Most antidepressant comparisons pitted a selective serotonin reuptake inhibitor antidepressant against a non-SSRI. In one comparative study sponsored by Wyeth-Ayerst, the rate of remission from depression in patients receiving its antidepressant, venlafaxine (Effexor), was compared to that in patients treated with the SSRI paroxetine(Drug information on paroxetine) (Paxil). In another Wyeth-sponsored study, the emergence of suicidal ideation was assessed in patients treated with either venlafaxine or one of several SSRIs.
In the first investigation, pooled original data from studies involving 1,108 patients with depression treated for eight weeks with venlafaxine, paroxetine or placebo were analyzed for achievement of remission, defined as a Hamilton Rating Scale for Depression (HAM-D-17) score of less than 7. The researchers reported a significantly greater remission rate at weeks 6 and 8 with venlafaxine (45%) than paroxetine (38%) and a significantly greater number of patients with an absence of symptoms (HAM-D-17 score of 0). They noted, however, that no significant treatment differences were discerned with the Montgomery-Asberg Depression Rating Scale (MADRS).
In the second study, emergence of suicidal ideation was defined as a change in HAM-D suicide item score at baseline from 0 or 1 to a score of 2 or more. Suicidal ideation was then found in 6%, 9.5% and 13.7%, respectively, of patients receiving venlafaxine, an SSRI or placebo. The differences on both the HAM-D and MADRS suicide items between venlafaxine and the SSRIs, and between venlafaxine and placebo, were significant, as were the differences between SSRIs and placebo.
Mirtazapine (Remeron) was compared with the SSRI sertraline(Drug information on sertraline) (Zoloft) in patients who had not improved with another SSRI. In this study, which was sponsored by Organon, 119 patients were treated for eight weeks with mirtazapine(Drug information on mirtazapine) (mean dose 30.4 mg) and 124 patients with sertraline (mean dose of 120.2 mg). The discontinuation rate due to adverse events was twice as high with mirtaza-pine (18.5%) as sertraline (9.5%). Antidepressant response on day 28, defined as a 50% reduction from baseline of HAM-D score, was demonstrated by 40.3% of patients receiving mirtazapine, compared to 27.4% of those on sertraline. Remission rates, however, were approximately 50% in both groups by day 56. Although this population had previously demonstrated resistance to an SSRI, these results were offered as evidence of earlier onset of action with mirtazapine.
In a retrospective analysis of pooled data from two eight-week trials, the effectiveness of bupropion sustained release (Wellbutrin SR) was compared to that of sertraline for alleviating anxiety symptoms in patients with depression. This GlaxoSmithKline-sponsored assessment determined that the antidepressants were similar in their antidepressant and anxiolytic effects. The researchers concluded, "Selection between these agents cannot be based on anticipation of differential anxiolytic effects."