6. Inventory

Inventory consisted of the following as of June 30, 2018 and December 31, 2017:

(In thousands)	June 30, 2018		December 31, 2017
Raw materials	$	1,150	$	928
Work in process		1,243		746
Finished goods		981		125
Total inventories	$	3,374	$	1,799

Inventory acquired prior to receipt of the marketing approval for ZILRETTA, totaling approximately $3.7 million, was expensed as research and development expense as incurred. The Company began to capitalize the costs associated with the production of ZILRETTA upon receipt of FDA approval of ZILRETTA on October 6, 2017.

Finished goods manufactured by the Company have a shelf life of approximately 24 months from the date of manufacture.

The Company reduces its inventory to net realizable value for potentially excess, dated or obsolete inventory based on an analysis of forecasted demand compared to quantities on hand and any firm purchase orders, as well as product shelf life. During the six months ended June 30, 2018, the Company expensed $3.5 million to cost of sales primarily for fixed overhead costs related to the operation of the United Kingdom facility at Patheon UK Limited. The Company determined that no write-downs to inventory for potentially excess, dated or obsolete inventory were required.