• Endpoint change from baseline to Week 24 in Digit Symbol-Coding Test, immediate recall, and delayed recall [ Time Frame: 24 weeks ] [ Designated as safety issue: Yes ]
• Baseline-to-peak Physician's Withdrawal Checklist change score during 6-week taper off alprazolam [ Time Frame: 6 week taper ] [ Designated as safety issue: Yes ]
• The incidence of treatment-emergent adverse event during treatment with alprazolam XR [ Time Frame: 24 weeks with taper ] [ Designated as safety issue: Yes ]

• Descriptive estimates of the persistence of safety events and adverse events at study endpoint [ Time Frame: 24 weeks with taper ] [ Designated as safety issue: Yes ]
• Endpoint change from baseline to Week 24 in the Panic Disorder Severity Scale-Adolescent version total and item scores [ Time Frame: 24 weeks ] [ Designated as safety issue: No ]
• Endpoint (Week 24) Clinical Global Impression (CGI)-Improvement score [ Time Frame: 24 weeks ] [ Designated as safety issue: No ]
• Endpoint change from baseline to Week 24 in CGI-Severity score [ Time Frame: 24 weeks ] [ Designated as safety issue: No ]
• Endpoint (Week 24) Pediatric Quality of Life, Enjoyment, and Satisfaction Questionnaire improvement score [ Time Frame: 24 weeks ] [ Designated as safety issue: No ]

The purpose of this study is to assess the long-term safety and tolerability of alprazolam extended release (XR) in adolescents with panic disorder, with or without agoraphobia, or in anxiety disorder with panic attacks. Efficacy, population pharmacokinetics of alprazolam XR and the relationship between alprazolam XR plasma concentrations and efficacy outcomes will also be evaluated.

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.

Inclusion Criteria:

• Subjects must meet one of the following 6 diagnoses: a. A current diagnosis of panic disorder with or without agoraphobia; b. Generalized anxiety disorder with a history of at least one panic attack in the course of their illness; c. Social anxiety disorder (social phobia) with a history of at least one panic attack in the course of their illness; d. Separation anxiety with a history of at least one panic attack in the course of their illness; e. Posttraumatic stress disorder with a history of at least one panic attack in the course of their illness; f. Anxiety not otherwise specified with a history of at least one panic attack in the course of their illness.
• Educational level, intelligence, or other mental condition in the subject and/or his/her parent(s) are judged by the investigator to be sufficient to permit adequate informed consent/assent to be obtained, and for study procedures to be complied with.

Exclusion Criteria:

• Current (in the past 6 months) diagnosis of obsessive compulsive disorder, major depressive disorder, dysthymic disorder, or alcohol and/or substance dependence.
• Current (in the past 3 months) diagnosis of alcohol and/or substance abuse.
• Primary diagnosis of conduct disorder, oppositional defiant disorder, or Attention Deficit Hyperactivity Disorder.
• Any current or past history of schizophrenia or psychosis; bipolar disorder or cyclothymia; dementia, delirium or other organic brain disease; an eating disorder; mental retardation, Asperger's disorder, or any other serious developmental disorder.
• A Childhood Depression Rating Scale, Revised score >35.