Normally, a drugmaker's stock goes down after the FDA denies it marketing rights for a new treatment -- but not when it raises earnings guidance in the same press release, apparently. Witness shares of Adams Respiratory Therapeutics (NASDAQ:ARXT), which have risen more than 8% this week.

On Monday, Adams announced that the FDA had issued it an approvable letter for a drug combining its already-approved Mucinex cough relief tablets and a low dose of the opioid Codeine. In the approvable letter, the FDA asked for extra data on the use of this combination product with food, as well as labeling questions.

This approval delay could take more than a year to rectify, if it requires new food interaction studies and a class 2 resubmission review. Luckily for investors, Adams guided that the setback would not affect its fiscal 2008 financial guidance.

Perhaps in order to prove the minimal impact that this FDA decision would have on its operations, Adams also raised its guidance for fiscal 2008 earnings per share. The company now expects sales at the high end of its previous $400 million to $440 million guidance, and it projects that EPS may top the previously expected $1.75 for the full fiscal year.

Adams also forecasted diluted EPS to grow to at least 30% in fiscal 2009, which would bring earnings to around $2.28 a share in fiscal 2009. That would leave Adams trading at a forward 2009 P/E of only 19, despite its rapid growth.

The past six months have been great for Adams. In May, the FDA declared that cold and cough medicines marketed by 20 different companies with the same active ingredient as Mucinex would have to be taken off shelves, since they were being sold without formal FDA regulatory approval. Perrigo (NASDAQ:PRGO) responded to this by filing an application in September to market a generic version of Mucinex; Adams has countered by filing a patent infringement case against Perrigo.

Those green monsters on the Mucinex advertisements are helping Adams to compete well against other cough and cold drugs from much larger companies such as Wyeth (NYSE:WYE) and Pfizer (NYSE:PFE). Retail sales of Mucinex were approximately $120 million in trailing 12 months ended last August, according to Perrigo. As long as the FDA doesn't allow any similar chest-congestion relievers on the market, Adams will continue to benefit from its direct-competition-free marketing position.

So while the FDA may hinder the Mucinex-codeine combination, it's also helping Adams fend off Mucinex competitors. Talk about a love-hate relationship.

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