| Schedule of intangible assets |
The following table reflects the gross carrying amounts and net book values of intangible assets as of December 31, 2021 and 2020 (dollar amounts in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | December 31, 2021 | | December 31, 2020 | | Product rights | | Remaining
Useful Life
(In years) | | Gross
Carrying
Amount | | Accumulated
Amortization | | Net Book
Value | | Gross
Carrying
Amount | | Accumulated
Amortization | | Net Book
Value | | INDOCIN | | 10.4 | | $ | 154,100 | | | $ | (20,654) | | | $ | 133,446 | | | $ | 154,100 | | | $ | (7,812) | | | $ | 146,288 | | | Otrexup | | 8.0 | | 44,086 | | | — | | | 44,086 | | | — | | | — | | | — | | | SPRIX | | 5.4 | | 39,000 | | | (8,960) | | | 30,040 | | | 39,000 | | | (3,389) | | | 35,611 | | | CAMBIA | | 1.0 | | 51,360 | | | (43,410) | | | 7,950 | | | 51,360 | | | (36,163) | | | 15,197 | | | Zipsor | | 0.2 | | 27,250 | | | (26,718) | | | 532 | | | 27,250 | | | (24,381) | | | 2,869 | | | Oxaydo | | 0.0 | | 300 | | | (300) | | | — | | | 300 | | | (183) | | | 117 | | | Total Intangible Assets | | | | $ | 316,096 | | | $ | (100,042) | | | $ | 216,054 | | | $ | 272,010 | | | $ | (71,928) | | | $ | 200,082 | |
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| Summary of the future amortization expenses of intangible assets |
The following table reflects future amortization expense the Company expects for its intangible assets (in thousands): | | | | | | | | | | Year Ending December 31, | | Estimated
Amortization
Expense | | 2022 | | $ | 32,406 | | | 2023 | | 23,924 | | | 2024 | | 23,924 | | | 2025 | | 23,924 | | | Thereafter | | 111,876 | | | Total | | $ | 216,054 | |
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