‘Frankenstein Opioids’: Drug Stronger Than Fentanyl Seized In All 50 States

A little-known drug that is many times stronger than fentanyl and has killed hundreds of people in Europe is showing up in U.S. drug seizures, especially in eastern states, a government report warns.

Nitazenes, or “Frankenstein opioids” as these synthetic drugs are sometimes called, were developed in the 1950s as an alternative for pain management. Up to 4,300 times stronger than morphine, nitazenes were never approved for medical use because they posed a significant risk of fatal overdose.

Outside pharmaceutical research, little was known about nitazenes. They slipped into the illicit drug supply almost unnoticed and add a new layer of complexity to the ongoing opioid epidemic, demonstrating how easily synthetic opioids can infiltrate the market ahead of regulatory efforts and public awareness.

In the United Kingdom, at least 400 people died of nitazene overdoses during the 18-month period ending January 2025, according to the government. Dozens of U.S. deaths have also been attributed to nitazenes.

“This is probably the biggest public health crisis for people who use drugs in the U.K. since the AIDS crisis in the 1980s,” Vicki Markiewicz, executive director of the U.K.-based substance abuse treatment provider Grow Live, told The Wall Street Journal.

Especially alarming, experts say, is that people often take nitazenes without knowing it.

"People have to keep in mind, with all the synthetic drugs out there, and the way they’re being mixed together, you never know what you’re actually buying," U.S. Drug Enforcement Administration Intelligence Analyst Maura Gaffney said in a briefing with reporters in 2022, after the drug turned up in the Washington, D.C., metropolitan area.

Here’s what you need to know:

How Potent Are Nitazenes?

Some nitazenes can be up to 40 times stronger than fentanyl, according to the University of Texas Medical Branch

Fentanyl itself is generally 25 to 50 times stronger than heroin, which is about twice as strong as morphine.

The most common form of nitazene is 250 to 900 times stronger than morphine, while the most potent form is up to 4,300 times stronger than morphine, the Inter-American Drug Abuse Control Commission said in a report last year.

How Common Are Nitazenes In The U.S.?

Nitazenes have been found in at least 4,300 U.S. drug seizures since 2019, according to a 2024 report from the Drug Enforcement Administration. It mostly was used to cut fentanyl, but it has also been found in heroin, cocaine and other recreational drugs; counterfeit painkillers; and anxiety medications.

The DEA said dozens of U.S. deaths in the last five years have been linked to nitazenes. The toll is likely much higher. The agency noted the data is limited because it’s based on self-reporting, and also that overdose toxicology tests don’t screen for nitazenes.

The Centers for Disease Control and Prevention said that four times as many nitazene-involved overdoses were identified in Tennessee in 2021 than in 2020, but also noted the numbers are likely an undercount because f low testing frequency.

“Nitazenes are an emerging group of highly potent psychoactive substances, tests for which are often not included in standard toxicology panels,” the CDC said in a weekly morbidity update in 2022. “Given their potency, raising awareness about nitazenes and implementing strategies to reduce harm through increased testing, surveillance, and linkage to treatment for substance use disorders are of vital importance.”

Where Has ‘Tranq’ Been Found?

Even more alarming is the emergence of a street drug called “tranq,” a dangerous mixture of fentanyl and xylazine, a powerful sedative used in veterinary medicine as a tranquilizer, pain reliever and muscle relaxant for animals like horses and cattle. It is not approved for use in humans by the FDA.

When it’s mixed with other drugs, especially fentanyl, but also heroin, cocaine and methamphetamine, it can slow breathing, heart rate and blood pressure to dangerously low levels, according to the National Institute on Drug Abuse. Given their ultra-potency, overdose reversal drugs like naloxone may be less effective.

Tranq showed up in drug seizures in all 50 states, but was most prevalent in eastern U.S. drug markets, including in New Jersey, Virginia, Ohio, Maryland, and Florida, according to the DEA.

Why Is Use Spreading?

People who have used tranq say the sensation is similar to being knocked unconscious for several hours, or days.

“Some people use it because its effects last longer than fentanyl, allowing them to use less often or last overnight,” according to the Maryland Department of Health. “Some people are using it unintentionally because they don’t know it’s in the drug supply.”

Not only is the overdose risk higher, the withdrawal symptoms are different from those associated with opioid withdrawal, and may include intense anxiety and distress. They do not respond to standard opioid withdrawal medication.

Xylazine use is linked to severe skin ulcers and abscesses, sometimes appearing at sites other than injection points, which can lead to infection and even amputation if untreated.

How Many Nitazenes Have Been Developed?

At least 13 different type of nitazenes have been identified. The most prevalent is isotonitazene, or (ISO). Other commonly reported nitazenes include metonitazene, protonitazene, butonitazene, etodesnitazene, flunitazene and-pyrrolidinio etonitazene.

Because they’re often mixed with other drugs, it’s difficult to know if a substance like fentanyl, heroin or counterfeit pills contains nitazenes without specialized testing.

How Are Nitazenes Sold?

Nitazenes are sold as a white powder, crystalline solid or a brown/yellow powder, and hey can be injected, snorted or swallowed, according to the Alcohol and Drug Foundation.

The DEA said drug cocktails are often mixed by mid-level and street-level dealers in the United States.

However, the agency cautioned that drug suppliers — mainly located in China — introduce new nitazenes when the ones currently used become riskier to produce due to regulatory actions and drug scheduling, or users look for novel opioids that are not yet illegal.

What’s Being Done?

The DEA temporarily classified several nitazenes that don’t have an approved medical use and have a high potential for abuse as dangerous Schedule I narcotics.

Several states, including Arizona, Florida, Ohio and Pennsylvania, are doing the same.