British specialty pharmaceutical company Shire (NASDAQ:SHPGY) announced its earnings results Friday after a busy third quarter. Revenues were again strong, thanks in large part to its flagship drug Adderall XR, but the real question for this company is what it can do to keep the growth coming in the long term.

Revenues for the third quarter of 2006 rose 19% year over year to $449 million. After adjusting for one-time events, net income was up 7% for earnings per American Depositary Share of $0.40 for the quarter. Shire also got more specific about its revenue guidance; it's calling for revenues to be 12%-14% higher for all of 2006, from a previously announced "low double-digit" expectation of growth.

Nearly half of Shire's revenues are derived from Adderall XR, which treats attention deficit and hyperactivity disorder (ADHD). So it was a good sign to see Adderall XR prescriptions grow 9%, even with the price increases Shire instituted for the drug. Sales of the drug climbed 25% to $208 million for the quarter.

The other big news event for the quarter was the announcement that Barr Pharmaceuticals (NYSE:BRL) and Shire made an agreement that Barr won't launch a generic version of Adderall XR until April 2009. That eliminates some of the near-term uncertainty about the drug's continued sales growth for Shire.

Shire expects to launch another ADHD drug, now called NRP-104, in the second quarter of 2007. The type of label the drug receives will have an impact on sales and also on how much Shire markets the drug relative to its other ADHD products -- although that's more of an issue for partner New River Pharmaceuticals (NASDAQ:NRPH) than for Shire.

Keep an eye on the May 21, 2007, date for a longer-lasting version of Adderall XR. While follow-on drugs with easier dosing do provide benefits to patients, the real benefit is to Shire as a way to extend its sales for its most important drug.

Shire has a strong near-term future, with an expected approval and launch of four drugs in the upcoming months in Europe and the United States. As it continues to bring new drugs to the market, Shire appears to be keeping its promise to remain a leader in treating certain diseases such as ADHD, which present a large market opportunity.

However, excluding the four drug candidates awaiting regulatory approval, Shire's pipeline is pretty bare, with only one drug in phase 2 trials or later. So Shire will have to do something with its nearly $1 billion in cash or shop itself to be acquired if it wants to ensure its continued long-term success.

Either way, investors should pay attention to how quickly sales grow for Shire's new products awaiting regulatory approval. Shire will need these products to continue revenue growth in the future, especially with the looming generic competition for Adderall XR coming in 2009. For the moment, how well these drugs penetrate their respective markets is the key to Shire's future.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article.