Early carbon dioxide challenge test may predict clinical response in panic disorder.

We examined whether responses to the carbon dioxide (CO(2)) challenge test were correlated with clinical response. Thirty-four panic disorder patients participated in a CO(2) test after 1 h, 2 weeks and 6 weeks of treatment with clonazepam (2 mg/day) or placebo. The clonazepam group had significantly fewer panic attacks in response to the CO(2) test and the test may predict clinical response.