solutions prior to spray freeze-drying, in order to prevent aggregation of powders, to enhance their dispersibility and improve air-flow properties. The clathrate-forming spray freeze-drying process in the multi-component system was optimized using low-temperature powder X-ray diffraction and thermal analysis.

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.

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.

Improving inhaler technique, adherence to therapy and the precision of dosing: major challenges for pulmonary drug delivery

INTRODUCTION

The inhaled route has many advantages, but requires the patient to use, and to master the use of, an inhaler device. Poor inhaler technique and non-adherence to therapy lead to a highly variable lung dose in clinical practice, with subsequent loss of clinical efficacy and wastage of economic resources.

AREAS COVERED

This paper discusses problems of poor inhaler technique, non-adherence to inhaler therapy, other issues relating to the precision of dose delivery, the consequences of these problems and how they can be addressed.

EXPERT OPINION

The precision of dosing by the pulmonary route can be improved by appropriate choice of inhaler device and by education. It is vital to educate patients about their disease, about the importance of taking prescribed medications and about correct inhaler use. One-on-one sessions with healthcare professionals probably represent the most effective educational method. For some drugs and patient groups, inhalers containing small microprocessors may also be used to control inhalation technique, and hence, to obtain a more reproducible lung dose. As the range of drugs delivered by inhalation increases, the need for correct inhaler technique, adherence to therapy and precise dosing becomes more and more important.

Hydrogels for controlled pulmonary delivery

A significant number of research articles have focused on pulmonary delivery as an alternative administration route owing to no first-pass metabolism, low protease activity, thin epithelium barrier and large surface area in the lung system. Controlled release in the pulmonary delivery system further reduces loading dose, frequency of dosing and systemic side effects, and also increases duration of action and patient compliance. Compared with other microparticles used in controlled-release pulmonary administration, hydrogels (3D polymeric matrix networks) have recently been investigated due to their swelling and mucoadhesive properties that could help bypass pulmonary delivery barriers. This review introduces controlled-release drug delivery to the lung, followed by a summary of currently available approaches for controlled-release pulmonary drug delivery. Lastly, the origin, advantages, detailed applications and concerns of hydrogels in pulmonary delivery are discussed.

Supercritical fluid technology based large porous celecoxib-PLGA microparticles do not induce pulmonary fibrosis and sustain drug delivery and efficacy for several weeks following a single dose

Although pulmonary dosing of large porous particles has been shown to sustain drug delivery for a few days, there are no reports on safety or long term delivery. In this study we prepared large porous poly(lactide-co-glycolide) (PLGA) microparticles of celecoxib using supercritical fluid pressure-quench technology and demonstrated 4.8-, 15.7-, and 2.1-fold greater drug levels in lung, bronchoalveolar lavage fluid (BAL), and plasma compared to conventional microparticles on day 21 after a single intratracheal dosing of dry powders in A/J mice. Porous particle based delivery was 50.2-, 95.5-, and 7.7-fold higher compared to plain drug in the lung, BAL, and plasma, respectively. Toxicity of the formulations was assessed on day 21 following a fibrosis assessment protocol in A/J mice. There was no significant change in lactate dehydrogenase (LDH), total protein, and total cell counts in the BAL, and soluble collagen levels in the lung tissue following particle or drug treatments. Lung histology indicated no significant hyperplasia, granuloma, or collagen deposition in the treated groups. Chemopreventive potential of celecoxib porous particles was assessed in a benzo[a]pyrene (B[a]P) induced lung cancer model in A/J mice, on day 60 following a single intratracheal dose with or without single intravenous paclitaxel/carboplatin treatment. The combination group was more effective than individual groups, with the inhibition of tumor multiplicity and reduction of vascular endothelial growth factor in the BAL being 70 and 58%, respectively. Thus, large porous celecoxib-PLGA microparticles prepared using supercritical fluid technology exhibited sustained drug delivery and anti-tumor efficacy, without causing any significant toxicity.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effects of physical activity on the deposition of traffic-related particles into the human lungs in silico

Traffic-related particle emissions have been a great concern over a number of years due to their adverse health effects. In this research project, traffic-related particle deposition in the human lungs is studied using lung deposition estimates based on the ICRP 66 model. This study covers four human groups, i.e. adult males, adult females and two groups of children aged 5 and 10 years. The study examines particle deposition in the human lungs in relation to four different physical exercise levels, i.e. sleeping, sitting, light exercise and heavy exercise. To conduct the study, the particle size distributions of diesel and compressed natural gas (CNG) busses were monitored in field laboratory conditions. The study indicates that the total number of diesel particles measured is greater than the total number of CNG particles. The results further display that most of the diesel particles measured are smaller than 0.2 μm, whereas the CNG particles are smaller than 0.05 μm in aerodynamic diameter. The level of physical exercise, as well as the age and gender of a person affects the deposition of particles in the lungs. An increase in the physical activity results in larger amounts of small-size particles penetrating deeper into the respiratory system. The lung deposition of particles in males was substantially different compared to that of females and children. The deposited dose of particles was generally lower for females than for males and further lower for children than for females. This article argues that these groups should be discussed separately when conducting exposure assessments and that the level of physical activity should be taken into account when assessing potential health consequences.

Comparative pharmacoscintigraphic and pharmacokinetic evaluation of two new formulations of inhaled insulin in type 1 diabetic patients

In this open, single-dose study, we compared the lung deposition and bioavailability of two newly developed insulin formulations for pulmonary delivery. Twelve type 1 diabetic patients were administered the two insulin products (2 U/kg b.w.), which had been radiolabelled with (99m)Tc. The formulations were either microparticles of insulin without excipients (F1) or lipid-coated insulin microparticles (F2). Lung deposition was assessed by γ-scintigraphy imaging performed immediately after administration. Bioavailability was evaluated by quantifying serum insulin levels over a period of 6 h. Lung deposition was found to be 50 ± 9% and 24 ± 8% for the F1 and F2 formulations, respectively. The insulin AUC₀₋₃₆₀ ratio of F1/F2 was 188%, which was consistent with scintigraphic imaging. The concordance between imaging and biological results suggests that the lower bioavailability of F2 is due to its lower lung deposition and not to a reduced absorption into the blood stream. Additional in vitro experiments indicated that the lower performance of F2 was most probably related to a lower disaggregation efficiency of the powder when administered at a sub-optimal flow rate. The two formulations showed interesting pharmacokinetic profiles (T(max) of 26 and 16 min for F1 and F2, respectively) that mimic the physiological insulin secretion pattern. The bioavailability of the developed formulations was within the range of other DPI insulin formulations that have reached the final stages of clinical development.

Insulin lung deposition and clearance following Technosphere® insulin inhalation powder administration

PURPOSE

To determine distribution and deposition of Technosphere® Insulin (TI) inhalation powder and the rate of clearance of fumaryl diketopiperazine (FDKP; major component of Technosphere particles) and insulin from the lungs.

METHODS

Deposition and distribution of (99m)pertechnetate adsorbed onto TI immediately after administration using the MedTone® inhaler was quantified by gamma-scintigraphy. Clearance from the lungs was studied in a second experiment by serial bronchoalveolar lavage (BAL) after administration of TI inhalation powder and assay of the recovered fluid for FDKP and insulin.

RESULTS

Following inhalation, ~60% of radioactivity (adsorbed on TI) emitted from the inhaler was delivered to the lungs; the remainder of the emitted dose was swallowed. Clearance from the lung epithelial lining fluid (ELF) of FDKP and insulin have a half-life of ~1 hour.

CONCLUSION

TI inhalation powder administered via the MedTone inhaler was uniformly distributed throughout the lungs; ~40% of the initial cartridge load reached the lungs. Insulin and FDKP are quickly cleared from the lungs, mainly by absorption into the systemic circulation. The terminal clearance half-life from the lung ELF, estimated from sequential BAL fluid measurements for both components, was ~1 hour. Since there is an overnight washout period, the potential for accumulation on chronic administration is minimal.

Exposure assessment of particulates of diesel and natural gas fuelled buses in silico

Lung deposition estimates of particulate emissions of diesel and natural gas (CNG) fuelled vehicles were studied by using in silico methodology. Particulate emissions and particulate number size distributions of two Euro 2 petroleum based diesel buses and one Euro 3 gas bus were measured. One of the petroleum based diesel buses used in the study was equipped with an oxidation catalyst on the vehicle (DI-OC) while the second had a partial-DPF catalyst (DI-pDPF). The third bus used was the gas bus with an oxidation catalyst on the vehicle (CNG-OC). The measurements were done using a transient chassis dynamometer test cycle (Braunschweig cycle) and an Electric Low Pressure Impactor (ELPI) with formed particulates in the size range of 7 nm to 10 microm. The total amounts of the emitted diesel particulates were 88-fold for DI-OC and 57-fold for DI-pDPF compared to the total amount of emitted CNG particulates. Estimates for the deposited particulates were computed with a lung deposition model ICRP 66 using in-house MATLAB scripts. The results were given as particulate numbers and percentages deposited in five different regions of the respiratory system. The percentages of particulates deposited in the respiratory system were 56% for DI-OC, 51% for DI-pDPF and 77% for CNG-OC of all the inhaled particulates. The result shows that under similar conditions the total lung dose of particulates originating from petroleum diesel fuelled engines DI-OC and DI-pDPF was more than 60-fold and 35-fold, respectively, compared to the lung dose of particulates originating from the CNG fuelled engine. The results also indicate that a majority (35-50%) of the inhaled particulates emitted from the tested petroleum diesel and CNG engines penetrate deep into the unciliated regions of the lung where gas-exchange occurs.

Assessment methods of inhaled aerosols: technical aspects and applications

The pulmonary route has been used with success for the treatment of both lung (asthma) and systemic diseases (diabetes). The fate of an inhaled drug (absorption and deposition) within human lungs has great importance, particularly in drug development and quality control. This article focuses on the various methods that are now applied for aerosol fate investigation. Several assessment methods, ranging from in vitro assays (impaction and optical systems) to in vivo experiments (imaging and pharmacological methods), are described. In vitro assays measure particle size distribution and emitted drug dose, which could be predictive of lung deposition pattern in vivo. However, in vivo methods provide direct information about the concentration and the location of inhaled drug within lung. Advantages and limitations of the different techniques are identified. In addition to these experimental techniques, mathematical deposition models, elaborated in more realistic conditions and designed to predict the fate of inhaled particles, are also illustrated.

Efficacy and safety of AIR inhaled insulin compared to insulin lispro in patients with type 1 diabetes mellitus in a 6-month, randomized, noninferiority trial

BACKGROUND

Patients with type 1 diabetes may prefer features of AIR inhaled insulin (developed by Alkermes, Inc. [Cambridge, MA] and Eli Lilly and Company [Indianapolis, IN]; AIR is a registered trademark of Alkermes, Inc.) over insulin injection, but the two methods need to be compared for efficacy and safety.

METHODS

This multicenter, 6-month, parallel-group, noninferiority trial had 500 patients with type 1 diabetes randomized to morning doses of basal insulin glargine plus either preprandial injectable insulin lispro or preprandial AIR insulin. We hypothesized that AIR insulin is noninferior (upper bound of the 95% confidence interval < or = 0.4%) to insulin lispro for change-from-baseline hemoglobin A1C (A1C).

RESULTS

Baseline A1C was 7.95 +/- 0.08% for both groups. At end point, A1C was lower with insulin lispro than with AIR insulin by 0.27% (95% confidence interval 0.11, 0.43; P< 0.001). Noninferiority of AIR insulin to insulin lispro was not demonstrated, but similar percentages of patients in each group achieved A1C <7.0% (P = 0.448). Overall daily blood glucose was similar between groups at baseline (P = 0.879) and end point (P = 0.161). Two-hour postprandial blood glucose change from baseline was significantly (P < 0.001) higher with AIR insulin (20.77 +/- 4.33 mg/dL at 3 months and 15.85 +/- 3.08 mg/dL at end point) than with insulin lispro (3.29 +/- 4.14 mg/dL at 3 months and 1.67 +/- 2.91 mg/dL at end point). Overall hypoglycemia was similar between treatment groups (P = 0.355). The AIR insulin group had greater decrease in diffusing capacity of the lung for carbon monoxide at end point (P = 0.020) and greater incidence of cough (P = 0.024) and dyspnea (P = 0.030). Body weight decreased in the AIR insulin group and increased in the insulin lispro group.

CONCLUSIONS

Insulin lispro provided lower A1C than AIR insulin, but the difference may not be clinically relevant.

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.

Nifedipine nanoparticle agglomeration as a dry powder aerosol formulation strategy

Efficient administration of drugs represents a leading challenge in pulmonary medicine. Dry powder aerosols are of great interest compared to traditional aerosolized liquid formulations in that they may offer improved stability, ease of administration, and simple device design. Particles 1-5microm in size typically facilitate lung deposition. Nanoparticles may be exhaled as a result of their small size; however, they are desired to enhance the dissolution rate of poorly soluble drugs. Nanoparticles of the hypertension drug nifedipine were co-precipitated with stearic acid to form a colloid exhibiting negative surface charge. Nifedipine nanoparticle colloids were destabilized by using sodium chloride to disrupt the electrostatic repulsion between particles as a means to achieve the agglomerated nanoparticles of a controlled size. The aerodynamic performance of agglomerated nanoparticles was determined by cascade impaction. The powders were found to be well suited for pulmonary delivery. In addition, nanoparticle agglomerates revealed enhanced dissolution of the drug species suggesting the value of this formulation approach for poorly water-soluble pulmonary medicines. Ultimately, nifedipine powders are envisioned as an approach to treat pulmonary hypertension.

Enhanced Dispersibility and Deposition of Spray-dried Powders for Pulmonary Gene Therapy

Spray-drying represents a viable alternative to freeze-drying for preparing dry powder dispersions for delivering macromolecules to the lung. The dispersibility of spray-dried powders is limited however, and needs to be enhanced to improve lung deposition and subsequent biological activity. In this study, we investigate the utility of leucine as a dry powder dispersibility enhancer when added prior to spray-drying a model non-viral gene therapy formulation (lipid:polycation:pDNA, LPD). Freeze-dried lactose-LPD, spray-dried lactose-LPD and spray-dried leucine-lactose-LPD powders were prepared. Scanning electron microscopy showed that leucine increased the surface roughness of spray-dried lactose particles. Particle size analysis revealed that leucine-containing spray-dried powders were unimodally dispersed with a mean particle diameter of 3.12 microm. Both gel electrophoresis and in vitro cell (A549) transfection showed that leucine may compromise the integrity and biological functionality of the gene therapy vector. The deposition of the leucine containing powder was however significantly enhanced as evidenced by an increase in gene expression mediated by dry powder collected at lower stages of a multistage liquid impinger (MSLI). Further studies are required to determine the potential of leucine as a ubiquitous dispersibility enhancer for a variety of pulmonary formulations.

Pharmaceutical particle engineering via spray drying

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

Dry powder inhalation of hemin to induce heme oxygenase expression in the lung

The purpose of this study was to formulate hemin as a powder for inhalation and to show proof of concept of heme oxygenase 1 (HO-1) expression in the lungs of mice by inhalation of hemin. Hemin was spray dried from a neutralized sodium hydroxide solution. The particle size distribution of the powder was between 1 and 5 microm. Dispersion from the Twincer dry powder inhaler showed a fine particle fraction (<5 microm) of 36%. A specially designed aerosol box based on the Twincer-inhaler was used for a proof of concept study of HO-1 induction by inhalation of hemin in mice. The aerosol in the exposure chamber of the aerosol box remained aerosolized up to 5 min. A rhodamin B containing aerosol was used to show that the aerosol box gave deposition over the entire lung indicating the suitability of the model. Additionally, inhalation of hemin showed a dose dependent increase in HO-1 protein expression in the lungs. In conclusion, hemin was successfully formulated as a powder for inhalation and the inhalation model allowed controlled HO-1 expression in the lungs of mice. Future studies investigating the utility of inhaled hemin in treating disease states are warranted.

AIR inhaled insulin in subjects with chronic obstructive pulmonary disease: pharmacokinetics, glucodynamics, safety, and tolerability

OBJECTIVE

In this open-label, randomized, crossover study, pharmacokinetic and glucodynamic responses were compared in healthy subjects versus subjects with moderate chronic obstructive pulmonary disease (COPD), following administration of 12 units equivalent AIR inhaled insulin versus 12 units subcutaneous insulin lispro.

RESEARCH DESIGN AND METHODS

Three nonsmoking groups (n = 15 each)--healthy subjects (baseline mean +/- SD age 38 +/- 13 years, forced expiratory volume in 1 s [FEV1] 4.06 +/- 1.04 l), subjects with chronic bronchitis (aged 53 +/- 9 years, FEV1 2.14 +/- 0.60 l), and subjects with pulmonary emphysema (aged 58 +/- 6 years, FEV1 1.67 +/- 0.61 l)--were randomly assigned to one of three treatment sequences. Three euglycemic glucose clamp procedures were performed.

RESULTS

In subjects with chronic bronchitis and emphysema, AIR inhaled insulin administration resulted in reduced insulin exposure (area under the serum insulin concentration curve from time zero until time of return to baseline [AUC(0-t')]) (55.7%, P = 0.13 and 78.5%, P < 0.001, respectively) and reduced total insulin effect (total glucose infusion rate) (60.4%, P < 0.01 and 67.1%, P < 0.01, respectively) relative to healthy subjects. Subcutaneous insulin lispro administration resulted in similar responses across study groups for insulin exposure and metabolic effect. Intrasubject pharmacokinetic and glucodynamic variability ranged from 17 to 52% across groups. No significant differences were shown for pre- and postclamp pulmonary function tests. During clamps, FEV1 and forced vital capacity declined modestly in both COPD groups, with no difference between AIR insulin and subcutaneous insulin lispro.

CONCLUSIONS

Short-term exposure to AIR inhaled insulin was well tolerated by COPD subjects, showing similar time-exposure and time-action profiles, but with reduced insulin absorption and metabolic effect compared with healthy subjects. Further clinical evaluation is warranted in patients with comorbid diabetes and COPD.

Characterization of a cyclosporine solid dispersion for inhalation

For lung transplant patients, a respirable, inulin-based solid dispersion containing cyclosporine A (CsA) has been developed. The solid dispersions were prepared by spray freeze-drying. The solid dispersion was characterized by water vapor uptake, specific surface area analysis, and particle size analysis. Furthermore, the mode of inclusion of CsA in the dispersion was investigated with Fourier transform infrared spectroscopy. Finally, the dissolution behavior was determined and the aerosol that was formed by the powder was characterized. The powder had large specific surface areas (~ 160 m(2)). The water vapor uptake was dependant linearly on the drug load. The type of solid dispersion was a combination of a solid solution and solid suspension. At a 10% drug load, 55% of the CsA in the powder was in the form of a solid solution and 45% as solid suspension. At 50% drug load, the powder contained 90% of CsA as solid suspension. The powder showed excellent dispersion characteristics as shown by the high emitted fraction (95%), respirable fraction (75%), and fine-particle fraction (50%). The solid dispersions consisted of relatively large (x(50) approximately 7 mum), but low-density particles (rho approximately 0.2 g/cm(3)). The solid dispersions dissolved faster than the physical mixture, and inulin dissolved faster than CsA. The spray freeze-drying with inulin increased the specific surface area and wettability of CsA. In conclusion, the developed powder seems suitable for inhalation in the local treatment of lung transplant patients.

NanoCipro encapsulation in monodisperse large porous PLGA microparticles

Pulmonary drug delivery of controlled release formulations may provide an effective adjunct approach to orally delivered antibiotics for clearing persistent lung infections. Dry powder formulations for this indication should possess characteristics including; effective deposition to infected lung compartments, persistence at the infection site, and steady release of antibiotic. Large porous particles ( approximately 10-15 microm) have demonstrated effective lung deposition and enhanced lung residence as a result of their large diameter and reduced clearance by macrophages in comparison to small microparticles ( approximately 1-5 microm). In this report, Precision Particle Fabrication technology was used to create monodisperse large porous particles of poly(d,l-lactic-co-glycolic acid) (PLGA) utilizing oils as extractable porogens. After extraction, the resulting large porous PLGA particles exhibited a low density and a web-like or hollow interior depending on porogen concentration and type, respectively. Ciprofloxacin nanoparticles (nanoCipro) created by homogenization in dichloromethane, possessed a polymorph with a decreased melting temperature. Encapsulating nanoCipro in large porous PLGA particles resulted in a steady release of ciprofloxacin that was extended for larger particle diameters and for the solid particle morphology in comparison to large porous particles. The encapsulation efficiency of nanoCipro was quite low and factors impacting the entrapment of nanoparticles during particle formation were elucidated. A dry powder formulation with the potential to control particle deposition and sustain release to the lung was developed and insight to improve nanoparticle encapsulation is discussed.

Design of fine particles for pulmonary drug delivery

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

Protein release behavior from porous microparticle with lysozyme/hyaluronate ionic complex

Porous microparticles (PMs) with a low density (<0.4 g/cm3) for pulmonary protein delivery were prepared by the water-in-oil-in-water (W1/O/W2) multi-emulsion method using a cyclodextrin derivative as a porogen. The complexation of positively charged lysozyme (Lys) and negative-charged hyaluronate (HA) was investigated for long-term protein release from PMs. The interaction of Lys and HA not only increased protein encapsulation efficiency but also stabilized Lys against a denaturing organic solvent (dichloromethane). Furthermore, PMs with Lys/HA complexes increased the Lys release period up to 7 days, as opposed to a 4h Lys release time from PMs without Lys/HA complexes. In particular, PMs containing 10mg of HA and 50mg of Lys showed almost zero-order Lys release kinetic for 7 days and preserved the bioactivity of Lys more than 98% during its entire release period. This result suggests that PMs with Lys/HA complexes may be applied in long-term pulmonary administration of protein or peptide drugs, including those that require particles to arrive at a deep lung epithelium with the help of low density (high porosity) of PMs.

Long acting porous microparticle for pulmonary protein delivery

This study investigated the porous-microparticle (PM) with low mass density and large size for pulmonary drug delivery. PM was prepared by the water-in-oil-in-water (W(1)/O/W(2)) multi-emulsion method with cyclodextrin derivative as a porogen and a stabilizer of peptide drugs. Herein, sucrose ethyl acetate (SAIB) was incorporated in PM for long acting protein release. In vitro release studies, the rapid release rate of proteins from PM was reduced due to the high viscosity of the added SAIB. As a result, BSA release from PM continued up to 7 days. This result suggests that PM having sustained release characteristics may be successfully applied for long-term pulmonary administration of protein or peptide drug. In addition, it is expected that these particles arrive at a deep lung epithelium due to low density (high porosity) and limit macrophage recognition because of big particle size (more than 5 microm).

Diabetes therapy trials with inhaled insulin

Administration of insulin by inhalation was first attempted > 50 years ago. At that time, little was known concerning effective delivery systems and insulin formulations. The recent development of pulmonary delivery systems for the administration of insulin is driven by the reluctance of patients and their providers to initiate insulin earlier in the course of Type 2 diabetes, the desire to reduce the number of daily insulin injections for both Type 1 and 2 patients, and the recent emphasis on intensified glycaemic control including postprandial glycaemic control. The deep lung is a unique mucosal tissue having a surface area of > 100 m2 and is readily accessible both to the external environment and to drug delivery, provided that appropriate conditions are met. There have been four mid- to late-phase pulmonary insulin programmes using modern inhalation devices that will be reported in this paper. The programmes differ in the choice of delivery systems, the formulations of insulin and reported bioavailability, pharmacokinetic and glucodynamic profiles and adverse events. However, all systems successfully deliver insulin to the deep lung and biological effectiveness compares favourably with injected subcutaneous insulins.

Efficacy and safety of preprandial human insulin inhalation powder versus injectable insulin in patients with type 1 diabetes

AIMS/HYPOTHESIS

The efficacy and safety of human insulin inhalation powder (HIIP) plus insulin glargine were compared to subcutaneously injected insulin (SC insulin) plus insulin glargine in patients with type 1 diabetes.

METHODS

This was a randomised, open-label crossover study in which one group of patients received preprandial HIIP plus insulin glargine for 12 weeks, followed by the same duration with preprandial SC insulin (lispro or regular) plus insulin glargine. Another group of patients received the reverse treatment sequence. The trial was designed as a non-inferiority comparison of the two treatments for effect on HbA(1c); blood glucose levels were also monitored. Safety assessments included adverse event reporting and hypoglycaemic events.

RESULTS

HbA(1c) at endpoint was 7.95+/-0.12% for the HIIP treatment and 8.06+/-0.12% for the SC insulin treatment; mean changes from baseline to endpoint were -0.08 and 0.00%, respectively, (p=NS). The upper limit of the 95% CI of mean difference in HbA(1c) between the two treatments was 0.02%, indicating that HIIP was not inferior relative to SC insulin, as measured against the pre-defined margin of 0.3%. Fasting blood glucose was significantly lower for HIIP treatment (8.09+/-0.33 mmol/l; n=117) than for SC insulin treatment (9.05+/-0.33 mmol/l; n=111) (p=0.01). Safety profiles were comparable between the two treatments. The rate of any hypoglycaemia (least-squares mean adjusted for 30 days+/-SE) was 8.9+/-0.7 and 8.2+/-0.8 for HIIP and SC insulin treatments, respectively, (p=0.29). The rate of nocturnal hypoglycaemia was greater for HIIP (4.2+/-0.4) than for SC insulin (2.7+/-0.4; p<0.001).

CONCLUSIONS/INTERPRETATION

HIIP was similar in efficacy to SC insulin for glycaemic control in type 1 diabetes mellitus. The two treatments had comparable safety profiles.

PLGA microcapsules with novel dimpled surfaces for pulmonary delivery of DNA

We describe the fabrication of DNA-loaded poly(lactic-co-glycolic acid) (PLGA) microcapsules with novel surface morphologies that will be of use in pulmonary delivery. Our approach was to examine surface morphology and DNA encapsulation efficiency as a function of primary emulsion stability; using two surfactant series based on hydrophile-lipophile balance and hydrophobe molecular weight. Hydrophilic non-ionic surfactants yielded the most stable water-in-dichloromethane emulsions (HLB values >8). These surfactants normally favor convex (o/w) interfacial curvatures and therefore this atypical behavior suggested a relatively high surfactant solvation in the dichloromethane 'oil' phase. This was consistent with the large fall in the glass transition temperature for microspheres prepared with Tween 20, which therefore efficiently penetrated the PLGA matrix and acted as a plasiticizer. Blends of Pluronic triblock copolymers performed poorly as water-in-dichloromethane emulsifiers, and were therefore used to generate hollow microspheres ('microcapsules') with low densities (0.24 g/cm(3)). Although the Pluronic-stabilized emulsions resulted in lower DNA loading (15-28%), microspheres (approximately 8 microm) with novel dimpled surfaces were fabricated. The depth and definition of the dimples was greatest for triblock copolymers with high MW hydrophobe blocks. By cascade impaction, the geometric mean weight diameter of the microcapsules was 3.43 microm, suggesting that they will be of interest as biodegradable pulmonary delivery vehicles.

Dose delivery characteristics of the AIR pulmonary delivery system over a range of inspiratory flow rates

The purpose of this study was to evaluate the in vitro and in vivo dose delivery characteristics of the AIR pulmonary delivery system over a range of flow rates. A 5-mg placebo powder of engineered particles with low densities (<0.4 g/cc) and large geometric diameters (>5 microm) was delivered via a simple, capsule based, passive dry powder inhaler. The emitted dose, geometric and aerodynamic particle size distributions (aPSDs) were obtained over a range of flow rates (15-60 LPM). The in vitro results demonstrated improved powder dispersion with increasing flow rate through the inhaler. The in vivo dose delivery characteristics were obtained by gamma scintigraphy. Twelve healthy subjects performed the following three inhalation maneuvers: (i) a targeted peak inspiratory flow rate (PIFR) of 20 +/- 10 LPM, (ii) a deep comfortable inhalation, and (iii) a deep forced inhalation. PIFR and inhaled volume were obtained during the inhalation of the dose using a spirometer. In vivo dose delivery was characterized by high and reproducible emitted doses (mean = 87%; inter and intra-subject CV = 5%) and high lung deposition (mean = 51% of the total dose), with low inter and intra-subject CVs (18% and 13%, respectively) across a range of PIFRs (12-86 LPM). Lung deposition of the total dose was shown not to be dependent on PIFR by analysis of variance across the range of inspiratory flow rates (p = 0.29). This was due to the competing effects of smaller aPSDs, increased extrathoracic deposition and higher emitted doses with increasing PIFR. Fully characterizing the effect of inspiratory flow rate requires analysis of the therapeutic response, as well as in vitro dose delivery and lung deposition.

Analysis of cascade impactor mass distributions

The purpose of this paper is to review the approaches for analyzing cascade impactor (CI) mass distributions produced by pulmonary drug products and the considerations necessary for selecting the appropriate analysis procedure. There are several methods available for analyzing CI data, yielding a hierarchy of information in terms of nominal, ordinal and continuous variables. Mass distributions analyzed as a nominal function of the stages and auxiliary components is the simplest approach for examining the whole mass emitted by the inhaler. However, the relationship between the mass distribution and aerodynamic diameter is not described by such data. This relationship is a critical attribute of pulmonary drug products due to the association between aerodynamic diameter and the mass of particulates deposited to the respiratory tract. Therefore, the nominal mass distribution can only be utilized to make decisions on the discrete masses collected in the CI. Mass distributions analyzed as an ordinal function of aerodynamic diameter can be obtained by introducing the stage size range, which generally vary in magnitude from one stage to another for a given type of CI, and differ between CIs of different designs. Furthermore, the mass collected by specific size ranges within the CI are often incorrectly used to estimate in vivo deposition at various regions of the respiratory tract. A CI-generated mass distribution can be directly related to aerodynamic diameter by expressing the mass collected by each size-fractionating stage in terms of either mass frequency or cumulative mass fraction less than the aerodynamic size appropriate to each stage. Analysis of the aerodynamic diameter as a continuous variable allows comparison of mass distributions obtained from different products, obtained by different CI designs, as well as providing input to in vivo particle deposition models. The lack of information about the mass fraction emitted by the inhaler that is not size-analyzed by the CI may be perceived as a disadvantage from the standpoint of comparing the total mass per actuation emitted from the inhaler mouthpiece. However, this is a limitation of the CI measurement technique rather than the data analysis procedure. Data reduction techniques can enable the large quantity of information conveyed in a mass-size distribution to be summarized in terms of representative parameters, but care needs to be exercised if utilizing model size distribution function fitting routines to avoid introducing error by the fitting procedure.

Novel Approach to DPI Carrier Lactose with Mechanofusion Process with Additives and Evaluation by IGC

The effect of lactose carrier surface property on the inhalation profile of dry powder inhaler (DPI) was evaluated using a micronized drug (Compound A) by inverse gas chromatography (IGC). Mechanofusion with magnesium stearate (Mg-St) or sucrose stearate increased the fine particle fraction (FPF), considered to be due to decrease in the interaction between Compound A and the lactose carrier. The effect of Compound A concentration on FPF was smaller in mechanofusion-processed lactose compared to intact lactose, especially when processed with Mg-St. The relationship between the IGC parameters of the lactose and FPF was also investigated. FPF increased as both the dispersive component of the surface energy and acidity similarity between the lactose carriers and Compound A increased. Although further investigation is necessary, it could be suggested that acidity similarity decreases the interaction between Compound A and lactose, thus contributing to the increase in the FPF. In conclusion, (1) mechanofusion with Mg-St or sucrose stearate could be an effective method to improve FPF of a DPI drug formulation; (2) IGC would be a valuable method to investigate the interaction between a drug and the DPI carrier; and (3) a relationship between surface acidity and inhalation profile was suggested.

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.

Dose response of inhaled dry-powder insulin and dose equivalence to subcutaneous insulin lispro

OBJECTIVE

To determine the pharmacokinetic (PK) and glucodynamic (GD) dose response of human insulin inhalation powder (HIIP) delivered via AIR particle technology and dose equivalence to subcutaneous (SC) insulin lispro.

RESEARCH DESIGN AND METHODS

Twenty healthy, nonsmoking, male or female subjects (aged 29.6 +/- 6.9 years, BMI 23.2 +/- 2.3 kg/m2, means +/- SD) with normal forced vital capacity and forced expiratory volume were enrolled in an open-label, randomized, seven-period, euglycemic glucose clamp, cross-over trial. Each subject received up to four single doses of HIIP (2.6, 3.6, 5.2, or 7.8 mg) and three doses of SC lispro (6, 12, or 18 units) from 5 to 18 days apart.

RESULTS

HIIP demonstrated a similar rapid onset but an extended time exposure and a prolonged duration of effect (late t(50%) 412 vs. 236 min, P < 0.001) compared with SC lispro. The HIIP versus SC lispro doses of 2.6 mg vs. 6 units, 5.2 mg vs. 12 units, and 7.8 mg vs. 18 units achieved similar PK area under the serum immunoreactive insulin (IRI) concentration-versus-time curve from time zero until the serum IRI concentrations returned to the predose baseline value [AUC(0-t')] and GD (G(tot)) responses. The median insulin (t(max)) was not different between HIIP and SC lispro (45 min for both), although the median time of return to baseline for PK was apparently longer for HIIP compared with SC lispro (480 vs. 360 min). Relative bioavailability and relative biopotency of HIIP were consistent across doses (8 and 9%).

CONCLUSIONS

While the time-action profile was longer for HIIP than for SC lispro, both treatments showed rapid initial absorption and similar overall PK exposure and GD effect. HIIP was as well tolerated as SC lispro, thereby offering a promising alternative to injectable insulin therapy.

Reducing bounce effects in the Andersen cascade impactor

The collection efficiency of the Andersen cascade impactor (ACI) can be affected by particle bounce, overload and re-entrainment (or blow-off), collectively referred to as bounce effects. Reduction of bounce effects in the ACI operated at 60 LPM was investigated for placebo large porous particles. Aerodynamic particle size distributions (aPSDs) obtained with the ACI and multi-stage liquid impinger (MSLI) were compared by observation of modes and statistical comparisons of the mass median aerodynamic diameter (MMAD) and geometric standard deviation (sigmag). Particle bounce effects were prevalent in the ACI with uncoated plates, i.e., bi-modal distribution with statistically significant differences in MMAD and sigmag (P<0.05). Coating the impaction plates with a thin layer of vacuum grease and decreasing the ACI stage jet velocities reduced, but did not minimize bounce effects. Bounce effects were minimized using 20-microm pore glass fiber filters saturated in water placed on inverted impaction plates, with good agreement obtained between the ACI and MSLI aPSDs, i.e., mono-modal with no statistically significant differences in MMAD and sigmag (P>0.05). Selection of the impaction substrate material and solvent must be evaluated with the drug product and analytical methods to minimize bounce effects and obtain an accurate measure of the aPSD.