Now that Wyeth Pharmaceutical's patent for the antidepressant Effexor is running out, the company is in the awkward position of having to argue that there is something better out there. And that superior something happens to be another drug developed by Wyeth— Pristiq. In 2010, any company will be able to produce a cheap generic copy of Effexor, but Wyeth claims that their new drug, which has just been approved by the FDA, is an improvement worth billions.
Pristiq is a serotonin-norepinephrine reuptake inhibiter (SNRI), just like Effexor. While most antidepressants modulate only serotonin levels, Pristiq affects both serotonin and norepinephrine. In January, we ran a piece by Dr. William Hapworth disputing the advantage of this double neurotransmitter targeting. He pointed out that the 2001 British study so heavily leaned on by Wyeth was dubious, but that the more severe withdrawal effects of Effexor are certain.
The New York Times cites the opinion of multiple experts, including pharmaceutical analyst Dr. Timothy Anderson, that Pristiq is not a substantial improvement over existing antidepressants. While the chemical formula is quite similar, it would be unfair to say that Pristiq has no advantages at all over its predecessor. The company press release claims that Pristiq does not require gradual ramping up to ideal dosage, meaning that patients can immediately begin taking the full dose and may (note: may) see faster results. This can be crucial, as many patients must try multiple drugs before they find a lifeline out of their depression, a search that can take many painful weeks. The second purported advantage of Pristiq is that it delivers the main metabolite of Effexor (venlafaxine HCl) in an already active state without having to pass through the liver. This may prevent many undesirable drug-drug interactions.
We will have to wait to see whether Pristiq offers a noticeable upgrade of Effexor, or at least a way to avoid the terrible withdrawal. The FDA gave its approval based on four 8-week double-blind studies, but as we pointed out last week, the results of antidepressant trials can be easily manipulated through selective reporting. Perhaps learning from its past mistakes, the FDA gave a conditional approval, contingent on Wyeth doing continued research into efficacy and safety issues. This includes a promise to conduct at least one study each of sexual dysfunction, pediatric reaction, dosing differences, and relapse prevention. Hopefully, every result from these studies will be open to public scrutiny. Stay tuned for future updates on this new compound.
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