Alprazolam, imipramine and placebo treatment of panic disorder: predicting therapeutic response.

Factors that predicted the outcome of drug treatment (alprazolam or imipramine) of panic disorder were studied in a sample of 123 Scandinavian patients participating in a multicenter placebo-controlled 8-week trial. The attrition rate was 95% for alprazolam, 73% for imipramine and 46% for placebo. For the intention-to-treat and 3-week-completer samples, drugs and anxiety symptoms at baseline were the best predictors of improvement on the Global Improvement Scale and on symptom scales focusing on panic attacks, phobic behavior and anticipatory anxiety. For completers of the 8-week trial, only baseline scores predicted outcome. Generally, more severe symptoms at baseline predicted a worse outcome. A subsample of patients had a marked placebo response. Avoidance, sex, age, childhood psychopathology and previous treatment experience had no or only a weak impact on the outcome. The relationship between panic disorder and mood disorder is presented elsewhere.