The FDA's approval for the shelf-life extension of Emergent Biosolutions' Narcan nasal spray is likely to have a positive impact on the company's stock in the short term. A longer shelf-life can lead to reduced waste, lower operating costs, and improved customer satisfaction, which may enhance the product's marketability and potentially increase sales. As this is a regulatory decision directly affecting one of the company's products, it is highly relevant and important to investors. The confidence in this analysis is high due to the clear connection between FDA approvals and pharmaceutical company performance.