Many large-cap pharmaceutical companies have touted "double-digit" earnings per share (EPS) growth this quarter -- but upon closer examinations of the income statement, this growth has often come only through share buybacks, not organic sales growth or cost-cutting measures. So I was pleasantly surprised when I saw that AstraZeneca's (NYSE:AZN) third-quarter results, announced earlier today, included organically grown EPS expansion.

Revenues were up 13% (with two percentage points of that due to exchange rates), to $6.5 billion for the quarter, on the back of strong sales growth for AstraZeneca's top three products.

Sales*

Y-O-Y Growth

Nexium

$1280

13%

Seroquel

$848

19%

Crestor

$536

62%
*in millions

Seroquel sales in particular should remain strong going forward, since its prescription trends remain robust. It just received approval in the U.S. to treat additional complications caused by bipolar disorder a week ago, and an improved formulation of the drug is awaiting regulatory response in the EU. Crestor has a lot of sales mileage left in it as well, as the drug penetrates new markets like Japan.

Operating margins expanded in the quarter to check in at a robust 32%, thanks to well-controlled SG&A costs, which only grew by 6%. The combination of improved margins and higher sales led to 29% higher earnings of $1.6 billion, or $1.01 a share.

Given how AstraZeneca's share price plunged today -- down almost 8% as I write -- you wouldn't know that it had such positive earnings for the quarter. Investors' dismal reaction to AstraZeneca was prompted by the company's announcement of the failure of a phase 3 trial for drug candidate NXY-059, which had blockbuster potential to treat certain types of strokes. Partner Renovis (NASDAQ:RNVS) was crushed on the news, falling more than 70%.

AstraZeneca's quarter also suffered from a failed phase 3 study testing the cancer drug Iressa in head and neck cancer. This was not nearly the loss that NXY-059 was, because Iressa is already approved. The drug has only brought in $170 million in sales for the year, and it already faced much better competition in this space.

Share price declines like today's can sometimes be ideal buying opportunities for pharmaceutical investors. Clinical trial failures are a fact of life for any pharmaceutical company as large as AstraZeneca, and there's no way every drug in the company's pipeline will succeed. Even with this failed trial, AstraZeneca still makes a fine investment, with its strong sales growth, earnings guidance of $3.85 to $3.95 per share for the year, and multiple opportunities for label expansions of many of its top drugs.

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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 .