Size analysis of a pressurized metered dose inhaler-delivered solution formulation by an Aerosizer-LD time-of-flight aerosol particle size spectrometer

Relationship Between Geometric and Aerodynamic Particle Size Distributions in the Formulation of Solution and Suspension Metered-Dose Inhalers

The relationship between the geometric particle size distribution (GPSD) and the aerodynamic particle size distribution (APSD) of commercial solution and suspension metered-dose inhaler (MDI) formulations was assessed to clarify the use of GPSD to estimate the APSD. The size distribution of particles discharged from four suspension and four solution MDIs was measured using the Inas®100 light-scattering spectrometer and a Next Generation Impactor. The conversion factor was calculated by measuring the GPSD and APSD of MDIs. The morphology and physical properties of MDIs were studied using scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Six of the eight MDIs showed similar conversion factor profiles, irrespective of their composition and formulation types. Applying the conversion factor obtained from one of the six MDIs resulted in a particle size distribution comparable to each APSD except for some formulations. The two other solution MDIs, which contained citric acid, had much higher and variable conversion factors. SEM images and DSC scans of the solids obtained by nebulization of the solutions containing beclomethasone and/or citric acid showed the formation of a paste-like amorphous solid. These results indicated that APSD of solution and suspension MDIs that form rigid particles may be estimated by using the conversion factor and GPSD. Contrarily, the estimation is more difficult in formulations that tend to lose the particle structure during the measurement.

The nanoscale in pulmonary delivery. Part 2: formulation platforms

This article is the second part of a review on the nanoscale in pulmonary drug delivery. Specifically it summarises and analyses the potential of the different inhalation delivery routes: nebulisers, dry powder inhalers, pressurised metered-dose inhalers, for the delivery of nanoparticles or nanodroplets. Few products and experimental studies have managed to fully exploit the nanoscale in inhalation delivery, although some may unknowingly benefit from it. Nebulisers are the most advanced in using the nanoscale, pressurised metered-dose inhalers require further developments to realise its full potential, and dry powder inhalers are specifically in need of a dry solid nanoparticle generation technique to make it a reality.

Efficacy of beclomethasone dipropionate HFA 200 microg once daily in chronic obstructive pulmonary disease and bronchial asthma

The efficacy and safety of once-daily beclomethasone dipropionate (BDP; 200 microg), in combination with the propellant hydrofluoroalkane-134a (HFA) was compared with that of budesonide turbuhaler (BUD-TH) 400 microg twice daily and fluticasone propionate inhaler (FP-IH) 250 microg twice daily in 40 patients with bronchial asthma or chronic obstructive pulmonary disease. All patients had used inhaled corticosteroids for at least 1 month. On randomization, 20 patients were switched to HFA-BDP and 20 patients remained on their existing BUD-TH or FP-IH treatment. After 8 weeks, HFA-BDP demonstrated a greater improvement in spirometric values, respiratory symptoms and beta2-agonist use. No significant local adverse effects were observed. Blood cortisol levels remained in the normal range in both groups. We conclude that HFA-BDP (200 microg once-daily) offered more benefit in terms of clinical and spirometry indices than BUD-TH (400 microg twice daily) or FP-IH (250 microg twice daily) in patients with moderate asthma and chronic obstructive pulmonary disease.

Pharmacokinetic and pharmacodynamic properties of inhaled beclometasone dipropionate delivered via hydrofluoroalkane-containing devices

Inhaled corticosteroids have a key role in the treatment of asthma and chronic obstructive pulmonary disease. In recent times, beclometasone dipropionate has been reformulated in pressurised metered dose inhalers (pMDIs), using hydrofluoroalkanes (HFAs) as a propellant. Extensive toxicological testing has shown that HFA-propellants are well tolerated. Among the reformulated beclometasone dipropionate-containing pMDIs, only the characteristics of the two Qvar formulations have been thoroughly explored. Compared to the reference beclometasone dipropionate formulation, the mass median aerodynamic diameter of the Qvar formulations are substantially smaller (1.1 vs 4.0 microm), whereas that of Modulite averages 2.6 microm. Scintigraphic and pharmacokinetic studies indicate a higher lung deposition for both the Qvar and the Beclazone formulations, compared with reference beclometasone dipropionate formulation. Since the 2- to 3-fold increase in pulmonary deposition results in a 2.6- to 3-fold difference in relative efficacy for Qvar, half the dose of the reference beclometasone dipropionate formulation has been currently recommended in adult patients with asthma, a recommendation that is supported by a large number of clinical trials. Conversely, the design of the studies conducted to compare the efficacy of Qvar with fluticasone propionate and budesonide does not allow establishing their equivalence on a milligram per milligram basis. Good studies on the bioequivalence between the reference beclometasone dipropionate formulation and the Modulite or Beclazone formulations are not available.

Sub-Micrometer Particle Production by Pressurized Metered Dose Inhalers

Evidence from both the air pollution and inhaled aerosol therapy fields suggests that the physiological impact of fine and ultrafine aerosols (defined as those below 1000 and 100 nm aerodynamic diameter, respectively) may be greater than their mass or volume of active agent alone might suggest. Traditionally, Andersen impactors and liquid impingers have been used for the sizing of particles produced by pressurized metered dose inhalers (pMDIs). However, these fail adequately to size particles in the ultrafine range (<100 nm aerodynamic diameter). In this paper, we report on a method of sizing pMDI particles down to 10 nm, using an electrical low pressure impactor (size range 30 nm to 10 microm) and a scanning mobility particle sizer (size range 3-150 nm). A range of pMDI drug formulations were assessed, including Flixotide (HFA-fluticasone propionate, GSK [Glaxo Smith Klein]), Salbulin (HFA-salbutamol sulphate, 3M), Qvar (HFA-beclomethasone dipropionate, 3M), Ventolin (HFA-salbutamol sulphate, GSK), Atrovent Forte (CFC-ipratropium bromide, Boehringer Ingelheim), Becotide (CFC-beclomethasone dipropionate, GSK), Pulmicort (CFC-budesonide, Astra Zeneca), and Serevent (CFC-Salmeterol xinafoate, GSK). All devices yielded high numbers of fine and ultrafine particles, with number median aerodynamic diameters (NMAD) of Qvar 68 nm, Becotide 73 nm, Salbulin 85 nm, and Pulmicort 89 nm, and %<100 nm Qvar 76%, Becotide 65%, Salbulin 61%, and Pulmicort 60%. We found a general trend of HFA-propelled pMDIs to produce smaller particles than the CFC units, but this trend was not statistically significant. These findings support previous published work, which suggests that significant bioactivity of pMDIs may reside in the ultrafine fraction.

Evaluation of the Malvern Spraytec® with inhalation cell for the measurement of particle size distribution from metered dose inhalers

The purpose of this study was to evaluate the Malvern Spraytec with inhalation cell attachment as a means of analyzing the particle size distribution of aerosols from pressurized metered dose inhalers (pMDIs). The aerosol particle size distribution of various commercially available, placebo, and experimental pMDI formulations was determined using Spraytec under various experimental conditions and the relevant data were compared with the Andersen cascade impactor data. The Spraytec volume median diameter (Dv 50) values for commercial chlorofluorocarbon- and hydrofluoroalkane (HFA)-based pMDIs were respectively smaller and higher compared with their reported mass median aerodynamic diameter values. It was possible to obtain a close agreement between Spraytec Dv 50 and the reported mass median aerodynamic diameter values for a solution-type pMDI formulation, Qvar 50, by equilibrating the pMDI to 55 degrees C before the measurement and using a 20-cm throat extension. Incorporation of a nonvolatile solvent propylene glycol (PG) in placebo pMDIs (15% w/w ethanol, 0.5-20.0% w/w PG in HFA 134a) showed an increase in Dv 50 with increasing concentration of PG. Furthermore, it was possible to obtain a correlation (R(2) = 0.8037) between Spraytec and Andersen cascade impactor data for the experimental nimesulide-pMDI formulations containing 0.1% w/w drug, 0.25-10% w/w PG, and 15% ethanol in HFA 134a.

Aerodynamic particle size analysis of aerosols from pressurized metered-dose inhalers: comparison of Andersen 8-stage cascade impactor, next generation pharmaceutical impactor, and model 3321 Aerodynamic Particle Sizer aerosol spectrometer

The purpose of this research was to compare three different methods for the aerodynamic assessment of (1) chloroflurocarbon (CFC)--fluticasone propionate (Flovent), (2) CFC-sodium cromoglycate (Intal), and (3) hydrofluoroalkane (HFA)--beclomethasone dipropionate (Qvar) delivered by pressurized metered dose inhaler. Particle size distributions were compared determining mass median aerodynamic diameter (MMAD), geometric standard deviation (GSD), and fine particle fraction <4.7 microm aerodynamic diameter (FPF(<4.7 microm)). Next Generation Pharmaceutical Impactor (NGI)-size distributions for Flovent comprised finer particles than determined by Andersen 8-stage impactor (ACI) (MMAD = 2.0 +/- 0.05 micro m [NGI]; 2.8 +/- 0.07 microm [ACI]); however, FPF(<4.7 microm) by both impactors was in the narrow range 88% to 93%. Size distribution agreement for Intal was better (MMAD = 4.3 +/- 0.19 microm (NGI), 4.2 +/- 0.13 microm (ACI), with FPF(<4.7 microm) ranging from 52% to 60%. The Aerodynamic Particle Sizer (APS) undersized aerosols produced with either formulation (MMAD = 1.8 +/- 0.07 micro m and 3.2 +/- 0.02 micro m for Flovent and Intal, respectively), but values of FPF(<4.7 microm)from the single-stage impactor (SSI) located at the inlet to the APS (82.9% +/- 2.1% [Flovent], 46.4% +/- 2.4% [Intal]) were fairly close to corresponding data from the multi-stage impactors. APS-measured size distributions for Qvar (MMAD = 1.0 +/- 0.03 micro m; FPF(<4.7 micro m)= 96.4% +/- 2.5%), were in fair agreement with both NGI (MMAD = 0.9 +/- 0.03 micro m; FPF(<4.7 microm)= 96.7% +/- 0.7%), and ACI (MMAD = 1.2 +/- 0.02 microm, FPF(<4.7 microm)= 98% +/- 0.5%), but FPF(<4.7 microm) from the SSI (67.1% +/- 4.1%) was lower than expected, based on equivalent data obtained by the other techniques. Particle bounce, incomplete evaporation of volatile constituents and the presence of surfactant particles are factors that may be responsible for discrepancies between the techniques.

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

The ability of the Model 3320 and newer Model 3321 Aerodynamic Particle Sizer Spectrometer (APS) to make accurate mass-weighted size distribution measurements of solution metered dose inhalers (MDIs) was evaluated. Measurements of experimental HFA-134a beclomethasone dipropionate MDIs were made with both the APS 3320 and APS 3321 and compared to the Andersen Cascade Impactor (ACI). The mass-weighted size distribution measurements from the ACI and APS 3321 agreed well but were very different than the APS 3320 measurements. Evaluation of the APS 3320 size distribution measurements indicated that the presence of a few erroneous particle measurements caused a gross overestimation of the mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD). When a previously described technique was used to eliminate erroneous particle size measurements from the size distribution calculation, the MMAD and GSD from the APS 3320 agreed well with those from the ACI and APS 3321. The GSD from the APS 3321 and the APS 3320 after a mask was applied were slightly larger than from the ACI. It is believed that both APS instruments slightly underestimate the GSD while the ACI slightly overestimates the GSD. Further experiments were conducted using the APS 3321 to examine the influence of drug concentration and cosolvent level on the size distribution of solution formulation MDIs. The MMAD was shown experimentally and theoretically to be proportional to drug concentration to the one-third power. Cosolvent concentration had minimal influence on MMAD over the range examined. The measurements reported in this paper demonstrate that it is possible to obtain accurate mass-weighted size distribution measurements with the APS 3320 and APS 3321. These instruments allow for accurate size distribution measurements to be made in minutes as opposed to the hours required to conduct and analyze size distribution measurements from cascade impactors.