Pfizer Inc. said Tuesday its first-quarter profit rose 10 percent, due to lower costs for production and research and a smaller tax bill.

The world's biggest drugmaker by revenue said its net income was $2.22 billion, or 28 cents per share. That's up from $2.03 billion, or 25 cents per share, in 2010's first quarter.

Excluding one-time items, income would have been $4.81 billion, or 60 cents a share, down just over 1 percent from a year ago.

The maker of cholesterol blockbuster Lipitor and impotence pill Viagra said revenue was $16.5 billion, down a half-percent from $16.58 billion a year ago.

Analysts surveyed by FactSet expected earnings per share of 58 cents and revenue of $16.59 billion. Typically, they exclude one-time items.

Pfizer maintained its forecast given in January for 2011 earnings per share of $2.16 to $2.26, excluding just over $1 in one-time items. But it reduced its revenue forecast, to about $66.2 billion from about $67 billion.

Pfizer for a second time reduced its prior 2012 revenue forecast, this time to $63.5 billion, from $64.25 billion. That year is crucial, because Lipitor, the world's top-selling drug with nearly $12 billion in annual sales, loses U.S. patent protection at the end of November and generic competition will quickly erode sales.

Chief Executive Ian Read said in a statement that he was pleased "with our solid financial performance during the quarter despite the loss of (patent) exclusivity of several products in the U.S." and other countries.

"I believe we are well positioned to succeed in fixing our innovative core, which, if successful, can lead to greater value in both the near and longer term," he added.

The company said it plans to repurchase between $5 billion and $7 billion in stock this year.

Pfizer shares slipped 22 cents to $20.80 in premarket trading.