(WTVO) — A new study has identified a class of opioids more powerful than fentanyl and 1,000 times more potent than morphine is among the fastest growing types of opioids detected in emergency room patients.

The study, published in the Journal of the American Medical Association, found novel synthetic opioids, like the nitazene drug class, are becoming increasingly common in overdose patients and are more difficult to treat than other opioids like fentanyl.

Nitazenes are lab-made opioids that enter the drug market after being mixed with substances like heroin.

Patients who overdosed on nitazenes often required twice as many doses of the opioid overdose reversal drug nalaxone compared to those suffering from a fentanyl overdose.

Of the 537 adults included in the study, 11 tested positive for only fentanyl and nine tested positive for nitazenes only.

Those who overdosed on one class of nitazenes also experienced cardiac arrest, intubation, and death at higher rates than those who overdosed on other substances.

“Nitazene and analogues entered the drug supply within the past few years because distributors and suppliers cut opioid drugs with them,” said Shiela Vakharia, deputy director of the Department of Research and Academic Engagement for the Drug Policy Alliance in an email to CNN.

“One reason why this new class of drugs has entered the fentanyl supply is because we have passed harsher fentanyl and fentanyl analogue penalties at the state and federal level,” she said.

Researchers urged medical professionals to be aware of the rise in novel opioids and anticipate different treatment actions.