ABSTRACT. Objective. To study the systemic activity of inhaled steroids in young children.Methods. Forty children with mild asthma aged 1 to 3 years were studied in a 3-way crossover, randomized, placebo-controlled, double-blind trial. Treatment with inhaled fluticasone propionate, 200 g twice daily delivered via pressurized metered-dose inhaler (pMDI) and Babyhaler (FP400), was compared with budesonide, 200 g twice daily delivered via pMDI and NebuChamber (BUD400), and to placebo. The Babyhaler was primed before use. Knemometry was used to detect systemic steroid activity. It was performed with a handheld knemometer after 1 and 4 weeks of treatment. The increase in lower-leg length within this 3-week period was used as the outcome measure. The intention-to-treat population was analyzed by analysis of variance.Results. The increases in the lower-leg length during placebo, BUD400, and FP400 treatments were 85, 45, and 34 m/d, respectively (adjusted mean). The growth in lower-leg length was significantly reduced from both steroid treatments. The difference between BUD400 and placebo was ؊40 m/d (n ؍ 25; 95% confidence interval [CI]: ؊8 to ؊72). The difference between FP400 and placebo was ؊51 m/d (n ؍ 26; 95% CI: ؊19 to ؊83). The difference between FP and BUD was ؊11 m/d and was not statistically significant (n ؍ 28; 95% CI: 20 to ؊42).Conclusion. FP and BUD are both systemically active in children 1 to 3 years old when administered for 4 weeks from their dedicated spacer devices in daily doses of 400 g with no difference between the 2 steroid regimens. These findings call for studies of clinical side effects from these treatments of preschool children. Pediatrics 2002;109(3). URL: http://www.pediatrics.org/ cgi/content/full/109/3/e40; inhaled corticosteroid, young child, knemometry, side effects, systemic effects.ABBREVIATIONS. ICS, inhaled corticosteroids; BUD, budesonide; FP, fluticasone propionate; pMDI, pressurized metereddose inhaler; RCT, randomized, controlled trial; Plac, placebo. I nhaled corticosteroids (ICS) are effective treatments for asthma in young children. Budesonide (BUD) and fluticasone propionate (FP) administered from pressurized metered-dose inhalers (pMDIs) and spacer devices have shown beneficial clinical improvements in 0-to 3-year-old children with asthma in randomized, controlled trials (RCTs) of health outcomes, 1-4 lung function and bronchial hyperreactivity, 5 and measurements of the inflammatory marker nitric oxide in exhaled air. 6 Therefore, the Global Initiative on Asthma International Guidelines recommend using ICS as controller treatment in young children with asthma with persistent symptoms. 7 Side effects are of concern for any chronic drug therapy in pediatrics, especially ICS. 8 Recent reassuring data have suggested that long-term treatment of schoolchildren with inhaled BUD for an average of 9 years does not affect final height. 9 However, some aspects of the assessment of safety are unique to preschool children, including the rapid growth velocity and somewhat dif...