A number of studies were presented the American Psychiatric Association’s annual meeting last week that showed the safety and efficacy of a new antidepressant, desvenlafaxine, which may be marketed under the brand name, Pristiq.

Although I don’t have access to the main efficacy study at the moment, I did look it up on Medline and saw a few items that caught my eye in the abstract of this study.

Treatment was given to four groups of patients (N ~= 115 per group), three of which were various dosing levels of desvenlafaxine (100, 200 and 400 mg/day), and one was given placebo.

The 200 mg/day treatment group is the black sheep in the results:

CGI-I and Montgomery-Asberg Depression Rating Scale results were significant for all groups; CGI-S results were significant with 100 mg/day and 400 mg/day.

The CGI-S measures the severity of illness, so for the 200 mg/day group, the illness remained as severe as pre-treatment. And here’s why:

Response rates were significantly greater for desvenlafaxine 100 mg/day (51%) and 400 mg/day (48%) versus placebo (35%; p = .017 and p = .046, respectively); the response rate for desvenlafaxine 200 mg/day was 45% (p = .142).

Response rates are great for the 100 and 400 mg/day groups, but not so much for the 200 mg/day group. Interesting.

And there’s always that placebo response rate to highlight — 35% of people respond positively to a sugar pill while being treated for depression.

Visual Analog Scale-Pain Intensity results were significant for desvenlafaxine 100 mg/day versus placebo (p = .002), but not for the higher doses.

This scale measures the self-reported intensity of pain by subjects in the study. Pain appears to still be an issue for the 100 mg/day group.

I’ll get a copy of the study to see if the authors have an explanation as to why the 200 mg/day group stood out in this manner.

But it looks like Pristiq (desvenlafaxine) is on track for FDA approval this year.

Followup: Folks representing Wyeth were kind enough to let me know that although this study was just published last month, it is based upon fairly old data (the study was conducted from Nov. 2003-2004). They are forwarding me some of the studies presented at APA this past week to review more recent data on this new antidepressant.

Reference: DeMartinis NA, Yeung PP, Entsuah R, Manley AL. (2007). A double-blind, placebo-controlled study of the efficacy and safety of desvenlafaxine succinate in the treatment of major depressive disorder. J Clin Psychiatry. 2007 May;68(5):677-88.

Dr. John Grohol is the founder & CEO of Psych Central. He is an author, researcher and expert in mental health online, and has been writing about online behavior, mental health and psychology issues -- as well as the intersection of technology and human behavior -- since 1992. Dr. Grohol sits on the editorial board of the journal Cyberpsychology, Behavior and Social Networking and is a founding board member and treasurer of the Society for Participatory Medicine.

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    Last reviewed: By John M. Grohol, Psy.D. on 1 Jun 2007
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