Antagonists Flashcards Preview

PM2C: Therapeutics and Patient Care: Autumn > Antagonists > Flashcards

Flashcards in Antagonists Deck (10):
1

Describe what an antagonist is?

1. A drug that binds to a receptor but does not activate it and has zero efficacy

2. A drug that completely blocks out the action of the agonist

3. Doesn't always compete with the agonist as it can inhibit the receptor action at a allosteric site

4. Has a high affinity

2

What does IC50 mean and what does it mean?

1. The concentration of antagonist to inhibit 50% an agonist-induced response

2. Approximates affinity of antagonist for competitive reversible antagonists

3. Other analysis are better for measuring affinity IC50 usually referred to as antagonist potency

3

How do you measure antagonist action?

By plotting a concentration response curves to an agonist in the presence of increasing antagonist concentrations

4

What is the dose ratio?

The fold increase in agonist concentration needed to evoke a given response (normally EC50) in presence of antagonist

5

What does the increase adding of an antagonist to do a dose ratio?

Increases it

6

What does a dose ratio of two represent?

Twice as much agonist is required to cause the same response

7

What does the Schild plot show?

1. Tells you if an antagonist is competitive and if so an estimate of its affinity

2. If it =1 it's a competitive antagonist

8

What does KB represent?

The concentration of antagonist (B) that binds to 50% of its receptors

9

What does -LogKb (pKb) represent?

- Also known as the pA2 value

- For a competitive inhibitor, it is a measure of affinity and potency

- The concentration of the agonist to reach a dose ratio of 2

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10

What does insurmountable antagonism mean?

In the presence of an antagonist, no matter how much agonist you add, you will never elicit a maximum response