Duration of imipramine therapy and relapse in panic disorder with agoraphobia

It has been suggested that maintenance treatment of patients who have remitted panic disorder with agoraphobia beyond the six months of acute phase imipramine treatment may decrease the risk of relapse. This study further explores the relationship between relapse and duration of imipramine treatment in this population.Fifty-one patients, all in remission at the end of six months acute phase open trial with imipramine 2.25 mg/kg/day and randomized to double-blind maintenance or placebo substitution, discontinued imipramine treatment eventually and were followed over a 12-month risk period: 27 during first year placebo substitution, 7 after 12 months of imipramine maintenance in placebo substitution, and 17 after variable durations of imipramine maintenance in open discontinuation. There were no behaviorally oriented interventions or instructions at any time during the acute and maintenance phases of treatment or during imipramine discontinuation. Duration of imipramine treatment, the method of discontinuation (open versus placebo substitution), or any of the 9 variables from the demographic, clinical, and open treatment domains that were entered in a Cox proportional hazard model did not predict relapse. The rate of relapse after only 6 months of treatment (10 out of 27, 37%) was identical to the rate of relapse after 12 to 30 months of treatment (9 out of 24, 37.5%). The results suggest a lack of specific protective effects beyond prophylaxis and underscore the difficulty in predicting relapse in fully remitted panic disorder with agoraphobia patients. Early detection of relapse in patients who discontinue treatment may be a viable alternative to prediction.