When it was legal in both Missouri and Kansas, the herb-based product known as synthetic marijuana was sold openly in coffeehouses, convenience stores and gas stations.
But since legislators outlawed it last year, it appears to have moved out of the stores and into the streets, where police are finding it with regularity.
Kansas City, Mo., police reported that investigators recovered more than 12 pounds of synthetic marijuana during an early August violent-crime initiative — more than the amounts of marijuana, cocaine and methamphetamine combined, according to the figures released by police.
"We're just raking it in," said Kansas City police Sgt. Brad Dumit. "We're seeing it all over the place."
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In another raid earlier this year, police recovered about 10,000 packets of synthetic marijuana, each weighing 3 to 5 grams, according to Maj. Jan Zimmerman, commander of the narcotics and vice division of the Kansas City Police Department.
More recently, a citizen complaint led to the seizure of 1,000 grams at a retail establishment, she said.
The synthetic marijuana is a mixture of herbs, sometimes marketed as incense, infused with chemicals that purportedly mimic the effects of the active ingredient in marijuana.
Most commonly known as K2 or K3, it also is called "spice" or a potpourri of other monikers, such as "syn smooth," "blueberry meltdown" and "head trip."
Lawmakers in both Kansas and Missouri last year outlawed chemicals used to produce it.
But a combination of entrepreneurial spirit and chemical know-how led to slight variations in the drug's chemical makeup that weren't covered by the law, allowing the colorfully named and packaged substances to once again proliferate.
"It's hard to stay ahead of designer drugs," said Sen. Vicki Schmidt, R-Topeka. "People designing them can be very creative."
Law enforcement officials in both states went back to lawmakers, who this year approved new laws covering the entire class of chemical compounds that were being used to circumvent the previous laws.
"I think the new law covers all of those variables," Zimmerman said of the new Missouri law. "The new legislation closes that loophole."
Much of the substance uncovered in Johnson County was found to have come from Kansas City or other parts of Kansas, said Deputy Tom Erickson of the Johnson County Sheriff's Department.
"We've found it in all typical places where we find other illegal drugs," Erickson said.
Schmidt, the Kansas senator, said concerns about its availability to young people and reports of users suffering adverse medical reactions prompted the laws.
The American Psychiatric Association announced a study in May that found that some people who used synthetic marijuana suffered prolonged psychotic episodes that included auditory and visual hallucinations and paranoid delusions.
"The compounds have not been approved by the FDA for human consumption, and little is known about their safety," the association reported.
Zimmerman said research she has read showed that first-time users who didn't regularly use other illegal drugs were more prone to suffering more severe reactions.
It was particularly troubling that with no legal restrictions, the substances often were available freely to anyone, including children, she said.
In Kansas and Missouri, distribution and manufacture of the banned substances is a felony. Possession of small amounts is considered a misdemeanor.