Smoking reduces the effects of alcohol and may encourage more drinking, scientists have found.
The research helps to explain why cigarettes and alcohol seem to be such natural social partners.
A team led by Dr Wei-Jung Chen, from the Texas A&M Health Science Centre in College Station, US studied rats exposed to a combination of alcohol and nicotine.
The scientists found that nicotine reduced blood alcohol concentrations in the rodents at levels which could have an impact in human smokers.
"Since the desired effect of alcohol is significantly diminished by nicotine - particularly among heavy or binge drink-ers such as college students -this may encourage drinkers to drink more to achieve the pleasurable or expected effect," said Dr Chen.
"In other words, cigarette smoking appears to promote the consumption of alcohol."
The findings appear in the latest issue of the journal Alcoholism: Clinical & Experimental Research.
Researchers administered a range of nicotine doses together with injections of alcohol to adult female rats.
Blood alcohol concentrations (BACs) were then measured at various time intervals.
"The presence of nicotine will significantly reduce peak BAC and such a pharmacokinetic interaction between alcohol and nicotine may be related to the nicotine dose," said Dr Chen.
Susan Maier, health scientist administrator at the US National Institutes of Health said: "In the human condition, persons desiring to drink 'to effect' will need to drink more alcohol while smoking in order to reach this effect, and this will lead to an increased amount and lingering presence of toxic by-products of alcohol metabolism, such as acetaldehyde.
"This would be particularly harmful for adolescents and young adult drinkers, since these populations are amenable to this type of drinking pattern, and may develop chronic alcohol-related diseases earlier in life because of it."
O ne effect of the nicotine/alcohol interaction might be to permanently alter metabolism, she added. This could reduce the effect of beneficial medicinal drugs in people who both smoke and drink.