The Effect of Active Pharmaceutical Ingredients on Aerosol Electrostatic Charges from Pressurized Metered Dose Inhalers.

Purpose:  This study investigated the effect of different active pharmaceutical ingredients (API) on aerosol electrostatic charges and aerosol performances for pressurised metered dose inhalers (pMDIs) using both insulating and conducting actuators.

Methods : Five solution-based pMDIs containing different API ingredients include beclomethasone dipropionate (BDP), budesonide (BUD), flunisolide (FS), salbutamol base (SB) and ipratropium bromide (IPBr) were prepared using pressure filled technique. Actuator blocks made from nylon, polytetrafluoroethylene (PTFE) and aluminum were manufactured with 0.3 mm nominal orifice diameter and cone nozzle shape. Aerosol electrostatics for each pMDI formulation and actuator were evaluated using electrical low-pressure impactor (ELPI) and the drug depositions were analysed using high performance liquid chromatography (HPLC).

Results : All three actuator materials showed the same net charge trend across the five active drug ingredients, with BDP, BUD and FS showing positive net charges ranging from 134.78 ± 127.29 pC to 332.74 ± 86.74 pC for both nylon and PTFE actuators. While SB and IPBr having significantly negative net charges across all three different actuators, which correlates to the ionic functional groups presented in the drug molecule structures.

Conclusions:  The API present in a pMDI has a dominant effect on the electrostatic properties of the formulation, overcoming the charge effect arising from the actuator materials. The results have shown that the electrostatic charges for a solution-based pMDI could be related to the interactions of the chemical ingredients and change in the work function for the overall formulation.