Investors pumped up shares of Andrx Group (NASDAQ:ADRX) Monday, after the company said it filed an ANDA for its generic version of AstraZeneca's (NYSE:AZN) angina and hypertension drug. Andrx shares rose about 5%, hit a new 52-week high, and surpassed their average daily trading volume by noon. But if the enthusiasm is based on that news alone, it appears a bit premature.

By filing the ANDA (Abbreviated New Drug Application), which tests a generic candidate to make sure it is bioequivalent to the original medication, Andrx hopes to get the fast track to offer a 50-mg version of the drug, known as Toprol-XL. Last year, AstraZeneca garnered $409.1 million in revenues for Toprol-XL at that dosage level -- and obviously, Andrx wants a bite of those sales. And of course, we all know that cardiovascular disease -- which includes both angina and hypertension, or high blood pressure -- is the top killer in the U.S.

According to its press announcement, Andrx believes it would be the first to file an ANDA for the generic version, which would give it 180 days of exclusivity for its version of the drug.

Regardless of all the hope, Andrx has not yet garnered FDA approval. Adding to the mix, AstraZeneca's filed a patent lawsuit against the company last week that could, of course, pose a major hurdle to marketing the generic version -- even if the FDA does give the green light.

Anyone who's been following Andrx knows the company is currently involved in several such patent entanglements. For example, another high-profile litigation involves Andrx's plans for Valproate, a generic version of Abbott Laboratories' (NYSE:ABT) medication for manic episodes, seizures, and migraines.

While the growth potential is there, in this case, it seems a little early for the excitement. Patent litigation is a great way to delay a generic drug's launch, and while it's the way of the world for generic drug makers, it adds a little more uncertainty for Andrx's revenue growth at this time.

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Alyce Lomax does not own shares of any of the companies mentioned. She welcomes your feedback via email.