In the United States a kind of fake pot has sparked new health concerns following at least three users being hospitalized for kidney failure, authorities in the western state of Wyoming said on Monday.
Often known as "Spice" or "K2," the substance is marketed to young people as herbal incense, and creates a marijuana-like high when it is smoked like a joint or a cigarette.
"At this point we are viewing use of this drug as a potentially life-threatening situation," Tracy Murphy, state epidemiologist with the Wyoming Department of Health, said in a statement sent to AFP.
There have been no deaths and no reports of connected cases in other areas, she added.
However, drug policy experts say that fake pot use has been on the rise in recent years, ever since it was first copied from a US scientist's lab research in the mid 1990s and quickly spread around the world.
The compound, known as JWH-018, was created in the lab of John Huffman, a professor of organic chemistry at Clemson University, who was researching how marijuana-like compounds act on brain receptors.
According to the US Drug Enforcement Agency, which in 2011 banned JWH-018 and four other synthetic cannabinoids, calls to poison control centers rose from just over 100 in 2009 to more than 2,700 nationwide in the space of a year.
"Technically it is an incense, it is not for human consumption, you know what I am saying?" said a smoke shop owner in Arizona who asked not to be named.
He said he continues to stock three kinds of herbal incense, but none that carry ingredients outlawed by the DEA.
"If there is a banned substance in there, then we don't have it in our store," he told AFP by phone, adding that brands and popularity change frequently.
"You know, people go from their K2 to their Dead Man Walking, to their Smoking Camel, there is all kinds of stuff out there," he said.
"I'll be happy when it's gone."