An advisory panel of the Food and Drug Administration yesterday rejected tobacco industry contentions that its products are not addictive, voting unanimously that "the amount of nicotine delivered by currently marketed cigarettes {is} likely to lead to addiction in the typical smoker."

The finding does not commit the agency to a course of action, but it allows the FDA to go forward in considering whether to regulate tobacco products, just as it regulates all drugs ranging from codeine to over-the-counter antihistamines. The FDA has said that it could regulate tobacco products if it determined that they are sold as drugs -- or, in the language of the laws governing the agency, to "affect a structure or function of the body."

FDA Commissioner David A. Kessler called the panel's decision about addictiveness "enormously important, because it changes the way you have to look at the whole issue." The industry has long contended that smokers choose their habit freely, but addictiveness would eliminate that choice, Kessler said.

Tobacco industry representatives, sitting grimly at the back of the meeting as the committee members voted, denounced the finding. "You can't determine, by their definition, the differences between caffeine and crack cocaine," said Maura Ellis, a spokeswoman for R.J. Reynolds Tobacco. "That's a ludicrous definition."

The eight-member panel was convened to evaluate evidence on nicotine's addictive potential and to vote on seven questions concerning dependence and thresholds of addiction. They spent the day at the Silver Spring Holiday Inn hearing radically conflicting testimony.

One group of speakers portrayed nicotine as a highly addictive drug that exposes smokers to numerous health risks. Another group, speaking during time allotted to the tobacco industry, vehemently denied that nicotine is addictive.

The panel also was asked to consider whether there is an apparent threshold of nicotine addiction -- a level below which persons could smoke but not become hooked. Finding that level would make it possible to mandate nonaddictive cigarettes, ensuring that people experimenting with tobacco products would not become addicted, researchers said.

Kessler, who sat in on the entire nine-hour meeting yesterday, said, "The more I read and the more I look at this, the more I realize our goal ought to be to prevent the next generation from becoming addicted."

Neal Benowitz of the University of California at San Francisco told the panel that it takes from two to three years for smokers to move from trying their first cigarette to daily smoking.

Benowitz said that research conducted with Jack E. Henningfield of the National Institute on Drug Abuse suggested that the nicotine levels in cigarettes could be reduced to nonaddictive levels. Benowitz said that the 10 to 15 percent of smokers who smoke five cigarettes a day or fewer do not appear to be addicted. They take in about 5 milligrams (mg) of nicotine a day, Benowitz said, and he estimated that "maybe 5 mg a day is a level below which addiction is not maintained."

Thus, cigarettes that contain 0.6 milligrams of nicotine and deliver 0.25 mg of nicotine to the smoker would fall below the addictiveness threshold for a person who consumed 20 cigarettes a day, Benowitz said.

No cigarette on the market offers such low nicotine levels, and nicotine-free cigarettes so far have failed in the market. Panelist Lynn Kozlowski, a researcher from Pennsylvania State University, said, "I'm kind of skeptical that there would be any smoking at all of a cigarette that doesn't have a buzz attached to it."

Benowitz said that to protect current smokers from the pains of cold-turkey withdrawal -- and to head off the prospect of a black market in high-nicotine cigarettes -- any plan to reduce nicotine levels should be phased in gradually over a period of at least 10 years.

R.J. Reynolds scientist John Robinson charged that the FDA is planning to embark on "a huge social experiment with what would amount to nicotine prohibition -- with 45 million American smokers as the test subjects."

Members of the advisory panel questioned Benowitz's thesis, however. Panelist Alice M. Young of Wayne State University suggested that gradual diminution of nicotine in cigarettes could result in current smokers increasing their intake to compensate.

Others pointed out that the low-nicotine route could not be tested scientifically by any means short of regulation.

A study to determine whether young people become addicted to low-nicotine cigarettes would be impossible to conduct, Benowitz said, because "you can't give kids cigarettes and watch them become addicted in the laboratory."

David Sachs of the Palo Alto (Calif.) Center for Pulmonary Disease Prevention offered supporting evidence that 5 mg per day was a reasonable addiction threshold. Analysis of the experiences of users of nicotine patches indicated that 5 mg a day does maintain physiological dependence, he said.

At the end of the day, a majority of the panel voted that some threshold existed, but that there was insufficient evidence to determine the exact amount of nicotine that causes dependence.

The pro- and anti-tobacco camps came into sharp conflict repeatedly throughout the day.

Robinson, speaking for the tobacco industry, said that nicotine is not addictive "by any meaningful definition of the word," because, according to him, addiction requires intoxication. "To conclude otherwise actually endangers our credibility as scientists," Robinson said.

Similarly, psychologist Dominec Ciraulo of Tufts University School of Medicine contended that because nicotine does not produce intoxication and euphoria as opiates do, it could hardly be considered in the same category.

But John Grabowski, an addiction specialist at the University of Texas Health Sciences Center, said in an interview that references to intoxication were misleading because there are substances, such as methadone, that are addictive yet produce no kick. Grabowski said that tobacco industry speakers were "misrepresenting the field" with "straw man" arguments.