Analysis of the patterns of particle dispersion from a dry powder inhaler
Dry powder inhalers (DPIs) are increasingly being considered for the delivery of pharmaceutical aerosols to the lungs. The administration of disodium cromoglycate delivered by the Spinhaler DPI is one of the oldest examples of this method of drug delivery. The device disperses powder from a capsule by means of a vibrating rotor onto the inspired airflow of the patient. The cohesive and adhesive forces of interaction between particles and surfaces may reduce the efficiency of aerosol delivery by a particular mechanism or device, and a description of powder behavior may assist in formulation development and optimization. Vibrations, or oscillations, in the motion of powders may be described in a regime that varies from a completely ordered, periodic, to random behavior. Dispersion of particles as aggregates might be expected to increase or reduce the capacity dimension, depending on the nature of the deviation from the pattern of rotor vibration. This method of analysis - and particularly the use of a single capacity dimension to describe behavior - may prove useful in formulation optimization.