Maintenance drug therapy of panic disorder.

The efficacy of tricyclics and benzodiazepines in the short term (approximately 2-4 months) treatment of panic disorder is well demonstrated, but efficacy over the longer term is not considered established. The present study provided systematic data from a double blind comparison of maintenance therapy (up to 8 months) of panic disorder with or without agoraphobia with alprazolam, imipramine, or placebo in 181 patients who had responded to the same regimen in a randomized 8-week treatment trial. All three groups had improved during the first 2 months (active treatments more than placebo and about equal to each other), and all maintained or extended their improvement over the next 6 months without any significant change in dose. More than twice as many alprazolam and imipramine than placebo patients (15%) remained in treatment for the full 8 months and did slightly better on symptom measures than the remaining placebo patients. Both medications were well tolerated during the maintenance period. The data suggest sustained efficacy and safety of imipramine and alprazolam over an extended period. More specifically, they suggest that tolerance does not develop to the therapeutic effects of either drug.