Updated from 4:43 p.m. EDTQuarterly revenue rose 10% at Biogen Idec ( BIIB), driven mainly by sales of the multiple sclerosis drug Avonex and the lymphoma treatment Rituxan, but the biotech company's results fell short of estimates. Total revenue in the third quarter rose to $596.2 million from $543.3 million a year ago. Calculated in accordance with generally accepted accounting principles, Biogen Idec posted third-quarter earnings of $27.2 million, or 8 cents a share, down from $36.8 million, or 10 cents a share, a year ago. Excluding various charges, the Cambridge, Mass., company would have earned 36 cents in the latest quarter. Analysts surveyed by Thomson First Call were looking for a profit of 42 cents and revenue of $620.9 million. Shares of Biogen Idec were falling after the close of regular trading Wednesday. Lately, the stock was losing $1.36, or 3.4%, to $38.65. Avonex worldwide sales climbed 8% to $375 million, remaining the market leader with a 40% share, according to the company. Rituxan revenue was up 14% to $182 million in the quarter. Biogen Idec co-promotes Rituxan in the U.S. with Genentech ( DNA). All U.S. sales of the product are recognized by Genentech, and Biogen Idec records its share of the pretax co-promotion profits on a quarterly basis. Domestic net sales of Rituxan were $456 million in the third quarter. Aside from Avonex, the company marketed another MS drug, Tysabri, with Elan ( ELN) before its sales were halted earlier this year. Tysabri was pulled after being linked to a serious brain disease known as PML. The companies are seeking regulatory approval to get the drug reinstated, and Biogen Idec expects a decision from the Food and Drug Administration by mid-2006. Biogen Idec anticipates European approval for the drug for MS in the second half of next year. Looking forward, Biogen Idec forecast that 2006 earnings, excluding the effect of stock option expensing, will be $1.95 to $2.10 a share. The company estimated next year's capital spending will range from $200 million to $275 million. The 2006 consensus earnings expectation is $1.99 a share.