Adverse Drug Effects I

Adverse Drug Effects
The desired (or intended) principal effect
of any drug is to modify body function
in such a manner as to alleviate
symptoms caused by the patient’s illness.
In addition, a drug may also cause
unwanted effects that can be grouped
into minor or “side” effects and major or
adverse effects. These, in turn, may give
rise to complaints or illness, or may
even cause death.
Causes of adverse effects: overdosage
. The drug is administered in
a higher dose than is required for the
principal effect; this directly or indirectly
affects other body functions. For instances,
morphine , given in the
appropriate dose, affords excellent pain
relief by influencing nociceptive pathways
in the CNS. In excessive doses, it
inhibits the respiratory center and
makes apnea imminent. The dose dependence
of both effects can be graphed
in the form of dose-response curves
(DRC). The distance between both DRCs
indicates the difference between the
therapeutic and toxic doses. This margin
of safety indicates the risk of toxicity
when standard doses are exceeded.
“The dose alone makes the poison”
(Paracelsus). This holds true for both
medicines and environmental poisons.
No substance as such is toxic! In order to
assess the risk of toxicity, knowledge is
required of) the effective dose during
exposure) the dose level at which
damage is likely to occur) the duration
of exposure.