One down, one to go for sanofi-aventis (NYSE:SNY).

Yesterday the company passed the FDA advisory panel review of its treatment for atrial fibrillation -- which interferes with contraction of the heart's upper chambers -- with a ten-to-three vote recommending approval of the drug. The committee said that the drug, Multaq, shouldn't be given to patients with severe heart failure, but that was to be expected. Multaq was rejected by the FDA in 2006 after a trial showed that patients in that category were more likely to die if given the drug than a placebo.

Still, even selling to a reduced population would be good for sanofi-aventis. Given the panel's concerns that patients with severe heart failure might be prescribed the drug, it seems possible that the FDA might not make a positive decision before the drug's PDUFA date of April 30. Unless sanofi-aventis covered all its bases with its Risk Evaluation and Mitigation Strategy (REMS) -- a company's plan to curtail off-label use -- it should probably expect a letter asking for a more compressive REMS, as the agency has done with Genzyme (NASDAQ:GENZ) and Eli Lilly (NYSE:LLY) recently. Maybe sanofi will even make a preemptive strike as Adolor (NASDAQ:ADLR) and GlaxoSmithKline (NYSE:GSK) did to get Entereg past the FDA after an advisory panel was similarly worried about off-label use.

Now that it's done with its panel, sanofi-aventis gets to be a spectator today, while the same FDA panel recommends the fate of a competitor of its blockbuster blood thinner, Lovenox. The panel is reviewing Johnson & Johnson (NYSE:JNJ) and Bayer's Xarelto, which, if approved, could cut into Lovenox's $3.7 billion a year in sales.

FDA advisory panels can be nerve-wracking for companies and their investors, but it looks like sanofi-aventis skirted by just fine yesterday and could even get some good news today if the panel is worried about side effects of Xarelto.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool's disclosure policy is like our REMS for you.