Dynamic electrostatic charge of lactose-salbutamol sulphate powder blends dispersed from a Cyclohaler®

Electrostatic forces have been claimed to be a mechanism for aerosol deposition in the lungs. However, the extent of its influence on aerosol performance is not clear, particularly for carrier-drug formulations.

To prepare lactose-salbutamol powder blends, varying in blend ratio, and identify any relationships between salbutamol dose, electrostatic characteristics and in vitro aerosol performance.

Decanted lactose and micronized salbutamol sulfate was mixed to produce five blends (equivalent to 50, 100, 200, 300 and 400 µg salbutamol per 33 mg of powder). 33 ± 1 mg of a blend was loaded into a Cyclohaler™ and dispersed into the electrical Next Generation Impactor (eNGI) at an air flow rate of 60 L/min. This was conducted in triplicate for all five lactose-salbutamol blends.

Fine particle fraction increased with salbutamol dose, from 5.89 ± 1.42 to 21.35 ± 2.91%. Specific charge (charge divided by mass) distributions for each blend were greatest in magnitude for the 50 µg blend and similar in magnitude between all other blends. However, in eNGI Stage 1 (>8.06 µm), specific charge decreased from 100 µg (-170.4 ± 45.8 pC/µg) to 400 µg (-10.0 ± 9.1 pC/µg).

The improvement in fine particle fraction with increased salbutamol dose was indicative of fine drug binding to high and low energy sites on the lactose carrier surface. This finding was supported by electrostatic charge results, but the aerosol charge itself was not found to influence aerosol performance by electrostatic forces.