After a quarter of hearing nothing good about its lead diabetes compound, Avandia, British drugmaker GlaxoSmithKline (NYSE:GSK) announced financial results yesterday. Turns out, Avandia wasn't the worst of its problems.

Avandia sales dropped 22% year-over-year in the second quarter, but the drug accounted for less than one-tenth of GSK's revenues. The bigger hit to its top-line growth came from the weakening of the dollar and other currencies versus the pound, which changed a positive 3% revenue gain using constant exchange rates into a 2% revenue shortfall.

Net income was likewise hit by the falling dollar and was virtually flat versus 2006 for the quarter. The huge drop in the dollar against certain currencies has been a problem for a lot of international firms like GSK, which receive a large chunk of sales from the United States. On a constant currency basis, earnings were up 11%.

On the brighter side, with less than a month on the market in the U.S., weight-loss drug Alli scored an amazing $150 million in sales. And human papillomavirus vaccine Cervarix is set to gain full regulatory approval in the European Union later this year.

On Monday, an FDA advisory panel will meet to discuss Avandia. Depending on how the meeting goes, Avandia sales could be headed even lower in the United States. Despite the potential for this decline, GSK is maintaining its earnings per share guidance for the year because the rest of its products "are doing well." Surely its share buyback program, which it is increasing to nearly $25 billion over the next two years, won't hurt it in meeting its earnings per share numbers, either.

With so many moving parts, it's amazing how fixated analysts and the media have become on Avandia. For example, with sales of Alli tracking so high, the drug could easily bring in more than $1 billion in revenue to GSK in less than half a year on the market. This alone would more than make up for the negative sales growth with Avandia. When excessive fears start to bring down shares of a drugmaker with good sales-growth potential over the long run, I see buying opportunity.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has a disclosure policy.