Associated Press
Four Loko, an alcoholic energy drink, sickened Washington college students.

Mixing alcohol and caffeine is hardly a new concept, but a rash of cases involving students and others who landed at hospitals after drinking beverages that combine the two in a single large can has alarmed college and health officials.

The drinks are dangerous, doctors say, because the caffeine masks the effects of the alcohol, keeping consumers from realizing just how intoxicated they are.

A brand called Four Loko — a fruit-flavored malt beverage that has an alcohol content of 12 percent and as much caffeine as a cup of coffee — has come under particular scrutiny after students who drank it this fall at Ramapo College in Mahwah, N.J., and Central Washington University in Ellensburg, Wash., ended up in emergency rooms, some with high levels of alcohol poisoning.

At the urging of 18 attorneys general, the Food and Drug Administration, which has never approved adding caffeine to alcohol, is reviewing whether the drinks are safe. And in July, Sen. Charles E. Schumer, D-N.Y., asked the Federal Trade Commission to investigate whether the drinks, with colorful packaging and flavors like watermelon, blue raspberry and lemon-lime, are "explicitly designed to attract under-age drinkers."

Lawmakers in several states have sought to ban the drinks, though no legislation has passed yet.

Dr. Peter Mercer, president of Ramapo College, went so far this month as to ban Four Loko and other energy drinks that combine caffeine and alcohol after six students were taken to the hospital after drinking Four Loko.

Chris Hunter, a co-founder and managing partner of Phusion Projects, the five-year-old Chicago company that owns Four Loko, said Tuesday that the drink, introduced in August 2008, was being unfairly singled out. The company takes steps to prevent its products from getting into the hands of minors, he said.

In a separate statement published on its website, Phusion Projects questioned why a police investigation into the Central Washington University incident had focused on Four Loko when, according to the police report, a number of other alcoholic beverages, including beer, vodka and rum, were also found at the off-campus party where students got sick.

Rob McKenna, the attorney general in Washington, said that while many students at the party had mixed alcohols, some of those who were hospitalized had drunk only Four Loko.

Also under scrutiny is Joose, a caffeinated alcoholic beverage made by United Brands, a San Diego company.