Melissa Cooper has learned the hard way that state's efforts this year to ban synthetic marijuana have not succeeded in stopping sales.

From time to time, she conducts her own undercover investigation. She goes to the smoke shop near her home and asks for "Spice," the street name for the drug. Much to her chagrin, the product is always available.

Back in March, the governor signed legislation that banned all known formulations of synthetic marijuana. But seemingly overnight, new variations of the drug hit the market. Law enforcement officials say the constant tweaking of ingredients has allowed manufacturers to skirt the law.

There are potentially hundreds of chemical compositions that can be used to make synthetic pot, a chemical-laced plant material that sells for $10 to $50 per half-ounce and first started appearing on the market about three years ago. That's why the banning of the known formulas only stifles the market temporarily.

That reality has left Cooper frustrated. She said her son suffered a psychotic break when he started smoking the drug.

"If he couldn't buy that crap, it would take a load off my mind," Cooper said.

She's written letters to the governor, talked to her local sheriff and even called the GBI. But state and local law enforcement officers say their hands are tied because they cannot bring criminal charges against the people who are buying and selling new formulations of the drug, which is typically sold in little foil packets or small plastic bags and is sometimes marketed as incense or potpourri. Police can take only what's displayed in plain sight, unless they obtain permission to search the premises.

Retailers — realizing that police powers are limited — have moved their stock from store shelves to behind the counter, where they continue to sell it to regular customers upon request, said Phil Price, who heads the Cherokee County Multi-Agency Narcotics Squad. The inability to catch the culprits is extremely frustrating for police.

"It's like trying to grab a handful of smoke," Price said.

Meanwhile, reports of hospitalizations and deaths attributed to the use of synthetic marijuana are on the rise.

Georgia Poison Center call data shows 10 users were admitted to hospital critical care units in 2010 after using the drug. Forty-five were admitted in 2011.

GBI testing confirmed that synthetic marijuana was in the system of three young men who died tragically this year. Peachtree City teen Chase Burnett drowned in his hot tub in March after smoking it; Kelvin Melton, 26, of Athens, died in February of a heart condition brought on by frequent use; and Dakota Dyer, 14, of Bremen, shot himself in March while high on the drug.

Brett Bagley, program director at Purple Inc., a residential drug treatment center for men in Lawrenceville, said he's starting to see more clients who prefer Spice over marijuana.

Zach, 21, who asked to be identified only by his first name so others wouldn't know about his drug abuse, is in his second month of drug treatment. He used Spice while on probation because it doesn't show up in drug tests. He said the effects of spice are more intense than marijuana and more physically addictive.

"The first couple times you smoke it, you feel like you can't even breathe," Zach said. "Your heart is pounding through your chest. My friends have had psychedelic experiences on it."

Over time, the Bartow County man had to smoke more and more to obtain the same high. He became a daily user. However, Zach sought rehab when his parents threatened to kick him out. Now, he supports outlawing the drug and wants to warn others about the dangers of using it.

Police hope that, by continuing to seize the products, eventually they'll hit retailers in the pocketbook and force them to stop restocking it.

The GBI is also putting pressure on manufacturers to try to disrupt the supply. Since June, agents have served about half a dozen search warrants on local factories, where they seized documents and carted away drugs to be tested.

No one has yet been arrested in connection with the search warrants, said Rusty Grant, supervisor of the Canton Regional Drug Enforcement Office of the GBI.

By the time the General Assembly reconvenes in January, state officials hope to have devised a way to outlaw the entire spectrum of synthetic marijuana compounds.

Removing the temptation might help those struggling with addiction to synthetic marijuana to finally get clean — or at least, that's Cooper's hope.

"I know it's not the whole solution to the problem," she said. "We're working on my son, too. But it doesn't help that he can drive two miles from our house and buy a pack of that stuff."

* Staff writer Willoughby Mariano contributed to this story.