OBJECTIVES: Guanfacine is a centrally-acting alpha-2 adrenoceptor agonist available in immediate (GIR) and extended release (GXR) formulations.  GIR is FDA-approved for hypertension, but is prescribed off-label for ADHD. GXR is US approved for symptomatic treatment of pediatric ADHD as mono- or adjunctive therapy.  No outcomes study has compared the two formulations. This study descriptively compares treatment patterns, resource utilization, and cost, between children and adolescents with ADHD initiating treatment with GIR versus GXR. METHODS: Patients, aged 6-17, with ≥ 1 claim for GIR or GXR from November 1, 2009-December 30, 2010 were identified from a large US commercial medical and pharmacy claims database. Patients had ≥ 1 primary diagnosis of ADHD (ICD-9 codes: 314.00, 314.01) during the baseline period, no prior guanfacine use or hypertension diagnosis, and continuous eligibility for 6-months pre- and post-guanfacine initiation. Patient characteristics, resource utilization and costs were descriptively compared using Chi-square and student t-tests. Treatment patterns were compared using Log-rank test.  RESULTS: The GIR and GXR cohorts included 743 and 2,344 patients, respectively. At baseline, patients initiating GIR had significantly more adjunctive therapy use (59.1% versus 54.6%, p=0.03), higher total health care costs ($4250 vs. $3384), and utilization (≥ 1 hospitalization [8.6% vs. 4.6%], ≥ 1 emergency room visit [17.2% vs. 14.0%]) than GXR initiators (all p<0.05). After 6-months, GIR patients switched or discontinued ADHD treatment more than GXR (21.3% vs. 12.8%; 73.5% vs. 53.7%, respectively (all p<0.01)).  Health care utilization remained significantly greater for GIR patients (≥ 1 hospitalization [5.4% vs. 3.8%]; p=0.05; ≥ 1 emergency room visit [16.0% vs. 12.5%]; p=0.02), while total health care costs ($4214 vs. $3934, P=0.41) were equivalent.  CONCLUSIONS:  Preliminary findings indicate children and adolescents may have higher rates of discontinuation/switching, and resource utilization when treated with GIR than GXR; costs were not different.  Further adjusted analyses are underway comparing outcomes between the two drugs.