 Shares of PLx Pharma Inc. PLXP, -9.41 dropped 9.2 in afternoon trading Thursday, but nearly halved their earlier loss, as the drug maker responded to recently raised concerns over the use of aspirin to prevent heart attacks. The stock was down as much as 17.7 at a three-month low of 13.38 in intraday trading, and had tumbled 24.9 at that price in two days, after the U.S. Preventive Services Task Force USPTF said Tuesday that it no longer recommended people take aspirin to prevent a first heart attack or stroke. 