Moderate Alcohol Intake May Raise Risk for Amphetamine Abuse

Megan Brooks

December 14, 2010

December 14, 2010 — Research published today provides more evidence that drinking moderate amounts of alcohol may increase an individual's vulnerability to amphetamine abuse.

The study showed that moderate drinkers were more sensitive to the reinforcing and subjective effects of a single dose of amphetamine than light drinkers.

"We need to educate adolescents and young adults about potential consequences — beyond the obvious (eg, drinking and driving) — of even moderate drinking," senior investigator Craig R. Rush, PhD, from the Department of Behavioral Science, University of Kentucky in Lexington, told Medscape Medical News.

The study was published online December 14 and in the March 2011 print issue of Alcoholism: Clinical & Experimental Research.

Dr. Rush and colleagues assessed the reinforcing effects of d-amphetamine in 17 light alcohol drinkers (<7 alcoholic beverages per week) and 16 moderate drinkers (≥7 alcoholic beverages per week), using a modified progressive-ratio procedure — a sensitive measure of drug reinforcement in humans.

During the course of 4 studies, the participants sampled placebo as well as both low (8 - 10 mg) and high (16 - 20 mg) doses of d-amphetamine. After these initial sessions, the patients then had the chance to earn up to a total of 8 capsules containing 12.5% (one eighth) of the previous dose by working on a computer task.

The investigators observed that both the low and high d-amphetamine doses functioned as a "reinforcer" in the moderate drinkers, whereas only the high dose did so in the light drinkers. "The moderate drinkers worked for significantly more capsules that contained the high dose of d-amphetamine than did the light drinkers," they report.

This suggests that drinking moderate amounts of alcohol may make an individual more vulnerable to the effects of stimulants such as amphetamine. The researchers say further research is needed to elucidate the behavioral and neuropharmacological mechanisms involved in alcohol consumption and stimulant abuse.

Reached for comment, Harriet de Wit, PhD, from the Human Behavioral Pharmacology Laboratory, University of Chicago, Illinois, said the study addresses "an important clinical issue, regarding the susceptibility for use of different drugs."

"Because of either biological or environmental factors, certain individuals may be at risk for use of various psychoactive drugs, based on their direct pharmacological responses to these drugs. Alternatively, it is also possible that extended use of one drug (in this case alcohol) increases an individual's responses to other drugs (in this case amphetamine)," she explained.

Dr. de Wit also said there is a large body of literature on the changes in drug responses that occur with repeated administration; alcohol is one of several drugs that exhibit "sensitization," or increased responsiveness to the drug with repeated administration.

"An extension of the sensitization phenomenon is 'cross-sensitization,' where repeated exposure to one drug increases responsivity to another drug. This is another credible mechanism," she said.

Dr. de Wit said the current study has many strengths, "including a good number of subjects, careful screening and testing methods, and most interestingly, a progressive-ratio task to measure the 'value' of the drug to the participant. This has proven to be a sensitive and valid measure to differentiate individual differences in the willingness to take the drug again. In all, the study makes a valuable contribution to the literature for these reasons."

Dr. Rush said his team is currently designing prospective studies to replicate these findings.

The research was supported by grants from the National Institute on Drug Abuse. The researchers and Dr. de Wit have disclosed no relevant financial relationships.

Alcohol Clin Exp Res. Published online December 14, 2010.

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