Sj. Donovan et al., DURATION OF ANTIDEPRESSANT TRIALS - CLINICAL AND RESEARCH IMPLICATIONS, Journal of clinical psychopharmacology, 14(1), 1994, pp. 64-66
The objective of our study was to demonstrate that additional antidepr
essant benefit occurs between weeks 4 and 6 in adult outpatients, even
when dose is not increased. Response between weeks 4 and 6 was studie
d among depressed outpatients randomly assigned to imipramine, phenelz
ine, or placebo under double-blind conditions. Patients were selected
for analysis only if they did not have a dose increase after the start
of the fourth week of treatment (day 22). Eighty-eight patients met t
his condition. Conditional probability analysis was performed. Nonresp
onders to 4 weeks (28 days) of treatment had a significantly greater L
ikelihood of responding by week 6 if they were on phenelzine rather th
an placebo. The same is probably true for patients on imipramine. In r
esearch and clinical care, 4 weeks is too short a trial of phenelzine
to conclude a lack of efficacy. Four weeks is probably also too short
a trial of imipramine.