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A Quick Course on Alcohol

July 1, 2006
by Carlton K. Erickson, PhD
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In my presentations around the country, I frequently am asked about how alcohol works in the body. Most addiction professionals have a good understanding of how excessive drinking causes problems in individuals and families, but they often are unaware of basic facts on alcohol pharmacology. Here's an overview:

  • Alcohol is a simple organic molecule that mixes in water and fat—therefore, it distributes easily throughout the whole body when consumed.

  • Although it is not very “potent” (large amounts are required in order to produce an effect), alcohol produces major behavioral, emotional, and cognitive effects, many of which are thought to be toxic.

  • Alcohol produces greater acute effects on behavior and perception as blood alcohol levels climb with increased drinking.

  • Unlike other drugs, alcohol has no specific receptor in the brain upon which it acts; therefore, it affects most receptors, such as those for opioids (like endorphins), cocaine (dopamine), and antidepressants (serotonin).

  • Sophisticated research on “intoxication” is looking at specific parts of nerve cells that might be altered to produce alcohol's depressant and stimulant effects—especially GABA, glutamate, N-methyl-D-aspartate (NMDA), and nicotine receptors.

Carlton k. erickson, phd

Carlton K. Erickson, PhD

Blood alcohol concentrations

Here's an overview that should be of interest to adolescents. One standard “beverage unit” (BU) of alcohol is one five-ounce glass of wine (12% by volume), one 12-ounce beer (4.9% by volume), or one cocktail containing 1.5 ounces of 80 proof spirits (40% by volume). Each of these contains roughly 14 grams (about one-half ounce) of absolute alcohol. If a 150-pound man drinks one BU in an hour, this will produce a blood alcohol concentration (BAC) of about 0.025%, excluding any calculation for liver metabolism. This is approximately one-third the national drunk-driving BAC limit of 0.08%. So when this person drinks four BUs in an hour, alcohol is removed by the liver at a constant rate of 0.25 to 0.30 ounces of beverage alcohol per hour, and the BAC will decline by about 0.02% every hour. This is the value for relatively alcohol-naïve drinkers.

For people with significant drinking experience, an increase in liver enzymes occurs so that the liver processes alcohol at higher rates, leading to significantly lower BACs. On the other hand, liver disease, some medications, and other factors might decrease the metabolism of alcohol, leading to higher-than-expected BACs. Of most interest to people with alcohol problems is that after many years of drinking significant amounts of alcohol daily, some people will experience a “reverse tolerance,” becoming very sensitive to alcohol again as the liver loses function.

It is important to understand that rough calculations of this type use “average” values that make determinations of probable BACs easy. Forensic toxicologists might use more complicated formulas that tweak a person's BAC based upon height, total body water, and other variables.

Effects at various BACs

What happens at certain BACs? At 0.08% a person's ability to drive is significantly impaired; that is, there is a loss of judgment, problems with attention tasks, and some perception and movement problems. At 0.15-0.20%, most people are “grossly intoxicated”; that is, they slur their speech and have difficulty walking. At 0.30%, most people will at least be on the verge of unconsciousness. At 0.35-0.40%, death is possible. Of course, such variability exists among people that these are only “textbook” guidelines.

Despite notions to the contrary, BAC levels cannot be lowered, or people “sobered up” by coffee, cold showers, or other methods. Time is needed for alcohol metabolism to occur and for alcohol to be removed from the body. This is why alcohol overdoses are so problematic—there is no “magic bullet” to overcome alcohol's effects. Proper treatment of overdose involves hospitalization with respiratory support.

A well-educated addiction professional knows the basic pharmacology of the substances clients are using. This professional will be more responsive to questions from clients about what the drugs are doing to their bodies.

Carlton K. Erickson, PhD, is Director of the Addiction Science Research and Education Center at the University of Texas at Austin's College of Pharmacy.


  1. Brick J, Erickson CK. Drugs, The Brain, and Behavior: The Pharmacology of Abuse and Dependence. Binghamton N.Y.:The Haworth Press; 1999.
  2. Brick J. Standardization of alcohol calculations in research. Alcoholism: Clinical and Experimental Research 2006 (in press).
  3. Erickson CK. Science of Addiction: From Neurobiology to Treatment. New York:W.W. Norton and Co.; 2007 (in press).