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Experts say a new synthetic opioid called “iso” is causing an increasing number of overdose deaths in the United States and is difficult to detect on standard opioid tests. Getty Images
  • A new synthetic opioid known as “iso” is causing an increasing number of opioid overdose deaths.
  • Isotonitazene is a synthetic version of etonitazene.
  • Experts say it’s rapidly becoming more popular in the illegal drug market in the United States.
  • They add that the drug is difficult to detect on standard opioid tests.

An addictive drug that — like fentanyl — is much more powerful than morphine is causing an increasing amount of overdose deaths across the United States.

Isotonitazene, commonly referred to as “iso,” is a synthetic version of etonitazene, an opioid that’s been around since 1957.

One report says the drug is causing about 40 to 50 deaths a month in the United States. That’s up from about six per month last summer.

“Etonitazene is 1,000 times more powerful than morphine,” Dr. Yili Huang, the director of the pain management center at Northwell Health’s Phelps Hospital in New York, told Healthline. “Although isotonitazene is less potent than etonitazene that it’s derived from, it’s still more potent than fentanyl.”

“The best way to think about it is that isotonitazene is a stronger cousin of fentanyl and therefore likely even more dangerous,” Huang added.

According to the Centers for Disease Control (CDC), more than 31,000 people died in the United States in 2018 from overdosing on synthetic opioids like fentanyl, which is typically used to treat pain in cases of advanced cancer.

Other opioids, such as oxycodone, hydrocodone, codeine, and morphine are used legally to treat pain and can be addictive. Heroin is also considered an opioid and is illegal.

Iso comes from China, Huang said, and is designed to mimic the effects of etonitazene, thereby avoiding classification in the United States until recently.

Etonitazene is classified as a schedule I controlled substance by the Drug Enforcement Administration (DEA), meaning it has high abuse potential.

Huang said there’s no current accepted medical use for etonitazene or iso in the United States. Part of the uptick in iso’s use is manufacturers responding to nations cracking down on fentanyl. China banned fentanyl and its derivatives in 2019.

“It certainly could be the new fentanyl,” Dr. Jill Thompson, the medical director at Harmony Recovery Center and Midwood Addiction Treatment in North Carolina, told Healthline. “Every few years, a new substance becomes popular for one of several reasons and it becomes the drug of choice.”

“Just as fentanyl has proven to be a highly addictive and dangerous substance, iso may actually surpass it in use and overdose rates over the next few years,” Thompson said. “Iso can be mixed with other substances, pressed into tablets, and is available in several forms.”

Part of iso’s potential for a jump in overdose deaths is that U.S. drug laws have had trouble keeping up.

It wasn’t until last week that DEA officials announced they were labeling isotonitazene as a schedule I drug.

“It has not been explicitly illegal and therefore sold online,” said Thompson. “It was being sold on the dark web, largely manufactured in China. Initially, it was most commonly found in Belgium, Canada, and Germany. Last year, it was showing up in Illinois, Iowa, Ohio, and Kentucky. Earlier this year, a drug raid seized 1,900 tablets of iso in Halifax (Canada).”

“Many experts in the field believe it will replace heroin quickly and may even surpass fentanyl use in the next few years,” she added.

Because iso is new, it’s difficult to get a clear picture on its use, said Dr. Steven Powell, the chief medical officer of PursueCare, which specializes in treating opioid addiction.

“Because data is just emerging, past overdoses attributable to it are unclear, and future projections are hard to make,” Powell told Healthline. “As we learn more and catch up to what is actually out there, we will learn that iso is one of several derivatives that has played a past role in death, and hopefully start to project how it might contribute to overall overdose rates in the bigger picture of all synthetic opioids.”

“Our understanding is that it can be more potent than fentanyl, extremely potent, but it hasn’t been extensively studied to know the toxicity,” he added.

Another problem is that in this stage of iso’s development, it’s difficult to detect in tests.

“Like other designer or novel psychoactive substances, iso is not detected in a standard opiate drug test,” Thompson said. “Special drug screens are currently being developed in order to detect the substance on a routine (drug screen).”

“Unique problems associated with iso is the lack of familiarity among law enforcement and even the medical community,” Thompson said. “If the ER does not suspect an iso overdose and opiate testing is negative, the correct diagnosis may be missed and potentially overlooked with deadly consequences.”

Naloxone is commonly used to treat opioid overdoses. Opinions vary as to its effectiveness on iso.

“Treatment of iso overdose is more difficult than that of other opiates,” Thompson said. “Reportedly, Narcan (a brand of naloxone) is effective but must be used in higher doses and perhaps multiple times.”

Huang said it’s important to note that naloxone only temporarily deals with the problem.

“Healthcare providers need to remain vigilant,” Huang said. “The development of this drug highlights a deeper concern. New drugs will continue to emerge as long as there is demand. We must continue to use resources to curb this demand with education surrounding judicious opioid use and addiction treatment.”

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