Systemic Bioavailability and Potency of High-Dose Inhaled Corticosteroids: Cortisol level
The elevated mean cortisol level for the group (652 nmol/L) reflects the inclusion of three subjects taking the combined oral contraceptive pill, which may increase levels of steroid binding proteins and therefore elevate cortisol levels. These subjects had cortisol levels of 1,470, 1,327, and 1,310 nmol/L with little variation between the values on the two placebo days. Their cortisol levels suppressed in a similar manner to the other subjects. The remaining 13 subjects had a mean serum cortisol level of 486 nmol/L. The data were reanalyzed for the 13 subjects who were not taking oral contraception, and the results were unaffected. inhalers for asthma
Devices that provide high lung deposition will be more effective in controlling asthma but more likely to cause systemic side effects such as adrenal suppression. The two devices in our study that produced the most suppression of 9:00 am cortisol levels were MDI alone and Turbohaler dry powder device. Four milligrams of budesonide given by MDI alone produced a 73% fall in 9:00 am cortisol level, and this was reduced to 43% by the addition of a large volume spacer. Conflicting evidence is available on the effect of spacer devices on systemic bioavailability. Toogood et al reported a nonsignificant increase in suppression of the HPA axis by the addition of a spacer to an MDI, whereas other authors found the opposite effect. In the present study, less adrenal suppression was seen when inhaled budes-onide was given through a large volume spacer. Normal subjects with good inhaler technique and absence of bronchospasm may achieve optimal delivery to the lung using MDI alone. Asthmatic subjects with poor inhaler technique and bronchos-pasm, however, may obtain better lung deposition using a spacer (and possibly greater systemic side effects).