5. PATENT COSTS

We amortize intangible assets with definite lives on a straight-line basis over their remaining estimated useful lives, ranging from two to ten years, and review for impairment on a quarterly basis and when events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. We analyze our intangible assets, specifically, capitalized patent costs, on an annual basis for any indicator that an impairment exist.

For the nine months ended September 30, 2017, we did not increase our capitalized patent costs based on reports provided to us by Endo. Patent costs may be creditable against future royalty revenues. For each period presented below, net patent costs consisted of:

	September 30, 2017			December 31, 2016
Patents	$	720,601		$	720,601
Accumulated amortization		(492,733	)		(462,246	)
	$	227,868		$	258,355

The amortization expense for patents for the three and nine months ended September 30, 2017 was approximately $10,200 and $30,500, respectively and for the three and nine months ended September 30, 2016 was approximately $10,300 and $29,600, respectively. The estimated aggregate amortization expense for the remaining three months of 2017 and each of the years below is approximately as follows:

October 1, 2017 - December 31, 2017	$	10,200
2018		40,600
2019		40,600
2020		28,600
2021		16,600
Thereafter		91,300