Ethanol, is a potent central nervous system
depressant, with a range of side effects.
The amount and circumstances of the consumption
of alcohol play a large part in determining the extent
of intoxication; e.g., consuming alcohol
after a heavy meal is less likely to produce
visible signs of intoxication than
consumption on an empty stomach. Hydration
also plays a role, especially in determining
the extent of hangovers. The concentration
of alcohol in blood is usually given by BAC.
Alcohol has a biphasic effect on the body,
which is to say that its effects change over
time. Initially, alcohol generally produces
feelings of relaxation and cheerfulness, but
further consumption can lead to blurred
vision and coordination problems. Cell
membranes are highly permeable to alcohol,
so once alcohol is in the bloodstream it can
diffuse into nearly every tissue of the
body. After excessive drinking,
unconsciousness can occur and extreme levels
of consumption can lead to alcohol poisoning
and death (a concentration in the blood
stream of 0.55% will kill half of those
affected). Death can also be caused by
asphyxiation when vomit, a frequent result
of overconsumption, blocks the trachea and
the individual is too inebriated to respond.
An appropriate first aid response to an
unconscious, drunken person is to place them
in the recovery position.
Intoxication frequently leads to a lowering
of one's inhibitions, and intoxicated people
will do things they would not do while
sober, often ignoring social, moral, and
legal considerations. The term intoxication
is typically used in legal proceedings when
some crime has been committed during a state
of inebriation.
Intoxication
Ethanol acts as a central nervous system
depressant. In small amounts, ethanol causes
a mild euphoria and removes inhibitions, and
in large doses it causes drunkenness,
generally at a blood ethanol content of
about 0.1%. At higher concentrations,
alcohol causes intoxication, coma, and
death. A blood ethanol content above 0.4%
can be fatal, although regular heavy
drinkers can tolerate somewhat higher levels
than non-drinkers. Eight to ten drinks per
hour is considered a fatal dosage for the
average 54 kg (119 lb.) person. One drink is
equivalent to one shot of 40% abv (80 proof)
liquor, one 12 US fl oz (355 ml) beer, or
one 4–5 US fl oz (120–150 ml) glass of wine.
In the UK, a "unit" of alcohol is 10 ml pure
ethanol; so examples of drinks containing
one unit of alcohol include one 25 ml
measure of spirits (40% ABV), one 125 ml
glass of weak wine (8% ABV), one half-pint
(284 ml) of weak (3.5% ABV) beer, or just
over one third of a pint (about 200 ml) of
"premium" (5% ABV) lager. (Note that in fact
most wines are about 12% ABV, so would
contain 1.5 units per 125 ml glass, and that
many establishments serve wine by the 175 ml
glass. A 175ml glass of 12% wine contains
2.1 units of alcohol).
To determine how many units an alcoholic
drink contains a simple formula may be used:
(ABV*ml)/1000
Thus, a "shot" of 40% ABV liquor in the US
(approximately 44ml vs. 1.5 US fl oz) is
actually 1.76 units of alcohol
((40*44)/1000). As a result, one U.S. "shot"
of alcohol is almost double the amount
experienced by the international community.
As a result, "shot-takers" in the United
States should be aware of the differences
between the two standards and adjust
accordingly to prevent alcohol
overconsumption. Alcoholism, addiction to
alcohol, is a major public health problem.
Alcoholics develop a number of health
problems, with cirrhosis of the liver among
the most significant. Unlike withdrawal from
some other drugs/intoxicants such as the
opioids, withdrawal from heavy alcohol
consumption can produce delirium tremens
that can be fatal.
Any alcohol consumption during pregnancy
carries a heavy risk of permanent mental and
physical defects in the child, known as
fetal alcohol spectrum disorder.
Action on the brain
Ethanol is quickly absorbed into the
bloodstream and reaches the brain. As a
small molecule, it is able to cross the
blood-brain barrier. The molecular targets
of alcohols actions remain essentially
unidentified, although many targets have
been suggested, including ion channels[1]
and intracellular signaling molecules
Alcohol works on the GABA system at the
synaptic level, and it has a rapid onset of
action. Essentially, it causes the GABA
receptor, which is an ion channel, to remain
open longer than it does without the
addition of ethanol into the synaptic cleft
(the space between two neurons, or brain
cells). This causes more negatively charged
particles, called ions, to enter brain cells
than they would under normal conditions. The
overall effect is to slow the functional
processes of the brain cell. GABA is
commonly known as the brain's "brake"
mechanism.
Blackouts
"Blacking out" or blackouts (a form of
anterograde amnesia) are a common problem
usually associated with heavy drinking. They
are characterized by a person's inability to
recall events which occurred during the
period of blacking out. Blackouts can be
avoided or prevented by drinking less,
drinking water and eating. A 2001
survey at Duke University found that 7.1% of
respondents had experienced blackouts within
2 weeks of the survey.
Dehydration
Consumption of ethanol has a rapid diuretic
effect, meaning that more urine than usual
is produced, since ethanol inhibits the
production of anti-diuretic hormone.
Over consumption can therefore lead to
dehydration (the loss of water). It is
impossible to replenish the body's fluids
using only conventional alcoholic beverages.
As these amounts of alcohol are consumed,
the diuretic effect causes the body to lose
more water than is contained in the
beverage.
Hangover
A common after-effect of ethanol
intoxication is the unpleasant sensation
known as hangover, which is partly due to
the dehydrating effect of ethanol. Hangover
symptoms include dry mouth, headache,
nausea, and sensitivity to light and noise.
These symptoms are partly due to the toxic
acetaldehyde produced from alcohol by
alcohol dehydrogenase, and partly due to
general dehydration. The dehydration portion
of the hangover effect can be mitigated by
drinking plenty of water between and after
alcoholic drinks. Other components of the
hangover are thought to come from the
various other chemicals in an alcoholic
drink, such as the tannins in red wine, and
the results of various metabolic processes
of alcohol in the body, but few scientific
studies have attempted to verify this.
Consuming water between drinks is the best
way to prevent or lessen the effects of a
hangover. |