Electrostatics and inhaled medications: influence on delivery via pressurized metered-dose inhalers and add-on devices.

The movement of inhaler-generated aerosols is significantly influenced by electrostatic charge on the particles and on adjacent surfaces. Particle charging arises in the aerosol formation process. Since almost all inhalers contain nonconducting components, these surfaces can also acquire charge during manufacture and use. Spacers and valved holding chambers used with pressurized metered-dose inhalers to treat obstructive lung diseases are particularly prone to this behavior, which increases variability in the amount of medication available for inhalation, and this is exacerbated by low ambient humidity. This may result in inconsistent medication delivery. Conditioning the device by washing it with a conductive surfactant (detergent) or using devices made of charge-dissipative/conducting materials can mitigate electrostatic charge. This review discusses sources of electrostatic charge, the processes that influence aerosol behavior, methods to mitigate electrostatic charge, and potential clinical implications.