An Open-Label Study of Tiagabine in Panic Disorder

γ-aminobutyric acid (GABA) has been implicated in the pathophysiology of anxiety disorders, including panic. Tiagabine, a selective GABA reuptake inhibitor (SGRI), has been shown to reduce symptoms of anxiety. This pilot study evaluated the efficacy and safety of tiagabine in patients with panic disorder. Male and female outpatients aged 18-64 years with a DSM-IV diagnosis of severe to moderately severe panic disorder (with or without agoraphobia) received open-label tiagabine 2-20 mg/day for 10 weeks. Outcome assessments included the Sheehan Panic Disorder Scale (SPS), Panic Disorder Severity Scale (PDSS), Bandelow Panic and Agoraphobia Scale (PAS), Hamilton Rating Scale for Anxiety (HAM-A), 21-point Clinician Global Improvement Scale (CGI-21), 21-point Patient Global Improvement (PGI-21) and the Sheehan Disability Scale (SDS). Scores were recorded at baseline and weekly intervals thereafter. Adverse events were monitored throughout the study. Of the 28 patients who enrolled in the study, 23 had one post-baseline visit and were available for LOCF outcome analysis. Although statistically significant reductions from baseline were observed for all of the outcome measures, the percentage improvements on individual scales were only in the 25-32% range which is not clinically significant. Tiagabine was generally well tolerated; the most common adverse events were nausea, dizziness and headaches. Only one patient discontinued tiagabine due to adverse events. These findings suggest that administration of tiagabine may be of little benefit in patients with panic disorder.