New designer drugs, made to bypass standing legislation that outlaw their original forms, are hitting the market, raising concern among U.S. physicians. Among them are shatter, a highly concentrated form of marijuana legal in Colorado; fentanyl, a stimulant up to 50 times stronger than heroin; and, at the forefront of many public health officials’ minds, “Flakka,” a tweaked version of bath salts that, in some cases, can cause heart palpitations and aggressive, violent behavior.

Following 2012 federal legislation that banned some varieties of bath salts, manufacturers have altered the chemical makeup of the amphetamine-like drug to concoct this stronger, more highly addictive and still-legal form of the drug, sold in Florida as Flakka but in other parts of the United States as “Gravel.” “Flakka” is derived from the Spanish word “flaca,” meaning “skinny,” and in Hispanic cultures is generally thought to refer to a beautiful, elegantly thin woman.

According to the Drug Enforcement Administration (DEA), in the United States, synthetic cathinones, which encompasses Flakka and bath salts, rose from 14,239 to 16,500 annual cases from 2012 to 2013, the most recent data available.

Some reports say Flakka can be traced to China, but its origin hasn’t been confirmed. In addition to Florida, law enforcement agencies have reported Flakka cases in Ohio and Texas.

'Excited delirium'

While there may be various chemical versions of the drug circulating in the United States, in the South, Flakka is being sold mostly as the synthetic cathinone alpha-PVP, said Jim Hall, an epidemiologist at Nova Southeastern University in Fort Lauderdale, Fla. Alpha-PVP is a substance that provides an instant sense of euphoria and a boost in physical strength similar to other stimulants like cocaine and ecstasy.

Abdul El-Sayed, assistant epidemiology professor at Columbia University, said it’s unclear how powerful the drug is, but some reports suggest it is even stronger than crystal meth and bath salts.

Like those stimulants, Flakka affects the reward center of the brain by releasing dopamine and flooding the user with a feeling of pleasure. When the body overdoses on euphoria, a phenomenon physicians refer to as “excited delirium” occurs. During this process, the body becomes overheated, inducing hypothermia, and then the muscles over-activate, and the mind begins hallucinating.

When people overdose on flakka, crystal meth or bath salts, their muscles can also disintegrate, releasing a protein into the blood that affects the kidneys. When the kidneys can’t filter that protein, this complication can lead to kidney failure or even death.

In South Florida— where hospitals are admitting 20 new patients per day for Flakka abuse, Hall said— the new synthetic drug has made headlines in recent months after two men exhibited symptoms of having used it. In March, it took five police officers to restrain a man in Miami who ripped off his clothes, screamed loudly, and began hallucinating after smoking a crystal-like drug believed to be alpha-PVP.

In early April, video taken from a bystander shows another Florida man who admitted to taking Flakka streaking the streets of Fort Lauderdale while he imagined unknown people stealing his clothes then chasing him.

“One of the reasons we think alpha-PVP is such a problem is because it is extremely dose-specific, and even just a little dose will give a person the desired effect of they want,” Hall told FoxNews.com. “Just a little more can create a number of serious adverse effects to the point the user doesn’t even know.”

A stronger addiction

Flakka comes in crystalline rock form, and it can be swallowed, snorted, injected or vaped in an e-cigarette. It’s generally snorted, Hall said, but it can also be cut and smoked in a cigarette, or used in a marijuana pipe coupled with marijuana. Effects are felt for three or four hours and can continue for days after.

When new drugs hit the streets, doses aren’t well characterized, so determining what potency can cause said erratic behavior is challenging. The drug is reportedly being sold in Florida for $5 for one-tenth of a gram.

“It’s cheap like crack cocaine,” Hall said. “This is as close as we’ve come to a crack cocaine problem since 1995 in terms of the severe reactions, low prices, and that it’s available to young kids, and even homeless populations are now impacted.”

Not knowing what strength of dose is being offered can also make it easy for users to take too much, El-Sayed said.

“It’s being marketed to folks with amphetamine addiction, and they market it as the latest and greatest,” El-Sayed told FoxNews.com, “but the reality of addiction is that the main hallmark is tolerance. A lot of these folks are really tolerant already. It’s not pure, so there’s no standard for how much people can take. People are basically playing with their lives by taking this.”

What makes synthetic cathinones like Flakka so addictive is their ability to block the reuptake transporters of dopamine.

“More of it remains active flooding the brain with excess dopamine, resulting in intense pleasure and its related anticipation that users come to crave— resulting in compulsive use and a stronger addiction,” Hall said. “Designing the molecule of a drug that blocks the exit door for dopamine in the brain makes it a more addictive substance.”

A growing public health issue

Today, 15 to 20 percent of the patients enrolled in treatment programs in South Florida were admitted for Flakka, Hall said.

Standard treatment for someone who overdoses on a stimulant involves not stimulating them anymore and actively sedating them, said Mark DeBard, an emergency physician and an emergency medicine professor at Ohio State University.

“In general, the best guidelines are to make them safe and yourself safe, and to minimize restraint as they undergo getting medical help,” DeBard told FoxNews.com.

He said in Ohio, treating stimulant overdoses isn’t an “everyday” problem, but that he sees at least one patient who has overdosed on some stimulant, most commonly cocaine in the last decade, every week.

As the variety of synthetic drugs— methylone, or “Molly,” and MDMA, or “ecstacy,” among them— grows due to an increasing demand on the streets, Hall and El-Sayed expressed concern over what their increasing strength could mean for public health.

“The immediate question that comes to mind is, ‘This is a really crazy drug, and how can we make sure we’re safe from people who use this drug?’” El-Sayed said. “But the question we should be asking as a society is, ‘Why are people turning to drugs like this, and why is there this increasing need for stronger drugs?’ So we should be looking at this not as a law enforcement problem but as a public health problem.”