Encyclopedia of Health and Medicine

316 Substance Abuse
health and social problem. In the United States,
alcohol is a factor in more than one third of MOTOR
VEHICLE ACCIDENTS. Long-term alcohol abuse contributes
to numerous health conditions including
permanent birth defects in children exposed to
alcohol during fetal development (FETAL ALCOHOL
SYNDROME). Alcohol is the most commonly abused
DRUG in the United States.
Alcoholic Beverages
From the perspective of intoxication, a drink is
merely the vehicle that carries alcohol into the
body. The alcohol in a distilled beverage such as
gin is no different from the alcohol in beer or
wine. What does differ is the concentration of
alcohol within the drink. A distilled drink may
contain 40 percent alcohol (represented as “80
proof” on the label); a beer is usually 4 percent
and wine is 10 to 14 percent. Thus a 1-ounce shot
of distilled spirits, 12-ounce glass of beer, and 5-
ounce glass of wine all contain roughly the same
amount of alcohol. Each of these is a “standard”
drink for purposes of assessing alcohol consumption.
Alcohol contains 7 calories per gram, 100 to
150 calories per standard drink. Mixers add additional
calories. Other than energy, alcohol has no
nutritional value.
Alcohol Absorption and Metabolism
Ethanol is a small molecule that the body rapidly
absorbs through the STOMACH and SMALL INTESTINE
and that, once in the BLOOD circulation, readily
crosses the BLOOD–BRAIN BARRIER to affect the BRAIN
directly. A person generally begins to feel the
effects of alcohol within 10 minutes of ingesting
an alcoholic drink; the amount of alcohol in the
blood circulation peaks about 45 minutes after
consumption. Factors that influence the rate of
absorption include carbonation and the presence
of food. The alcohol from carbonated alcoholic
beverages, such as beer and champagne, enters
the blood circulation more rapidly than from noncarbonated
alcoholic beverages such as wine.
Foods, particularly those high in fat and protein,
significantly slow the absorption of alcohol.
Once in the blood circulation, however, alcohol
metabolizes at a consistent, predictable rate
regardless of its ingested form. The body metabolizes
alcohol far more slowly than it absorbs alcohol.
Though alcohol METABOLISM varies among
individuals, in general the body takes 60 to 90
minutes to metabolize one standard drink’s worth
of the alcohol. Men tend to metabolize alcohol
more quickly than women because they have
higher quantities of the enzyme acetaldehyde
dehydrogenase, which breaks down acetaldehyde
(a harmful toxin) to acetic acid (a harmless waste
product) that the body can excrete in the URINE.
Ingesting large quantities of ethanol
(alcoholic beverages) or of alcohols
other than ethanol such as methanol
(wood alcohol) and isopropyl alcohol
(rubbing alcohol) is potentially fatal.
Alcohol Intoxication
Intoxication (drunkenness) occurs with alcohol
consumption because alcohol, which is chemically
a solvent, literally softens the neural membranes
(the outermost structure of a NEURON), disrupting
their ability to respond to electrical impulses
(action potential). The highest concentration of
neurons is in the brain; the brain neurons most
significantly affected appear to be those of the prefrontal
cortex, a part of the brain responsible for
coordinating numerous functions of cognition,
judgment, memory, and inhibition. From a physiologic
perspective these changes and the behaviors
that result define intoxication. The return to normal
follows the same path in reverse, with the less
complex functions returning first as the neural
membranes essentially “dry out.”
Alcohol also alters the presence and balance of
chemicals in the brain. Among them are
• gamma-aminobutyric acid (GABA), an
inhibitory NEUROTRANSMITTER that carries NERVE
impulses in the cerebral cortex to facilitate
processes related to inhibitions
• DOPAMINE, a neurotransmitter that is key for
nerve impulses related to mood, emotion, and
the perception of pleasure
• glutamate, an excitatory neurotransmitter that
increases activity among neurons
Alcohol blocks the actions of GABA and glutamate,
suppressing the mechanisms in the brain
that inhibit inappropriate behaviors and create a