2nd year maintenance and discontinuation of imipramine in panic disorder with agoraphobia

The results from our 1 year placebo-controlled maintenance/discontinuation study in remitted panic disorder with agoraphobia patients confirmed the significant prophylactic effectiveness of imipramine maintenance treatment but suggested that this may be necessary in only 37% of the patients who relapse following discontinuation of 6 months acute imipramine treatment. This paper presents pilot data from a second year extension of the above-mentioned study with the aim of exploring the putative protective effects of maintenance imipramine therapy beyond the 1st year.

Eighteen patients from the 30 who survived, in stable remission, the first 12 months of the maintenance/discontinuation study gave written consent to participate in a double-blind 2nd year extension phase with the knowledge that those on placebo will continue on the same condition (N = 7, PBO-PBO) and those on imipramine (N = 11) will be rerandomized to 2nd year maintenance (N = 4, IMI-IMI) or placebo substitution (N = 7, IMI-PBO). The procedures continued unchanged from that of the 1st year of the study and patients were followed with planned assessments every 2 months over the second 12-month experimental period of the study.

None of the IMI-IMI patients relapsed, two (28.5%) of the IMI-PBO patients relapsed, and two (28.5%) of PBO-PBO patients relapsed. The mean estimated time without relapse was 10 months and 9 months for IMI-PBO and PBO-PBO, respectively. The estimated probability of not relapsing was .64 for IMI-PBO and .60 for PBO-PBO (Mantel-cox test chi2 =.84, p = .77).

These interlocking controlled observations tentatively suggest that a substantial degree of prophylactic efficacy continues and that a substantial need for continued prophylaxis exists beyond the 1st year of maintenance imipramine treatment in panic disorder with agoraphobia patients.