6.	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 exists.

For the nine months ended September 30, 2018, we increased 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, 2018			December 31, 2017
Patents		1,020,416		$	925,016
Accumulated amortization		(580,524	)		(527,023	)
	$	439,892		$	397,993

The amortization expense for patents for the three and nine months ended September 30, 2018 was approximately $19,000 and $54,000, respectively and for the three and nine months ended September 30, 2017 was approximately $10,000 and $31,000, respectively. The estimated aggregate amortization expense for the remaining three months of 2018 and each of the years below is approximately as follows:

October 1, 2018 - December 31, 2018	$	19,400
2019		72,700
2020		55,800
2021		38,900
2022		38,900
Thereafter		214,200