Evaluation of a new Aerodynamic Particle Sizer Spectrometer for size distribution measurements of solution metered dose inhalers

Real-time characterization of chemical threat agent aerosols for improvement of inhalation studies

OBJECTIVES

Deliberate or accidental release of chemical treat agents in the aerosol form can cause an inhalation hazard. Since the relationship between aerosol properties and health hazards is poorly understood, research into the toxicological consequences of exposure to aerosols is needed. The aim of the present study was to improve the characterization of particles for inhalation studies.

METHODS

Several aerosol measurement technologies were compared for their potential to physically and chemically characterize particles in the inhalation size range in real-time. For that purpose, we compared the performance of an aerodynamic particle sizer (APS), a scanning mobility particle sizer (SMPS) and an electrical low-pressure impactor (ELPI) in an experimental set-up in which particles were generated by a Collison nebulizer and subsequently delivered into a nose-only inhalation exposure system.

RESULTS

We found that more than 95% of the number of particles, equating to more than 83% of the mass generated by the 6-jet Collison nebulizer, were below 0.5 µm. To characterize the entire size range, the APS as single detector has only limited value, therefore the addition of supplementary instrumentation such as the SMPS or the ELPI is required. After real-time measurements in the size range of 30 nm to 10 µm, ex-situ chromatographic chemical analysis is essential for quantification of the delivered mass concentration.

CONCLUSIONS

In summary, the present work demonstrates the utility of the ELPI technology, in combination with off-line analysis, for characterizing aerosols with various size, shape, charge, and composition. This makes the aerosol generation and analysis suite described a promising tool for quantitative inhalation exposure studies.

Development of Aggregation-Caused Quenching Probe-Loaded Pressurized Metered-Dose Inhalers with Fluorescence Tracking Potentials

Recently, pressurized metered-dose inhalers (pMDIs) are getting more attention as an effective approach of pulmonary drug delivery, and nanoparticle-based formulations have become a new generation of pMDIs, especially for water insoluble drugs. Up until now, there is no clinical application of nanoparticle-based pMDIs. The main hurdle remains in the lack of knowledge of the in vivo fate of those systems. In this study, a fluorescent probe named P4 with aggregation-caused quenching (ACQ) effect was loaded in the nanoparticle-based pMDIs to track the in vivo fate. P4 probe expressed strong fluorescence when distributed in intact nanoparticles, but quenched in the in vivo aqueous environment due to molecular aggregation. Experimentally, P4 probe was encapsulated into solid lipid nanoparticles (SLN) as P4-SLN, and then, the formulation of pMDIs was optimized. The content (w/w) of the optimal formulation (P4-SLN-pMDIs) was as follows: 6.02% Pluronic® L64, 12.03% ethanol, 0.46% P4-SLN, and 81.49% 1,1,1,2-tetrafluoroethane (HFA-134a). P4-SLN-pMDI was transparent in appearance, possessed a particle size of 132.07 ± 3.56 nm, and the fine particle fraction (FPF) was 39.53 ± 1.94%, as well good stability was shown within 10 days. The results indicated P4-SLN-pMDI was successfully prepared. Moreover, the ACQ property of P4-SLN-pMDIs was verified, which ensured the fluorescence property as a credible tool for in vivo fate study. Taken together, this work established a platform that could provide a firm theoretical support for exploration of the in vivo fate of nanoparticle-based pMDIs in subsequent studies. Grapical abstract.

Particle sizing of pharmaceutical aerosols via direct imaging of particle settling velocities

We present a novel method for characterizing in near real-time the aerodynamic particle size distributions from pharmaceutical inhalers. The proposed method is based on direct imaging of airborne particles followed by a particle-by-particle measurement of settling velocities using image analysis and particle tracking algorithms. Due to the simplicity of the principle of operation, this method has the potential of circumventing potential biases of current real-time particle analyzers (e.g. Time of Flight analysis), while offering a cost effective solution. The simple device can also be constructed in laboratory settings from off-the-shelf materials for research purposes. To demonstrate the feasibility and robustness of the measurement technique, we have conducted benchmark experiments whereby aerodynamic particle size distributions are obtained from several commercially-available dry powder inhalers (DPIs). Our measurements yield size distributions (i.e. MMAD and GSD) that are closely in line with those obtained from Time of Flight analysis and cascade impactors suggesting that our imaging-based method may embody an attractive methodology for rapid inhaler testing and characterization. In a final step, we discuss some of the ongoing limitations of the current prototype and conceivable routes for improving the technique.

Inhalation Properties and Stability of Nebulized Naked siRNA Solution for Pulmonary Therapy

The use of naked unmodified small interfering RNA (N-siRNA) without vector has previously been investigated as a pulmonary therapy. However, little is known regarding stabilities and aerodynamic particle sizes of N-siRNA-containing droplets; nebulizers have not yet been optimized for N-siRNA solutions. Thus, in this study, we investigated the feasibility of inhaled N-siRNA solutions for pulmonary therapy using nebulization. Various nebulizers and N-siRNA concentrations were assessed in terms of siRNA integrity after nebulization, and inhalation properties including aerodynamic particle size were examined. In comparison with ultrasonic-, air-jet-, and vibrating-mesh nebulizers, N-siRNA integrity was not affected by nebulization. Thus, in further experiments, performances of N-siRNA aerosols with different nebulizers and N-siRNA concentrations were evaluated and screened using an aerodynamic particle sizer (APS) which employed the time-of-flight principle or a cascade impactor. Mean mass aerodynamic diameters of N-siRNA-containing droplets from vibrating-mesh nebulizers tended to decrease with increasing N-siRNA concentrations, reflecting the influence of N-siRNA solutions on surface tension, as indicated by contact angles. These data indicate the utility of APS instruments for investigating the nebulized characteristics of expensive drugs including siRNAs and may facilitate the development of N-siRNA inhalation formulations.

Laboratory Evaluation of the Shinyei PPD42NS Low-Cost Particulate Matter Sensor

OBJECTIVE

Finely resolved PM2.5 exposure measurements at the level of individual participants or over a targeted geographic area can be challenging due to the cost, size and weight of the monitoring equipment. We propose re-purposing the low-cost, portable and lightweight Shinyei PPD42NS particle counter as a particle counting device. Previous field deployment of this sensor suggests that it captures trends in ambient PM2.5 concentrations, but important characteristics of the sensor response have yet to be determined. Laboratory testing was undertaken in order to characterize performance.

METHODS

The Shinyei sensors, in-line with a TSI Aerosol Particle Sizer (APS) model 3321, tracked particle decay within an aerosol exposure chamber. Test atmospheres were composed of monodisperse polystyrene spheres with diameters of 0.75, 1, 2 3 and 6 um as well as a polydisperse atmosphere of ASHRAE test dust #1.

RESULTS

Two-minute block averages of the sensor response provide a measurement with low random error, within sensor, for particles in the 0.75-6μm range with a limit of detection of 1 μg/m3. The response slope of the sensors is idiomatic, and each sensor requires a unique response curve. A linear model captures the sensor response for concentrations below 50 μg/m3 and for concentrations above 50 μg/m3 a non-linear function captures the response and saturates at 800 μg/m3. The Limit of Detection (LOD) is 1 μg/m3. The response time is on the order of minutes, making it appropriate for tracking short-term changes in concentration.

CONCLUSIONS

When paired with prior evaluation, these sensors are appropriate for use as ambient particle counters for low and medium concentrations of respirable particles (< 100 ug/m3). Multiple sensors deployed over a spatial grid would provide valuable spatio-temporal variability in PM2.5 and could be used to validate exposure models. When paired with GPS tracking, these devices have the potential to provide time and space resolved exposure measurements for a large number of participants, thus increasing the power of a study.

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

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

Designing CAF-adjuvanted dry powder vaccines: spray drying preserves the adjuvant activity of CAF01

Dry powder vaccine formulations are highly attractive due to improved storage stability and the possibility for particle engineering, as compared to liquid formulations. However, a prerequisite for formulating vaccines into dry formulations is that their physicochemical and adjuvant properties remain unchanged upon rehydration. Thus, we have identified and optimized the parameters of importance for the design of a spray dried powder formulation of the cationic liposomal adjuvant formulation 01 (CAF01) composed of dimethyldioctadecylammonium (DDA) bromide and trehalose 6,6'-dibehenate (TDB) via spray drying. The optimal excipient to stabilize CAF01 during spray drying and for the design of nanocomposite microparticles was identified among mannitol, lactose and trehalose. Trehalose and lactose were promising stabilizers with respect to preserving liposome size, as compared to mannitol. Trehalose and lactose were in the glassy state upon co-spray drying with the liposomes, whereas mannitol appeared crystalline, suggesting that the ability of the stabilizer to form a glassy matrix around the liposomes is one of the prerequisites for stabilization. Systematic studies on the effect of process parameters suggested that a fast drying rate is essential to avoid phase separation and lipid accumulation at the surface of the microparticles during spray drying. Finally, immunization studies in mice with CAF01 in combination with the tuberculosis antigen Ag85B-ESAT6-Rv2660c (H56) demonstrated that spray drying of CAF01 with trehalose under optimal processing conditions resulted in the preservation of the adjuvant activity in vivo. These data demonstrate the importance of liposome stabilization via optimization of formulation and processing conditions in the engineering of dry powder liposome formulations.

In vitro evaluation of dry powder inhaler devices of corticosteroid preparations

BACKGROUND

Although investigations of the drug aerosols generated from inhaled corticosteroid (ICS) preparations and combined drug preparations provide basic information about inhalation therapy, many clinicians have one-sided data about the precision of drug aerosols from the manufacturer. The present study was conducted to analyze and compare the performances of dry powder inhaler (DPI) devices of ICS and combined drug preparations.

METHODS

The particle size of individual aerosols was measured according to the time-of-flight principle in terms of their aerodynamic diameter by using the aerodynamic particle sizer spectrometer Model 3321. Percent aerosolization was measured using only stage #0 and backup filters of the Andersen non-viable sampler model AN-200.

RESULTS

The particle size distribution of aerosols generated from a Turbuhaler™ and Twisthaler™ showed a mono-modal distribution of less than 5 μm. In contrast, Diskus™ showed a polydisperse distribution, ranging from 0.5 to 20 μm. The percentages of DPI preparations converted into aerosols with a particle size less than 11 μm at a suction flow rate of 28.3 L/min were 5.7-6.2% for Diskus, 37.5-47.0% for Turbuhaler, and 19.8% for Twisthaler. At a suction flow rate of 60 L/min, the conversion percentages for DPI preparations into aerosols with a particle size less than 7.6 μm were 5.9-7.5%, 78.2-86.7%, and 43.5%, respectively.

CONCLUSIONS

Because in vitro differences in the aerosolization among different DPI devices containing ICS and combined drug preparations were observed, prescribers of these preparations should consider whether the patients will benefit more from the treatment of the central airways versus the peripheral airways.

Inhalation of an ethanol-based zileuton formulation provides a reduction of pulmonary adenomas in the A/J mouse model

Potential efficacy of zileuton, a 5-LOX inhibitor, was evaluated for the reduction of pulmonary adenomas in the A/J murine model when administered via nose-only inhalation. Development of pulmonary adenomas was induced with benzo(a)pyrene. Animals were treated with a zileuton solution (5 mg/mL in 85:15 ethanol/water) either twice weekly or five times a week via nose-only inhalation; The placebo solution (85:15 EtOH/H2O, no active) was also evaluated. Dose delivered was calculated to be 1.2 mg/kg per exposure for each zileuton group. After 20 weeks of treatment, surface tumors were enumerated and histologically assessed. A significant reduction in tumor count was noted for both the twice weekly administration (40%) and the five times a week administration (59%). The data also showed a significant reduction for the group, which received the placebo (approximately 58%). The treatment groups were also found to have an impact on the histological stages of adenoma development.

Spray drying of siRNA-containing PLGA nanoparticles intended for inhalation

Local delivery of small interfering RNA (siRNA) to the lungs constitutes a promising new area in drug delivery. The present study evaluated parameters of importance for spray drying of siRNA-loaded poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) into nanocomposite microparticles intended for inhalation. The spray drying process was optimised using a statistical design of experiment and by evaluating powder characteristics upon systematic variation of the formulation parameters. Concentration, carbohydrate excipient (trehalose, lactose and mannitol) and the ratio of NP to excipient were varied to monitor the effects on moisture content, particle morphology, particle size and powder yield. The identified optimum conditions were applied for spray drying of siRNA-loaded nanocomposite microparticles, resulting in a product with a low water content (0.78% w/w) and an aerodynamic particle diameter considered suitable for inhalation. The use of mannitol in the formulation allowed a significantly lower moisture content than trehalose and lactose. The inclusion of 50% (w/w) or higher amounts of NPs resulted in a marked change in the surface morphology of the spray-dried particles. Importantly, the integrity and biological activity of the siRNA were preserved during the spray drying process. In conclusion, the present results show that spray drying is a suitable technique for producing nanocomposite microparticles comprising siRNA-containing PLGA NPs for potential use in inhalation therapy.

Comparative analysis of methods to measure aerosols generated by a vibrating mesh nebulizer

Different approaches have been employed for in vitro assessment of the aerosol particle size generated by inhalation devices. In this study, aerosols from the Omron MicroAir vibrating mesh (VM) nebulizer were measured by cascade impaction (CI) using the MSP Next Generation Pharmaceutical Impactor (NGI), the ThermoAndersen Cascade Impactor (ACI), and by time-of-flight (TOF) analysis with the TSI 3321 Aerodynamic Particle Sizer Spectrometer (APS). The VM nebulizer was evaluated with sodium fluoride (NaF; 2.5%) and with generic albuterol (0.083%). Aerosol particle size (MMAD), respirable fractions (RF < 5 microm), and fine particle fractions (FPF < 3.3 microm) were determined with each method at room temperature (RT) and 4 degrees C using 50% average relative humidity. By NGI at either RT or 4 degrees C, aerosol particle sizes were similar for both NaF and albuterol (4.3-4.5 microm MMAD) with 55-61% RF and 27-43% FPF. With ACI, the distribution of particles at RT was similar except at the extremes of the dispersion and the MMAD was smaller (3.3 microm MMAD; p = 0.03). At 4 degrees C, particle sizes determined by ACI results were similar to the NGI (MMAD 4.1 microm; p > 0.05). TOF analysis by APS with albuterol gave significantly larger calculated MMAD (cMMAD) than either CI method (7.2 microm; p < 0.001). TOF measurements of nebulized albuterol at RT and 4 degrees C were equivalent. In summary, the results of VM nebulized NaF and albuterol were more consistent and generally equivalent when determined by NGI (at RT and 4 degrees C) and ACI analysis (at 4 degrees C). In contrast, aerosol particle sizes measured by TOF in the APS at both RT and 4 degrees C were larger than results obtained by CI. Differences in aerosol particle distribution obtained by different analysis methods should be considered while evaluating the in vitro performance of VM nebulizers.

Metered-dose inhalers: actuators old and new

The actuator has been the patient interface of the metered-dose inhaler for the past 50 years. The original 1956 design remains a significant influence upon today's actuators and, moreover, its distinct geometry is still recognisable on the market. The actuator has contributed to the metered-dose inhaler's success as a clinically effective and cost-effective device. This review focuses upon developments since the actuator's introduction as an integral part of the metered-dose inhaler and discusses key aspects of its design that influence lung deposition potential. The ability of the actuator to reduce unwanted oropharyngeal drug deposition, facilitate correct patient use and provide valuable patient feedback is highlighted.

Applicability of an ultrasonic nebulization system for the airways delivery of beclomethasone dipropionate in a murine model of asthma

PURPOSE

We have assessed the use of an ultrasonic nebulization system (UNS), composed of ultrasonic nebulizer and diffusion dryer filled with charcoal, for the effective delivery of beclomethasone to the airways in a murine asthma model.

METHODS

Solution of beclomethasone in ethanol was aerosolized using an ultrasonic nebulizer. Passage of the aerosol through a drying column containing charcoal and deionizer produced dry beclomethasone particles. Particles were delivered to BALB/c mice placed in a whole-body exposition chamber 1 h before intranasal challenge with ovalbumine. Efficacy of beclomethasone delivery was evaluated by examining bronchoalveolar lavage fluid (BALF) cytology.

RESULTS

Effect of three UNS system parameters on aerosol particle size was investigated. The critical parameter affecting the size of dry particles was beclomethasone concentration in aerosolized solution and solution flow rate while power level of ultrasonic nebulizer generator had no effect. Administration of beclomethasone at calculated dose of 150 microg/kg to mice significantly decreased total cell number and relative eosinophil number in BALF.

CONCLUSIONS

The UNS system produces a monodisperse aerosol that can be used for inhalative delivery of poorly water soluble substances to experimental animals. The UNS system minimizes formulation requirements and allows rapid and relatively simple efficacy and toxicity testing in animals.

Evaluation of the TSI aerosol impactor 3306/3321 system using a redesigned impactor stage with solution and suspension metered-dose inhalers

The purpose of this research was to evaluate a redesigned impactor stage for the TSI Model 3306 Impactor Inlet with nozzles adjusted to obtain a target cut-point of 4.7 microm. It has been determined that the previous cut-point used in the Model 3306 was nominally closer to 4.14 microm, thus potentially impacting the characterization of aerosol mass. The reassessment of the Model 3306 was performed on 4 solution and 2 suspension metered-dose inhaler (MDI) formulations. The redesigned impactor stage resulted in a 5% to 6% increase in aerosol mass when compared with the previous impactor stage for the products Ventolin-HFA, Proventil-HFA, and 2 cyclosporin solution formulations with high ethanol concentrations (15% wt/wt). For the formulations with low ethanol concentrations (3% wt/wt), minimal differences were observed between the 2 cut-points. In addition, this study reevaluated the requirement of a vertical inlet extension length when using the TSI 3306/3321 system with the redesigned cut-point. It was shown that the use of a 20-cm extension provides mass and aerosol size distributions that are comparable to the Andersen 8-stage Cascade Impactor, for both solution and suspension MDIs. This work indicates that the TSI 3306/3321 system is suitable for preformulation studies of both suspension and solution MDI systems.

Application of USP inlet extensions to the TSI impactor system 3306/3320 using HFA 227 based solution metered dose inhalers

The objective of this study was to further evaluate the need for a vertical inlet extension when testing solution metered dose inhalers using the TSI Model 3306 Impactor Inlet in conjunction with the TSI Model 3320 Aerodynamic Particle Sizer (APS). The configurations tested using the TSI system were compared to baseline measurements that were performed using the Andersen Mark II 8-stage cascade impactor (ACI). Seven pressurized solution metered dose inhalers were tested using varied concentrations of beclomethasone dipropionate (BDP), ethanol, and HFA 227 propellant. The inhalers were tested with the cascade impactor, and with the TSI system. The TSI system had three different configurations as the manufacturer provided (0 cm) or with inlet extensions of 20 and 40 cm. The extensions were located between the USP inlet and the Model 3306 Impactor Inlet. There were no practical differences between each system for the stem, actuator, or USP inlet. The fine particle mass (aerodynamic mass < 4.7 microm) was affected by extension length and correlated well with the ACI when an extension was present. APS particle size measurements were unaffected by the extension lengths and correlated well to particle size determined from the ACI analysis. It has been confirmed that an inlet extension may be necessary for the TSI system in order to give mass results that correlate to the ACI, especially for formulations having significant concentrations of low volatility excipients. Additionally, the results generated from this study were used to evaluate the product performance of HFA 227 based solution formulations that contain varying concentrations of ethanol as a cosolvent.

Effects of extreme temperatures on drug delivery of albuterol sulfate hydrofluoroalkane inhalation aerosols

PURPOSE

The effects of extreme temperatures on drug delivery of two albuterol sulfate hydrofluoroalkane, metered-dose inhalers (MDIs) were evaluated.

METHODS

Three Proventil HFA and three Ventolin HFA MDIs were stored at room temperature and served as controls while three of each product were placed in the trunk of a vehicle in Tucson, Arizona. The temperature in the vehicle was monitored for six months. Product performance for each of the MDIs was evaluated at room temperature. An additional study was performed to investigate the performance of the two products when actuated at 4, 22, 47, and 60 degrees C.

RESULTS

The products subjected to extreme environmental temperatures had a modest increase in propellant-leak rate, but the emitted-particle size, dose per actuation, respirable mass, and non-respirable mass were unaffected. The inhalers tested at temperatures outside the recommended storage conditions exhibited a decrease in particle size, dose per actuation, shot weight, and non-respirable mass as temperature increased. Conversely, increased temperature caused an increase in respirable mass.

CONCLUSION

Despite exposure to extreme temperatures exceeding the manufacturers' recommended storage conditions, drug delivery from Proventil HFA and Ventolin HFA MDIs was not significantly altered. However, drug delivery did change appreciably when the inhalers were tested at different temperatures outside recommended storage conditions.

A theoretical and experimental analysis of formulation and device parameters affecting solution MDI size distributions

The influence of formulation and device configurations on the initial droplet and residual particle size distribution from solution MDIs was theoretically and experimentally examined. Aerodynamic size distribution tests were conducted to characterize the size distribution of the residual particles formed when a solution MDI is actuated. The measured size distributions were approximately log-normally distributed, and did not show evidence of a secondary large particle mode. Theoretical relationships were developed to relate the residual particle size distribution to the initial size distribution of the atomized droplets. The residual particle size distribution was shown to be proportional to the nonvolatile concentration to the one-third power. Ethanol concentration, propellant type, valve size, and actuator orifice diameter were all shown to affect the initial droplet size distribution. Deposition of drug in the mouthpiece and USP inlet affect the measured size distribution during aerodynamic particle size measurements. Although there is a significant increase in the size of initial droplets as ethanol concentration increases, there is only a minor increase in the size of the residual particles measured when the USP Inlet is used due to size dependent deposition in the USP inlet and actuator mouthpiece. Vapor pressure was shown to explain only part of the differences in the size of the atomized droplets for various formulations. Theoretical and empirical equations were developed that make it possible to predict the residual particle size distribution for solution MDIs.

Optimized dose delivery of the peptide cyclosporine using hydrofluoroalkane-based metered dose inhalers

The goal of this study was to illustrate the potential to deliver relatively high doses of a therapeutic peptide using hydrofluoroalkane (HFA) metered dose inhaler (MDI) drug delivery systems. For the purposes of this study, cyclosporine was used as the model compound. Cyclosporine formulations, varying in peptide concentration, ethanol cosolvent concentration, and propellant type, were evaluated and optimized for product performance. As ethanol concentration was decreased from 10 to 3% by weight, fine particle fraction (the mass of cyclosporine which passes through a 4.7-micron cut point divided by the total mass of cyclosporine delivered ex-valve) increased from 34 to 68% for 227 and 33 to 52% for 134a formulations. Because of the excellent solubility properties of cyclosporine in HFA-based systems, minimal or no ethanol was needed as a cosolvent to achieve cyclosporine concentrations of 1.5% w/w. With these formulations, it was possible to obtain a fine particle mass (mass of particles <4.7 microns) greater than 500 microg per actuation. In addition, one formulation was chosen for stability analysis: 0.09% w/w cyclosporine, 10% w/w ethanol, 134a. Three different types of container closure systems (stainless steel, aluminum, and epoxy-coated canisters) and two storage configurations (upright and inverted) were evaluated. Cyclosporine was determined to be stable in HFA 134a-based MDI systems, regardless of container closure system and configuration, over a 2-year period. Cyclosporine represents a compelling example of how significant peptide doses are attainable through the use of solution-based MDIs. It has been shown that through formulation optimization, 2-3 mg of the peptide, cyclosporine, may be delivered in five actuations to the lung for local or systemic therapy.

Comparison of the TSI Model 3306 Impactor Inlet with the Andersen Cascade Impactor: Solution Metered Dose Inhalers

The product performance of a series of solution Metered Dose Inhalers (MDIs) were evaluated using the TSI Model 3306 Impactor Inlet and the Andersen Cascade Impactor (ACI). The goal of the study was to test whether the fine particle and coarse particle depositions obtained using the Model 3306 were comparable to those results obtained by ACI testing. The analysis using the Model 3306 was performed as supplied by the manufacturer as well as with 20 cm and 40 cm vertical extensions that were inserted between the Model 3306 and the USP Inlet. Nine different solution formulations were evaluated. The drug concentrations ranged from 0.08 to 0.8% w/w and the ethanol cosolvent concentration varied between 5 and 20% w/w. In general, it was found that good correlations between the two instruments were obtained. However, for formulations containing 10-20% w/w ethanol it is shown that an extension fitted to the Model 3306 yielded an improved correlation to those obtained from the ACI.