Action Effect Sequence
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‘Drug action’ and ‘drug effect’ are often loosely used interchangeably, but are not synonymous.
ACTION EFFECT
SEQUENCE
‘Drug
action’ and ‘drug effect’ are often loosely used interchangeably, but are not
synonymous.
Drug Action
It
is the initial combination of the drug with its receptor
resulting in a conformational change in the latter (in case of agonists), or
prevention of conformational change through exclusion of the agonist (in case of
antagonists).
Drug Effect
It
is the ultimate change in biological function brought about as a consequence of
drug action, through a series of intermediate steps (transducer).
Receptors
subserve two essential functions, viz, recognition of the specific ligand
molecule and transduction of the signal into a response. Accordingly, the receptor
molecule has a ligand binding domain (spatially and
energetically suitable for binding
the specific ligand) and an effector domain (Fig. 4.4) which undergoes a functional conformational change. These domains
have now actually been identified in some receptors. The perturbation in the
receptor molecule is variously translated into the response. The sequential
relationship between drug action, transducer and drug effect can be seen in fig 4.6.
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