AKRON, Ohio -- A medical examiner in Ohio has issued a public warning about a dangerous drug that hit the streets this summer. Far more powerful than heroin, it has sent dozens to the hospital -- and dozens more to the morgue.

Longtime addict Kevin McCutcheon took what he thought was heroin earlier this month, and nearly died.

“I’m here and I’m alive, and I shouldn’t be,” he told CBS News’ Anna Werner.

Addicts often don’t know what’s mixed into the heroin they get from dealers, but McCutcheon believes that most recent dose contained the powerful opioid carfentanil.

Carfentanil is so deadly, it is not even prescribed for humans -- it’s typically used to tranquilize large animals like elephants. The drug is 100 times more potent than the similar drug prescribed for humans, fentanyl, and 10,000 times more potent than morphine.

But carfentanil abuse is spreading. Authorities say at least 30 people have died from these overdoses in the Akron, Ohio​ area since the July 4th weekend.

The treatment drug Narcan​ can be used to save people who overdose​ on carfentanil -- if they get enough.

“How much more Narcan do you need for a person who’s taken carfentanil as opposed to heroin, or heroin and fentanyl​?” Werner asked Dr. Nick Jouriles with Akron General Hospital.

“It starts at five times the amount ... and many times we have to give a double dose, so 10 times the usual dose,” Jouriles told her. He said it’s the most powerful drug he has seen people taking through heroin use​.

“Just this morning we were able to go on the internet and get a quote for 100 grams of carfentanil, and that was $400,” said Keith Martin, head of the local office of the DEA.

According to him, 100 grams “would kill thousands of people.”

McCutcheon escaped that fate, and has been sober​ since his overdose. “It’s gonna kill you,” he wants to tell other addicts. “It’s gonna kill you.”

The drug is so dangerous police are being told to wear protective gear and not do field tests on it, because accidental exposure could prove deadly.