Long-term evaluation of paroxetine, clomipramine and placebo in panic disorder. Collaborative Paroxetine Panic Study Investigators.

Paroxetine has been shown to be effective in panic disorder in three 10- to 12-week studies. This trial studied the longer term effects of paroxetine in patients with DSM-III-R defined panic disorder. Patients who satisfactorily completed a 12-week, double-blind, placebo-controlled study of paroxetine and clomipramine could choose to continue receiving their randomized treatment for a further 36 weeks. Efficacy assessments included the daily panic attack diary, the Clinical Global Impression Scale, the Hamilton Anxiety Rating Scale, the Marks Sheehan Phobia Scale and the Sheehan Disability Scale. In total, 176 patients were included in the intention-to-treat population. The number of full panic attacks decreased in all three groups during the 12-week study, and improvements continued with long-term therapy. Paroxetine was statistically significantly more effective than placebo throughout the long-term study with respect to reduction from baseline of full panic attacks, and at the end of treatment with respect to the proportion of patients who eventually experienced no panic attacks. There were no significant differences between paroxetine and clomipramine. The proportion of patients who withdrew from the study due to adverse effects was greater in the clomipramine group (19%) than in either the paroxetine group (7%) or the placebo group (9%). Paroxetine was significantly more effective than placebo and as effective as (but better tolerated than) clomipramine in the long-term treatment of panic disorder. Not only was efficacy maintained, but continued improvement was also seen, indicating the importance of long-term treatment in patients with panic disorder.