L5 - Drug Receptor Theory III - Antagonists Flashcards
What are antagonists?
A drug that prevents the response of an agonist.
What 5 classes can antagonism be divided into?
1) Chemical
2) Pharmacokinetc
3) Physiological
4) Non-Competitive
5) Cometitive
How does chemical antagonism work?
Substances combine in soluton so that the effects of the agonist is lost. Making the agonist chemically altered by the antagonist.
What is pharmacokinetic antagonism?
Reduction in amount of drug absorbed, metabolised or excreted by another, causes a change in excretion of an agonist.
What is physiological antagonism?
The interaction of 2 drugs with opposing actions in the body, eg noradrenaline and histamine in arterial pressure
What is non-competitive antagonism?
Blocks some steps in the process between receptor activation and response. Doesn’t compete for the orthosteric receptor site.
What are competeitive antagonists?
Drugs that binds to a receptor to form a complex, however it cannot stimulate any downstream signaling.
How are the effects of competive antagonists overcome?
By increasing the concentration of the agonist
What is meant by the dose ratio?
How many more times agonist is needed in the presence of an antagonist
How is the dose ratio calculated?
The concentration of the agonist in the presence of the antagonist divided by the concentration of the agonist in the absense of the antagonist.
What does the schild analysis measure?
The competitive antagonist activity
What do partial agonists do?
They behave like competeitive antagonists causing a shift to the right in the concentration response curve
What are irreversible competitive antagonists?
antgonists that cannot be reversed by washing the tissue, they are also time dependant.
