Some cigarettes 'more addictive'
Some cigarette brands are likely to be far more addictive than others, new research warns.
For the first time, scientists have measured the amount of super-addictive "freebase" nicotine different cigarettes deliver to the smoker.
Like crack cocaine, freebase nicotine vaporises and passes rapidly through the lungs into the bloodstream.
Because it reaches the brain so quickly it is thought to be more addictive than normal nicotine, which stays in the form of sooty smoke particles.
Until now it has not been known how much freebase nicotine various types of cigarette contain.
The new research, from a team at Oregon Health and Science University in Portland, US, could lead to ways of rating the addictiveness of different brands.
Scientists compared 11 brands of cigarette available in the US.
They found that some brands contained 10 to 20 times higher percentages of freebase nicotine than experts had previously been led to believe.
Brands were compared with a laboratory "reference" cigarette containing 1 per cent freebase nicotine.
They varied greatly, ranging from 1 per cent or 2 per cent to 36 per cent for a specialty US brand called American Spirit.
The popular Marlboro brand contained up to 9.6 per cent freebase nicotine. Other well known brands included Camel (2.7 per cent), Winston (5 per cent-6.2 per cent) and Gauloises Blondes (5.7 per cent-7.5 per cent).
Professor James Pankow, who led the study reported in the journal Chemical Research in Toxicology, said: "We found big differences in the percentages of freebase nicotine among 11 commercial cigarette brands.
"During smoking, only the freebase form can volatise from a particle into the air in the respiratory tract. Gaseous nicotine is known to deposit super-quickly in the lungs. From there, it's transported rapidly to the brain.
"Since scientists have shown that a drug becomes more addictive when it is delivered to the brain more rapidly, freebase nicotine levels in cigarette smoke thus are at the heart of the controversy regarding the tobacco industry's use of additives like ammonia and urea, as well as blending choices in cigarette design."
A 1997 study led by Professor Pankow linked ammonia additives with increased freebase nicotine levels in cigarettes.