LUNG DEPOSITION FROM THE TURBUHALER(R) IN CHILDREN WITH CYSTIC-FIBROSIS

Drug delivery to patients using dry powder inhalers, such as the Turbu haler(R), is believed to be influenced by the inspiratory flow used. C linical studies have indicated that this delivery system can be used e ffectively by children, However, it is not known how the total and wei ght-corrected dose delivered to the airways varies with age, A deposit ion study using technetium-99m (Tc-99m)-labelled budesonide was perfor med in order to determine the effect of age on delivery. Twenty one ch ildren with cystic fibrosis, aged 4-16 yrs, were recruited, They were clinically stable with normal lung function, Initially, a gamma camera scan was taken in front of a flood source containing 37 MBq of Tc-99m , Subsequently, subjects inhaled through a low resistance inspiratory filter connected to a commercially available Turbuhaler(R). Immediatel y afterwards they inhaled from a noncommercial Turbuhaler(R) containin g budesonide labelled with Tc-99m, and then underwent anterior and pos terior gamma camera scans. Both Turbuhaler(R) inhalers were attached t o a portable spirometer and the peak inspiratory flow through the Turb uhaler(R) was recorded for each inhalation, The total body dose was ca lculated from the dose deposited on the inspiratory filter connected t o the commercial Turbuhaler(R). Analysis of the gamma camera images pr ovided information on the proportion of the radiolabel delivered to th e lungs compared to that deposited in the upper airway and stomach. As expected, a highly significant positive correlation was noted between the peak inspiratory flow generated by the patient through the Turbuh aler(R) and the dose delivered to the lung, Similarly, there was a hig hly significant positive correlation between age and ''total lung dose '', However, when total lung dose was corrected for body weight, there was a nonsignificant negative correlation with age. This study sugges ts that the ''weight corrected lung dose'' achieved when children aged >6 yrs use the Turbuhaler(R), is largely independent of age, It would appear that the flow-dependent properties of this device are such tha t the reduced peak inspiratory flow generated by younger children resu lts in a lower dose to the lungs, but that this is off-set by their lo wer body weight, This is unlikely to be a property of other devices wi th different flow/drug delivery characteristics.