Amgen's ( AMGN) fourth-quarter earnings surged 26% from a year ago on a 24% jump in sales, but the company indicated it would struggle to hit 2005 earnings estimates.

The biotech giant earned $689 million, or 53 cents a share, in the quarter, compared with $547 million, or 41 cents a share, last year. Sales were $2.91 billion in the latest quarter compared with $2.35 billion a year ago.

Adjusted for special items, Amgen earned $749 million, or 58 cents a share, in the 2004 fourth quarter. On that basis, analysts had been forecasting earnings of 61 cents a share on sales of $2.83 billion.

For 2005, the company expects total revenue growth to be in the high single-digits to low-teens range, and expects adjusted earnings of $2.70 to $2.85 a share. Analysts were forecasting earnings of $2.85 a share on revenue of $12.05 billion.

The shares were recently down $1.96, or 3.1%, to $61.60 on Instinet.

Amgen said each of its major treatments maintained or raised market share in 2004. In the fourth quarter, combined sales of anemia drugs Epogen and Aranesp rose 21% from a year ago to $1.4 billion. Combined sales of anit-infection drugs Neulasta and Nepogen rose 13% from a year ago to $778 million.

Fourth-quarter sales of anti-inflammatory Enbrel rose 49% from a year ago to $567 million.