SILVER SPRING, Md. (AP) _ Scientists began debating the addictiveness of nicotine Monday, using as a case study an experimental nicotine nasal spray to help hard-core smokers quit.

But some fear such a spray could be abused, and advisers to the Food and Drug Administration agreed that was possible. The FDA should allow sales only with prescriptions, strong warnings about its danger and a limit on refills, the scientists recommended Monday.

''I'm worried we've found a new dosage form for an old drug of abuse,'' said Dr. E. Douglas Kramer of the FDA.

The agency is considering whether to approve Pharmacia Inc.'s new nicotine nasal spray, a pump bottle holding 100 milligrams of pure nicotine that smokers can inhale to ward off cigarette cravings.

Smokers now can seek prescriptions for nicotine gum or patches to help them kick the habit. But the nasal spray is much more powerful, and the FDA asked a panel of scientific advisers Monday whether some smokers would find themselves still addicted to nicotine - from a bottle instead of a cigarette.

It was a prelude to a bitter fight expected when the FDA asks the advisory committee Tuesday to determine the level at which nicotine in cigarettes becomes addictive. That's the latest step in the FDA's move to regulate nicotine as a drug.

Cigarette makers Monday showed reporters 1,700 documents they said support their position that smokers puff solely by free choice - and that the government shouldn't interfere.

''Cigarette smoking is a habit, not an addiction,'' said R.J. Reynolds Tobacco Co. vice president Charles Blixt, noting that different nicotine levels give different cigarettes individual tastes.

Anti-smokers want FDA Commissioner David Kessler to mandate nicotine levels in cigarettes. Less than 1 milligram per cigarette by weight is the latest proposal, but that's lower than the lowest-nicotine cigarette ever sold, one smokers refused to buy.

That would in effect outlaw cigarettes, Blixt contended.

Philip Morris vice president Steven Parrish said the FDA stacked the deck, giving the entire industry only one hour of Tuesday's daylong meeting to make its case to a panel of scientists who get significant funding from an anti- smoking government.

As cigarette makers chafed, scientists began telling the panel Monday that nicotine is addictive.

Dr. Richard Hurt hospitalizes hard-core smokers at the Mayo Clinic. But he said even hospitalization and nicotine patches didn't help one 30-year-old patient, who still smokes despite suffering a tobacco-caused disease that is cutting off blood flow to her fingers so they'll eventually have to be amputated.

FDA scientists said one woman sniffed pure nicotine for a year in what was supposed to be a three-month trial of the nasal spray. Despite suffering a nasal ulcer, she plotted to get unused bottles from other study participants and watered down her last supply to make it last longer, finally resuming smoking.

In three studies involving 369 spray users, only 26 people used the spray for a full year. Researchers said 95 people kicked the habit thanks to the spray - but it still had a 43 percent relapse rate.

FDA officials said they fear abuse of the spray because it hits the bloodstream faster and at a higher rate than nicotine gum or patches. People also could poison themselves by inhaling too much - 40 to 60 milligrams at once is lethal.

But the spray is so unpleasant to squirt up the nose that doctors say they have a hard time getting some patients to use it, said Pharmacia's Karl-Olav Fagerstrom.

Even the spray isn't strong enough to help some people stop smoking, said Gay Sutherland, who tested the spray at London's National Addiction Centre. ''We need more effective treatments.''