Drug delivery to the respiratory tract using dry powder inhalers

Pharmacoscintigraphic Comparison of HMR 1031, a VLA-4 Antagonist, in Healthy Volunteers Following Delivery Via a Nebulizer and a Dry Powder Inhaler

A pharmacoscintigraphic study was conducted to compare the dose deposition of HMR 1031 from the existing nebulizer formulation and the new Ultrahaler device to help determine the doses for future phase 2 trials. This was a single-dose, open-label, randomized, two-way crossover study in which HMR 1031 (3 mg) was delivered by the Ultrahaler and the Pari LC Star nebulizer to 12 healthy male subjects. For both treatments, the formulations were radiolabeled with technetium-99m pertechnetate such that a maximum of 10 MBq was delivered on each study day. Scintigraphic images were acquired immediately after dosing to estimate the percentage of the dose delivered to the lungs and oropharynx. Serial plasma samples were collected up to 12 hours post-dose on each occasion and analyzed for HMR 1031 by a LC/MS/MS method with a lower limit of quantitation of 10 pg/mL (0.01 ng/mL). Pharmacokinetic parameters were calculated for HMR 1031 using noncompartmental methods. No serious adverse events were reported. The systemic absorption of HMR 1031 following inhalation administration was relatively rapid, with median T(max) values of 0.5 hours and 1.0 hours post-dose after administration via Ultrahaler and nebulizer, respectively. The mean plasma AUC(0-12) (Ultrahaler, 15.8 ng*h/mL; nebulizer, 11.1 ng*h/mL) and C(max) (Ultrahaler, 4.96 ng/mL; nebulizer, 2.28 ng/mL) values were approximately 42% and 118% higher for the Ultrahaler compared with the nebulizer. The mean terminal half-life of HMR 1031 was similar after administration from both devices (2.91 and 3.18 hours). Based on the scintigraphic data, the lung deposition of HMR 1031 after administration by Ultrahaler (24.6% of the administered dose) was approximately 37% higher compared with the lung deposition from the nebulizer (18.0% of the administered dose). This observation was in agreement with the relative difference in the plasma AUC values achieved after administration of the two formulations. The in vivo results based on the scintigraphic data were also comparable with those from in vitro studies for the Ultrahaler. Based on the ratio of the dose delivered by both the formulations, the required doses for the future Ultrahaler formulation can be predicted.

Alternative sugars as potential carriers for dry powder inhalations

Most dry powder inhaler (DPI) formulations rely on lactose monohydrate as a carrier in the drug powder blends. However, lactose cannot be used for compounds that interact with the reducing sugar function of the lactose, such as formoterol, budesonide or peptides and proteins. In this study, alternative carriers like mannitol, glucose, sorbitol, maltitol and xylitol have therefore been evaluated for their potential use in DPI formulations. Raw materials were characterised physico-chemically and blends with the model drug substance budesonide were tested with respect to the aerosolization behaviour of the powders. It was found out that similarly to the problems known for lactose monohydrate, such as supplier variability, variability between different qualities of one supplier, the same difficulties apply to the alternative carriers investigated. Different sources and qualities of mannitol led to significant differences in the fine particle fraction (FPF), varying from 15 to 50% for two different qualities of mannitol. Similar observations were made for the other carrier materials studied. Also, the influence of conditioning the raw material at different relative humidity was found to have substantial influence on the performance of drug/carrier blends which is characterised by a strong decrease in the FPF. In summary, mannitol showed potential as a drug carrier to be used in DPIs whereas the more hygroscopic sugars only showed poor dispersibility.

Formulation and characterization of spray-dried powders containing nanoparticles for aerosol delivery to the lung

Spray-drying is a common practice of powder preparation for a wide range of drugs. Spray-dried powders can be used to deliver particles to the lungs via a dry powder inhaler (DPI). The present study investigated the feasibility of developing a platform for aerosol delivery of nanoparticles. Lactose was used as the excipient and spray-dried with two different types of nanoparticles: gelatin and polybutylcyanoacrylate nanoparticles. Results showed that some carrier particles were hollow while others had a continuous matrix. Gelatin nanoparticles were incorporated throughout the matrix and sometimes accumulated at one end of the lactose. Polycyanoacrylate nanoparticles mostly clustered in different spots within the lactose carriers. The mean sizes of both nanoparticle types were characterized at two different times: before they were spray-dried and after they were redissolved from the spray-dried powders. Both nanoparticle types remained in the nano-range size after spray-drying. The mean nanoparticle sizes were increased by approximately 30% after spray-drying, though this increase was statistically significant only for the gelatin nanoparticles. Dispersion of the powder with an in-house passive dry powder inhaler and subsequent cascade impaction measurements showed that incorporation of the nanoparticles did not affect the fine particle fraction (FPF) or mass median aerodynamic diameter (MMAD) of the powders. FPF was approximately 40% while MMAD was 3.0+/-0.2 microm, indicating the present formulations yield aerosols of a suitable particle size for efficient lung delivery of nanoparticles. The present work demonstrates that nanoparticles can be delivered to the lungs via carrier particles that dissolve after coming in contact with the aqueous environment of the lung epithelium. This opens the way for new drug-targeting strategies using nanoparticles for pulmonary delivery of drugs and diagnostics.

Effect of shape of sodium salicylate particles on physical property and in vitro aerosol performance of granules prepared by pressure swing granulation method

The purpose of this research was to investigate the effect of the shape of sodium salicylate (SS) particles on the physical properties as well as the in vitro aerosol performance of the granules granulated by the pressure swing granulation method. SS was pulverized with a jet mill (JM) to prepare the distorted particles, and SS aqueous solution was spray dried (SD) to prepare the nearly spherical particles. The particle size distribution, crushing strength, and pore size distribution of the granules were measured. The adhesive force of the primary particles in the granules was calculated according to Rumpf's equation. The in vitro aerosol performance of the granules was evaluated using a cascade impactor. Both JM and SD particles can be spherically granulated by the pressure swing granulation method without the use of a binder. The size of SD granules was smaller than that of JM granules. Although the crushing strength of the JM and SD granules is almost the same, the internal structures of JM granules and SD granules were found to differ, and the SD particles appear to have been condensed uniformly, resulting in a nearly spherical shape. In the inhalation investigation, the percentage of SS particles of appropriate size delivered to the region for treatment was noticeably higher for SD granules than for JM granules. This finding might be because the adhesive force of the SD primary particles was smaller than that of the JM primary particles in the granules and because the SD granules could be easily separated by air current to obtain the primary particles.

Improvement of Insulin Absorption from Intratracheally Administrated Dry Powder Prepared by Supercritical Carbon Dioxide Process

The purpose of this study was to improve insulin absorption from dry powder after administration in lung without an absorption enhancer. The dry powders, with mannitol as a carrier, were prepared with or without an absorption enhancer (citric acid) by supercritical carbon dioxide (SCF) and spray drying (SD) processes. Insulin powder was precipitated from dimethyl sulfoxide and aqueous solutions by dispersing the insulin solutions from parallel and V-type nozzles, respectively, into supercritical carbon dioxide, which is an antisolvent for insulin. In vitro aerosol performance was evaluated with a cascade impactor. Insulin powder containing citric acid prepared by the SCF method (MIC SCF) showed improved inhalation performance compared with insulin powder prepared by the SD process, although the particle size of the former powder was larger than that in powders prepared by SD. Insulin absorption was estimated from the change in plasma glucose level. The blood glucose level after administration of the insulin powder without citric acid prepared by the SCF process (MI SCF) decreased rapidly, and a significant difference was observed for areas under the curve of change in plasma glucose concentration versus time (AUCs) between MI SCF and the insulin powder without citric acid prepared by the SD process (MI SD). These results suggest that the SCF technique would be useful to prepare dry powders suitable for inhalation.

The effect of carrier surface and bulk properties on drug particle detachment from crystalline lactose carrier particles during inhalation, as function of carrier payload and mixing time

The effect of carrier payload and mixing time on the redispersion of drug particles from adhesive mixtures during inhalation for two different drugs (budesonide and disodium cromoglycate) has been investigated. A special test inhaler which retains carrier crystals during inhalation was used at 30 and 60 l/min. The special inhaler enabled the analysis of residual drug on the carrier yielding so called carrier residue (CR) values. Mixtures with carrier size fractions of 32-45; 150-200 and 250-355 microm, derived from marketed lactose brands, with increasing carrier payload (0.4-6.0% w/w of drug) were prepared. It was found that with increasing carrier payload, the CR increases for the coarse carrier fraction, decreases for the fine fraction and remains roughly constant for the intermediate fraction at 30 l/min. At 60 l/min, the CR decreased for all carrier fractions with increasing payload. The effect of powder bulk properties on the adhesive forces between drug and carrier (during mixing) as well as changes in the balance between adhesion and separation forces (during inhalation) explain the results found. An improved understanding of the different effects is obtained through the recently introduced force distribution concept. The ratio of (mean) separation force to (mean) adhesion force increases with the flow rate. The adhesive forces (during mixing) increase with increasing carrier diameter (higher press-on and kneading forces) and longer mixing time.

Influence of single versus multiple actuations on the particle size distribution of beclometasone dipropionate metered-dose inhalers

The particle size distributions of beclometasone dipropionate delivered from Becotide and Respocort inhalers after single and multiple actuations were investigated using the Andersen Mark II Cascade impactor and the drug was quantified using high performance liquid chromatography. The fine particle mass and the mass median aerodynamic diameter were calculated. An apparent increase in mass median aerodynamic diameter was observed when the number of actuations increased. In addition, the fine particle mass decreased as the number of actuations increased. When performing and analysing cascade impaction study data differences between single versus multiple actuations must be considered. Regulatory guidelines should be amended to stipulate the number of actuations to be loaded into devices used to evaluate the particle size distribution of inhaled aerosol products.

The inhalers of the future? A review of dry powder devices on the market today

International agreements to ban the use of environmentally damaging chlorofluorocarbons (CFCs) have signalled an end to the traditional CFC-propelled pressurised metered dose inhaler (pMDI) which has long been the mainstay of topical asthma therapy. The need for acceptable and cost-effective replacement inhalers, combined with opportunities to develop generic formulations of patent-expired drugs, has fueled a lively response from the pharmaceutical industry. Improvements in pMDI design and reformulation with propellants such as hydrofluoroalkanes may offer significant advantages over CFC-pMDIs and prolong the widespread use of pressurised drug delivery systems for many years to come. In the longer term, however, another likely candidate for success in providing economical, efficient and acceptable inhaled therapies is the breath-actuated, multiple-dose dry powder inhaler (DPI). This review concentrates on the multiple-dose DPIs available within Europe today.

Optimisation of treatment by applying programmable rate-controlled drug delivery technology

A number of programmable rate-controlled drug delivery technologies have been developed during the last two decades with the aim of regulating the rate of drug delivery, sustaining the duration of therapeutic action and/or targeting the delivery of drug to a specific tissue. As a result, several therapeutically beneficial outcomes can be achieved, such as: (i) controlled delivery of a therapeutic dose at a desirable rate of delivery; (ii) maintenance of drug concentrations within an optimal therapeutic range for prolonged duration of treatment; (iii) maximisation of efficacy-dose relationship; (iv) reduction of adverse effects; (v) minimisation of the need for frequent dose intake; and (vi) enhancement of patient compliance. The treatment of illness can thus be optimised. To gain a better understanding of how to optimise the treatment of illnesses by applying programmable rate-controlled drug delivery technologies, this article reviews the scientific concepts and technical principles behind the development of various programmable rate-controlled drug delivery systems that have been marketed or are under active development. Finally, the roles of these technologies in optimising therapeutic outcomes in nine therapeutic areas are discussed.

Systemic delivery of parathyroid hormone (1-34) using inhalation dry powders in rats

The aim of this work was to prepare and characterize inhalation dry powders of human parathyroid hormone (PTH), as well as to assess their efficacy for systemic delivery of the peptide and safety in rats. The powders were prepared by spray-drying using PTH, sugars, dipalmitoylphosphatidylcholine, and/or albumin. They presented an average primary particle diameter of 4.5 microm and tap density of 0.06 g/cm(3), a mass median aerodynamic diameter between 3.9 and 5.9 microm, and reached up to 98% emitted dose and up to 61% fine particle fraction in the multi-stage liquid impinger using a Spinhaler inhaler device. Varying the airflow rate from 30 to 100 L/min had limited influence on the aerodynamic behavior of the aerosols. The absolute PTH bioavailability was 21% after intratracheal administration of the powder formed of PTH/albumin/lactose/dipalmitoylphosphatidylcholine and 18% after subcutaneous injection in rats. Equilibrium dialysis revealed a 78% binding of PTH to albumin and the withdrawal of albumin from the powder increased absolute bioavailability after inhalation from 21 to 34%. No acute inflammation appeared in the lung up to 48 h after a single inhalation. The increased bioavailability of the optimized powder aerosol of PTH makes it a promising alternative to subcutaneous injection.

Drug delivery to the lungs from dry powder inhalers

When asthma is being treated, it is essential that sufficient drug is deposited at the site(s) where it is needed. In recent years, many dry powder inhalers have been developed by the pharmaceutical industry. Drug delivery to the lung from dry powder inhalers is dependent upon the patient's peak inhaled flow rate, and so it is very important to be able to assess the amount and location of drug delivered from different devices. Lung deposition has recently been assessed from a new dry powder inhaler, the Novolizer (ASTA Medica, now VIATRIS GmbH & Co. KG, subsidiary Sofotec GmbH & Co. KG, Frankfurt, Germany), using gamma scintigraphy. It was shown that the Novolizer deposited significantly more budesonide in the lungs than a Turbuhaler used either at similar inspiratory flow rates or with similar inspiratory effort. Equivalent clinical efficacy and safety profiles have also been shown in asthmatic patients treated with budesonide from each device.

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.

Micronization of anti-inflammatory drugs for pulmonary delivery by a controlled crystallization process

Jet-milling as the common way for micronization of drugs shows several disadvantages. Drug powder properties are decisive for pulmonary use because, besides a small particle size, a good deagglomeration behavior is required. In this study, several anti-inflammatory drugs [beclomethasone-17,21-dipropionate (BDP), betamethasone-17-valerate (BV), triamcinolone acetonide, ECU-R2, budesonide, and prednisolone] were micronized by controlled crystallization without any milling processes. First the drug is dissolved in an organic solvent (BDP/BV: 4%; ECU-R2: 1% in acetone) and precipitated by a solvent change method in the presence of a cellulose ether (hydroxypropylmethylcellulose) as stabilizing hydrocolloid. By rapid pouring the solution of hydroxypropylmethylcellulose in water (BDP/BV: 0.005%; ECU-R2: 0.025%) into the drug solution under stirring in a relationship (v/v) of 1:16 (BDP/BV), 1:4 (ECU-R2), the previously molecularly dispersed drug was associated to small particles and stabilized against crystal growth simultaneously. This dispersion was spray-dried, resulting in a drug powder with a uniform particle-size distribution and a drug load of up to 98% (BDP, BV). The mean particle size of the drug was lower than 5 microm in most cases and consequently in the respirable range. Whereas the fine particle fraction (<5 microm, measured without excipients and without an inhalation device) of jet-milled drugs is 9.5 (BDP) or 13.1 (ECU-R2), fine particle fractions of 25.6% (BDP) resp. 78.2% (ECU-R2) are obtained with the spray-dried powders. As the formation of the small crystals requires a rapid solvent change process, the affinity of the hydrocolloid, and a high difference between the solubility in the solvent and nonsolvent, the drug's partition coefficient limits the method as drugs which are more hydrophilic form larger particles.

Lung deposition of salbutamol in healthy human subjects from the MAGhaler dry powder inhaler

The MAGhaler (Mundipharma GmbH) is a multidose dry powder inhaler (DPI) containing a novel formulation of drug and lactose compacted by an isostatic pressing technique (GGU GmbH). On actuation, a precise dose is metered from a compacted ring-shaped drug tablet. In this study, the lung deposition of salbutamol from this device has been assessed. Ten healthy non-smoking subjects completed a two-way cross-over study assessing the pulmonary deposition of salbutamol (200 microg) from the MAGhaler at high (60 l/min) and low (30 l/min) peak inhaled flow rates (PIFRs), representing maximal and sub-maximal inspiratory efforts. The formulation was radiolabelled with 99mTc, and lung and oropharyngeal depositions were quantified by gamma scintigraphyThe mean (SD)% ofthe delivered dose deposited in the lungs was 26.4 (4.3)% at 60 l/min and 21.1 (5.1)% at 30 l/min (P < 0.05), corresponding to mean lung depositions of 52.8 and 42.2 microg salbutamol, respectively. The distribution of drug within different lung regions did not vary significantly with inhaled flow rate. The data provided proof of concept for the novel inhaler device and the innovative drug formulation. In comparison with previous deposition data obtained with other DPIs, the lung deposition was relatively high, relatively reproducible (coefficient of variation 16% at 60 l/min) and relatively insensitive to the change in peak inhaled flow rate.

Dry powder inhalation of antibiotics in cystic fibrosis therapy, part 1: development of a powder formulation with colistin sulfate for a special test inhaler with an air classifier as de-agglomeration principle

The aim of this study was to investigate the pulmonary administration of antibiotics as dry powder to patients with cystic fibrosis (CF), as an alternative for nebulization. This part of the study describes the development of a powder formulation with colistin sulfate as model substance. The aim of the new dosage form was to increase pulmonary deposition, therapeutic efficiency and, by that, compliance by the CF patients. A physical powder mixture of colistin and a size fraction of lactose (106-150 microm) was prepared and the mixture was optimized with respect to colistin content (83.3%) for use in a special test inhaler. A laser diffraction apparatus with special inhaler adapter was applied for analysis of the size distribution of the aerosol cloud from the inhaler. The size distributions of the aerosol clouds from the test inhaler at flow rates between 30 and 60 l/min for the optimized formulation showed nearly the same median diameter as that for the primary drug particles. But the X(100)-value was much lower, because of an effective large particle separation from the inspiratory air by an air classifier in the test inhaler. The results suggest that dry powder inhalation might be a suitable and highly efficient alternative for nebulization of antibiotic drugs in CF therapy.

Relative lung and systemic bioavailability of sodium cromoglycate inhaled products using urinary drug excretion post inhalation

The relative lung and systemic bioavailability of sodium cromoglycate following inhalation by different methods have been determined using a urinary excretion pharmacokinetic method. On three separate randomised study days, 7 days apart, subjects inhaled (i) 4x5 mg from an Intal metered dose inhaler (MDI), (ii) 4x5 mg from an MDI attached to a large volume spacer (MDI+SP) and (iii) 20 mg from an Intal Spinhaler (DPI). Urine samples were provided at 0, 0.5, 1, 2, 5 and 24 h post dose. The mean (S.D.) amount of sodium cromoglycate excreted in the urine during the first 30 min post inhalation was 38.1 (27.5), 222.3 (120.3) and 133.1 (92.2) microg following MDI, MDI+SP and DPI, respectively. The mean ratio (90% confidence interval) of these amounts excreted in the urine over the first 30 min for MDI+SP vs. MDI, DPI vs. MDI and MDI+SP vs. DPI was 801.0 (358.0, 1244; p<0.002)%, 457.0 (244.0, 670.0; p<0.02)% and 262.4 (110.2, 414.5)%, respectively. Similarly for the 24 h cumulative amount of sodium cromoglycate excreted over the 24 h post inhalation the ratios were 375.4 (232.9, 517.9; p<0.005)%, 287.5 (183.4, 391.6; p<0.02)% and 211.4 (88.3, 334.5)%, respectively. The results highlight better lung deposition of sodium cromoglycate from a metered dose inhaler attached to a large volume spacer.

Dry powder inhaler: influence of humidity on topology and adhesion studied by AFM

In the dry powder inhalers (DPIs), the adhesion results of the interactions between the active substance and the excipient. The carrier and the micronized drug particle morphologies are believed to affect the delivery of the drug. In this work, the couple studied was the lactose monohydrate and micronized zanamivir, used for the treatment of influenza. In a first approach, observations by scanning electron microscopy (SEM) have shown that the relative humidity (RH) greatly influenced the zanamivir amount fixed on the lactose monohydrate surface. This paper deals with the direct measurement in controlled atmosphere by atomic force microscopy (AFM) of the forces and the interaction ranges between a zanamivir probe and a lactose substrate. Selected zanamivir crystals were attached to the standard AFM probe. Different RH have been used in order to determine influent parameters permitting to identify the nature of adhesion forces between them. This study demonstrated that the increase of RH modified progressively the surface topology of the two components and increased the adhesion force.

The effect of different concentrations of lactose powder on the airway function of adult asthmatics

Lactose is widely used as a carrier of drugs in inhalation devices for asthmatic patients, but some clinicans have suspected that it may cause bronchoconstriction. Only a few studies have been done to examine this and the results are not uniform. This study was conducted to determine the effects of inhalation grade lactose delivered by Diskhaler on lung function and airway conductance in asthmatic subjects. The effect of five doses of lactose ranging from 6.25 mg to 100 mg and placebo were investigated using spirometry and constant volume plethysmography. Nineteen subjects (nine females) with stable asthma and a proven reversibility of at least 12% in forced expiratory volume in 1 sec (FEV) (compared to baseline) in the last 6 months, were included in this single-centre, randomized, placebo-controlled, double-blind, cross-over study. The subjects received placebo plus five doses of lactose on one study day and six doses of placebo on another study day. Both doses and study days were assigned in a random order, and intervals of 1 h were allowed between each dose and at least 36 h between study days. Specific airways conductance (sGaw) and FEV were measured periodically over the course of 1 h after each dose of lactose or placebo. Administration of lactose at four or eight times the concentration in the Diskus and Diskhaler dry powder inhalers did not result in any statistically significant changes in FEV1. sGaw also showed no statistical difference between lactose and placebo at 1 or 3 min post-dosing. Both placebo and lactose produced both dilatation and constriction of the airways in the same patients, with no consistency in direction and no dose-response relationship. No adverse effect of lactose on a rways conductance or FEV1 of stable asthmatic patients was found in this study when given at higher than normal clinical doses.

A comparison of the lung deposition of budesonide from Easyhaler, Turbuhaler and pMDI plus spacer in asthmatic patients

Inhaled corticosteroids in pressurized metered does inhalers (pMDIs) are often delivered via a large volume spacer device, but these are bulky and inconvenient. Dry powder inhalers (DPIs) provide a highly portable and convenient propellant-free alternative to pMDIs for asthma maintenance therapy However, each DPI could have unique in vivo delivery characteristcs. In order to quantify the total and regional lung deposition of budesonide (200 microg) from (a) Easyhaler, (b) Turbuhaler and (c) pMDI plus Nebuhaler 750 ml spacer, a three-way randomized cross-over study was carried out in 12 mild to moderate asthmatic patients. Deposition was quantified by the imaging technique of gamma scintigraphy Optimal inhalation techniques were used throughout. Mean (SD) whole lung deposition (% metered dose) was similar for Easyhaler [18.5 (7.8) %] and Turbuhaler [21.8 (8.2) %], but was significantly higher for pMDI plus Nebuhaler [44.1 (10.0) %, P < 0.01]. The regional distribution patterns in the lungs were predominantly central for all three devices. Nebuhaler reduced oropharyngeal deposition significantly compared with the two DPIs. Easyhaler showed comparable deposition to Turbuhaler and hence drugs delivered by Easyhaler would be expected to have a similar clinical effect to those delivered by Turbuhaler in asthma maintenance therapy.

Effect of additives on insulin absorption from intratracheally administered dry powders in rats

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.

The use of lactose recrystallised from carbopol gels as a carrier for aerosolised salbutamol sulphate

Lactose was crystallised either from Carbopol gel without stirring or from a constantly-stirred aqueous solution, to obtain lactose crystals designated as Carbo and control lactose, respectively. The Carbo lactose was shown to have a more regular shape with smoother surface as compared with the control lactose. These lactoses were fractionated by sieving to produce batches with different sizes before blending separately with salbutamol sulphate (SS, VMD 5.8 microm) in a ratio of 67.5:1 w/w using the same mixing procedure. SS dispersion and deaggregation were investigated using a 4-stage liquid impinger after aerosolisation at 28.3, 60.0 and 96.0 l/min via a Rotahaler. At all flow rates, the Carbo lactose produced significantly higher (ANOVA, P<0.01) emission of SS from the Rotahaler as compared with the control lactose of a similar size. The Carbo lactose also resulted in a significantly (P<0.05) higher fine particle fraction of SS than the control lactose. Moreover, drug emission from formulations containing the Carbo lactose was consistently more reproducible than those of the control lactose blends. In conclusion, the efficiency and reproducibility of drug delivery by dry powder inhalers can be improved using carrier particles of precisely defined morphological features.

The use of different sugars as fine and coarse carriers for aerosolised salbutamol sulphate

The aim of this study was to investigate the dispersion and deaggregation of a model drug, salbutamol sulphate (SS), using lactose, mannitol or sorbitol as coarse and fine carriers. Binary and tertiary formulations containing micronised salbutamol sulphate (SS) and sieved (63-90 microm) coarse sugar crystals or salbutamol sulphate (SS) with a mixture of coarse and fine sugar particles were prepared. Factorial design was employed to investigate the effects of three variables, i.e. the chemical entity of the coarse sugar carrier, the chemical entity of the fine sugar and the concentration of fine sugar, on the dispersion and deaggregation of salbutamol sulphate after aerosolisation at 60 l/min via a Rotahaler(R) into a twin stage liquid impinger (TSI). The binary formulations containing the different sugar entities produced differences in the fine (<6.4 microm) particle fraction (FPF) of SS in a decreasing order of mannitol >sorbitol >lactose, but failed to produce efficient dispersion of SS since the FPF was <10%. Adding fine sugar particles and increasing their concentration to the binary mixtures generally resulted in an increase in the FPF of salbutamol sulphate. The chemical nature of the fine carriers was found to play a less important role in determining respirable fraction of the drug than the coarse carriers. In conclusion, other sugars such as mannitol or sorbitol, besides lactose, may be employed as coarse and/or fine carriers for incorporation into dry powder aerosol formulations to increase FPF.

Human lung deposition data: the bridge between in vitro and clinical evaluations for inhaled drug products?

Regulatory dossiers for new inhaled drug products generally contain in vitro data, which assess delivered dose and particle size distribution, together with clinical efficacy and safety data. Human lung deposition data may be generated using radionuclide imaging techniques or appropriate pharmacokinetic methods, and can act as a 'bridge' via which a seamless transition can be made between in vitro testing in the laboratory and efficacy/safety testing in the clinic. By enabling informed decisions to be made about the evaluation of new devices or formulations in man, lung deposition data permit a long and expensive clinical trials programme to be commenced with much greater certainty of a successful outcome. Human lung deposition data should be considered for supplementing the information required for regulatory dossiers.

Use of a novel modified TSI for the evaluation of controlled-release aerosol formulations. I

When considering the development of potential controlled-release pulmonary drug delivery systems, there is at present no standard method available for the assessment of in vitro drug release profiles necessary to understand how the drug might release following deposition in the lungs. For this purpose, the twin-stage impinger (TSI), apparatus A of the BP, has been redesigned and tested. This modified TSI was found capable of discriminating between drug release rates from conventional and different dry powder formulations consisting of model controlled-release excipients, providing information related to (a) drug diffusion properties of controlled-release dry powder blends with different excipient components and (b) the effect of varying drug concentration within a given formulation.

The effects of carrier size and morphology on the dispersion of salbutamol sulphate after aerosolization at different flow rates

We have investigated the interdependence of various factors (particle size, surface smoothness, carrier particle shape, inhalation flow rate) on the deposition of a model drug (salbutamol sulphate) after aerosolization from a model inhaler device (Rotahaler). Different batches of alpha-lactose monohydrate were prepared to have different particle size, particle shape and surface smoothness. Each batch of lactose was then mixed separately with salbutamol sulphate in a ratio of 67.5 : 1 (w/w), under similar conditions. Drug deposition from each formulation was investigated using a 4-stage liquid impinger after aerosolization at 28.3, 60.0 and 96.0 L min(-1) via a Rotahaler. At a flow rate of 28.3 L min(-1), a large portion of drug particles was not emitted from the inhaler, the % emission varying from 29.6% to 66.6% for all formulations investigated. Drug emission tended to increase with particle size of the carrier whilst fine particle fraction, fine particle dose and dispersibility appeared to increase with decreasing particle size but increasing elongation ratio of the carrier particles. Increasing the flow rate to 60.0 L min(-1) was shown to increase drug emission since > 75% total dose was found to be emitted from the inhaler. Again, smaller or more elongated lactose particles resulted in a higher fine particle dose or fine particle fraction of salbutamol sulphate than the coarser carrier, although they produced a similar (analysis of variance P > 0.05) drug emission. Increasing the flow rate to 96.0 L min(-1) did not increase drug emission. Increasing the flow rate resulted in an increase in the fine particle fraction and fine particle dose of salbutamol sulphate from all formulations. The flow rate of the airstream appeared to play the most important role, followed by particle size and elongation ratio of the carrier particles, with the surface smoothness relatively less significant in determining the deposition of salbutamol sulphate from the Rotahaler.

Pulmonary drug delivery from the Taifun dry powder inhaler is relatively independent of the patient's inspiratory effort

The Taifun dry powder inhaler (Leiras OY, Turku, Finland) is a breath-actuated, multidose device, each metered dose containing 200 micrograms of budesonide. A two-way randomized crossover gamma scintigraphic study was performed in 10 asthmatic patients to determine the in vivo deposition pattern of budesonide inhaled from the Taifun. In vitro radiolabelling validation studies demonstrated that the radiolabel could be used as an accurate marker to assess in vivo drug deposition. Patients used either maximal inspiratory effort (targeted peak inhalation flow 30 L/min) or submaximal inspiratory effort (targeted peak inhalation flow 15 L/min) on each study day. Mean (S.D.) whole lung deposition (% of metered dose) was 34.3 (5.8)% and 29.6 (5.9)% for the two inhalation flows. The intersubject coefficient of variation in lung deposition was less than 20% on both study days. Drug was deposited uniformly across the central, intermediate, and peripheral lung regions for maximal and submaximal inspiratory efforts. The study suggests that the Taifun is a superior drug delivery device compared with many other inhalers, in terms of the amount of drug deposited in the lungs, the reproducibility of the lung dose, and the relative flow--independence of lung deposition.

A new beclomethasone dipropionate multidose powder inhaler in the treatment of bronchial asthma

The clinical efficacy, tolerability and acceptability of a new multidose powder inhaler (MDPI) containing beclomethasone dipropionate (BDP) were compared with those of a BDP aerosol administered with a large volume spacer (MDI-spacer) among adult asthmatics currently receiving from 500 to 1,000 microgram/day of an inhaled corticosteroid. During the study, the dosage of BDP from both devices was 400 microgram twice daily. Ninety-one patients were randomized to the MDPI group and 42 to the MDI-spacer group. The trial was performed as an open, randomized, parallel group multicenter study. The duration of the treatment period was 12 weeks, and the study was preceded by a 2-week run-in period. During the run-in period, the mean morning peak expiratory flow (PEF) was 487 and 466 1/min in the MDPI and MDI-spacer groups, respectively. After the 12-week treatment, the morning PEF was 491 1/min in the MDPI group and 463 1/min in the MDI-spacer group. The evening values were 500 and 479 1/min during the run-in period and 496 and 476 1/min after the 12-week treatment, respectively. Asthma symptom scores and the use of rescue medication were low in both groups, indicating good efficacy of the preparations tested. The median dose of histamine required to decrease forced expiratory volume in 1 s by 15% increased during the study from 800 to 1,098 microgram in the MDPI group and from 795 to 960 microgram in the MDI-spacer group. The most frequent adverse events in both groups were hoarseness and sore throat. There were no statistically significant differences between the treatment groups in serum cortisol values or in the number of patients with thrush. Seventy-two percent of the patients regarded the MDPI easier to use while 95% considered it more portable. Over 80% of the patients felt that the MDPI was also easier to clean and as easy or easier to learn to use than the MDI-spacer. To conclude, the novel powder inhaler is well tolerated and at least equally effective as the conventional MDI-spacer combination in the treatment of asthma with BDP. However, in everyday use, patients clearly favored the powder inhaler.

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.

The influence of crystallization conditions on the morphology of lactose intended for use as a carrier for dry powder aerosols

Lactose has been widely used as a carrier for inhalation aerosols. The carrier morphology is believed to affect the delivery of the drug. The aim of this study was to investigate the effects of crystallization conditions on the morphology of alpha-lactose monohydrate intended for use as the carrier for dry powder aerosols. The crystallization of lactose was carried out from aqueous solutions at different supersaturations, temperatures, different stages of crystallization and in the presence of different water-miscible organic solvents. The majority of lactose crystals were found to be either tomahawk-shaped or pyramidal after crystallization at an initial lactose concentration between 33-43% w/w, but these became prismatic if the lactose concentration was increased to 50% w/w. A further increase in the lactose concentration to 60% w/w led to the preparation of elongated cuboidal crystals. Higher initial lactose concentrations tended to result in the crystallization of more elongated particles. Crystallization at 40 degrees C was shown to prepare lactose crystals with a more regular shape and a smoother surface than those crystallized at 0 degrees C. Lactose particles generated during the later stage of crystallization were found to be more regular in shape with a smoother surface than those prepared in the earlier stage. The addition of 10% (v/v) methanol or ethanol or acetone to the mother liquor increased the growth rate of lactose particles whereas addition of propanol or glycerine inhibited the rate of crystal growth. Lactose crystals prepared in the presence of glycerine were more regularly shaped with a smoother surface than those prepared in the presence of ethanol or acetone. All the resultant crystals were shown to comprise alpha-lactose monohydrate. Lactose crystals could be prepared with a precisely defined morphology by means of carefully controlling the crystallization conditions.

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

Metered dose inhalers (MDIs) are the most popular vehicle for drug delivery into the lungs and some 500 million are manufactured each year. All MDIs marketed prior to 1995 contained chlorofluorocarbons (CFC) as a propellant. These are implicated in the depletion of stratospheric ozone and, except for specific exemptions, their production has been banned since 1996 under the terms of the Montreal Protocol. Hydrofluoroalkanes have been identified as suitable alternatives for MDI propellants but their physico-chemical properties differ significantly from CFCs and an extensive redevelopment and testing programme has been required to demonstrate the safety, quality and efficacy of HFA containing MDIs. Hydrofluoroalkanes contribute to global warming but the benefit to human health through continued MDI availability currently outweighs the environmental concern. Several HFA-MDIs have reached the market and the transition to replace existing CFC-MDIs is now underway.

The influence of carrier morphology on drug delivery by dry powder inhalers

Alpha-lactose monohydrate was prepared to have different morphological features but with similar particle size. The crystal shape and surface smoothness of lactose were quantified by a number of shape descriptors and these were supported qualitatively by the visual examination of scanning electron (SE) micrographs of the crystals. All batches of lactose were subjected to a similar history of processing before blending separately with micronised salbutamol sulphate (SS) in a ratio of 67.5:1, w/w, using similar procedures. In vitro deposition of SS from these formulations was investigated after aerosolisation of the formulations at 60 l min(-1) via the Rotahaler and the Cyclohaler into a twin stage liquid impinger. The formulations prepared using the different batches of lactose produced different deposition profiles of SS. The fine particle (< 6.4 microm) fraction (FPF) of aerosolised SS varied from 12.6 +/- 2.4 to 25.6 +/- 1.5% after aerosolisation from the Cyclohaler whilst it changed from 15.0 +/- 2.2 to 24.4 +/- 0.8% after aerosolisation from the Rotahaler. The fine particle dose (FPD) and dispersibility of SS followed a similar trend to the change in the FPF of the drug. No significant difference (ANOVA P > 0.05) was observed for the deposition profiles of SS after aerosolisation from the Rotahaler and the Cyclohaler. The FPF and dispersibility of SS increased with either the surface smoothness (P < 0.01) or elongation ratio (P < 0.01) of lactose crystals. The t-ratio values of FPF and dispersibility of SS generated by changes in the surface smoothness were similar to those resulting from changes in elongation ratio. Increasing either the surface smoothness or the elongation ratio of lactose crystals will increase the potentially respirable fraction of SS from dry powder formulations for inhalation.

The influence of lactose carrier on the content homogeneity and dispersibility of beclomethasone dipropionate from dry powder aerosols

Dry powder formulations for inhalation usually comprise a mixture of coarse lactose (CL), employed as a carrier, and micronized drug. It was the aim of this study to determine the effects of fine lactose (FL), blended as a tertiary component on the mixing homogeneity and dispersibility of a model hydrophobic drug, beclomethasone dipropionate (BDP). BDP particles (volume median diameter (VMD) 4.6 microm) existed mainly as agglomerates, the majority of which were not dispersed into primary particles after aerosolization at a high shear force (4.7 psi). The resultant particle size distribution of BDP was multi-modal with VMD varying between 4.7 and 30.2 microm. Ternary interactive mixtures were prepared to consist of CL, FL and BDP with a fixed ratio of lactose to BDP of 67.5:1 w/w, but two concentrations of FL, i.e. 2.5 and 5%, w/w. The mixing was carried out using different sequences of adding the three components for two mixing times (15 and 60 min). Binary mixtures composed of CL and BDP were prepared for both mixing times as the controls, and these exhibited a coefficient of variation (COV) in BDP content <= 5%. Addition of FL to the binary formulations greatly reduced the content uniformity of BDP if the final powder were prepared by first mixing CL with FL before mixing with the drug (COV>20%, after mixing for 15 min). However, the mixtures, prepared using other mixing sequences, had a similar uniformity of BDP content to the binary mixtures. All ternary mixtures containing 2.5% FL consistently produced a significantly higher (ANOVA P<0.01) fine particle fraction (FPF, 3.1--6.1%) and fine particle dose (FPD, 13.6--30.1 microg) of BDP than the binary mixtures (FPF, 0.3-0.4%; FPD, 1.6-2.1 microg) after aerosolization at 60 l min(-1) via a Rotahaler into a twin stage liquid impinger. The mixing sequences exerted a significant (P<0.05) effect on the dispersion and deaggregation of BDP from the formulations prepared using a mixing time of 15 min but such an effect disappeared when the mixing time was lengthened to 60 min. The dispersibility of BDP was always higher from the ternary mixtures than from the binary mixtures. BDP delivery from dry powder inhalers was improved markedly by adding FL to the formulation, without substantial reduction in the content uniformity of the drug.

Pulmonary deposition of lactose carriers used in inhalation powders

Dry powder dosage forms are generally formulated by mixing the micronized drug particles with the larger carrier particles. Lactose is a commonly used carrier. Carriers enhance the flowability of powder mixtures and therefore enable low dosing of active substances. During inhalation, the drug particles are dispersed from the surface of carrier particles. The aim of this study was to compare how different qualities of 99mTc-labelled lactose carrier systems deposit in the lungs. The sizes of the labelled and unlabelled alpha-lactose monohydrate particles were compared by using a laser diffraction method. Distribution of radiolabel between different particle size fractions was determined using the Andersen cascade impactor. The in vivo depositions of lactose carrier systems were investigated in ten healthy men using the technique of gammascintigraphy. In addition, redispersion of budesonide from the carrier materials was evaluated by using the Andersen cascade impactor. According to the validation data the particle size of the lactose carriers remained unchanged during the labelling process. Low pulmonary deposition varying between 2.5 and 3.3% was detected. Only a small amount of lactose was deposited in the lungs, thus pulmonary deposition is not a limiting factor for lactose selection. According to in vitro redispersion data the fine particle fraction of the delivered dose in the impactor varied between 10.3 and 26.0%. Thus, the redispersion of the budesonide particles can be altered by the properties of the carrier system.

Influence of Storage at Low Temperatures on the Aerosol Output from Metered-Dose and Dry-Powder Inhalation Devices

Objective:

To determine whether storage at low temperatures affects the drug delivery efficacy of a chlorofluorocarbon (CFC)-free aerosol and a dry-powder inhaler (DPI).

Design:

Aerosol output from a CFC-free hydrofluoroalkane (HFA-134a) metered-dose inhaler (albuterol) and a multidose DPI (terbutaline) were examined at different ambient temperatures and canister loads.

Results:

After the HFA-134a formulation was stored at low temperatures for 24 hours, a small decrease of aerosol output (2.1–2.7% at 0 °C, 5.0–8.0% at −10 °C; p < 0.05 from 22 °C) was observed. In addition, the aerosol output from devices with one-half or one-fifth the initial content was marginally decreased compared with output from inhalers with full content. Image analysis techniques applied to fully formed aerosol plume emitted from the HFA-134a formulation showed that the product could still be aerosolized at 10 °C, but there was a reduction of the distance reached by the aerosol. In contrast, condensed droplets markedly altered the aerosols formed from CFC inhalers at −10 °C. Aerosol output from the DPI apparently was not altered following 24-hour storage at −10 °C.

Conclusions:

Aerosols emitted by the HFA-134a and DPIs studied were less affected by exposure to cold temperatures compared with those from marketed CFC devices.

Optimization of a dry powder inhaler formulation of nacystelyn, a new mucoactive agent

The aim of this study was to optimize a dry powder inhaler formulation containing a new mucoactive drug, nacystelyn. Formulations were made using three types of lactose, crystalline alpha-lactose, spray-dried lactose and a roller-dried anhydrous beta-lactose. The roller-dried anhydrous beta-lactose possessed the most adequate surface properties, resulting in a significantly higher (P < 0.05) in-vitro lung deposition of nacystelyn than the conventional crystalline alpha-lactose and spray-dried lactose. The particle size distribution of roller-dried beta-lactose was optimized also. Within the size ranges tested (63-100, 90-125 and 100-160 microm), the coarser the lactose, the higher the in-vitro deposition of the drug (up to 40%). In contrast, the in-vitro lung deposition of 100-160 microm roller-dried beta-lactose was very low (< 0.5%), so limiting the potential risk of lung irritation due to the carrier. The influence of the ratio of active ingredient/excipient (w/w) was also investigated. No difference was observed for mixtures from 1:2 to 1:4 while higher dilutions (1:5 and 1:6) showed significantly (P < 0.005) lower deposition results. Finally, the influence of the airflow rate was assessed. No dependence of the fine particle dose was observed between 40 and 80 L min(-1) while significantly higher results were obtained at 100 L min(-1). The dry powder inhaler formulation of nacystelyn using the unusual roller-dried anhydrous beta-lactose resulted in very high and reproducible in-vitro deposition results. However, the latter needs to be confirmed by in-vivo studies.

A critical comparison of the dose delivery characteristics of four alternative inhalation devices delivering salbutamol: pressurized metered dose inhaler, Diskus inhaler, Diskhaler inhaler, and Turbuhaler inhaler

Salbutamol is a short-acting beta 2 agonist which is effective as a rescue therapy in the treatment of asthma. This study uses in vitro test methods to compare the capability of four alternative devices to deliver an accurate and precise dose of salbutamol. It is demonstrated that the conventional metered dose inhaler (MDI) achieves excellent accuracy and precision in dose delivery. Additionally, it is the most efficient inhaler in terms of generating in-vitro a fine particle fraction from the dose. A spacer device has been shown to further enhance the dosing characteristics. When tested over a wide range of inspiratory air flow rates, the Diskus (GlaxoWellcome, Hertfordshire, UK) has comparable accuracy and precision to the MDI tested at 60 L/min, and it offers an advantage over two alternative dry powder inhalers (DPIs), delivering a more consistent dose across the range of flow rates tested and being more efficient at generating a fine particle fraction than either Turbuhaler (Astra, Lund, Sweden) or Diskhaler (GlaxoWellcome) at both 28 and 60 L/min inspiratory flow rates. Diskus, Diskhaler, Ventolin, Volumatic, and Rotadisk are trademarks of the GlaxoWellcome Group of companies. The Accuhaler is the alternative to the Diskus in those countries where the Diskus trademark is not available. Inspiryl and Turbuhaler are trademarks of the Astra Group of companies.

Inhalation of estradiol for sustained systemic delivery

Large porous estradiol particles were formulated by spray drying estradiol in combination with various U.S. Food and Drug Administration (FDA)-approved or endogenous excipients. The powders were characterized in terms of their geometrical size, mass density, and aerosolization properties. Small nonporous particles were also prepared using the same excipients and were physically characterized to insure that they possessed a similar mean aerodynamic size as the large porous particles. The two powders were aerosolized into the lungs of rats via an endotracheal tube or subcutaneously injected as a control to assess relative bioavailability. Two different large porous particle formulations were found to produce elevated systemic estradiol concentrations upon inhalation for approximately 5 days, with relative bioavailabilities of 59.7% and 86.0%. Systemic estradiol concentrations following inhalation of two different small nonporous particle powders remained elevated for only approximately 1 day, with relative bioavailabilities of 18.3% and 38.7%. Bronchoalveolar lavage was performed up to 96 hours after inhalation of porous and nonporous estradiol powders. Small changes in neutrophil and macrophage populations were observed following inhalation of both the porous and nonporous powders.

Influence of flow rate on aerosol particle size distributions from pressurized and breath-actuated inhalers

Particle size distribution of delivered aerosols and the total mass of drug delivered from the inhaler are important determinants of pulmonary deposition and response to inhalation therapy. Inhalation flow rate may vary between patients and from dose to dose. The Andersen Sampler (AS) cascade impactor operated at flow rates of 30 and 55 L/min and the Marple-Miller Impactor (MMI) operated at flow rates of 30, 55, and 80 L/min were used in this study to investigate the influence of airflow rate on the particle size distributions of inhalation products. Total mass of drug delivered from the inhaler, fine particle mass, fine particle fraction, percentage of nonrespirable particles, and amount of formulation retained within the inhaler were determined by ultraviolet spectrophotometry for several commercial bronchodilator products purchased in the marketplace, including a pressurized metered-dose inhaler (pMDI), breath-actuated pressurized inhaler (BAMDI), and three dry powder inhalers (DPIs), two containing salbutamol sulphate and the other containing terbutaline sulphate. Varying the flow rate through the cascade impactor produced no significant change in performance of the pressurized inhalers. Increasing the flow rate produced a greater mass of drug delivered and an increase in respirable particle mass and fraction from all DPIs tested.

Effects of particle size and adding sequence of fine lactose on the deposition of salbutamol sulphate from a dry powder formulation

Ternary mixtures composed of coarse lactose (CL) (90.8 microm), salbutamol sulphate (SS) (5.8 microm) and either micronised lactose (ML) (5 microm) or intermediate sized lactose (IML) (15.9 microm) in a ratio of 66.5:1:1 w/w were prepared using different mixing sequences of the various components. In addition, a binary mixture composed of CL and SS (67.5:1 w/w) was also prepared as the control. The in vitro deposition of SS was measured using a twin stage impinger after aerosolisation at 60 and 90 l min-1 via a Rotahaler. The aerodynamic particle size distribution of both the aerosolised SS and lactose was further analysed using an Andersen cascade impactor at 60 l min-1. All ternary mixtures produced a significantly higher (analysis of variance, P<0.01) fine particle fraction (FPF) and fine particle dose (FPD) of SS than the control after aerosolisation at either 60 or 90 l min-1. Formulations containing the ML produced significantly (P<0.05) higher FPF and FPD of SS than those containing the IML at both aerosolisation flow rates. Different mixing sequences were also shown to result in different deposition profiles of both SS and lactose after aerosolisation of the ternary mixtures containing ML at 60 l min-1. The formulation prepared by first blending ML with CL before mixing with SS produced a higher FPF and FPD of SS but a lower FPF of lactose than the same formulation in terms of composition but prepared using different mixing orders of the three components. In contrast, the formulations containing IML produced a similar deposition profile to SS, regardless of the mixing sequences, and so did the formulations containing ML aerosolised at 90 l min-1. These results suggest that the effect of mixing sequences on drug deposition may become more prominent at lower aerosolisation flow rates and by reducing the size of any added fine lactose.

Recent advances in pulmonary drug delivery using large, porous inhaled particles

The ability to deliver proteins and peptides to the systemic circulation by inhalation has contributed to a rise in the number of inhalation therapies under investigation. For most of these therapies, aerosols are designed to comprise small spherical droplets or particles of mass density near 1 g/cm3 and mean geometric diameter between approximately 1 and 3 micron, suitable for particle penetration into the airways or lung periphery. Studies performed primarily with liquid aerosols have shown that these characteristics of inhaled aerosols lead to optimal therapeutic effect, both for local and systemic therapeutic delivery. Inefficient drug delivery can still arise, owing to excessive particle aggregation in an inhaler, deposition in the mouth and throat, and overly rapid particle removal from the lungs by mucocilliary or phagocytic clearance mechanisms. To address these problems, particle surface chemistry and surface roughness are traditionally manipulated. Recent data indicate that major improvements in aerosol particle performance may also be achieved by lowering particle mass density and increasing particle size, since large, porous particles display less tendency to agglomerate than (conventional) small and nonporous particles. Also, large, porous particles inhaled into the lungs can potentially release therapeutic substances for long periods of time by escaping phagocytic clearance from the lung periphery, thus enabling therapeutic action for periods ranging from hours to many days.