LONDON -- Shares of AstraZeneca (LSE:AZN) (NYSE:AZN) dropped 1% to 3,353 pence during early London trade this morning after the FTSE 100 member reported first-quarter sales falling 13% to $6.4 billion.

AstraZeneca, the world's fifth-largest pharmaceutical group, revealed profits for the quarter had declined 31% to $1 billion, compared to $1.6 billion last year. Core operating margins fell from 40.8% to 36.4%.

The company confirmed that the "key drivers" for the revenue shortfall were anticipated expiry of patents and the loss of exclusivity in certain markets of major anti-psychotic and heart medicines. While emerging-market revenues increased by 9%, this performance was more than offset by U.S. and European sales falling 16%.

Looking ahead, AstraZeneca revealed it expected group profits to "decline at a rate that is significantly higher than the decline in revenue in 2013," while maintaining current sales expectations.

Chief executive Pascal Soriot commented:

As anticipated, the first quarter performance reflects the loss of exclusivity for several large products. We remain focused on our strategic priorities of returning to growth and achieving scientific leadership."

"Brilinta, the diabetes franchise, Emerging Markets, Japan and our Respiratory products have all made good progress and we continued to invest in distinctive science that will advance our knowledge of disease physiology and help to identify new drug targets.

The company will hold its annual general meeting later today, where shareholders are expected to vote on Soriot's $11 million pay package.

With a market cap of 42 billion pounds, AstraZeneca is valued at around 9.8 times expected earnings and offers an impressive prospective dividend yield of 5.5%.

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