Bristol-Myers Squibb Co's first-quarter results beat expectations, bolstered by the weaker dollar and demand for its drugs to treat cancer, rheumatoid arthritis and hepatitis B.

The company said on Thursday it earned $1.37 billion, or 57 cents per share. That compared with $1.1 billion, or 43 cents per share, in the year-earlier period.

Excluding special items, Bristol-Myers earned 58 cents per share. Analysts on average expected 53 cents, according to Thomson Reuters I/B/E/S.

Revenue rose 4 percent to $5.01 billion, topping a Wall Street forecast of $4.95 billion.

Sales of the company's biggest product, blood-clot preventer Plavix, rose 6 percent to $1.76 billion. The pill, sold in partnership with Sanofi-Aventis , will face competition from cheaper generics a year from now.

Bristol-Myers, whose first-quarter results were also helped by lower taxes, reaffirmed it expects earnings this year, excluding special items, of $2.10 to $2.20 per share. That would be little changed from last year.

(Reporting by Ransdell Pierson; Editing by Derek Caney and John Wallace)