Quantification of Drug Action I

Dose–Response Relationship
The effect of a substance depends on the
amount administered, i.e., the dose. If
the dose chosen is below the critical
threshold (subliminal dosing), an effect
will be absent. Depending on the nature
of the effect to be measured, ascending
doses may cause the effect to increase in
intensity. Thus, the effect of an antipyretic
or hypotensive drug can be quantified
in a graded fashion, in that the extent
of fall in body temperature or blood
pressure is being measured. A dose-effect
relationship is then encountered.
The dose-effect relationship may
vary depending on the sensitivity of the
individual person receiving the drug,
i.e., for the same effect, different doses
may be required in different individuals.
Interindividual variation in sensitivity is
especially obvious with effects of the
“all-or-none” kind.