The wait wasn't pretty, but the final result was. Yesterday, the Food and Drug Administration approved Novo Nordisk's (NYSE:NVO) Victoza after a 10-month wait beyond its PDUFA date.

Better late than never? Maybe not.

Victoza is in the same class as Amylin Pharmaceuticals' (NASDAQ:AMLN) and Eli Lilly's (NYSE:LLY) Byetta, but is injected just once a day, instead of twice a day for Byetta. That's a pretty good advantage -- except that the marketing window is slowly closing. Amylin has developed a once-weekly version of Byetta using Alkermes' (NASDAQ:ALKS) extended-release technology. Assuming it doesn't run into the same long delay Victoza saw, the FDA should be making an announcement about once-weekly Byetta in March.

Needless to say, Novo Nordisk is trying its best to hit the ground running with a launch within weeks, but that may not be enough. Doctors who know that once-weekly Byetta could be just a few months off probably will be less likely to switch patients from twice-daily Byetta to once-daily Victoza now.

Even if once-weekly Byetta gets delayed, Novo Nordisk may have trouble getting new patients onto Victoza. The label says the drug shouldn't be used as a first line treatment, probably because of the thyroid cancer seen in studies done in rats. Twice-daily Byetta, on the other hand, is approved as a first-line treatment. While I'm not convinced that many doctors would prescribe Byetta before trying oral medications developed by Merck (NYSE:MRK), Bristol-Myers Squibb (NYSE:BMY), and others, the FDA's prior approval of Byetta for early use makes it sound safer than Victoza.

At this point, Novo Nordisk's best chance at a victory for Victoza is if once-weekly Byetta gets hung up at the FDA. Or better yet, hung out to dry.

Timing is everything. Except when it's not, says Rex Moore.

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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.