Alcohol is classified as a central nervous system depressant and its psychoactive properties affect the
individual’s cognition, mood and behavior. The
main psychoactive component in the alcohol is ethanol (C2H5OH).
Most individuals consume alcohol orally through beverages. However, there are
also other ways in which the alcohol is consumed like intravenous ethanol injections, ethanol vapors and recently through nebulizers called AWOL
(Alcohol without liquid). In the US, a standard alcoholic drink is about 0.6
fluid ounces of alcohol and this amount may vary depending on the type beverages
such as beer, wine, or spirits.
Alcohol can be readily dissolve in water and thus rapidly circulate
into total body water of an individual. Since there are gender differences in
the total body water composition, even if men and women take the same amount of
alcohol, women would have a higher blood alcohol level compared to that of men.
Alcohol absorption is done via the small intestine and the stomach primarily by
diffusion. Small intestine performs the most alcohol absorption (about 80%) due
to its rich blood supply and big surface area. The rate of alcohol absorption
is influenced by the method of alcohol consumption, alcohol concentration, food
intake and individual factors (gender, age, drinking history, gastric metabolism).
Once the alcohol is absorbed, it is transported to the liver. 95% of the
alcohol is metabolized in the liver yielding carbon dioxide and water and the
rest is excreted through saliva, urine, or feces.
Chronic alcohol consumption can cause adverse health effects in an
individual. In the initial stage, when the blood alcohol level is increasing, disinhibition,
euphoria, increased talkativeness and assertiveness often occur. With continued
drinking, reduction in the reaction time, sleep disturbances, impairment in the
judgement, loss of body control, and emotional outburst can be clearly seen. In
the long term intoxication, an individual may end up suffering from alcoholism,
liver damage and eventually death. Moreover, the tolerance level may also buildup
in which the individual may no longer feels the effects of alcohol even if they
take larger quantity.
In the presence of other drugs, alcohol can interact with them in two
ways: a) pharmacokinetic interaction b) pharmacodynamics interaction. Pharmacokinetic
interaction of alcohol generally takes place in the liver where the alcohol
changes the metabolism of the other drug by the same enzymes. For instance,
alcohol enhances the sedative effect of tricyclic antidepressants (TCA) by
interfering with its metabolism and thereby increasing its content in the blood
causing seizures and dysfunctioning in the heart rhythms. Similarly, the intake
of alcohol with opioids has high lethal effect. Overdose of these drugs taken
together can cause breathing difficulty and reduction in the cough reflex.
In contrast, pharmacodynamics interaction of alcohol mainly occurs in
the central nervous system where it may not necessarily involve enzyme
activation or inhibition, but cause effect on one another. Without altering the
level of the other substance, the alcohol acts on the same molecule in which
the other substance reacts and increases its side-effects. This causes a
synergistic effect where the combined effect of alcohol and the other substance
is much more than their individual effects. For instance, barbiturates and
benzodiazephines which are categorized as sedative-hypnotic agents, when
combined with alcohol, may cause severe memory impairments.