Dry powder inhaler (DPI) product performance may be influenced by the build-up of electrostatic on the inhaler. This study considered how electrostatic present on a DPI could affect performance, together with the practical challenges of assessing this in a laboratory environment.
Assessing the effect of an electrostatic charge on an inhaler during use poses several challenges. These include; dissipation of charge through handling of the inhaler, accurate measurement of charge present during assessment, practicality of rubbing an inhaler with a specific material to generate a charge, and variability of charges generated by rubbing.
The use of an electrostatic charging unit in applying a charge directly to an inhaler enables application of a consistent charge to a precise location. Applying the charge during evacuation of the dose provides certainty that a charge is present and not dissipated during assessment.
An electrostatic charge was applied to the Vectura Lever Operated Multidose Inhaler (LOMI) using a charging unit during the evacuation of doses, for the assessment of the particle size distribution of emitted dose (PSDED) and potential drug build-up within the inhaler. The effect of -1 kV and +1 kV charges were assessed, and compared against controls where no charge was applied. Electrostatic charges between -1 kV and +1 kV that may build up on the LOMI during patient handling were shown to have no significant impact on PSDED or inhaler drug build-up.
A process to directly apply a known electrostatic charge to a specific location on an inhaler was identified. This was used to assess the effect of electrostatic build-up on the Vectura Lever Operated Multidose Inhaler. Build-up of electrostatic charge on the LOMI has no significant effect on drug delivery performance.