The impact of electrostatic charge in pharmaceutical powders with specific focus on inhalation-powders

The aim of this work is to give an overview about the literature available on the topic of electrostatic charge in pharmaceutical powders. The main focus is on powders used in dry powder inhaler devices. Pharmaceutical powders mainly consist of fine particles of electrical insulating materials. On the one hand, the insulating properties disfavor electrostatic charge dissipation. On the other hand, small particle sizes in general result in high cohesive forces in relation to gravitational forces. For these reasons the powder may show very cohesive characteristics. In order to overcome the problems associated with cohesivity and deposit the active pharmaceutical ingredient in the deeper regions of the lung, it is important to understand how electrostatic charge is acquired and by which factors acquisition is influenced. The work includes an overview about different operations in pharmaceutical process engineering in which charge may be introduced and the associated influencing process variables. Furthermore related topics like the utilization of electrostatic charge for improving lung deposition of powders intended for pulmonary drug delivery are reviewed. To complete the overview several static and dynamic measuring procedures for net charge and charge distribution are presented and compared. (C) 2011 Elsevier Ltd. All rights reserved.