Top 5 Reasons to Forget about Pristiq — (Carlat Psychiatry Blog)

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The Carlat Psychiatry Blog   Keeping Psychiatry Honest Since 2007

Daniel J. Carlat

Saturday, March 1, 2008

Yesterday, the FDA gave official approval to Wyeth’s antidepressant Prisiq. Here are the top 5 reasons for doctors to keep it off their prescription pads.

1. It’s a blatant patent extender. Effexor XR, which brought in $3.8 billion for Wyeth in 2007, is losing patent protection this year, and Wyeth is introducing desvenlafaxine, which is simply Effexor’s main metabolite, as a “novel antidepressant.” There’s nothing novel about it. Every patient who takes Effexor produces Pristiq in their own body, at no additional charge.

2. It’s not very effective. In the studies released so far, Pristiq just barely squeaks by placebo on the Hamilton Depression scale. In the U.S. study, Pristiq decreased the HamD by only 2 points (-11.5 vs. -9.5 for placebo), and in the European study, the differences was 2.5 points. And for the higher 100 mg dose, there was no difference between drug and placebo for U.S. patients.

3. It is not more easily dosed than Effexor XR. The main Wyeth marketing point for Pristiq is that patients can get better by taking the beginning dose of 50 mg, eliminating the need for a complicated upward dose titration process. Sorry, but this is not different from Effexor. If you look at one of the original fixed-dose studies of Effexor, comparing patients taking 75 mg, 225 mg, or 375 mg, you’ll find that the 75 mg dose separated from placebo as well as Pristiq’s 50 mg. Psychiatrists typically begin Effexor at either 37.5 or 75 mg/day. At least with Effexor XR, when you keep increasing the dose, efficacy improves, meaning it actually has an efficacy advantage over Pristiq, because when you increase the dose of Pristiq, you lose efficacy, according to the U.S. study data.

4. It has no meaningful metabolic advantages. Wyeth will highlight the fact that Pristiq is not metabolized by the P-450 system and therefore does not have any drug-drug interactions. Well, guess what, Effexor has no clinically meaningful drug-drug interactions either.

5. Wyeth’s own lead investigator is unimpressed. I spoke briefly with Dr. Michael Liebowitz, the Columbia University psychiatrist who led the major Pristiq trials. Pristiq, he said, “is another SNRI–it is not a revolutionary drug.” It may be more tolerable at the starting 50 mg dose, he said, but only time will tell if it truly is clinically useful. “If it is useful, then it will make money for the company, and if it is not, it won’t.”