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ICPP > Pharmacodynamics > Flashcards

Pharmacodynamics Flashcards

1
Q

Do most drugs bind reversibly or irreversibly to receptors?

A

Reversibly

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2
Q

How is drug concentration measured?

A

Molarity

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3
Q

What is intrinsic efficacy?

A

Ability of a drug to activate a receptor

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4
Q

What is efficacy?

A

Ability of a ligand to cause a response

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5
Q

What do agonists and antagonists have in reference to efficacy, affinity and intrinsic efficacy?

A

Agonists - have affinity, intrinsic efficacy and efficacy

Antagonists - have affinity, NO intrinsic efficacy/efficacy

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6
Q

How can drug-receptor interactions and binding affinity be measured? What sort of graph can be plotted?

A

Using a radioligand - radioactively labelled ligand
Graph plotted of [drug] against proportion of bound receptors
Gives a hyperbolic curve

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7
Q

What is Bmax?

A

Maximum binding capacity (number of receptors)

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8
Q

A high Kd = _________ affinity

A

Low

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9
Q

What is Kd?

A

Ligand concentration that occupies 50% of the available receptors (1/2 Bmax)

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10
Q

Drug concentration is usually measured using which type of scale? Therefore graphs with [drug] on one axis usually give which shape curve?

A

Logarithmic

Sigmoidal

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11
Q

How can you measure drug efficacy?

A

With a concentration-response curve

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12
Q

What does a concentration-response curve measure?

A

% response vs. [drug]

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13
Q

What is Emax?

A

100% drug response (maximal drug response)

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14
Q

What is EC50?

A

Effective [drug] giving 50% of the maximal response

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15
Q

What is concentration (of a drug)?

A

Known concentration of a drug at the site of action

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16
Q

What is dose?

A

Unknown concentration of drug at site of action (what you give to the patient)

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17
Q

EC50 gives an indication of _______/________

A

Efficacy and potency of a drug

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18
Q

What is potency?

A

Generation of a measurable response

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19
Q

What is required for a ligand to have potency? (3)

A

Affinity
Intrinsic efficacy
Things to happen to cause a response

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20
Q

Giving drugs for asthma is an example of functional antagonism. What is meant by this?

A

Drugs for asthma cause relaxation of smooth muscle rather than just preventing contraction of smooth muscle

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21
Q

Drugs for asthma act on which receptors?

A

B2-adrenoceptors

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22
Q

Activation of B1-adrenoceptors results in what?

A

Increased heart rate/force of contraction of the heart

23
Q

What two drugs work on B2-adrenoceptors for the treatment of asthma?

A

Salbutamol

Salmeterol

24
Q

What selectivity and selective efficacy does salbutamol show to b2-adrenoceptors?

A

Has poor selectivity for b2-adrenoceptors - so similar affinity

Has good selective efficacy for b2-adrenoceptors - causes a greater response in b2-adrenoceptors)

25
Q

What selectivity and selective efficacy does salmeterol show to b2-adrenoceptors?

A

Has good selectivity for B2-adrenoceptors

No selective efficacy between the receptors

26
Q

How does salmeterol work compared to salbutamol?

A

Salmeterol is longer lasting

27
Q

Why are there problems in prescribing salmeterol and salbutamol to patients with cardiac problems?

A

Salmeterol = insoluble

Salbutamol = will cause increased heart rate/contraction

28
Q

You would expect a 50% binding to result in 50% response but this is not the case, why? What does this result in?

A

There is only so much a muscle can contract and so much a gland can secrete

It means there will be some spare receptors that do not contribute to a response

29
Q

What are spare receptors?

A

Receptors that don’t contribute to a response

30
Q

If a situation existed where there were spare receptors, what would the binding curve look like compared to the response curve?

A

Response curve shifted to the left compared to the binding curve

31
Q

Where are spare receptors often found?

A

When receptors are catalytically active e.g. GPCRs

32
Q

What is the benefit of having spare receptors?

A

Allows increased sensitivity

E.g. A response at a low [agonist]

33
Q

Changing receptor numbers changes agonist _____

A

Potency

34
Q

Are receptor numbers fixed?

A

No

35
Q

What can cause an increase or decrease in receptor numbers? What can this result in, in reference to drugs?

A

Increase when there is low activity
Decreases when there is high activity

Drug tolerance/toxicity

36
Q

What is a full agonist? Are there spare receptors found in a full agonist?

A

Can give a full, maximal response

Has spare receptors

37
Q

What is a partial agonist? Does it have spare receptors?

A

Does not give a full response - low intrinsic efficacy

No spare receptors

38
Q

What is the benefit of using partial agonists as drugs?

A

They allow a more controlled response

39
Q

How can heroin cause death?

A

Can result in respiratory depression —> death

40
Q

What is buprenorphine?

A

A high affinity partial agonist - used to gradually withdraw use of illicit opioids

41
Q

How can a change in the number of receptors affect the action of a partial agonist?

A

It could change a partial agonist into a full agonist

42
Q

What is the efficacy of a partial agonist compared to a full agonist?

A

Partial agonist has a lower efficacy

43
Q

What do antagonists do?

A

Block the action of agonists - bind and do not cause a response

44
Q

What are 3 types of antagonism?

A

Reversible competitive antagonism
Irreversible competitive antagonism
Non-competitive antagonism (allosteric)

45
Q

What is IC50?

A

The [antagonist] giving 50% inhibition

46
Q

What does IC50 give an indication of?

A

Antagonist potency

47
Q

What happens in reversible competitive antagonism? How can this inhibition be surmounted?

A

Antagonist competes with the agonists for binding

By increased agonist concentration

48
Q

What result does reversible competitive inhibition have on the % response-concentration curve?

A

Shift to the right

49
Q

What happens in irreversible competitive antagonism?

A

Antagonist dissociates from receptor very slowly/not at all

Usually as a result of covalent modification/very high affinity

50
Q

Is irreversible competitive antagonism surmountable by increasing [agonist]?

A

No

51
Q

What effect does irreversible competitive antagonism have on the % response - concentration curve?

A

Shifts it to the right and can lower the maximal response at high [antagonist] as there are not enough receptors

52
Q

What is the site where ligands bind called?

A

The orthosteric site

53
Q

What happens in non-competitive antagonism?

A

Antagonist binds to allosteric site

Reduce or enhance the effects of the agonist

ICPP (8 decks)

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