Co-Promotion Agreement	12 Months Ended
Dec. 31, 2018
Co Promotion Agreement [Abstract]
Co-Promotion Agreement	(14) Co-Promotion Agreement On March 31, 2014, the Company entered into a Co-Promotion Agreement (the “Agreement”) with Kowa Pharmaceuticals America, Inc. related to the commercialization of Vascepa^® (icosapent ethyl) capsules in the United States. Under the terms of the Agreement, Amarin granted to Kowa Pharmaceuticals America, Inc. the right to be the sole co-promoter, together with the Company, of Vascepa in the United States during the term. The Agreement was amended on July 25, 2017 to reflect evolving promotional needs, including refinement of target lists. Amarin and Kowa Pharmaceuticals America, Inc. intentionally designed the co-promotion to naturally end as of December 31, 2018 and mutually agreed not to renew the agreement. During the term, Kowa Pharmaceuticals America, Inc. and Amarin agreed to use commercially reasonable efforts to promote, detail and optimize sales of Vascepa in the United States. The performance requirements included a negotiated minimum number of details to be delivered by each party in the first and second position, and the use of a negotiated number of minimum sales representatives from each party. Kowa Pharmaceuticals America, Inc. agreed to bear the costs incurred for its sales force associated with the commercialization of Vascepa and to pay for certain incremental costs associated with the use of its sales force, such as sample costs and costs for promotional and marketing materials. Amarin recognized all revenue from sales of Vascepa and used commercially reasonable efforts to maintain a minimum amount of inventory of Vascepa for use in the United States. In exchange for Kowa Pharmaceuticals America, Inc.’s co-promotional services, Kowa Pharmaceuticals America, Inc. was entitled to a quarterly co-promotion fee based on aggregate Vascepa gross margin that varied during the term. The percentage of aggregate Vascepa gross margin earned by Kowa Pharmaceuticals America, Inc. was, as amended, approximately eighteen percent (18%) in 2017, partially offset by certain other refinements. During 2018, which was the last year of the Agreement, as amended, the Company incurred expense for both the annual co-promotion fee, which in 2018 was calculated as eighteen-and-a-half percent (18.5%) of Vascepa gross margin, plus accrual for co-promotion tail payments which were calculated as a percentage of the 2018 co-promotion fee. Kowa Pharmaceuticals America, Inc. is eligible to receive $17.8 million in co-promotion tail payments, the present value of which of $16.6 million was fully accrued as of December 31, 2018. No amount was accrued for the co-promotion tail payments as of December 31, 2017. The accrued tail payments will be paid over three years with declining amounts each year. As of December 31, 2018 and 2017, the Company had a net payable to Kowa Pharmaceuticals America, Inc. of $27.6 million and $8.3 million, respectively, of which $18.1 million and $8.3 million, respectively, was classified as current on the consolidated balance sheets, representing co-promotion fees, including accrual of the tail payments, net of reimbursable amounts incurred for samples and other marketing expenses.

Co-Promotion Agreement

12 Months Ended

Dec. 31, 2018

(14) Co-Promotion Agreement

On March 31, 2014, the Company entered into a Co-Promotion Agreement (the “Agreement”) with Kowa Pharmaceuticals America, Inc. related to the commercialization of Vascepa^® (icosapent ethyl) capsules in the United States. Under the terms of the Agreement, Amarin granted to Kowa Pharmaceuticals America, Inc. the right to be the sole co-promoter, together with the Company, of Vascepa in the United States during the term. The Agreement was amended on July 25, 2017 to reflect evolving promotional needs, including refinement of target lists. Amarin and Kowa Pharmaceuticals America, Inc. intentionally designed the co-promotion to naturally end as of December 31, 2018 and mutually agreed not to renew the agreement.

During the term, Kowa Pharmaceuticals America, Inc. and Amarin agreed to use commercially reasonable efforts to promote, detail and optimize sales of Vascepa in the United States. The performance requirements included a negotiated minimum number of details to be delivered by each party in the first and second position, and the use of a negotiated number of minimum sales representatives from each party. Kowa Pharmaceuticals America, Inc. agreed to bear the costs incurred for its sales force associated with the commercialization of Vascepa and to pay for certain incremental costs associated with the use of its sales force, such as sample costs and costs for promotional and marketing materials. Amarin recognized all revenue from sales of Vascepa and used commercially reasonable efforts to maintain a minimum amount of inventory of Vascepa for use in the United States.

In exchange for Kowa Pharmaceuticals America, Inc.’s co-promotional services, Kowa Pharmaceuticals America, Inc. was entitled to a quarterly co-promotion fee based on aggregate Vascepa gross margin that varied during the term. The percentage of aggregate Vascepa gross margin earned by Kowa Pharmaceuticals America, Inc. was, as amended, approximately eighteen percent (18%) in 2017, partially offset by certain other refinements. During 2018, which was the last year of the Agreement, as amended, the Company incurred expense for both the annual co-promotion fee, which in 2018 was calculated as eighteen-and-a-half percent (18.5%) of Vascepa gross margin, plus accrual for co-promotion tail payments which were calculated as a percentage of the 2018 co-promotion fee. Kowa Pharmaceuticals America, Inc. is eligible to receive $17.8 million in co-promotion tail payments, the present value of which of $16.6 million was fully accrued as of December 31, 2018. No amount was accrued for the co-promotion tail payments as of December 31, 2017. The accrued tail payments will be paid over three years with declining amounts each year.

As of December 31, 2018 and 2017, the Company had a net payable to Kowa Pharmaceuticals America, Inc. of $27.6 million and $8.3 million, respectively, of which $18.1 million and $8.3 million, respectively, was classified as current on the consolidated balance sheets, representing co-promotion fees, including accrual of the tail payments, net of reimbursable amounts incurred for samples and other marketing expenses.