A new front in the U.S. government’s war on drugs is underway in America’s poorest neighborhoods, say drug policy reform advocates, as authorities struggle to control the spread of synthetic marijuana, which medical professionals say causes erratic behavior and severe health problems in users.

Reform advocates say that 20th-century prohibition tactics are unlikely to stop people, many of them homeless and mentally ill, from smoking synthetic cannabis, also known as K2. They say a better approach is to increase efforts to reduce the drug’s harm rather than making its possession or sale illegal.

“This idea that we can ban synthetic marijuana and stop people from using, history tells us that that doesn’t work,” said Alyssa Aguilera, political director at VOCAL, a New York based non-profit that opposes drug criminalization.

As marijuana witnesses increasing acceptance across the U.S., the drug’s synthetic form stands out as an exception, with states increasingly passing measures that impose harsher penalties on its sale and possession. And federal authorities, citing a 229 percent increase in hospitalizations related the synthetic cannabis in the last year, have recently followed suit.

A New York City bill introduced this week would set criminal penalties for storeowners who sell the synthetic drug. Penalties would include one year in jail and a $5,000 fine. New York already prohibits synthetic cannabis, but only if its contents meet a specific standard.

The chemicals vary widely from batch to batch, and some include legal ingredients. Synthetic marijuana does not show up on standard drug tests administered to people on parole. That's one of its main draws to users, many of whom are entangled with the criminal justice system.

The bill's sponsor, City Council Chairwoman Melissa Mark-Viverito, said laws against marijuana possession could be behind the popularity of the synthetic drug. The measure would criminalize the sale of any drug the seller markets as being synthetic marijuana, no matter what is contained in the package.

“Our policing of marijuana may . . . have led users to K2,” Mark-Viverito told the New York Daily News. “This is an opportunity to look at issues of marijuana policy that might be driving folks to this dangerous drug."

While Aguilera praised the bill for targeting sellers instead of users, she said criminalizing its sale could make the drug more dangerous.

New York medical professionals say they have seen synthetic marijuana smokers demonstrate disturbing behavior and painful reactions to the drug.

“I've seen patients become extremely psychotic and aggressive from K2 use,” said a psychiatric resident at a New York hospital who works with patients who have taken the drug but who is was not authorized to speak on the record. "They may appear sedated and withdrawn at first, but within minutes they can easily become violent.”

Cities across the country have seen spikes in hospitalizations and arrests related to synthetic cannabis, which the federal government outlawed in 2012. In New York City last week, the federal Drug Enforcement Agency (DEA) arrested an alleged ring of synthetic marijuana manufacturers, raiding 80 convenience stores on suspicion of selling the product. The operation confiscated the equivalent of 260,000 1-gram packets.