antagonism /an·tag·o·nism/ (an-tag´o-nizm) opposition or contrariety between similar things, as between muscles, medicines, or organisms; cf. antibiosis.
antagonism
antagonism,
an·tag·o·nism ( n-tg  -n z m)n. Mutual opposition in action between structures, agents, diseases, or physiological processes. Also called mutual resistance. |
antagonism
[antag′əniz′əm]
Etymology: Gk, antagonisma, struggle
1 an inhibiting action between physiologic processes, such as muscle actions.
2 the opposing actions of drugs.
antagonism,
n situation that occurs when an intervention brings about an opposite effect.
antagonism
1. opposition or contrariety between similar things, as between muscles, medicines or organisms, cf. antibiosis; the characteristic displayed by an antagonist.
2. epidemiologically speaking, the opposite of synergism. When the combined effects of two factors is smaller than the effect of any one of them.
antibiotic antagonism
is said to occur when the antibiotic effect of a dual administration is less than the antibiotic efficiency of the most effective of the individual drugs. Chloramphenicol and tetracyclines are considered to be antagonists to penicillins and aminoglycosides but particular combinations do not necessarily have the same effect on all bacteria.
competitive antagonism
the antagonism which blocks or reverses the effects of an agonist, provided that the antagonist is given at an appropriate dosage. The antagonism is completely reversible, and an increase in the biophasic concentration of the agonist will overcome the effect of the antagonist.
drug antagonism
drug antagonists are drugs that compete for the available receptors. They may be noncompetitive and have no pharmacological effect of their own, or competitive in that they are capable of reversing or altering an effect already achieved.
noncompetitive antagonism
is when the antagonist removes the receptor or its response potential from the system; this may be by preventing the agonist from producing its effect at a receptor site by irreversible change to the receptor or its capacity to respond. The antagonism is not reversible by increasing the concentration of the agonist.
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