Effect of Variable Inspiratory Flow Rate on the Performance of the Budesonide Rhinocort Turbuhaler™

To investigate the effect of variable nasal inspiratory flow rates in vitro on total drug delivery and deposition patterns of budesonide delivered from the Rhinocort Turbuhaler™.

The total dose of budesonide delivered at flow rates of 15, 30 and 60 L/min and the particle size distribution of the delivered drug at flow rates of 28 and 60 L/min were determined at regular intervals throughout the life of six Rhinocort Turbuhalers™, each containing 200 × 100μ,g doses of budesonide. The delivered dose was determined by drawing individual doses of budesonide through separate G0120 Filtrete electrostatic filters. Acascade impactor was used to determine the particle size distribution of the delivered drug.

The amount of budesonide delivered from each Turbuhaler™ device was variable throughout the life of the devices and was dependent on the inspiratory flow rate. Variability was greatest at the lower flow rates and decreased slightly with increasing inspiratory flow rate. Similarly, the particle size distribution of budesonide throughout the cascade impactor was variable and dependent on the flow rate.

This study suggested that the efficiency of the Rhinocort Turbuhaler™ device in the management of allergic rhinitis may be influenced by the severity of nasal symptoms, particularly rhinorrhoea and nasal blockage, which determine the peak nasal inspiratory flow rates in symptomatic individuals.