Purchased Patents

12 Months Ended

Dec. 31, 2012

Purchased Patents

Purchased Patents

7. Purchased Patents

In connection with a purchase agreement with Shire Laboratories, Inc., the Company acquired certain patents in 2005. The following sets forth the gross carrying amount and related accumulated amortization of the patents, in thousands:

			December 31, 2011				December 31, 2012
	Weighted- Average Life		Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
Purchased patents		10.0	$	2,292	$	1,380	$	2,292	$	1,609

Amortization expense for the years ended December 31, 2010, 2011 and 2012 was approximately $229,000 each year. The estimated annual aggregate amortization expense through December 31, 2015 is $229,000. The net book value of intangible assets as of December 31, 2011 and 2012 was approximately $0.9 million, and $0.7 million, respectively.