More than eighty people across the country have died in recent weeks after injecting heroin laced with fentanyl, a powerful synthetic opiate.

Heroin, which has long been cheaper than prescription painkillers, is now widely seen as one of the most potent narcotics. Heroin dealers are adding fentanyl – a synthetic opioid often given to cancer patients to cope with pain – or other ingredients to give heroin a boost. They are sometimes replacing heroin with pure fentanyl, which is fatal if injected.

Fentanyl is a narcotic that is typically administered to people in chronic pain, including end-stage cancer patients. It is also used as an anesthetic. It is considered 80 times more powerful than morphine and can kill by inhibiting breathing.

“The dealers push this as being a super high, which it is, but it’s also lethal,” said Ellen Unterwald, director of the Center for Substance Abuse Research at the Temple University School of Medicine. Users typically don’t know how much fentanyl is mixed in, and she said just a small amount can be fatal because the drug is so potent.

In Maryland, at least 37 people have died from the combined drugs, according to the Maryland Department of Health and Mental Hygiene, and in western Pennsylvania, authorities said they caused 22 deaths in recent weeks. In Rhode Island, 25 people have died from the laced heroin, and in Vermont state police have warned that pure fentanyl is being sold as heroin.

After Philip Seymour Hoffman was found dead with a syringe in his arm this month, investigators in New York tested the heroin found in his apartment for fentanyl, but found that it did not include the additive.

Last month the Drug Enforcement Administration put out a bulletin warning local authorities of what it dubbed “killer heroin,” a mixture that was up to half fentanyl. It urged first responders to “exercise extreme caution” when coming into contact with any heroin because Fentanyl can be absorbed through the skin.