The agency sent warning letters to four manufacturers of these beverages including Phusion Projects LLC, which makes Four Loko, and United Brands Co., which makes Joose.

If the companies do not comply, the FDA can seize the products under federal law.

"FDA does not find support for the claim that the addition of caffeine to these alcoholic beverages is 'generally recognized as safe,' which is the legal standard," said Joshua M. Sharfstein, principal deputy commissioner for the FDA. "To the contrary, there is evidence that the combinations of caffeine and alcohol in these products pose a public health concern."

The FDA said it expects "prompt action" from these manufactuers in removing the drinks from shelves.

Charge Beverages Corp. and New Century Brewing Co. also received warning letters for their products.

Just one day before the ruling, Four Loko's Phusion Projects said it would drop the caffeine and two other ingredients to "reformulate" the beverage.

In a press call Wednesday morning, the FDA said it views Phusion Projects' announcement "as a positive step."

The caffeinated alcoholic beverage commonly referred to as a "blackout in a can" is making waves on college campuses and beyond where people are "getting Loko.”

In the statement released Tuesday night, Phusion Projects LLC said, "We are taking this step after trying – unsuccessfully – to navigate a difficult and politically-charged regulatory environment at both the state and federal levels. Over the last several months we have been more than willing to talk with regulators and policymakers on the national, state and local levels. Our company has a history of being as cooperative as we possibly can to ensure that our products are consumed safely, responsibly and only by of-age adults."

While medical officials decry the drink’s dangers, a very vocal contingent defends it, calling for underage drinkers to simply be responsible.

The debate has brought the drink, its 12 percent alcohol content and its manufacturers into the limelight in recent weeks as state after state takes action to ban the beverage from shelves.  

Michigan, Oklahoma, Utah and Washington have already prohibited vendors from stocking and selling Four Loko. Other states are weighing a ban on the sale of these drinks.

Massachusetts regulators announced a ban on Monday, and some beer distributors in New York agreed to a voluntary ban on Saturday. The Pennsylvania Liquor Control Board has discouraged vendors from selling the beverage until the FDA rules on its safety. The Chicago City Council is also reportedly looking into a ban.

Attorney generals in 18 states, including California, urged the FDA to look into the safety of the drinks, recommending the "immediate removal of [Alcoholic Energy Drinks] from the marketplace."

The caffeine-laced alcoholic beverages have become popular on college campuses since first marketed in 2005.

Nine underage students at Central Washington University were hospitalized in October for reportedly becoming "dangerously ill" from drinking "large amounts" of Four Loko at an off-campus party.

More than 20 students have been hospitalized for Four Loko-related incidents at Ramapo College in New Jersey. The school has since banned the drink.

Other schools including Harvard University, Lebanon Valley College in Pennsylvania and the University of Rhode Island are warning students of the dangers of the beverage or prohibiting it on campus.

College officials at Elizabethtown College in Pennsylvania are attempting to discourage drinkers by stressing its caloric value, which hovers somewhere between 600 and 800 calories.

One 23.5-ounce can of Four Loko is said to contain the equivalent of four or five beers and the caffeine in two cups of coffee.

Phusion Projects has repeatedly defended its product, issuing statements after the incident at Central Washington University and after various state bans.

“No one is more upset than we are when our products are abused or consumed illegally by underage drinkers – and it appears that both happened in [the CWU] instance. This is unacceptable. But so too is placing blame for the incident squarely on Four Loko when the police report, toxicology reports and witness testimony all show that other substances, including beer, hard liquors like vodka and rum, and possibly illicit substances, were consumed as well,” the company said in a statement about CWU.  

To enter Four Loko’s website, visitors have to enter their birth date to ensure they are 21 years of age and confirm their birth year, and then are prompted by a pop-up window to read an open letter to state and federal regulators from Phusion Projects. The company has also added a “Responsible Drinking” section to its site in light of recent media and government attention.

In the open letter, the company’s founders write, “While we don’t agree with the notion that mixing caffeine and alcohol is inherently unsafe, we do agree with the goal of keeping adults of legal age who choose to drink responsibly as safe and as informed as possible.”

FDA spokesman Michael L. Herndon said the agency notified manufacturers of caffeinated alcoholic beverages in November 2009 that it was looking more closely into the safety of the beverages.

The drink's 12 percent alcohol content, when combined with caffeine and other ingredients, has experts and medical officials worried.

Deborah Feller, a New York psychotherapist dealing with alcohol and substance abuse and dependency, said one of the biggest risks with a drink like Four Loko is the mixture of the caffeine, a stimulant, and the alcohol, a central nervous system depressant.

“When you put caffeine in with alcohol you can drink more alcohol without being put to sleep, and you're in much more danger of OD'ing and getting ill or dying,” she said. “It doesn't get more dangerous than that because you're not feeling the effects of the alcohol because the caffeine is acting as a stimulant or an antidote.”

Dr. Jeff Baldwin, a professor at the University of Nebraska Medical Center College of Pharmacy and a substance abuse educator, refers to the combination’s effects as an “awake drunk.” 

“The old wives tale of drinking coffee to sober you up is not true,” he said. “All it does is make you a more awake person who is still equally impaired. You're just not sleeping.”

Baldwin stressed that one big issue with drinks like Four Loko is how fast people drink them. 

“It's like a 6-pack of beer in a can or a liter of wine—nobody in their right mind would think about drinking a liter of wine in an hour and yet these kids are drinking a full can,” he said.

Websites and parodies have sprung up in light of the drink’s recent popularity.

Fourlokostories.com serves as a forum for visitors’ best Four Loko stories.

Some examples:

4loko runaway: i seem to have a reoccurring incident with fourlokos whenever i drink them each time i black out and try to leave wherever i am naked and drive home. loco for lokos!!!
beckster: I had a mixture of a few different Four Lokos and ended the night in the ER with a broken ankle, singing Juicy by Notorious B.I.G to everyone.

The site has its own “Four Lokator,” which tracks where in the U.S. bans have been placed on the beverage.

But many college students are criticizing the bad rap the drink has gotten and are making the case that drinking Four Loko is just like drinking any other kind of alcohol—it has to be done responsibly.

“On Four Loko cans, it is clearly stated that the drink contains caffeine and is 12 percent alcohol by volume. If you are capable of absorbing this information and choose to consume said drink anyway, you should be prepared to take responsibility for whatever repercussions may arise from your consumption," writes the editorial staff of the student newspaper at the State University of New York at Geneseo.

Though some use the drink as a pregame—or warmup—before drinking other kinds of alcohol, one 19-year-old USC student, said she and her friends know their limits.

“If I’m drinking Four Loko, that’s my drink for the night and I’m sipping it.”

A student at Columbia College’s Columbia Spectator wrote, “Four Loko is the fast food of alcoholic beverages. It’s unhealthy and widely available. It’s also quick, cheap and, to some, a satisfying if shamefully hedonistic indulgence. Sure, Four Loko isn’t the best for you. Neither is fast food, but would you want a law denying you the occasional greasy burger?”

To reach editor-in-chief Callie Schweitzer, click here.
To follow her on Twitter: @cschweitz
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