Plasma concentrations of fluticasone propionate and budesonide following inhalation: effect of induced bronchoconstriction

What is already known about this subject • All inhaled corticosteroids are absorbed into the systemic circulation and hence have the potential to cause adverse systemic effects. • Plasma drug concentrations following inhalation of 1000 µg fluticasone are considerably lower in people with airflow obstruction than in healthy volunteers but this is not the case for budesonide. What this study adds • This is the first study to determine whether changes in airflow obstruction within an individual affect the systemic absorption of inhaled fluticasone and budesonide; • Plasma concentrations of fluticasone and, to a lesser extent, those of budesonide were lower when the drugs were inhaled following induced bronchoconstriction; • The lower plasma concentrations of corticosteroids seen when the drugs were inhaled following induced bronchoconstriction is likely to reflect variations that will occur with fluctuations in airway caliber in asthma. Aims To determine whether and to what extent bronchoconstriction affects plasma concentrations of fluticasone and budesonide following inhalation. Methods Twenty people with mild asthma inhaled 1000 µg fluticasone (Accuhaler®) plus 800 µg budesonide (Turbohaler®) on two visits. On one occasion, prior to drug inhalation, FEV1 was decreased by at least 25% using inhaled methacholine. Plasma drug concentrations were measured for each drug over 5 h and area under the plasma concentration-time curve (AUC(0,5 h)) compared between visits. Results The mean difference in FEV1 prior to drug inhalation on the 2 days was 33%. AUC(0,5 h) values for fluticasone and budesonide were lower by a median of 60% (IQR 36–75) and 29% (IQR 2–44), respectively, when administered following bronchoconstriction; the reduction was greater for fluticasone than for budesonide, P = 0.007. Conclusions The lower plasma concentrations of fluticasone and, to a lesser extent, budesonide seen when the drugs were inhaled following induced bronchoconstriction, is likely to reflect variations that will occur with fluctuations in airway caliber in asthma.