Dose–response studies of fluticasone propionate and budesonide: Classification based on asthma severity

There are discrepancies in the results of dose–response studies of inhaled steroids. Although some studies show a dose–response relationship, others show no change in outcome with increasing the dose of inhaled steroids. These discrepancies are partly caused by the heterogeneity of dose–response studies. One area of heterogeneity is the subjects' level of asthma severity at baseline. The objective of this study was to classify dose–response studies of two widely used inhaled steroids for asthma, fluticasone propionate (FP), and budesonide (BUD), according to the subjects' level of asthma severity at baseline. A PubMed search, limited to the English language and human subjects, was conducted from January of 1983 to January of 2004, using "dose response and budesonide" (331 articles) and "dose–response and fluticasone" (211 articles). Bibliographies of selected articles were searched for more references. Articles with at least two doses of the same inhaled steroid and one objective marker of asthma were included, resulting in 29 articles for FP and 32 articles for BUD. Studies vary widely in their assessment and reporting of indicators of asthma severity and control at baseline but could be classified according to the level of steroid use at baseline as an indicator of asthma severity. Studies with all or some patients on oral steroids at baseline consistently showed a dose response. Although heterogeneity of dose–response studies make their classification and interpretation difficult, a dose response was consistently noted when all or some patients were on oral steroids at baseline.