Officials at the Banner Poison Control Center in Phoenix, Arizona have announced that they have responded to two cases of people using “krokodil,” a cheap, synthetic heroin knockoff that is popular in Russia and can rot away users’ flesh.

“We’ve had two cases this past week that have occurred in Arizona,” said Dr. Frank LoVecchio, the co-medical director at Banner’s Poison Control Center, in an interview with CBS5 Phoenix. “As far as I know, these are the first cases in the United States that are reported. So we’re extremely frightened.”

Krokodil is synthesized by combining codeine from painkillers with various toxic chemicals such as iodine, gasoline, paint thinner, lighter fluid, and cleaning oil. Users employ a complex series of steps to mix the various ingredients and distill them down to a brownish gunk known as “desomorphine” — an opiate that is far more powerful than heroin, according to the UK-based Independent. This material is then injected into users’ vein in order to experience the high.

The drug, which is far cheaper and easier to manufacture than it is to afford or obtain heroin, has become a scourge among the Russian poor. Until 2012, Russia did not require a prescription in order to purchase codeine over-the-counter. But that changed as rates of krokodil use increased exponentially alongside purchases of codeine pills.

Among the drug’s most stomach-churning effects is its potential to literally rot away skin and flesh. That’s because users are rarely able to completely separate the opiate from the chemical fuels required to synthesize it. In turn, users end up injecting themselves with traces of gasoline, iodine, and other potentially lethal chemicals. A quick Google image search of krokodil turns up plenty of images of what effect that has on the human body — but be warned, the pictures are extremely graphic.

More: Flesh-Rotting Drug Makes Its Way to the U.S. for the First Time, Health Officials Are ‘Frightened’