'Crack' nicotine in cigarettes varies widely
15:24 28 July 03
NewScientist.com news service
Some cigarettes have a "kick" containing 35 times more "freebase" nicotine - the most addictive form - than others, researchers have found. The findings could help rate the addictiveness of different brands, they say.
"Free-base" nicotine is a particularly potent form of the naturally-occurring tobacco drug because it is in an extremely volatile, uncombined form. This means it can be much more rapidly absorbed by the lungs and brain than nicotine derivatives such as nornicotine or its salts.
The new study is the first into the amount of "free-base" nicotine contained in common brands of cigarettes and found wide-ranging differences. The researchers at Oregon Health and Science University used a laboratory smoking device and a gas chromatograph-mass spectrometer to collect and analyse smoke from 11 brands of cigarettes. The study measured the first three puffs of smoke from each cigarette.
"Measurements ranged from about one per cent free-base nicotine in the first few puffs to 36 per cent for a specialty US brand," says lead researcher James Pankow. "One type of Marlboro, the leading US brand of king-sized filter cigarettes, contained about 10 per cent free-base nicotine."
Previous research has shown that a drug's addictiveness is influenced by the speed at which it is delivered to the brain and absorbed into and from the blood stream.
"The study shows that the modern cigarette does to nicotine what crack does to cocaine," says addiction expert Jack Henningfield, at the Johns Hopkins University School of Medicine. The notorious addictiveness of smoking crack results from the vapourised cocaine reaching the brain almost immediately.
Ian Jones, a nicotine expert at Bath University, UK, adds: "Free-base nicotine is the most damaging form because it is the optimal configuration for binding to the nicotine receptors in the brain, heart and rest of the body. If the binding efficiency is increased, it means the concentration of nicotine at the receptors is higher and so it is very addictive."
"The first few puffs are the most important in terms of addiction, because nicotine reaches the brain within seconds," Jones told New Scientist
Ammonia and urea
The amount of freebase nicotine in cigarette smoke increases as the alkalinity, or pH, increases. This factor can be influenced by the use of certain additives.
"It is likely that ingredients such as ammonia and urea account for this addiction-enhancing effect. But you can also adjust the chemistry of the smoke by adjusting the blend. Some types of tobacco give a more basic blend," Pankow told New Scientist.
"There was tremendous amount of documentation revealed during litigation in the US of manipulation of the freebase levels and the FDA certainly believed there was manipulation of cigarette chemistry," he adds.
"What is clear is that the modern cigarette is a highly engineered nicotine delivery device and it's not just a matter of tobacco rolled-up in a piece of paper," Pankow says. "Even the so-called 'additive-free' cigarettes are highly engineered."
Journal reference: Journal of Chemical Research in Toxicology (DOI: DOI: 10.1021/tx0340596)