An elephant tranquilizer 10,000 times the strength of morphine might be making the U.S. heroin epidemic worse.
Symptoms of fentanyl include shallow breathing, slowed heart rate and confusion, among others.
But carfentanil can be fatal to humans. Just a couple milligrams can knock out large animals like elephants and moose.
Over the past several months, the drug has been linked to many deadly overdoses in humans. Officials said the drug first appeared in central Ohio in July.
In some cases, users don't even realize they're taking carfentanil. Dealers are reportedly selling the drug as heroin or lacing heroin with the tranquilizer. The opioid is cheaper and stronger than heroin, so dealers can make their supplies last longer.