The contribution of different formulation components on the aerosol charge in carrier-based dry powder inhaler systems

Purpose To measure aerosol performance of a lactose carrier/salbutamol sulphate powder blend and identify contributions of non-formulation and formulation components on the resulting aerosol charge.

Methods A 67.5:1 (%w/w) blend of 63–90 μm lactose with salbutamol sulphate, and lactose alone (with and without the blending process), was dispersed from a Cyclohaler™ into the electrical Next Generation Impactor at 30, 60 and 90 L/min. Mass and charge profiles were measured from each dispersion, as a function of impactor stage. The charge profile from an empty capsule in the Cyclohaler™ was also studied.

Results Lactose deposition from the blend was significantly greater, and net charge/mass ratios were smaller, in the pre-separator compared to formulations without drug. Fine particle fraction of salbutamol sulphate increased with flow rate (9.2 ± 2.5% to 14.7 ± 2.7%), but there was no change in net charge/mass ratio. The empty capsule produced a cycle of alternating net positive and negative discharges (∼200 pC to 4 nC).

Conclusions Capsule charge can ionize surrounding air and influence net charge measurements. Detachment of fine drug during aerosolisation may reduce net specific charge and lead to increased lactose deposition in the pre-separator. Increase in FPF may be due to increased force of detachment rather than electrostatic forces.