Published online by Cambridge University Press: 05 August 2016
Alcoholism and alcohol abuse
Alcoholism is a chronic disease characterized by addiction to ethanol; the alcoholic craves and consumes alcoholic beverages without apparent satiation. Alcoholics are remarkably tolerant to the intoxicating effects of ethanol. When drinking is discontinued, however, they exhibit the neurological symptoms and signs of alcohol withdrawal; this is considered to be evidence of physical dependence on ethanol. Addiction to ethanol also occurs as a secondary complication in patients with specific neuropsychiatric disorders, but the vast majority of alcoholics do not have an antecedent history of major psychiatric disease; they are considered to have primary alcoholism. Alcohol abuse is characterized by prodigious drinking without evidence of physical dependence upon withdrawal. Such individuals continue to drink excessively, sometimes as binge drinkers for several days at a time, despite considerable personal socioeconomic hardship and serious medical complications.
Almost two-thirds of Americans older than 14 years of age drink alcoholic beverages. The per capita ethanol consumption in this group is the equivalent of nearly 90 gallons of beer, 31 gallons of wine, or 10 gallons of whisky per year (Seventh Special Report to the US Congress on Alcohol and Health, 1990). However, only 7% of Americans are heavy drinkers. This small group accounts for approximately 50% of the alcohol consumed in the USA and probably most of the socioeconomic and medical complications of alcoholism and alcohol abuse. These alcohol-related complications are not trivial; in 1990, the annual cost to US society is estimated to have been $136 billion (Seventh Special Report to the US Congress on Alcohol and Health, 1990). The prevalence of alcoholic disorders among hospitalized patients is about 25%.
Clinical pharmacology of ethanol
Ethanol is rapidly and completely absorbed from the gastrointestinal tract into the circulation within minutes after drinking (Goldstein, 1983). It is then widely distributed to all organs and fluid compartments in the body, readily equilibrates into total body water, and intercalates into biologic membranes. Ninety to 98% of ethanol is removed by metabolism in the liver, and the remainder is excreted by the kidneys, lungs and skin. An important rate-limiting step in ethanol metabolism is oxidation to acetaldehyde by alcohol dehydrogenase in the liver. Acetaldehyde is then converted to acetate by aldehyde dehydrogenase, a metabolic step with significant clinical ramifications.