Stock prices of pharmacy chains and drug companies took a double hit Thursday afternoon as President Trump announced a "national public health emergency" for the opioid crisis and the St. Louis Post-Dispatch reported that Amazon gained approval in several states to be a wholesale drug distributor.

Key takeaways:

• Stocks likely fell in anticipation of a government crackdown on drug distribution companies, but Trump's speech did not contain specifics about federal action against distributors.
• News that Amazon is entering new markets has had the same effect on other industries, such as grocery chains. Amazon's move into pharmacy services was long-anticipated.
• The end-of-day spike in CVS's share price might be explained by a Wall Street Journal report that CVS is considering an acquisition of insurance giant Aetna.