R. Entsuah et al., EARLY-ONSET OF ANTIDEPRESSANT ACTION OF VENLAFAXINE - PATTERN-ANALYSIS IN INTENT-TO-TREAT PATIENTS, Clinical therapeutics, 20(3), 1998, pp. 517-526
Pattern analysis has been used to distinguish between the true effect
of an antidepressant and a placebo effect. The placebo effect constitu
tes clinical improvement that is attributable to the caregiver, treatm
ent setting, or placebo substance. Pattern analysis allows identificat
ion of patients who have early persistent responses, delayed persisten
t responses, or no responses to a drug. In our study, we used this met
hod to assess the onset and persistence of antidepressant activity of
high daily doses of venlafaxine. Our analysis considered scores on the
Global Improvement item of the Clinical Global Impressions scale for
intent-to-treat patients in two double-masked, placebo-controlled stud
ies of at least 6 weeks' duration. Dosages in both studies were rapidl
y titrated upward so patients received at least 200 mg/d within the fi
rst week of treatment. Improvement within the first 2 weeks was consid
ered early, and improvement not followed by a relapse through the sche
duled end of treatment was considered persistent. Significantly greate
r percentages of patients in the venlafaxine group (27% and 20% in stu
dy 1 and study 2, respectively) than in the placebo group (9% and 2.%,
respectively) had a clinically meaningful drug response within the fi
rst 2 weeks of treatment. This early response persisted for the durati
on of each trial. We concluded that venlafaxine in dosages of at least
200 mg/d demonstrates an early and persistent onset of efficacy compa
red with placebo.