Imipramine is Effective in Preventing Relapse in Electroconvulsive Therapy-responsive Depressed Inpatients with Prior Pharmacotherapy Treatment Failure: a Randomized, Placebo-controlled Trial

Objective: To compare the efficacy of imipramine versus placebo in preventing relapse after successful electroconvulsive therapy (ECT) in depressive inpatients with pharmacotherapy treatment failure prior to ECT.

Method: During a 6-month period, the incidence of relapse was assessed. Two centers, both inpatient units for treatment of depressed patients, participated in this trial. Patients with DSM-IV-diagnosed major depressive disorder resistant to an anti-depressant and subsequent lithium addition and/or a monoamine oxidase inhibitor were included. Patients were randomly assigned to double-blind treatment with imipramine with adequate plasma levels (N=12) or placebo (N=15) after successful ECT. The mean imipramine dosage was 209 mg/day (standard deviation: 91.7, range: 75-325 mg/day). The main outcome measure was relapse defined as at least "moderately worse" compared with baseline score on the Clinical Global Impressions-Improvement scale. Treatments were compared with survival analysis using the Cox proportional hazards model, including psychotic features and the score on the Hamilton Rating Scale for Depression (HAM-D) at baseline as prespecified covariables. Patients were enrolled in the study from April 1997 to July 2001.

Results: In the placebo group, 80% (12/15) of the patients relapsed compared with 18% (2/11) in the imipramine group. The Cox regression analysis showed a significant reduction in the risk of relapse of 85.6% with imipramine compared to placebo (p=.007; 95% confidence interval [CI]=24.6% to 97.2%) adjusted for the covariables. There was an 18% increase in the relapse rate (p=.032; 95% CI=2% to 36%) per unit increase in HAM-D score before the start of the trial; psychotic features had no significant effect (p=.794).

Conclusions: Depressed patients with pharmacotherapy treatment failure may benefit from the prophylactic effect of the same class of drug during maintenance therapy after response to ECT.