It was proposed that pre-post regression slopes be used to index treatment response when the effect of baseline scores differed among treatments (interaction between treatment and baseline score). Reanalyses of two studies using
imipramine and
fluoxetine in
panic disorder showed doserelated decreases in pre-post slopes for the frequency of unexpected
panic attacks, but not for the frequency of situational
panic attacks or measures of
agoraphobia. This report presents similar analyses of data from a study using
moclobemide. Patients (N = 452) with
panic disorder were randomized to placebo or a fixed dose of
moclobemide (75, 150, 300, 600, or 900 mg/day). They were treated double-blindly and evaluated at baseline and 1, 2, 3, 4, 6, and 8 weeks later. The authors analyzed the frequency of unexpected and situational
panic attacks compiled from a daily diary, and fear and avoidance ratings based on the patient's main
phobia using baseline (pre) and end-point (post) values for all randomized patients. Adjoining dose groups were combined. Both unexpected and situational
panic attacks showed systematic doserelated suppression of pre-post treatment slopes. Neither pre-post slopes nor adjusted posttreatment means for fear and avoidance differed reliably between treatment arms. This study replicates the authors' earlier findings, except for situational
panic attacks, which probably were not reliably identified.
Antidepressants selectively suppress
panic attacks, especially unexpected attacks, but not
agoraphobia. The findings are consistent with the hypothesis that
panic disorder with
agoraphobia has clinically separable
biologic and cognitive components that respond differentially to treatment.
Antidepressants benefit primarily patients with many unexpected
panic attacks. Investigators should evaluate pre-post treatment slopes before comparing adjusted posttreatment means (analysis of covariance).