Net loss per share (Tables)

9 Months Ended

Sep. 30, 2013

Net loss per share

Schedule of antidilutive securities excluded from the computation of earnings per share

	Nine months ended September 30,
	2013	2012
Stock options	21,065,995	22,165,802
Common shares issuable upon conversion of 4.75% Senior Notes(1)	24,958,298	45,584,040
Common shares issuable upon conversion of Pfizer Note due 2013(2)	—	1,461,496
Common shares issuable upon conversion of Pfizer Note due 2014 (3)	—	1,025,641
Total potential common shares excluded from diluted net loss per share computation	46,024,293	70,236,979

(1) In May, June and September 2013, we entered into separately negotiated agreements with certain holders of the 4.75% Senior Notes to convert $181.0 million principal amount into 20,625,403 shares of common stock.

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

(3) In August 2013, the holder of the Pfizer Note due 2014 elected to convert the $10.0 million principal amount into 1,025,641 shares of common stock.