• Baseline-to-peak Physician Withdrawal Checklist change score during taper off Alprazolam [ Time Frame: Week 24 (taper baseline), Weeks 25-29, and end of taper visit ] [ Designated as safety issue: No ]
• The incidence of treatment-emergent adverse events during 6 months of treatment with alprazolam XR [ Time Frame: Weeks 6, 8, 12, 16, 20, and 24 ] [ Designated as safety issue: No ]
• Endpoint change from baseline in Digit Symbol-Coding Test, immediate recall, and delayed recall [ Time Frame: Week 24 ] [ Designated as safety issue: No ]

• Endpoint change from baseline in Hamilton Anxiety Rating scale [ Time Frame: Weeks 12 and 24 ] [ Designated as safety issue: No ]
• Endpoint change compared with baseline in the Panic Disorder Severity Scale - Adolescent Version total and item scores [ Time Frame: Weeks 12 an 24 ] [ Designated as safety issue: No ]
• Endpoint compared with baseline for Clinical Global Impression (CGI)-Improvement scale [ Time Frame: Weeks 12 and 24 ] [ Designated as safety issue: No ]
• Endpoint change compared with baseline in CGI-Severity score [ Time Frame: Weeks 12 and 24 ] [ Designated as safety issue: No ]
• Endpoint compared with baseline in Pediatric Quality of Life, Enjoyment, and Satisfaction Questionnaire improvement score [ Time Frame: Weeks 12 and 24 ] [ Designated as safety issue: No ]
• Descriptive estimates of the persistence of safety events and adverse events [ Time Frame: Week 24 ] [ Designated as safety issue: No ]

The purpose of this study is to evaluate the long-term (6-month) efficacy, safety, and tolerability of alprazolam XR in adolescents with panic disorder.

Due to recruitment difficulties in this adolescent population, the clinical program for alprazolam XR was cancelled and this study was terminated on 1 September 2004. There were no safety concerns that led to this decision.

• Other: placebo
• Drug: alprazolam XR

Inclusion Criteria:

• A primary Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision diagnosis of panic disorder with or without agoraphobia based on the Mini-International Neuropsychiatric Interview for Children and Adolescents
• Subjects with an average of 1) at least one 4-symptom panic attack per week over the last 4 weeks before screening; 2) at least one 4-symptom panic attack per week over the last 4 weeks before baseline; and 3) at least one 4-symptom panic attack in the 7 days prior to baseline
• To enter Study A6131007, subjects must have completed Study A6131002, had an acceptable tolerability to study drug, and in the clinical judgment of the investigator, could have benefited from continued study treatment.

Exclusion Criteria:

• Subjects must continue to meet all of the exclusion criteria enumerated in the Acute Efficacy Study (Protocol A6131002) with the following exception: Subjects will be allowed to undergo cognitive-behavioral or other panic-specific therapy and any other psychotherapy (e.g., supportive and/or family therapy) during the expected study period in this study.