The U.S. Food and Drug Administration says drug makers have recalled more than a half-million bottles of the blood pressure medication prazosin hydrochloride over concerns it may include a cancer-causing chemical. New Jersey-based Teva Pharmaceuticals USA and drugs distributor Amerisource Health Services issued voluntary nationwide recalls earlier this month of more than 580,000 bottles of various strengths of prazosine capsules, according to the FDA. Doctors prescribe prazosin, which relaxes blood vessels, to help lower blood pressure.