Role of gamma-aminobutyric acid in antipanic drug efficacy.

All effective pharmacologic agents used to treat panic disorder augment gamma-aminobutyric acid (GABA) transmission. Anxiolytics and antidepressants that lack GABA activity are not effective in panic disorder. To test the hypothesis that GABA activity is a component of antipanic drug efficacy, the authors treated nine medication-free panic disorder subjects with oral baclofen (30 mg/day for 4 weeks) in a double-blind, placebo-controlled crossover trial. Baclofen, a selective GABA agonist, was significantly more effective than placebo in reducing the number of panic attacks and scores on the Hamilton anxiety scale, Zung scale, and Katz-R nervousness subscale. The authors discuss possible mechanisms of antipanic drug efficacy.