Alprazolam blockade of CO2-provoked panic in patients with panic disorder.

The primary aim of this study was to determine if pretreatment with a single dose of alprazolam reduces anxiety and panic provoked by the inhalation of 35% carbon dioxide (CO2) in patients with panic disorder. Ten panic disorder patients participated in a CO2 challenge test after pretreatment with a single dose of alprazolam (1 mg p.o.) or placebo in a randomized, double-blind, within-subjects design. Seventy percent of the subjects had a panic attack with placebo, compared to only 10% with alprazolam. Alprazolam reduced the number and severity of panic symptoms and baseline anxiety significantly more than placebo. This study demonstrates the efficacy of the acute administration of alprazolam to block panic attacks and supports the usefulness of the CO2 challenge as an analogue method to study panic disorder.