The purpose of this study was to estimate pharmacokinetics, safety, and tolerability of single doses of an extended release formulation of alprazolam (Xanax XR) in adolescent and adult healthy volunteers. This was a randomized, open-label, single-dose, 2-period crossover study. Twelve adolescent healthy volunteers (13-17 years) and 12 adult healthy volunteers (20-45 years) received single doses of Xanax XR 1 mg or 3 mg tablets. Blood samples were obtained predose and for 48 hours postdose. Plasma samples were assayed for alprazolam and its two active metabolites alpha-hydroxy-alprazolam and 4-hydroxy-alprazolam using a validated LC-MS/MS method. Safety assessments included clinical laboratory tests, vital signs, and adverse event monitoring. At both dose levels, mean plasma concentration-time profiles of alprazolam, alpha-hydroxy-alprazolam, and 4-hydroxy-alprazolam were similar in adolescent and adult subjects. The ratios of estimated geometric means for AUC(0-infinity) and Cmax between adolescents and adults for both dose levels were 115% (95% CI: [93, 143]) and 111% (95% CI: [95, 129]), respectively. An assessment of dose proportionality between the 3 mg and 1 mg alprazolam doses within both age groups indicated that the AUC(0-infinity) and Cmax were both within 80-125% equivalence limits. Parent-metabolite ratios were similar in both age groups and were consistent with those previously reported. Alprazolam was well tolerated by both age groups. The most common adverse event was somnolence, which occurred in a dose-related manner. Based on the similar pharmacokinetic profiles, dosing of Xanax XR should be similar in adolescents and adults.