Coexisting asthma and allergic rhinitis (AR) are often treated with both intranasal and inhaled corticosteroids. This study investigated whether intranasal ciclesonide 200 microg once daily has an additional effect on cortisol suppression when coadministered with inhaled hydrofluoroalkane-beclomethasone dipropionate (HFA-BDP). Adult patients (n = 150) with perennial AR received HFA-BDP 320 microg twice daily and placebo once daily during a run-in period. Patients were then randomized to ciclesonide or placebo and HFA-BDP (43 days). A single 2-mg dose of dexamethasone was administered on the last treatment day. Plasma cortisol decreased by 67.8 microg x h/dL (p < 0.001) during the run-in period. When ciclesonide was added, the change in mean plasma cortisol was similar for ciclesonide and placebo (8.5 microg x h/dL and 1.0 microg x h/dL, respectively). Dexamethasone decreased mean plasma cortisol (p < 0.001), demonstrating that further cortisol suppression was possible. This study suggests that intranasal ciclesonide can be used with an inhaled corticosteroid without increased cortisol suppression.