Pensacola doctors and anti-drug advocates believe there is a strain of heroin in Pensacola that can kill users with just one hit. It has been laced with carfentanil, a large animal tranquilizer that is considered to be 10,000 times more potent than morphine. Sacred Heart Hospital Director of the Emergency Department Dr. Trish Stephens said the lethal dose of carfentanil is the size of a poppy seed. It shuts down the respiratory system, the heart and there is sudden death. Heroin deaths have gone up in Florida and Stephens believes carfentanil is to blame.