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. Its review began a year ago, and Mr. Schumer expressed frustration on Wednesday that the agency had yet to announce any findings.

“It’s about time they hurry up with their report,” he said, “before more tragedies occur.”

The bans are to go into effect in Washington on Nov. 18 and in Michigan on Dec. 4.

Four Loko came under particular scrutiny after students who drank it this fall at Ramapo College in New Jersey and Central Washington University in Ellensburg, Wash., ended up in emergency rooms, some with high levels of alcohol poisoning. Both institutions banned the drink on their campuses, and many others have since warned students not to drink it.

In a statement released Wednesday, Phusion Projects, the five-year-old Chicago company that makes Four Loko, said it was “disappointed” by calls to ban the drink, adding that it was safe.