Old standbys led the way for AstraZeneca (NYSE:AZN) in the first quarter: Stronger sales of Nexium, Seroquel, and Toprol all helped boost performance.

That led to sales climbing 9% on a constant-currency basis, to about $5.7 billion. Within that number, U.S. sales climbed 10%, and the company's management estimated that true underlying growth in the U.S. was more on the order of 17% once adjustments to wholesaler inventory were stripped out. Although I'm not going to cotton to this shell-game financial philosophy, sales in the U.S. were certainly nothing to be embarrassed about in the first quarter.

As I mentioned, sales growth was led largely by the usual suspects. Nexium grew about 11% (though only about 3% in the U.S.) to $1.06 billion and constituted about 18% of total sales. Seroquel (up 39% to $633 million), Arimidex (up 49%), Symbicort (up 23%), and Seloken/Toprol (up 21%) were also all strong contributors to AstraZeneca's success in the first quarter.

The company also got a welcome reprieve with respect to Crestor. The FDA denied a petition from the non-profit Public Citizen's Health Research Group asking the agency to order Crestor removed from the market as a result of safety concerns. In rejecting the petition, the FDA reaffirmed its belief that Crestor is safe and efficacious.

That said, this lisn't ikely to be the end of the Crestor story. Sales were up more than 100% in the first quarter, but it's unlikely that critics are going to stop speaking out against Crestor simply because the FDA didn't do as they wanted. What's more, Pfizer's (NYSE:PFE) Lipitor and Schering-Plough (NYSE:SGP)/ Merck's (NYSE:MRK) Vytorin are both strong competitors in the space that will continue to pressure Crestor.

As I've said before, AstraZeneca's near-term pipeline of new drugs is pretty weak. While the company has interesting compounds for stroke, ulcers, cancer, and diabetes, none of those are likely to see approval before 2007 (and that's assuming the clinical data stays positive and warrants approval). What's more, the company will face generic competition for Toprol in a couple of years and could face generic competition and/or patent challenges for Nexium and Seroquel as well.

Although growth could stagnate in a couple of years, AstraZeneca is posting good earnings growth today and the company does have promising new drugs under development. With a reasonable relative valuation and a decent dividend, investors focused more on the long-term might want to think about holding on to AstraZeneca even if the short-term road gets a little rocky in a few years.

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Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).