"I pretty much went into my inebriation without really realizing it," he said in an e-mail. "I was talking a lot, being loud, yet I also felt very alert and sober as if the drink was doing nothing to me."
A website for the manufacturer of Four Loko — Chicago-based Phusion Projects — said the drink is distributed in 47 states.
Phusion says the Philadelphia case is exactly why the company goes to "great lengths" to make sure its drinks are not sold to underage consumers.
"Our cans feature seven different warnings about the product's alcohol content and the necessity of an ID for purchase," the company said in a statement provided to ABC News. "And we're the only manufacturer to prominently place a 'WE ID' message on our can. We also offer free, point-of-sale materials to stores selling our products that reinforce the importance of asking for identification when selling any alcoholic beverage."
The company says it has also rejected social marketing tactics used by some of its competitors.
"There is no company-sponsored "Four Loko" Facebook page or You Tube channel," the statement says.
Fans, however, are using social media to create popular -- if unofficia l— places for Four Loko enthusiasts to spread the word.
One Facebook page bearing the title "four lokos are blackouts in a can and the end of my morals" has more than 71,000 "likes."
As the alcohol-caffeine concoctions -- sometimes dubbed "cocaine in a can" -- are becoming more popular on college campuses, officials are taking notice.
Attorneys general in several states are investigating whether the drinks are being marketed to underage drinkers.
One New Jersey college banned the drinks this month after 23 students were hospitalized with alcohol-related problems. At least some of them reportedly drank Four Loko.
"There's no redeeming social purpose to be served by having the beverage," Ramapao College President Peter Mercer told The Associated Press.
But across Twitter, many people seem to think the ban will only make the drink more popular.
"Four Loko stock is goin (sic) to go thru the roof this weekend," wrote Reacy23.
A Food and Drug Administration spokesman told ABC News that determining whether drinks like Joose and Four Loko are legal is a high priority for the federal agency.
The FDA says food additive regulations currently do not allow mixing caffeine with booze. Drink manufacturers maintain their products contain ingredients that are "generally recognized as safe" but now the FDA wants them to prove it.
Last year the agency sent 27 letters to drink makers seeking more information. 19 companies responded.
"FDA intends to evaluate the information submitted by the manufacturers and other available scientific evidence as soon as possible in order to determine whether caffeine can be safely and lawfully added to alcoholic beverages," spokesman Michael Herndon said in an email.
Herndon said the timing of any FDA decision to regulate the drinks is difficult to predict. Until then, the drinks will continue to be sold. If the agency determines the drinks are illegal or should be regulated, sanctions against the manufacturers could range from a warning letter to having their products seized.
"FDA intends to exercise all options that are appropriate for the product in question," said Herndon.
Dr. O'Brien believes the FDA is dragging its feet by allowing the drinks to stay on store shelves.