Before the long weekend, the Food and Drug Administration approved Johnson & Johnson (NYSE: JNJ) and Bayer's anticoagulant Xarelto, but don't expect firework sales just yet.

The FDA gave Xarelto the OK to treat venous thromboembolism -- formation of blood clots -- in patients undergoing knee- and hip-replacement surgery. It'll have to compete with Sanofi's (NYSE: SNY) well-established Lovenox in that indication. Xarelto is taken orally, but that's not much of an advantage in hospitals, where it's a lot easier for nurses to give patients injectable medications than get them to take pills. Post-discharge, patients would prefer to use an oral drug, but courses of Lovenox only run for a couple of weeks at the most, so it's not like patients have to inject themselves for the rest of their lives.

There's also a generic version of Lovenox from Momenta Pharmaceuticals (Nasdaq: MNTA) and Novartis (NYSE: NVS). Still doctors' prescription decisions will likely be based more on experience and ease of use than price. Until Teva Pharmaceuticals (Nasdaq: TEVA) is able to gain approval for its generic, the price of Momenta's generic will remain close to that of the branded drug.

The real potential for Xarelto lies in a heart-rhythm disorder called atrial fibrillation. The FDA is expected to rule on that indication in November.

The competition in atrial fibrillation isn't any easier, though. Doctors will be happy to ditch the current standard of care -- generic warfarin -- because it's really hard to find the proper dose, but Xarelto will run into new branded competition. Boehringer Ingelheim's Pradaxa is already on the market, and Pfizer (NYSE: PFE) and Bristol-Myers Squibb's (NYSE: BMY) Eliquis has produced data that suggests it's better than Xarelto, although the two weren't compared head-to-head.

All three drugs are taken orally, but Xarelto has the advantage of once-a-day dosing, compared with twice-daily regimens for the other two. Whether that'll be enough to capture some of the atrial fibrillation market despite weaker data remains to be seen.

Of course, Johnson & Johnson and Bayer still need to get the drug approved for atrial fibrillation. Last week's nod should give investors a little confidence that the FDA considers Xarelto's risks manageable -- at least for one indication.

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Fool contributor Brian Orelli holds no position in any company mentioned. Click here to see his holdings and a short bio. The Motley Fool owns shares of Momenta, Teva, and Johnson & Johnson. Motley Fool newsletter services have recommended buying shares of Novartis, Pfizer, Johnson & Johnson, Momenta, and Teva, as well as creating a diagonal call position in Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.