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 exists.

For the six months ended June 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:

	June 30, 2018			December 31, 2017
Patents		1,004,502		$	925,016
Accumulated amortization		(561,534	)		(527,023	)
	$	442,968		$	397,993

The amortization expense for patents for the three and six months ended June 30, 2018 was approximately $18,000 and $35,000, respectively and for the three and six months ended June 30, 2017 was approximately $10,000 and $20,000, respectively. The estimated aggregate amortization expense for the remaining six months of 2018 and each of the years below is approximately as follows:

July 1, 2018 - December 31, 2018	$	36,000
2019		69,700
2020		53,700
2021		37,800
2022		37,800
Thereafter		208,000