Alcohol
is a general term denoting a family of organic
chemicals with common properties. Members of
this family include ethanol, methanol, isopropanol,
and others. This introduction discusses the
physical, chemical, and physiological aspects
of the most commonly ingested of these ethanol.
Alcohol (ethanol) is a clear, volatile liquid
that burns (oxidizes) easily. It has a slight,
characteristic odor and is very soluble in water.
Alcohol is an organic compound composed of carbon,
oxygen, and hydrogen; its chemical formula is
C2H5OH.
Alcohol is a central nervous system depressant
and it is the central nervous system which is
the bodily system that is most severely affected
by alcohol (see chart below). The degree to
which the central nervous system function is
impaired is directly proportional to the concentration
of alcohol in the blood.
When ingested, alcohol passes from the stomach
into the small intestine, where it is rapidly
absorbed into the blood and distributed throughout
the body. Because it is distributed so quickly
and thoroughly the alcohol can affect the central
nervous system even in small concentrations.
In low concentrations, alcohol reduces inhibitions.
As blood alcohol concentration increases, a
person's response to stimuli decreases markedly,
speech becomes slurred, and he or she becomes
unsteady and has trouble walking. With very
high concentrations - greater than 0.35 grams/100
milliliters of blood (equivalent to 0.35 grams/210
liters of breath ) - a person can become comatose
and die. The American Medical Association has
defined the blood alcohol concentration level
of impairment for all people to be 0.04 grams/100
milliliters of blood (equivalent to .04 grams/210
liters of breath). The following is a generally
accepted guide to the affects of alcohol.
Stages of alcohol
intoxication
BAC (g/100
ml of bloodor g/210 l of breath) |
Stage |
Clinical symptoms |
0.01 - 0.05 |
Subclinical |
Behavior nearly
normal by ordinary observation |
0.03 - 0.12 |
Euphoria |
Mild euphoria,
sociability, talkitivenessIncreased self-confidence;
decreased inhibitionsDiminution of attention,
judgment and controlBeginning of sensory-motor
impairmentLoss of efficiency in finer performance
tests |
0.09 - 0.25 |
Excitement |
Emotional instability;
loss of critical judgmentImpairment of perception,
memory and comprehensionDecreased sensitory
response; increased reaction timeReduced
visual acuity; peripheral vision and glare
recoverySensory-motor incoordination; impaired
balanceDrowsiness |
0.18 - 0.30 |
Confusion |
Disorientation,
mental confusion; dizzinessExaggerated emotional
statesDisturbances of vision and of perception
of color, form, motion and dimensionsIncreased
pain thresholdIncreased muscular incoordination;
staggering gait; slurred speechApathy, lethargy |
0.25 - 0.40 |
Stupor |
General inertia;
approaching loss of motor functionsMarkedly
decreased response to stimuliMarked muscular
incoordination; inability to stand or walkVomiting;
incontinenceImpaired consciousness; sleep
or stupor |
0.35 - 0.50 |
Coma |
Complete unconsciousnessDepressed
or abolished reflexesSubnormal body temperatureIncontinence |
Absorption
Alcohol is absorbed from all parts of the gastrointestinal
tract largely by simple diffusion into the blood.
However the small intestine is by far the most
efficient region of the gastrointestinal tract
for alcohol absorption because of its very large
surface area. In a fasting individual, it is
generally agreed that 20% to 25% of a dose of
alcohol is absorbed from the stomach and 75%
to 80% is absorbed from the small intestine.
Because of this peak blood alcohol concentrations
are achieved in fasting people within 0.5 to
2.0 hours, while non-fasting people exhibit
peak alcohol concentrations within 1.0 to as
much as 6.0 hours.
Distribution
Alcohol has a high affinity for water and is
therefore found in body tissues and fluids inasmuch
as they contain water. Absorbed alcohol is rapidly
carried throughout the body in the blood and
once absorption of alcohol is complete an equilibrium
occurs such that blood at all points in the
system contains approximately the same concentration
of alcohol.
Elimination
The liver is responsible for the elimination
- through metabolism - of 95% of ingested alcohol
from the body. The remainder of the alcohol
is eliminated through excretion of alcohol in
breath, urine, sweat, feces, milk and saliva.
The body uses several different metabolic pathways
in its oxidation of alcohol to acetaldehyde
to acetic acid to carbon dioxide and water.
Healthy people metabolize alcohol at a fairly
consistent rate. As a rule of thumb, a person
will eliminate one average drink or .5 oz (15
ml) of alcohol per hour. Several factors influence
this rate. The rate of elimination tends to
be higher when the blood alcohol concentration
in the body is very high or very low. Also chronic
alcoholics may (depending on liver health) metabolize
alcohol at a significantly higher rate than
average. Finally, the body's ability to metabolize
alcohol quickly tend to diminish with age.
Body Weight and
Body Type
In general, the less you weigh the more you
will be affected by a given amount of alcohol.
As detailed above, alcohol has a high affinity
for water. Basically one's blood alcohol concentration
is a function of the total amount of alcohol
in one's system divided by total body water.
So for two individuals with similar body compositions
and different weights, the larger individual
will achieve lower alcohol concentrations than
the smaller one if ingesting the same amount
of alcohol. However, for people of the same
weight, a well muscled individual will be less
affected than someone with a higher percentage
of fat since fatty tissue does not contain very
much water and will not absorb very much alcohol.
Rate Of Consumption
Blood alcohol concentration depends on the amount
of alcohol consumed and the rate at which the
user's body metabolizes alcohol. Because the
body metabolizes alcohol at a fairly constant
rate (somewhat more quickly at higher and lower
alcohol concentrations), ingesting alcohol at
a rate higher than the rate of elimination results
in a cumulative effect and an increasing blood
alcohol concentration.
Alcohol Content
It's not how many drinks that you have, but
how much alcohol that you consume. As you can
see from the chart below some drinks are more
potent than others.
Alcohol Content
of Some Typical Drinks
Drink |
Alcohol Content |
Manhattan |
1.15 oz. (34
ml) |
Dry
Martini |
1.00 oz. (30
ml) |
Malt
liquor -12 oz. (355 ml) |
0.71 oz. (21
ml) |
Airline
miniature |
0.70 oz. (21
ml) |
Whiskey
Sour/Highball |
0.60 oz. (18
ml) |
Table
Wine - 5 oz. (148 ml) |
0.55 oz. (16
ml) |
Beer
- 12 oz. (355 ml) |
0.54 oz. (16
ml) |
Reduced
Alcohol Beer |
0.28 oz. (8
ml) |
Mixed drinks
are based on typical drink recipes using 80
proof liquor.
The amount of alcohol in actual mixed drinks
may vary.
Alcohol Content
(in Percent) of Selected Beverages
Beverage |
Alcohol Content (%) |
Beers (lager) |
3.2 - 4.0 |
Ales |
4.5 |
Porter |
6.0 |
Stout |
6.0 - 8.0 |
Malt Liquor |
3.2 - 7.0 |
Sake |
14.0 - 16.0 |
Table wines |
7.1 - 14.0 |
Sparkling wines |
8.0 - 14.0 |
Fortified wines |
14.0 - 24.0 |
Aromatized wines |
15.5 - 20.0 |
Brandies |
40.0 - 43.0 |
Whiskies |
40.0 - 75.0 |
Vodkas |
40.0 - 50.0 |
Gin |
40.0 - 48.5 |
Rum |
40.0 - 95.0 |
Tequila |
45.0 - 50.5 |
The concentration of the drinks
that one ingest can have a slight effect on
the peak alcohol concentration due to the differences
in absorption rate of different concentrations
of alcohol. Alcohol is most rapidly absorbed
when the concentration of the drink is between
10% and 30%. Below 10% the concentration gradient
in the gastrointestinal tract is low and slows
absorption and the added volumes of liquid involved
slow gastric emptying. On the other hand concentrations
higher than 30% tend to irritate the mucous
membranes of the gastrointestinal tract and
the pyloric sphincter, causing increased secretion
of mucous and delayed gastric emptying.
Food
Food taken along with alcohol results in a lower,
delayed blood alcohol concentration peak (the
point of greatest intoxication). There are two
major factors involved in this phenomenon. First,
because alcohol is absorbed most efficiently
in the small intestine, the ingestion of food
can slow down the absorption of alcohol into
one's system. The pyloric valve at the bottom
of the stomach will close in order to hold food
in the stomach for digestion and thus keep the
alcohol from reaching the small intestine. While
alcohol will be absorbed from the stomach it
is a slower and less efficient transition. Second
and equally important is the fact that alcohol
elimination rates are inversely proportional
to alcohol concentration in the blood. Therefore
the suppressed levels of alcohol due to food
ingestion cause the body to eliminate the alcohol
that is absorbed at a faster rate. The type
of food ingested (carbohydrate, fat, protein)
has not been shown to have a measurable influence
on this affect but the larger the meal and closer
in time between eating and drinking, the greater
the diminution of peak alcohol concentration.
Studies have shown reductions in peak alcohol
concentration (as opposed to those of a fasting
individual under otherwise similar circumstances)
of 9% to 23%.
Medication
If you are taking any medication, it could increase
the effects of alcohol. You should always consult
your physician or the medical information that
accompanies the medication when drinking alcohol
in conjunction with any medication.
Fatigue
Fatigue causes many of the same symptoms that
are caused by alcohol intoxication. These and
other symptoms will be amplified if alcohol
intoxication is concurrent with fatigue.
Tolerance
Tolerance is the diminution of the effectiveness
of a drug after a period of prolonged or heavy
use of that drug or a related drug (cross-tolerance).
There are two types of tolerance at work with
alcohol. The first is metabolic tolerance in
which the alcohol is metabolized at a higher
rate (up to 72% more quickly) in chronic users.
Because of the higher metabolic rate for alcohol
lower peak blood alcohol concentrations are
achieved by chronic alcohol users than the average
drinker when the same amount of alcohol is ingested.
The second is functional tolerance in which
there is an actual change in the organ or system's
sensitivity to the drug. Studies have shown
that chronic alcohol users can have twice the
tolerance for alcohol as an average person.
It is important to note however that even in
light of these tolerance factors, it has been
shown conclusively that even in heavy alcohol
users functional impairment is clearly measurable
at the blood alcohol concentration levels that
are currently used for traffic law enforcement
and safety sensitive job performance.
Gender Differences
As outlined above in the section on Body Weight
and Body Type different body types coincide
with different body water percentages. In general,
but by no means in all cases, women tend to
have a higher percentage of body fat and thus
a lower percentage of body water. Therefore,
in general, if a man and a woman of the same
weight ingest the same amount of alcohol the
woman will tend to achieve a higher alcohol
concentration. This, of course, would not be
true if the woman was very fit and the man was
somewhat obese, but on average, this is the
case. Furthermore, total body water tends to
decrease with age, so an older person will also
be more affected by the same amount of alcohol.
According to the table below the differences
in alcohol concentration due to average body
composition differences based on gender would
be between 16% and 10% depending on age.
Average Total
Body Water as a function of Sex and Age
Age |
Male |
Female |
18 to 40 |
61% |
52% |
over 60 |
51% |
46% |