Metal versus plastic spacers: an in vitro and in vivo comparison

Physical characterization of component particles included in dry powder inhalers. II. Dynamic characteristics

Characteristics of particles included in dry powder inhalers is extended from our previous report (in this journal) to include properties related to their dynamic performance. The performance of dry powder aerosols for pulmonary delivery is known to depend on fluidization and dispersion which reflects particle interactions in static powder beds. Since the solid state, surface/interfacial chemistry and static bulk properties were assessed previously, it remains to describe dynamic performance with a view to interpreting the integrated database. These studies result in complex data matrices from which correlations between specific properties and performance may be deduced. Lactose particles were characterized in terms of their dynamic flow, powder and aerosol electrostatics, and aerodynamic performance with respect to albuterol aerosol dispersion. There were clear correlations between flow properties and aerosol dispersion that would allow selection of lactose particles for formulation. Moreover, these properties can be related to data reported earlier on the morphological and surface properties of the carrier lactose particles. The proposed series of analytical approaches to the evaluation of powders for inclusion in aerosol products has merit and may be the basis for screening and ultimately predicting particle performance with a view to formulation optimization.

Effect of Oropharyngeal Length in Drug Lung Delivery via Suspension Pressurized Metered Dose Inhalers

PURPOSE

To determine the effect of the oropharyngeal length in adults on the lung dose of a suspension pressurized metered dose inhaler, and whether employing small volume spacers can alter this role.

METHODS

Depositions of Ventolin Evohaler (100) microg in the oropharyngeal models of two healthy adult subjects with 17.1 cm (short cast) and 19.9 cm (long cast) centerline lengths via three small volume spacers [two spacers with 3 cm effective length but one with 6.5 cm2 (L3) and the other with 24.6 cm2 (L3W) cross sections, and the Optimiser] were studied.

RESULTS

Without using spacers, lung dose of the long cast (19.52 +/- 2.32 microg, mean +/- standard deviation) was significantly larger than that for the short cast (8.08 +/- 1.01 microg, p < 0.006). However, using the L3 spacer with the short cast made the lung dose (18.59 +/- 3.33 microg) similar to that for the long cast alone. Lung doses of the short cast (20.43 +/- 1.42 microg) and the long cast (30.81 +/- 1.84 microg) with the L3W spacer were similar to those with the L3 spacer. However, using the Optimiser spacer increased the lung dose for the short cast (22.27 +/- 6.03 microg) and significantly for the long cast (35.61 +/- 2.19 microg, p < 0.006) compared to those for the L3 spacer. Using spacers increased drug deposition in the oropharynx part of the short cast, and this reduced the lung dose compared to that for the long cast.

CONCLUSION

The oropharyngeal length in adults may affect the lung dose via the pMDIs, which may not be eliminated by using small volume spacers.

An investigation into the predictive value of cascade impactor results for side effects of inhaled salbutamol

The aim of this study was to compare the Multistage Liquid Impinger (MSLI) and the Andersen Cascade Impactor (ACI) with respect to their power to predict differences in side effects of salbutamol delivered by a dry powder inhaler. Three preparations with the same nominal dose and the same inhaler device but generating aerosols with different aerodynamic particle size distributions were administered to six healthy volunteers in a randomized, placebo-controlled, four-way crossover study. Cumulative doses from 400 up to 1600 microg were given. The serum potassium level (K+-serum) and the heart rate (HR) were measured at baseline and 15 min after each dose. Both the MSLI and ACI showed large differences between the aerodynamic particle size distributions of the three preparations. The decrease in K+-serum revealed significant differences between the three active preparations and was significant for doses of 800 microg and higher. The HR results showed differences between the active preparations only at a nominal dose of 1600 microg and only for the preparation with the highest fine particle dose (FPD) compared to the other two preparations. The K+-serum appears to be a more sensitive measure for side effects than the HR. In vivo-in vitro correlations (IVIVCs) were established between the amounts of salbutamol deposited on the various cumulative impactor stages and the K+-serum. The best IVIVCs were obtained in the FPD range, resulting in correlation coefficients of at least 0.78. It is concluded that cascade impactor results in the FPD range of the MSLI as well as the ACI correlate well with the K+-serum. Cascade impactor analysis thus provides a clinically meaningful tool in the development and the quality control of salbutamol inhalation powders.