Study Design:
This study will be a randomised, open-label, single-dose, crossover study in healthy subjects (males and females), performed at a single study centre.
The study will comprise:
* A screening period of maximum 28 days;
* Four treatment periods during which subjects will be resident from the afternoon before dosing with Symbicort until at least 24 hours after dosing; discharged on the morning of Day 2; and
* A final visit within 5 to 7 days after the last administration of Symbicort. There will be a minimum washout period of 3 days between each dose administration of Symbicort. Subjects will receive single doses of Symbicort on 4 occasions under fasted conditions. During screening, spirometry testing will be performed by a technologist or a qualified designee to ensure subjects perform adequate manoeuvres to achieve optimal lung function. Device and inhalation training will be conducted on admission to each treatment period, and prior to dosing on Day 1 of each treatment period.
Duration:
Approximately 7 weeks
Statistical Analysis:
* For total systemic exposure: Treatment B versus Treatment A
* For lung exposure: Treatment D versus Treatment C Treatment ratio will be assessed on the ratio of log-transformed Cmax, AUC0-t and AUC of budesonide and formoterol using a 2-sided 90% confidence interval (CI) approach based on a repeated measures analysis of variance (ANOVA) model including period and treatment as fixed effects, and subject as a random effect. The estimated treatment differences and the 90% CIs on the log scale will be back-transformed to obtain the Gmean ratios for each pair of treatments. The least squares means (and 95% CIs), Gmean ratios and 90% CIs will be tabulated for each comparison and analyte (budesonide and formoterol).
Sample Size:
The sample size is 56 to ensure adequate number of subjects are randomised and at least 44 evaluable subjects complete the study.
Assuming an intra-subject coefficient of variation (CV) of 33% (based on the variability of AUC0-12 for budesonide and AUC0-12 and Cmax for formoterol observed in a similarly designed crossover study in healthy adults), 44 evaluable subjects will give at least 80% power to show that the 90% CI for the treatment effects lies entirely within the range 0.8 to 1.25, i.e., would rule out a 20% change (on a log scale) in exposure to budesonide and formoterol.