Alcohol tolerance refers to a decreased response to the functional effects of ethanol in alcoholic beverages.

Consumption-induced tolerance

Alcohol tolerance is increased by regular drinking. This reduced sensitivity requires that higher quantities of alcohol be consumed in order to achieve the same effects as before tolerance was established. Alcohol tolerance may lead to (or be a sign of) alcohol dependency. Heavy alcohol consumption over a period of years can lead to "reverse tolerance". A liver can be damaged by chronic alcohol use, leading to a buildup of fat and scar tissue. The reduced ability of such a liver to metabolize or break down alcohol means that small amounts can lead to a high BAC and more rapid intoxication.

Laws establishing maximum blood alcohol concentration (BAC) levels for legal operation of motor vehicles do not take into consideration alcohol tolerance. In one study, of a group of alcoholics whose BAC was brought to .10, only 24% showed any clinical signs of impairment. Conversely, a person who drinks only rarely may be dangerously impaired even when his/her BAC is still under the legal limit.

Physiology of alcohol tolerance

The alcohol tolerance is connected with activity of alcohol dehydrogenases (a group of enzymes responsible for the breakdown of alcohol) in the liver, and in the bloodstream. High level of alcohol dehydrogenase activity results in fast transformation of ethanol to more toxic acetaldehyde. Such atypical alcohol dehydrogenase is less frequent in alcoholics than in nonalcoholics. Furthermore, among alcoholics, the carriers of this atypical enzyme consume lower ethanol doses, compared to the individuals without the allele.

• Drunk Driving (71)
• Minimum Drinking Age@ (4)

See also:

• Health: Addictions: Substance Abuse: Alcohol (834)
• Health: Specific Substances: Alcoholic Beverages (83)
• Recreation: Food: Drink: Drinking (8)

• FACE - Truth and Clarity on Alcohol
  faceproject.org
  A national non-profit organization that supports sensible alcohol practices through the development of messages, strategies, and training.
• Intoxication: Its Benefits and Costs
  alcohol-drug.com
  Intoxication is rewarding for precisely the same reason it produces suffering - it diminishes the influence of remote stimuli.
• College Drinking: Changing the Culture
  collegedrinkingprevention.gov
  Resources for changing the college drinking culture. Includes research and approaches to prevention, with interactive tools for students and educators.