Net loss per share

3 Months Ended

Mar. 31, 2013

Net loss per share

Net loss per share

9.    Net loss per share

For all periods presented, both basic and diluted net loss per common share are computed by dividing the net loss by the number of weighted average common shares outstanding during the period. Stock options and potential common shares issuable upon conversion of the 4.75% Senior Notes and the Pfizer Note were excluded from the computation of diluted net loss per share, as their share effect was anti-dilutive for all periods presented. The potential common shares that were excluded from the diluted net loss per share computation are as follows:

	2013	2012
Outstanding stock options	24,208,663	24,729,232
Common shares issuable upon conversion of 4.75% Senior Notes	45,583,814	45,584,040
Common shares issuable upon conversion of Pfizer Note due 2013(1)	—	1,461,496
Common shares issuable upon conversion of Pfizer Note due 2014	1,025,641	1,025,641
Total potential common shares excluded from diluted net loss per share computation	70,818,118	72,800,409

(1) In December 2012, the holder of the Pfizer Note due 2013 elected to convert all $10.0 million principal amount into 1,461,496 shares of common stock.