What is a drug?
The ancient Greeks believed drugs to be
both poison and medicine. In modern
society, a drug is whatever is ingested
to treat any medical or psychological
condition. Often what determines whether
a substance is a drug is its manner of
use. For example, alcohol is a beverage
but it may be considered a drug if it is
used for relaxation or to remove
inhibitions. Similarly, it is used as a
drug if it is taken to stimulate
appetite.
Clinical definition of a drug
A drug is a therapeutic agent; any
substance other than food, used in the
prevention, diagnosis, alleviation,
treatment or cure of disease in man or
animals.
General definition of a drug
A drug is a substance other than food
intended to affect the structure or
function of a physiological system such
as the human body.
Popular definition of a drug
The term drug refers mainly to chemical
or plant-derived substances that affect
psychological, behavioral or physical
functions and lead to varying degrees of
dependence or addiction.
Polydrug use
The taking of two or more drugs in
combination either intentionally or
inadvertently. For instance:
- Alcohol interacts with barbiturates
- Alcohol interacts with sedative
hypnotics
- Alcohol interacts with
antihistamines
- Amphetamine interacts with cocaine
Subjective Changes
Drug users may experiment with two
different drugs to experience a range of
effects simultaneously that neither drug
could yield by itself. For instance:
LSD taken with an amphetamine would
yield the amphetamine high in
combination with the perceptual
distortions of LSD.
Quantitative changes
These are the changes in the magnitude
of the drug effect as a result of the
drug combination. Quantitative effects
are of two types:
- pharmacokinetic interference occurs
when the presence of one drug in the
body, or past exposure to it,
influences the way the body handles a
second drug;
- pharmocodynamic interference occurs
when two or more drugs interact,
causing a modified effect on body
systems.
Several effects can be produced when
two or more drugs are taken together.
They are:
- Synergism, in which the action of
one drug aids or enhances the action
of another;
- Addition, in which the effects of
two drugs are simply additive;
- Potentiation, in which there is a
degree of synergism that is greater
than additive;
- Antagonism, in which the
pharmacological effect of one drug
(agonist) is reduced by a second drug
(antagonist). The second drug
diminishes some or all of the expected
effects of the first drug.
Any of the above drug interactions
could result in death, depending upon
the drugs involved.
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