Lê, A.D., Corrigall, W.A., Watchus, J., Harding, S., Juzytsch,W., & Li, T. K. (1999, February). Involvement of nicotine receptors in alcohol self-administration. Alcoholism: Clinical and Experimental Research, 24(2), 155-163.
It is no secret that alcohol beverages and tobacco are often consumed/used at the same time. The exact mechanisms, however, for the concurrent use of the two substances have stumped researchers for some time. A recent study published in the February edition of Alcoholism: Clinical & Experimental Research, has shown that nicotine, the active ingredient in smoking, increases alcohol consumption.
"We knew that many more alcoholics smoked than members of the general population," said Dzung Anh Lê, senior scientist at the Centre for Addiction & Mental Health, assistant professor of pharmacology at the University of Toronto, and the study’s lead author. "We also knew that the active ingredient in smoking is nicotine. So we asked ourselves: Does nicotine increase alcohol consumption?"
Of the five experiments that comprised Lê’s study, three confirmed their suspicions. "We found that nicotine can indeed promote alcohol consumption," said Lê. "Furthermore, it’s likely that nicotine and alcohol can act through the same rewarding system in the brain."
Nicotine is defined as "a poisonous volatile alkaloid derived from tobacco." It is also the ‘addictive’ component of tobacco. On average, between 80 and 90 percent of the nicotine that reaches the lungs through cigarette smoking is absorbed into the body. After reaching the brain, nicotine activates a group of proteins called nicotinic receptors. These proteins, located on the surface of certain brain cells, normally regulate a number of physiological functions, some of which may contribute to aspects of reinforcement or dependency. Ultimately, nicotine brings about the release of dopamine in the nucleus accumbens. Alcohol consumption also leads to dopamine release, but the mechanisms by which this occurs are not completely understood.
"This is an elegant series of studies designed to look at the effects of nicotine on alcohol consumption," said Stephanie S. O’Malley, professor of psychiatry at Yale University School of Medicine. "We knew that smoking was associated with heavy drinking; these findings suggest that in fact smoking may directly increase the amount of alcohol consumed."
The January 1998 edition of Alcohol Alert reported that between 80 and 95 percent of alcoholics smoke tobacco, which is roughly three times higher than those among the general population (about 30 percent) who smoke. Moreover, 70 percent of the heaviest alcohol consumers (alcoholics) are also the heaviest consumers of tobacco, smoking more than one pack a day. In comparison, about 10 percent of the general population smoke more than one pack a day. Clearly there is a strong connection, which is why many alcohol treatment professionals have been hesitant to jeopardize an alcoholic’s recovery by adding the stress of quitting smoking.
"If you’ve ever been to an AA meeting, where they help people stop drinking," said Lê, "you’ll see a number of people there who smoke quite heavily. We need to better understand how these two drugs interact with one another. We need to better understand why these two drugs are co-abused, and to develop an effective treatment of that co-dependency."
The remaining two experiments of the five in Lê’s study looked at the use of nicotinic receptor antagonists in the brain, which may "block" nicotine’s effects and, possibly, alcohol’s effects. Although that aspect of the study’s findings remains somewhat preliminary, both Lê and O’Malley believe that future research needs to focus on treatment of both drinking and smoking.
One possibility is naltrexone, approved by the Food and Drug Administration as a pharmacological adjunct for the treatment of alcohol dependence. Although initially studied for the treatment of alcoholism, several more recent studies have begun to investigate its effects on smoking behaviors in both members of the general population as well as in individuals who have alcohol problems. O’Malley herself is currently studying the effects of naltrexone, in conjunction with the nicotine ‘patch,’ on smoking cessation.
"Studies of treatments for both alcoholism and smoking need to combine their efforts, so to speak," said O’Malley. "Because there’s such a strong relationship between nicotine and alcohol consumption, greater attention should be given to both of these drugs when we’re developing and evaluating behavioral and pharmacological treatment options for either."