Alya, 17, undergoes treatment for addiction to drugs including heroin, krokodil, and others at City Without Drugs, one of the few drug treatment facilities in Russia.

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There's a good chance that you've seen one of those posters showing before-and-after pictures of methamphetamine addicts, who morph from normal-looking humans into sallow, skeletal wraiths with gray, eroded teeth. But believe it or not, there's a drug that reportedly wreaks even more extreme carnage upon users. How extreme is more extreme? Check this out: It actually eats away your flesh, destroying tissue and blood vessels and leaving your skin a greenish, scaly mess [source: Ehrenfreund].

The drug we're talking about is krokodil (pronounced "crocodile"), the street name of desomorphine. It earned its name because it tends to make users look reptilian. It's an inexpensive but potent homemade narcotic that's caught on big-time in Russia. Russian addicts make krokodil by taking codeine tablets, a painkiller that, until 2012, could be easily purchased in that country, and mixing it with solvents such as gasoline, paint thinner or hydrochloric acid [sources: Shuster, Grimm, Rylkov]. The result is a mixture that they inject into their veins to get a high that's as powerful and pleasurable as heroin, but a lot easier and cheaper to obtain [sources: Winter, Priymak].

A 2011 study found that at least 100,000 people in Russia had injected krokodil [source: Christensen]. But of course, there are some major downsides to this drug. For one, it is highly addictive, perhaps even more so than heroin [sources: Priymak, Drug Enforcement Administration]. Worse yet, it rots away the addicts' bodies, bit by bit, leaving them looking eerily like the decaying zombies from apocalyptic movies and TV thrillers [source: Christensen].

Where did krokodil come from, and why is it so destructive? And will it ever catch on in the U.S.?