Local and systemic delivery of high-molecular weight drugs by powder inhalation

The pulmonary route has recently attracted attention as a noninvasive administration route for peptide and protein drugs, and an insulin powder for inhalation was approved by authorities in Europe and the USA. The present study examined usefulness of insulin and gene powders for systemic and local inhalation therapy. We prepared several dry insulin powders by spray drying to examine the effect of additives on insulin absorption. Citric acid appears to be a safe and potent absorption enhancer for insulin in dry powder. However, in the powder with citric acid (MIC0.2 SD) insulin was unstable compared with the other powders examined. To improve insulin stability, a combination of insulin powder and citric acid powder was prepared (MIC Mix). MIC Mix showed hypoglycemic activity comparable to MIC0.2 SD while the insulin stability was much better than that of MIC SD. Next, dry insulin powders with mannitol were prepared with supercritical carbon dioxide (SCF); the powder thus prepared reduced blood glucose level rapidly and was more effective than that prepared by spray drying. Chitosan-pDNA complex powders as a pulmonary gene delivery system were also prepared with SCF and their in vivo activity was evaluated. The addition of chitosan suppressed the degradation of pCMV-Luc during preparation and increased the storage stability. The luciferase activity in mouse lung was evaluated after pulmonary administration of the powders. The chitosan-pDNA powder with an N/P ratio=5 increased the luciferase activity to 27 times that of the pCMV-Luc solution. These results suggest that gene powder with chitosan is a useful pulmonary gene delivery system.     

Pharmacokinetics of a new antitumor 3-arylisoquinoline derivative, CWJ-a-5

The lungs are useful for administration of macromolecules, which are poorly absorbed from the intestine. In the present study, we prepared several dry powder formulations of insulin using a spray drying technique to examine the effect of additives on insulin absorption. The bioavailability of insulin was estimated from the change in the plasma glucose level. The bioavailability of insulin from dry powder with no additive exceeded that obtained from pH 7.4 solution. The absolute bioavailability of insulin administered as a solution with 1.4 mg/dose of bacitracin or 1.0 mg/dose of Span 85 was almost 100%. The bioavailability of dry powder with 0.42 mg/dose of bacitracin was 20% that of the solution with 1.4 mg/dose of bacitracin. The insulin dry powder with 0.21 mg/dose of Span 85 showed a bioavailability less than that for the insulin solution with 0.1 mg/dose of Span 85. Bacitracin and Span 85 were not as effective in dry powder as in solution in the present study. While citric acid was more effective in dry powder that in solution to increase the hypoglycemic effect. The pH 5.0 and pH 3.0 solutions containing 0.19 mg of citric acid in 0.1 ml showed absolute bioavailabilities of 43% and 57%, respectively, while the bioavailabilities for dry powders containing 0.025 and 0.036 mg/dose citric acid were 42% and 53%, respectively. In addition, the hypoglycemic effect of dry powders continued for a longer period and remained at 240 min with the dry powders, while it disappeared at 180 min with the solutions. When the insulin dry powder containing 0.036 mg/dose of citric acid was administered, the lactate dehydrogenase activity, a sensitive indicator of acute toxicity to lung cells, in bronchoalveolar lavage was as low as that for saline administration, suggesting citric acid is a safe additive. Thus, citric acid appears to be a safe and potent absorption enhancer for insulin in dry powder.     

Preparation and physicochemical characterization of supercritically dried insulin-loaded microparticles for pulmonary delivery.

In the search for non-invasive delivery options for the increasing number of therapeutic proteins, pulmonary administration is an attractive route. Supercritical fluid (SCF) drying processes offer the possibility to produce dry protein formulations suitable for inhalation. In this study, insulin-loaded microparticles suitable for pulmonary administration were prepared and characterized. N-Trimethyl chitosan (TMC), a polymeric mucoadhesive absorption enhancer and dextran, a non-permeation enhancer, were used as carriers for insulin. The particles were prepared by spraying an acidic water/DMSO solution of insulin and polymer into supercritical carbon dioxide. The mean size of the particles was 6-10microm (laser diffraction analysis) and their volume median aerodynamic diameter ca. 4microm (time-of-flight analysis). The particles had a water content of ca. 4% (w/w) (Karl-Fischer), and neither collapsed nor aggregated after preparation and storage. In the freshly prepared dried insulin powders, no insulin degradation products were detected by HPLC and GPC. Moreover, the secondary and tertiary structures of insulin as determined by circular dichroism and fluorescence spectroscopy were preserved in all formulations. After one-year storage at 4 degrees C, the particle characteristics were maintained and the insulin structure was largely preserved in the TMC powders. In conclusion, SCF drying is a promising, protein-friendly technique for the preparation of inhalable insulin-loaded particles.     

Physical characteristics and aerosolization performance of insulin dry powders for inhalation prepared by a spray drying method

The objective of this study was to investigate the influence of formulation excipients on the physical characteristics and aerosolization performance of insulin dry powders for inhalation. Insulin dry powders were prepared by a spray drying technique using excipients such as sugars (trehalose, lactose and dextran), mannitol and amino acids (L-leucine, glycine and threonine). High performance liquid chromatography and the mouse blood glucose method were used for determination of the insulin content. The powder properties were determined and compared by scanning electron microscopy, thermo-gravimetric analysis and size distribution analysis by a time-of-flight technique. The in-vitro aerosolization behaviour of the powders was assessed with an Aerolizer inhaler using a twin-stage impinger. Powder yield and moisture absorption were also determined. Results showed that there was no noticeable change in insulin content in any of the formulations by both assay methods. All powders were highly wrinkled, with median aerodynamic diameters of 2-4 microm, and consequently suitable for pulmonary administration. The tapped density was reduced dramatically when glycine was added. The powders containing mannitol, with or without L-leucine, were less sensitive to moisture. The highest respirable fraction of 67.3 +/- 1.3% was obtained with the formulation containing L-leucine, in contrast to formulations containing glycine and threonine, which had a respirable fraction of 11.2 +/- 3.9% and 23.5 +/- 2.5%, respectively. In addition, powders with good physical properties were achieved by the combination of insulin and trehalose. This study suggests that L-leucine could be used to enhance the aerosolization behaviour of the insulin dry powders for inhalation, and trehalose could potentially be used as an excipient in the formulations.     

胰岛素吸入粉雾剂的体外沉降及大鼠体内吸收促进剂的药效学评价

目的采用喷雾干燥法制备胰岛素吸入粉雾剂，对吸入粉雾剂体外沉降性质进行考察，并对其吸收促进剂在大鼠体内的药效学进行初步研究。方法采用中国药典(2000版)附录XH的装置测定粉末的体外有效部位沉积量，以葡糖氧化酶法（GOD-PAP法）测定大鼠的血糖浓度来评价其降血糖效果。结果喷雾干燥法制得的胰岛素吸收粉雾剂沉积量在各湿度下均大于40％，在气流量≥18 L·min^-1的情况下其有效部位沉积量变化不大。8 mmol·L^-1/dose牛黄胆酸钠［PA=59.91%,C_nadir=(33±6)%］和10 mmol·L^-1/dose去氧胆酸钠［PA=47.46%，C _nadir=(32±7)%］对胰岛素肺部吸收促进作用明显。而1%辛酸钠、1%十二烷基硫酸钠、250 μg/dose卵磷脂和10 mmol·L^-1/dose EDTA并未显示明显效果。结论制得的胰岛素吸收粉雾剂沉积量受湿度影响小，环境湿度依赖性和吸气流量依赖性小。8 mmol·L^-1/dose牛黄胆酸钠和10 mmol·L^-1/dose去氧胆酸钠可有效促进胰岛素干粉吸入剂的降血糖效果。     

Enhanced insulin absorption in the rabbit airways and lung by sodium dioctyl sulfosuccinate.

The objective of this investigation was to study regional absorption of inhaled insulin together with an enhancer (sodium di-octyl-sulfosuccinate [DOSS]) in the rabbit airways and lung. Insulin was administered with or without DOSS by aerosol inhalation, intratracheal infusion, intranasally, sublingually, and without DOSS intravenously. Blood glucose and plasma levels of insulin were measured during 100 min from the start of administration. Inhalation of insulin (3 U) with 0.25% or 1% DOSS decreased average blood glucose levels significantly more than inhalation of insulin (3 U) without DOSS. Intratracheal administration of 1.5 U of insulin with 0.25% DOSS in 0.3 mL of vehicle decreased the average blood glucose level significantly compared with intratracheal administration of 1.5 U of insulin and no DOSS in 0.3 mL of vehicle and compared with 1.5 U of insulin with 0.25% DOSS in 0.15 mL of vehicle. Intravenous insulin (1.5 U) and inhaled (1.5 U) insulin in 0.25% DOSS decreased average blood glucose levels significantly compared with intratracheal (0.15 mL), intranasal, and sublingual administration of 1.5 U of insulin with 0.25% DOSS. The bioavailability of inhaled insulin (1.5 U) with 0.25% DOSS was estimated to be 16% in comparison with 7% for intratracheally (0.15 mL), 1% intranasally, and 0.8% sublingually administered insulin (1.5 U with 0.25% DOSS), respectively. Inhaled insulin together with the absorption enhancer DOSS decreased the blood glucose level more effectively than insulin given intratracheally, intranasally, or sublingually. The effect on blood glucose reflected the difference in plasma insulin concentration for the different routes of administration.     

Pulmonary Delivery of Salmon Calcitonin Dry Powders Containing Absorption Enhancers in Rats

Purpose. To evaluate the effects of absorption enhancers in dry powders and in liquids, pulmonary absorption of salmon calcitonin (sCT) in various formulations was measured. Methods. The dry powder of sCT was prepared by a freeze-drying method with a jet mill. After intratracheal administration of sCT dry powder and liquid (solution) preparations to rats, plasma sCT levels and calcium levels were measured. Results. After intratracheal administration without absorption enhancers, sCT in the dry powder and in the liquid were absorbed nearly to the same degree. Absorption enhancers (oleic acid, lecithin, citric acid, taurocholic acid, dimethyl-β-cyclodextrin, octyl-β-D-glucoside) were much more effective in the dry powder than in the solution. The reason may be that the enhancers added to the dry powder dissolved at high concentrations in a trace volume of the fluid lining the alveolar epithelium. Conclusions. The present results suggest that the pulmonary absorption of peptides and proteins can be greatly improved by formulating them into dry powders with smaller amounts of enhancers than in liquid dosage forms.     

Characterisation of salmon calcitonin in spray-dried powder for inhalation. Effect of chitosan

Salmon calcitonin (sCT) powders suitable for inhalation, containing chitosan and mannitol as absorption enhancer and protection agent, respectively, were prepared using a spray-drying process. The effect of chitosan on physicochemical stability of sCT in the dry powder was investigated by different analytical techniques. High-performance liquid chromatography (HPLC) analysis indicated that sCT was chemically stable upon spray-drying. With the proportion of chitosan in spray-drying formulation being increased, dissolution of sCT from the dry powders was decreased both in phosphate buffer and acetate buffer. The thioflavine T fluorescence assay showed that no fibrils were present in the spray-dried powder. However, sCT partly fibrillated in the phosphate buffer, but not in acetate buffer. Fourier transform infrared (FTIR) spectra showed that the secondary structure of sCT was slightly changed in the dry powder, yet no aggregate signal was observed. Circular dichroism analysis indicated that the structure of sCT in an aqueous formulation was slightly altered by addition of chitosan. Nevertheless, recovery of sCT was not influenced by chitosan in the aqueous formulation as indicated by HPLC analysis. This study suggested that sCT, in absence of any additives, was stable during the spray-drying process under certain conditions. Addition of chitosan affects recovery of sCT from spray-dried powders, which may be due to formation of a partially irreversible complex between the protein and chitosan during the spray-drying process.     

A novel apparatus for rat in vivo evaluation of dry powder formulations for pulmonary administration

The lungs have attracted increasing attention as a site for administration of drugs, including macromolecules that are poorly absorbed from the intestine. There have been a number of basic studies in which peptide solutions were administered to experimental animals via the lungs. Although there have been several studies of pulmonary peptide absorption from dry powder formulations, a simpler and more inexpensive apparatus for administration of dry powders would enhance rapid screening of the formulations. In this study, we developed a simple apparatus to disperse dry powders. The apparatus has two 3-way stopcocks; one allows dispersal of powders at a constant pressure and airflow, and the other allows rats to breathe before and after administration. Dry powders of fluorescein (FL) and FITC-dextran (FD4) were manufactured by the spray-drying technique. The effects of operating conditions on the absorption of these model drugs were examined in rats. The C(max) for FL from dry powder was lower than that from solution and mean residence time was extended, suggesting that dissolution was the rate-determining step for FL absorption from dry powder. For FD4, the rate of absorption may not be regulated by dissolution but by epithelial transport. Absorption of insulin from spray-dried powder via the rat trachea was investigated using this apparatus. Intratracheally administered spray-dried insulin powder decreased plasma glucose level to a greater extent than spray-dried insulin solution administered via the same route. Thus, the apparatus is simple, inexpensive, and useful for rapid screening of dry powder formulations.     

Pulmonary gene delivery by chitosan-pDNA complex powder prepared by a supercritical carbon dioxide process

Chitosan-plasmid DNA (pDNA) complex powders as a pulmonary gene delivery system were prepared with a supercritical carbon dioxide (CO(2)) process and their in vivo activity was evaluated. The powders with mannitol as a carrier were prepared by dispersing aqueous solutions of a luciferase expression plasmid driven by the cytomegalovirus promoter (pCMV-Luc) with or without chitosan as a cationic vector in a supercritical CO(2)/ethanol admixture. The supercritical CO(2) process with a V-shaped nozzle successfully produced chitosan-pDNA powders. The addition of chitosan suppressed the degradation of pCMV-Luc during the supercritical CO(2) process and increased the yield of powders. The luciferase activity in mouse lung was evaluated after pulmonary administration of the powders or pCMV-Luc solutions. The chitosan-pDNA powders increased the luciferase activity in mouse lung compared with pCMV-Luc powders without chitosan or pCMV-Luc solutions with or without chitosan. The chitosan-pDNA powder with an N/P ratio = 5 increased the luciferase activity to 2700% of that of the pCMV-Luc solution. These results suggest that gene powder with chitosan is a useful pulmonary gene delivery system.     

硫酸特布他林干粉吸入剂制备工艺的优化研究

目的:优化硫酸特布他林干粉吸入剂的制备工艺。方法:采用喷雾干燥技术制备硫酸特布他林干粉吸入剂,采用双层液体碰撞器测定其体外肺沉积率,扫描电镜观察干粉的表观形貌,热重分析仪测定干粉的水分含量,激光粒度测定仪测定粒径大小,以产品收率、水分含量、粉末的空气动力学粒径及体外肺沉积率为考察指标,通过正交设计结合多指标综合评价法优化最佳制备工艺。结果:通过正交试验-多指标综合评价,最佳制备工艺为:喷雾压力190 kPa,干燥风速0.7 m3.min-1,供液速度7.0 mL.min-1,入口温度120℃。结论:按最佳制备工艺制得的干粉收率为50.54%,水分含量为0.467%,空气动力学粒径为1.80μm,体外肺沉积率为55.19%。正交试验结合多指标综合评价法用于硫酸特布他林干粉吸入剂制备工艺的优化有效可用。     

SCF-engineered powders for delivery of budesonide from passive DPI devices

The objective of this study was to develop SEDS-engineered budesonide particles suitable for dry powder inhalation delivery and to evaluate their aerosol performance across a range of passive dry powder inhalers (DPI). SEDS budesonide powders were manufactured in Nektar's SCF manufacturing plant and compared to the micronized drug and commercial powder (Pulmicort Turbuhaler, AstraZeneca). Aerosol performance was evaluated by determining emitted dose (ED) by a variation of the USP method and fine particle fraction (FPF) using Andersen cascade impaction. The SCF powder dispersed best in the Turbospin and Eclipse devices, exhibiting high EDs (70%-80%) and relatively low variability (RSD 8%-13%). Regardless of the device, the SEDS material outperformed both the micronized drug and the commercial powder, while exhibiting good batch-to-batch reproducibility (RSD <5%). All powders exhibited flow rate-dependent ED, albeit for the SEDS material it was minimized at reduced fill weights. This was attributed to inadequate and variable powder clearance from the capsules at low inspiratory flow rates, which was more pronounced in the Eclipse and Cyclohaler. The results demonstrate that SEDS is an attractive particle-engineering process that may enhance pulmonary performance of budesonide and possibly facilitate development of other small molecule pulmonary products in passive DPI.     

Sustained release of insulin from insoluble inhaled particles

Conventional slow‐acting insulin preparations for subcutaneous injection, e.g., suspensions of the complex with protamine and/or zinc, were reformulated as dry powders for inhalation and the insoluble aerosol tested for providing sustained insulin plasma levels. Large porous particles made of lactose, albumin, and dipalmitoylphosphatidylcholine, and incorporating insulin, protamine, and/or zinc chloride were prepared using spray‐drying. Integrity of insulin after spray‐drying and insulin insolubilization in spray‐dried particles was verified in vitro. The pharmacokinetic profile of the formulation delivered by inhalation and subcutaneous injection was assessed in vivo in the rat. The formulation process of insulin as dry powders did not alter insulin integrity and did not impede, in most cases, insulin insolubilization by protamine and/or zinc. Large porous insulin particles presented 7 μm mass mean geometric particle diameters, 0.1 g/cm³ bulk powder tap densities and theoretical aerodynamic diameters suitable for deep lung deposition (in the range of 2.2–2.5 μm). The dry powders exhibited 40% respirable fractions in the Andersen cascade impactor and 58–75% in the Aero‐Breather™. Insoluble inhaled insulin provided sustained insulin plasma levels for half a day, similar to injected insulin, and exhibited a bioavailability of 80.5% relative to subcutaneous injection of the same formulation. Drug Dev. Res. 48:178–185, 1999. ©1999 Wiley‐Liss, Inc.     

pH与吸收促进剂对胰岛素中空栓剂中胰岛素吸收的影响

目的 研究pH值及吸收促进剂对胰岛素中空栓剂中胰岛素吸收的影响,筛选胰岛素中空栓剂的最佳pH值和吸收促进剂.方法 用普通栓剂模具制备,以半合成脂肪酸脂为基质,甘油为溶剂,制成每枚含胰岛素4 U的中空栓剂,再将其置家兔直肠内,用酶-苯酚法测定家兔的血糖.结果 胰岛素中空栓剂的降糖效果在pH4时,氮酮作吸收促进剂最好,与皮下注射胰岛素1 U相当.结论 胰岛素中空栓剂在适当的pH值下,辅以吸收促进剂,有较好的吸收,可能成为胰岛素非注射给药的有效载体.     

胰岛素粉雾剂与注射剂治疗2型糖尿病的随机对照临床研究

目的:评价胰岛素粉雾剂治疗2型糖尿病的疗效及安全性。方法:232例18～70a的2型糖尿病病人随机分为2组。保持原口服降糖药不变,试验组加用吸入性胰岛素治疗;对照组加用胰岛素皮下注射治疗,疗程均为13 wk。比较治疗前后2组糖化血红蛋白、空腹及餐后2 h血糖、常规实验室检查、胸片变化及不良事件的发生率。结果:治疗后,试验组糖化血红蛋白、空腹和餐后2 h血糖均下降,分别为(0.8±s 1.2)%、(1.1±2.1)mmol·L~(-1)、(3±4)mmol·L~(-1),对照组下降了(1.2±1.6)%、(0.9±2.2)mmol·L~(-1)、(2±4)mmol·L~(-1);均下降明显(P>0.01),下降幅度2组无显著差异(P>0.05)。试验组低血糖发生率14.0%(16/114),低于对照组24.6%(29/118),P<0.05。呼吸道不良反应试验组发生1例,对照组无(P>0.05)。结论:胰岛素粉雾剂能安全有效地控制2型糖尿病病人的血糖水平,是临床医生和病人的一个新选择。     

Vaginal Absorption of Insulin in the Rat: Effect of Penetration Enhancers on Insulin Uptake and Mucosal Histology

The absorption of insulin across the vaginal mucosa into the systemic circulation was studied in ovariectomized rats given subsequent estrogen treatment. Blood glucose levels were determined as an indirect measure of insulin absorption, and the effect of various enhancers on the hypoglycemic response was investigated. In the absence of any enhancer, no decrease in blood glucose levels was observed after vaginal administration of insulin. However, the coadministration of sodium taurodihydrofusidate, polyoxyethylene-9-lauryl ether, lysophosphatidylcholine, palmitoylcarnitine chloride, and lysophosphatidylglycerol significantly increased hypoglycemia, whereas citric acid had little effect. The histological changes in the vaginal epithelium after treatment with the enhancer systems were variable and often severe. While the efficacy of these compounds in promoting the vaginal absorption of insulin is encouraging, their mechanisms of action and long-term histological effects are yet to be defined.     

Formulation of pH responsive peptides as inhalable dry powders for pulmonary delivery of nucleic acids

Nucleic acids have the potential to be used as therapies or vaccines for many different types of disease, but delivery remains the most significant challenge to their clinical adoption. pH responsive peptides containing either histidine or derivatives of 2,3-diaminopropionic acid (Dap) can mediate effective DNA transfection in lung epithelial cells with the latter remaining effective even in the presence of lung surfactant containing bronchoalveolar lavage fluid (BALF), making this class of peptides attractive candidates for delivering nucleic acids to lung tissues. To further assess the suitability of pH responsive peptides for pulmonary delivery by inhalation, dry powder formulations of pH responsive peptides and plasmid DNA, with mannitol as carrier, were produced by either spray drying (SD) or spray freeze drying (SFD). The properties of the two types of powders were characterised and compared using scanning electron microscopy (SEM), next generation impactor (NGI), gel retardation and in vitro transfection via a twin stage impinger (TSI) following aerosolisation by a dry powder inhaler (Osmohaler™). Although the aerodynamic performance and transfection efficacy of both powders were good, the overall performance revealed SD powders to have a number of advantages over SFD powders and are the more effective formulation with potential for efficient nucleic acid delivery through inhalation.     

Stability of chitosan-pDNA complex powder prepared by supercritical carbon dioxide process

The present study examined the stability of a gene in powders prepared with supercritical carbon dioxide (CO₂) from the viewpoints of the ternary structure of DNA and in vivo transfection potential. An aqueous chitosan–pCMV-Luc complex solution containing mannitol was injected into the stream of a supercritical CO₂/ethanol admixture to precipitate a gene powder. The obtained gene powders and gene solutions were placed in stability chambers at 25 or 40 °C for 4 weeks. The integrity and transfection potency of the gene were examined by electrophoresis and in vivo pulmonary transfection study in mice. The supercritical CO₂ process decreased the supercoiled DNA during the manufacturing process; however, the decrease in the remaining supercoiled and open circular DNA in the powders during storage was much slower than that in solutions. In addition, the powders had higher transfection potency than the solutions containing the same amount of DNA. The effect of chitosan on the stability of DNA in solutions was not obvious in the solutions but it improved the stability of DNA in powders during manufacturing and storage. Thus, a gene powder with a cationic vector is a promising ready-to-use formulation for inhalation therapy of pulmonary diseases.     

The addition of calcium ions to starch/Carbopol mixtures enhances the nasal bioavailability of insulin.

To evaluate the influence of calcium poly(acrylates) on the nasal absorption of insulin in rabbits, starch/poly(acrylic acid) (ratio 25/75) (SD 25/75) was neutralised with NaOH and/or Ca(OH)(2). After neutralisation, a mixture of sodium and/or calcium carboxylate was formed depending on the Ca(OH)(2) concentration in the formulation. IR spectroscopy confirmed that most of the calcium molecules in the formulation interacted with acid groups of the acrylic acid polymer. Addition of Ca(OH)(2) to aqueous dispersions containing starch/poly(acrylic acid) yielded powders with an enhanced absorption of insulin after nasal delivery to rabbits in comparison with the equivalent powder without Ca(OH)(2). A mixture of SD 25/75 and Ca(OH)(2) at a ratio of 90/10 neutralised to pH 7.4 with NaOH induced the highest absorption of insulin, obtaining a bioavailability of +/-29% (vs. 19% for an equivalent formulation without Ca(OH)(2)). This increase in nasal delivery was possibly due to a higher elasticity after dispersing this formulation in nasal fluid and to a higher water absorbing capacity. Furthermore, after nasal delivery of (SD 25/75)/Ca(OH)(2) 90/10, a decrease in t(max) was observed, possibly due to a progressive dissociation of Ca(2+)-ions after hydration of the powder resulting in the closing of the tight junctions.     

Cyclodextrins in the production of large porous particles: Development of dry powders for the sustained release of insulin to the lungs

The aim of this work was to develop dry powders intended for insulin pulmonary delivery. To this purpose, large porous particles (LPP) made of poly(lactide-co-glycolide) (PLGA) were produced by the double emulsion-solvent evaporation technique. Hydroxypropyl-beta-cyclodextrin (HPbetaCD), also known as absorption enhancer for pulmonary protein delivery, was tested as aid excipient to optimize the aerodynamic behaviour of the microparticles. Several microsphere formulations, differing in HPbetaCD and insulin loadings, were produced and their properties compared. A contemporary release of insulin and HPbetaCD from the system can be achieved by selecting appropriate formulation conditions. HPbetaCD-containing LPP with flow properties and dimensions suitable for aerosolization and deposition in deep regions of the lung following inhalation were produced. In conclusion, the developed system turns to be of great potential for the combined delivery of the protein and the adsorption promoter in the respiratory tract.