Merck & Co reported higher-than-expected first-quarter earnings, fueled by strong sales of its drugs for diabetes, asthma and rheumatoid arthritis.

The second-largest U.S. drugmaker said it earned $1.04 billion, or 34 cents per share. That compared with $299 million, or 9 cents per share, a year earlier, when it took a number of big charges and a tax expense related to U.S. healthcare reform. Excluding special items, Merck earned 92 cents per share. Analysts on average expected 84 cents, according to Thomson Reuters I/B/E/S. Global sales of $11.58 billion topped the analysts' average forecast of $11.37 billion.

Merck trimmed its full-year forecast for research and development spending to between $8 billion and $8.4 billion. It has previously expected $8.1 billion to $8.5 billion. The company said it expects earnings this year of $3.66 to $3.76 per share, excluding special items - nudging up by 2 cents the lower end of its earlier estimate. That would reflect profit growth of 7% to 10% from 2010.