Effect of Spacers on the Bipolar Electrostatic Charge Properties of Metered Dose Inhaler Aerosols-A Case Study With Tilade®.

Aerosols emitted from metered dose inhalers (MDIs) are generally electrically charged and bipolar in nature. Although a spacer can effectively dampen the charge magnitude of aerosols, the electrostatic interactions between the positively and negatively charged particles and the spacer have not yet been characterized separately. The Bipolar Charge Analyzer (BOLAR) was employed to investigate interactions between the spacer and the charged aerosols. Three individual actuations of Tilade® MDI were introduced without a spacer and through an antistatic AeroChamber Plus® Z Stat®, an uncoated and a detergent-coated AeroChamber Plus® spacer into the BOLAR at 60 L/min. Charge and mass profiles were determined. The surface potential of spacers followed the order of uncoated > detergent-coated > antistatic spacer. The spacers had minimal impact on the positively charged particles but the charge magnitude of the negatively charged particles was in the opposite order as the spacer surface potential. The charge-to-mass ratio of particles had little alteration for all measurements. Negatively charged particles had a higher tendency to deposit on the spacer walls, possibly due to their higher abundance in the confined spacer volume. The bipolar data may prove useful for designing better MDIs and spacers and modelling lung deposition of charged aerosol particles.

Applicability of Bipolar Charge Analyzer (BOLAR) in Characterizing the Bipolar Electrostatic Charge Profile of Commercial Metered Dose Inhalers (MDIs).

PURPOSE: To investigate the applicability of Bipolar Charge Analyzer (BOLAR), a new commercial instrument developed by Dekati Ltd., in simultaneously characterizing the bipolar electrostatic charge profile and measuring the size distribution of commercial metered dose inhalers (MDIs). METHODS: Intal Forte(®) (sodium cromoglycate), Tilade(®) (nedocromil sodium), Ventolin(®) (salbutamol sulphate), and QVAR(®) (beclomethasone dipropionate) were used as model MDIs in this study. Three individual actuations of each MDI were introduced into the BOLAR at an air flow rate of 60 l/min. Charge and mass profiles for each actuation were determined. RESULTS: The BOLAR was found to have better performance in collecting valid charge data (≥80%) than valid mass data (≥50%). In all tested products, both positively and negatively charged particles were found in five defined size fractions between zero and 11.6 µm, with the charge magnitude decreased with increasing particle size. The net charge profiles obtained from the BOLAR qualitatively agreed with the results reported previously. In all suspension type MDIs, negligible masses were detected in the smallest size fraction (<0.95 µm), for which the charge was most likely caused by the propellant and excipients. QVAR was the only solution MDI tested and the charge and mass profiles were significantly different from the suspension-type MDIs. Its mass profile was found to follow closely with the charge profile. CONCLUSIONS: Positively and negatively charged MDI particles of different size fractions and their corresponding charge-to-mass profiles were successfully characterized by the BOLAR.