Pfizer ( PFE) reported first-quarter earnings of $2.73 billion, or 40 cents a share, compared with earnings of $2.78 billion, or 41 cents a share, a year earlier as revenue in the quarter fell 8% to $10.87 billion.

On an adjusted basis, excluding certain items and acquisition-related costs, the drug company earned $3.7 billion, or 54 cents a share, in the first quarter.

Analysts surveyed by Thomson Reuters expected Pfizer to earn 49 cents a share in the quarter on revenue of $11.08 billion.

In a statement Tuesday, Pfizer said foreign exchange unfavorably impacted first-quarter revenue by about $640 million, or 5%.

U.S. revenue in the first quarter was $5.0 billion, down 10% from a year earlier, while international revenue declined 7% to $5.9 billion.

Pfizer lowered its full-year 2009 guidance to a range of $1.20 to $1.35 a share to reflect certain costs related to the company's pending acquisition of Wyeth ( WYE). Pfizer previously expected to earn $1.34 to $1.49 a share in 2009.

Pfizer reaffirmed adjusted earnings for 2009 are expected at $1.85 to $1.95 a share, Pfizer said. Analysts expect 2009 earnings of $1.95 a share.