W8 - Antagonist Flashcards

1
Q

What is an antagonist

A

a drug that binds to a receptor but does not activate it, blocking the action of an agonist

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2
Q

what is IC50

A

concentration of antagonist to reduce response by 50%

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3
Q

How can we measure antagonistic action of a drug

A

plot a concentration response curve to an agonist in presence of increasing antagonist concentration then form a dose ratio or schild plot

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4
Q

What is a dose ratio

A

it is the fold increase in agonist concentration needed to evoke a given response in presence of antagonist to produce the same ec50 value

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5
Q

how do we calculate a dose ratio

A

ec50 + antagonist / ec50 control

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6
Q

How can we calculate dose ratio in fractional occupanc

A

1 + (Antagonist concentration / KD)

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7
Q

how can we calculate kd in fractional occupancy

A

log (dose ratio - 1) = Log ([Antagonist]) - log (Kd)

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8
Q

What does a schild plot tell us

A

if an antagonist is competitive and if so an estimate for the affinity of it

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9
Q

what value denotes a competitive inhibitor on a schild plot

A

-1

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10
Q

what does it mean if schild slope does not equal 1

A

insurmountable antagonism present

multiple binding sites

pharmacokinectic effects

allosteric interactions

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11
Q

what is insurmountable antagonism

A

in the presence of the antagonist no matter how much agonist you add you will never elicit the maximum response

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