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Flashcards in Receptor theory 4 Deck (17)
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What are the five types of antagonist?

1. Chemical antagonist
2. Pharmacokinetic antagonism
3. Physiological antagonism
4. Non-competitive antagonism
5. Competitive antagonism by receptor block


What is an antagonists affinity for a receptor commonly used for

Used to identify and classify receptors


What is a chemical antagonist

A substance that combines in solution so that the effects of the active drug are lost


How does a chemical agent inactivate heavy metals?

Addition of a chelating agent


What is a pharmacokinetic antagonist

A substance that reduces the amount of drug absorbed e.g. drugs that inhibit opiates will reduce absorption by the oral route


How do pharmacokinetic drugs work

Creates changes in drug metabolism - patients taking warfarin have to be careful when taking antibiotics as they can stimulate the metabolism of warfarin so reducing its effective concentration in the blood stream


What is a physiological antagonist

The interaction of two drugs with opposing actions in the body


Give an example of physiological antagonism

Noradrenaline raises arterial BP by acting on the heart and peripheral blood vessels whereas histamine acts to lower arterial BP by causing vasodilation


What is non-competitive antagonism

Substance that blocks some step in the process between receptor activation and response


Give an example of non competitive antagonisim

Dihyldropyridines bind to and block certain calcium channels rather than the receptor that noradrenaline binds to


What is competitive antagonism

A substance that competes with the agonist for the occupancy of the receptor


What effect does atropine have on Ach binding in guinea pig ileum

Increased concentrations in antagonist cause a parallel shift to the right in the concentration response curve - the max response of Ach can still be reached but at a higher concentration


What is the dose ratio

How many more times the agonist is needed in the presence of the antagonist to cause the same percentage response - conc of agonist in the presence of the antagonist/ conc of agonist without the antagonist present


What is schild analysis used for

Derive the affinity of an antagonist for its receptor


How is pA2 related to Kd

pA2 is where the x intercept x-1 - and is -1(logKd)


What is irreversible competitive antagonism

Antagonism that cannot be reversed by the washing of the tissue as a covalent bond has formed between the antagonist and the receptor


How, after irreversible competitive binding would a full response for the agonist be seen again?

After waiting enough time for the cell to make new receptors.