Drugs And Receptors (8) Flashcards Preview

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Flashcards in Drugs And Receptors (8) Deck (31)
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0

How do drugs exert their effects?

- By binding to a target.

1

What's the most common drug target?

- Proteins
- GPCRs

2

What is the equation for molarity?

- Molarity= g/L / MWt

3

How many atoms are thee in a mole?

- 6x10^23

4

Drug action on a receptor is dictated how?

- Affinity and intrinsic efficacy

5

How is binding governed?

- Association and dissociation
- Affinity

6

The activation of a drug and receptor is governed how?

- Intrinsic efficacy

7

How do antagonists work in respect to affinity and intrinsic efficacy?

- Have affinity only
- No intrinsic efficacy
- Blocks effects of agonists

8

How can drug-receptor interactions by binding be measured?

- Via binding of radioactively labelled ligand to cells/membranes prepared from cells.
- Low ligand conc = low binding
- High ligand conc = high binding

9

What is Kd?

- Dissociation constant
- Measure of affinity
- Concentration of ligand required to occupy 50% of the available receptors
- Lower Kd = higher affinity

10

What is B max?

- Max binding capacity - gives information about receptor number

11

What are examples of responses from drugs?

- Change in signalling pathway
- Change in cell/tissue behaviour (e.g. Conc)

12

What is meant by EC50, what is it a measure of and what is it dependent on?

- Effective concentration giving 50% of maximal response
- Measure of potency
- Affinity+efficacy=potency

13

What is meant by concentration?

- Known concentration of drug at site of action e.g. Cells and tissues

14

What is meant by dose?

- Concentration at site of action unknown (don't know how body will react)

15

What are the characteristics of drugs that need to be taken into account in a clinical setting?

- Affinity
- Efficacy
- Selectivity (off target effects?)
- Drug metabolism/pharmacokinetics (how body deals with it)
- Physicochemical properties (solubility/pH/stability/crystallinity)

16

Why may selectivity be a problem?

- If isn't selective then will have effects on other receptors
- e.g adrenaline on B adrenoceptors, useful for asthma but may also increase heart rate.

17

What is selectivity based on?

- Affinity

18

In some cases <100% occupancy leads to 100% response why is this?

- Spare receptors

19

Why may spare receptors exist?

- Amplification in signal transduction pathway response limited by post-receptor event.

20

What do spare receptors allow for in terms of sensitivity?

- Increases
- Allows responses at low concentrations of agonist

21

A change in receptor number can lead to what?

- Change in agonist potency (max response)
- E.g. 10,000 is full response. If only have 5000 receptors means can't get full response

22

How does tolerance to drugs arise?

- Receptor number decreases when there's a high activity
- Too high=no receptors available.

23

When is buprenorphrine used and why?

- Adequate pain relief but no respiratory problems
- Higher affinity but lower efficacy than morphine

24

What role can a partial agonist act as?

- Act as an antagonist to a full agonist
- Has a higher affinity but doesn't turn on receptor as well

25

What are partial agonists dependent on?

- Compound and systemic
- Increase receptor number can change a partial agonist into a full agonist, still has a low intrinsic efficacy but there are sufficient receptors to contribute to a full response

26

What are the types antagonists?

- Reversible/irreversible competitive antagonism
- Non-competitive antagonism (allosteric/post-receptor)

27

Describe what reversible competitive antagonism is.

- Competitive inhibition
- Relies on dynamic eqm between ligands and receptors
- As antagonist concentration concentration increase response decreases

28

What is irreversible competitive antagonism?

- When agonists slowly dissociate or not at all
- With more time or antagonist concentration more receptors are blocked by antagonist. Non-surmountable
- At higher conc suppresses max response

29

What effect does irreversible competitive antagonist have on an agonist - conc response curve?

- Parallel shift to the right as spare receptors filled by antagonist