Teva Pharmaceutical (Nasdaq: TEVA) and Amphastar Pharmaceuticals won a court case yesterday, but there's no need to break out the confetti and champagne. The court cleared the way for the duo to produce a generic version of a drug that treats blood clots, but the FDA hasn't yet OK'd it for sale. The timing could cost the companies millions of dollars.

The win for Teva and Amphastar was another loss for Sanofi-Aventis (NYSE: SNY), which wanted the court to uphold a key patent on its blockbuster drug Lovenox. The drug is rather complicated, and the FDA has demanded additional information from generic-drug makers interested in making knockoff versions.

In exchange for proving that a patent is invalid, the FDA awards a generic-drug maker an exclusive selling period of 180 days. Unfortunately for Teva and Amphastar, that clock will start in about six to eight weeks, regardless of whether the FDA has given approval. So, further delay by the FDA would cut into the competition-free period.

The court decision couldn't have come quickly enough for Novartis (NYSE: NVS) and Momenta Pharmaceuticals (Nasdaq: MNTA), which are also working on a generic version of Lovenox. These two companies recently heard back from the FDA about what they need to do to get their Abbreviated New Drug Application approved, and are planning to resubmit the application in the third quarter. Novartis has said that it typically takes three months to get approval of a resubmission, but Momenta is being a little more cautious, saying that it could take longer. Given that it took more than two years to hear back from the FDA the first time, I'd say a little caution is definitely in order. Because the two likely can't start selling their drug until next year, thanks to the exclusivity period, a decision before then won't help them much.

The patent lawsuit and the launches for Lovenox have been as complex as the drug itself. Don't be surprised if there's another wrinkle before a generic version finally gets approved.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.