Pharmaceutical giant Merck (NYSE:MRK) doesn't have the goods for what ails you this quarter. First-quarter earnings came up short of top-line consensus estimates by Capital IQ analysts, even as it beat on the bottom line. Even so, it had to lower guidance for the full year as competition from generic drugs continue to sap its strength.

Merck reported revenues for the three months ending on March 31 of $10.67 billion, down 9% from the same period last year, when it recorded revenues of $11.73 billion, and falling short of analysts' expectations of $11.10 billion. The pharma recorded GAAP profits $0.52 per share, 7% below the $0.56 it posted in the year-ago quarter but well ahead of the $0.46 in GAAP earnings Wall Street expected.

Merck now expects full-year 2013 non-GAAP earnings per share to be in a range of $3.45 and $3.55, or $0.15 per share lower than what it guided toward at the end of 2012. Generic competition for its asthma and allergy drug Singulair caused sales of the drug to plunge 75% in the quarter.

While saying he still remains confident of the pharma's future opportunities, Merck Chairman and CEO Kenneth C. Frazier said: "Our first quarter performance reflects the challenges of major patent expiries coupled with the impact of currency and other headwinds. During the quarter, we took focused actions to reach our EPS target while at the same time advancing Merck's pipeline in our laboratories and through strategic deals and partnerships."

Merck operates and has customers in more than 140 countries around the globe. It had revenues of $47.3 billion in 2012.

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