Abstract 6 Adolescent Medicine II Platform, Monday, 5/3

Purpose: To analyze the effectiveness of daily versus weekly iron supplementation in adolescent female cross country runner Methods: 70 female cross country runners (ages 14-18 years) were screened for iron deficiency (ferritin <20mg/dl) before the season. The participants in this 12 week study were randomized to the daily treatment group(648mg FeSO4 qd [130 mg elemental iron/d]) or the weekly group(648mg FeSO4q week [130 mg elemental iron/week]). Repeated measures analysis of variance was used to compare changes in outcome variables over time, with intention to treat analysis used to assess treatment effect of daily versus weekly therapy. Chi-square and Fisher's exact test were used to analyze categorical data. There were no differences between two groups with respect to baseline demographic and hematologic variables (hemoglobin, hematocrit, ferritin, MCV, transferrin saturation) and iron absorption. Iron absorption was determined using thermal ionization mass spectrometry of multiple-trace stable isotope technique using 58Fe at baseline and 57Fe at 6 weeks. The daily group had higher VO2 max at baseline (52.3±4.4 mlO2/kgBW/min) than the weekly group(45.3±6.7 mlO2/kgBW/min, p=.02). Results: Of 30 runners who qualified for the study, 18(9 daily, 9 weekly) completed the study protocol (6 refused to participate after the screening process, 6 [4 daily, 2 weekly, p=.65] were noncompliant[less than 50% of prescribed medication]). Those with side effects from the medication were more likely to be noncompliant(p=.03). Those who were compliant in the daily group had a greater improvement in their serum ferritin concentration(daily 22.2±15.8, weekly 7.0±6.8, p=.01) and final serum ferritin level(daily 35.4±16.2, weekly 17.7±9.3, p=.02). The proportion of group treated successfully (final serum ferritin >20mg/dl) was higher in the daily group (69.2±48.0%) than in the weekly group(36.3±50.4%) (p=0.10). Intention to treat analysis demonstrated the same findings. There was no statistically significant change in aerobic fitness within or between groups. Iron absorption decreased more in the daily group(75%[initially 15.2%±10.5 to 3.8%±4.9]) than the weekly group(55%[initially 28.3%±15.5 to 14.9%±5.7],p=.02). The total amount of elemental iron absorbed per week for the daily group was only 1.8 times the weekly group(daily 35.2±44.8mg, weekly 19.4±7.4mg, p=.67). Conclusions: Decreased iron absorption limits the effectiveness of daily iron therapy in adolescent female runners with iron deficiency. However, daily iron therapy was more effective in treating iron deficiency when compared to weekly therapy, which may improve with optimized dosing and absorption parameters.