Lack of Differences Among Antidepressants
Abstract & Commentary
By Mary Elina Ferris, MD, Clinical Associate Professor, University of Southern California. Dr. Ferris reports no financial relationship to this field of study.
Synopsis: Only minimal differences in efficacy for treatment of major depressive disorders were found when SSRIs and 4 other 2nd generation antidepressants were compared to each other in randomized controlled trials, and almost all of the trials were sponsored by pharmaceutical companies.
Source: Hansen RA, et al. Efficacy and safety of second-generation antidepressants in the treatment of major depressive disorder. Ann Intern Med. 2005:143;415-426.
Forty-six head-to-head randomized trials comparing 6 SSRIs (Citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, setraline) and 4 other 2nd generation antidepressants (bupropion, duloxetine, mirtazapine, venlafaxine) were analyzed to evaluate treatment effectiveness and efficacy, and safety and tolerability. Out of 894 literature citations first identified, the final sample was narrowed to those in primary care settings with general population inclusions and a minimum of 3 months follow-up. Observational studies considered required a minimum of 100 patients for at least one year, and included some placebo-controlled trials.
Most trials reported no difference among SSRIs in efficacy or speed of patient response. In the few trials where statistical differences were reported, these were contradicted by similar trials that showed no difference.
Comparison of SSRIs to the 4 other 2nd generation antidepressants also showed similar efficacy, although there was a suggestion that venlafaxine had a better rate of response in 3 trials funded by pharmaceutical sponsors, and in comparison to fluoxetine. Speed of response suggested mirtazapine had a faster onset of action, but no differences in response rates existed at study end in any of the trials.
Health-related quality-of-life measures also did not differ in any of the comparisons, although sleep quality was rarely assessed. Only 13% of the trials used an assessment scale for adverse events, leading to poor reliability in the other studies. Discontinuation rates and adverse events were similar among all.
Commentary
As the authors conclude in this unbiased article, identifying an appropriate antidepressant for any given patient is difficult. While individual drugs may show some differences on certain scales for speed of onset, response rates and adverse effects, the distinctions were found to be minimal and often contradicted by other studies. They point out, "Finally, evidence-based medicine is only as powerful as the available evidence."
It’s no surprise that pharmaceutical companies have a huge financial interest in studies to promote their products, and it is widely acknowledged that inconclusive studies are less likely to be published. Almost all of the studies identified in this review of the last 25 years were either completely sponsored by, or had one author affiliated with a pharmaceutical company. That certainly reflects on the state of research funding, and unfortunately undermines our reliance on individual articles. Our best hope of accurate future information is either unbiased head-to-head trials using standardized reporting, or at least more articles like this one reviewing the overall results.
Only minimal differences in efficacy for treatment of major depressive disorders were found when SSRIs and 4 other 2nd generation antidepressants were compared to each other in randomized controlled trials, and almost all of the trials were sponsored by pharmaceutical companies.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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