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Pharmacology > Drug-Receptor Interactions > Flashcards

Drug-Receptor Interactions Flashcards

1
Q

Drug or ligand which binds to the same site as the endogenous ligand and produces the same signal

A

Agonist

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2
Q

Drug or ligand which binds to a different site than the endogenous agonist without producing a signal itself; it enhances the response of the endogenous agonists

A

Allosteric agonist

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3
Q

Drug which produces a lower response when at full receptor occupancy than do full agonists (these by themselves evoke a response, but in the presence of a full agonist, they act to competitively inhibit full agonist binding to the receptor)

A

Partial agonist

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4
Q

Drug that binds to the receptor or components of the effector system used by the endogenous ligand and inhibits the action of the agonist; these initiate no effect themselves

A

Antagonist

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5
Q

Typical drugs that bind reversibly to the receptor; inhibition can be overcome by increasing the concentration of the agonist, ultimately achieving the same maximal effect

A

Competitive antagonist

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6
Q

Typical drugs that bind irreversible or allosterically to the receptor; this is a drug that prevents the agonist at any concentration from producing a maximum effect on a given receptor

A

Non-competitive antagonist

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7
Q

What is the receptor, signal, and response for an agonist, compared to an agonist?

A

Receptor: same
Signal: same
Response: same

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8
Q

What is the receptor, signal, and response for an allosteric agonist, compared to an agonist?

A

Receptor: different
Signal: none (by itself)
Response: greater than an agonist (with an agonist)

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9
Q

What is the receptor, signal, and response for a partial agonist, compared to an agonist?

A

Receptor: same
Signal: same
Response: less than an agonist (b/c not full effect

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10
Q

What is the receptor, signal, and response for an antagonist, compared to an agonist?

A

Receptor: same (with some exceptions)
Signal: none (just blocks receptor)
Response: less than an agonist

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11
Q

What can look like an antagonist sometimes?

A

Partial agonist

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12
Q

What is it if the line does not reach 100% on the scale?

A

Partial agonist

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13
Q

Besides in potentiation, what does the line on the very left represent?

A

Control (agonist all by itself)

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14
Q

What happens to the max effect during competitive antagonism?

A

Max effect does NOT decrease; curve just shifts to the right

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15
Q

What kind of bonds are present in competitive antagonism?

A

Weak ionic bonds (H+ bonds)

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16
Q

In competitive antagonism, as the antagonist goes up, what do we do to combat it?

A

Give more agonist as well

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17
Q

What happens to the max effect in noncompetitive antagonism?

A

Max effect decreases b/c it reduced amount of available receptors

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18
Q

What’s the difference between competitive antagonism and noncompetitive antagonism?

A

Competitive antagonism: curve (max effect) doesn’t decrease, shifts only to the right
Noncompetitive antagonism: curve (max effect) decreases; shifts down and to the right like swinging on a door hinge

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19
Q

What are the 2 types of noncompetitive antagonism that you can have? Which one is more common?

A

Irreversible or allosteric

Irreversible is more common

20
Q

What kind of bonds are in noncompetitive antagonism?

A

Covalent (strong) bonds

21
Q

In irreversible noncompetitive antagonism, what can’t you do?

A

You can’t give more agonist to maintain the max effect

22
Q

What happens to the curve during potentiation?

A

The curve shifts to the left

23
Q

What kind of curve is on the left in potentiation?

A

An allosteric agonist plus an agonist

24
Q

What can the allosteric agonist in potentiation do?

A

Enhance activity of agonist, which shifts the curve in the opposite direction of allosteric antagonist

25
Q

You do a study to see the effect of beta blockers dosage on a patient’s heart rate. The results are below:

10mg dec HR x 10 beats
20mg dec HR x 20 beats
40mg dec HR x 30 beats
80mg dec HR x 30 beats

What can you conclude from this?

A
  • As the dose increases, the response increment diminishes until a dose is reached where no further increase in response can be achieved
  • Give pt 40mg at most, because 80mg is not going to do anything extra for the patient
26
Q

What 2 things do you need to know in order to calculate the effect of the drug?

A

E(max) and EC(50)

27
Q

What’s the equation to find the effects of a drug

A

E = (Emax x C)/(C + EC50)

28
Q

What’s the equation to find the receptor’s affinity to bind a drug?

A

B = (Bmax x C)/(C + Kd)

Bmax = total number of receptor sites
Kd = concentration of free drug at which 1/2 max binding is observed
29
Q

When you see Emax and EC50 on a graph, what is being plotted?

A

Drug concentration per drug effect

30
Q

When you see Bmax and Kd on a graph, what is being plotted?

A

Drug concentration per receptor-bound drug

31
Q

If given a response curve and the Emax, how can you calculate EC50?

A
  • Divide Emax by 2 (ex: Emax can change HR by 100 beats/min, so 100/2 = 50)
  • Find where the curve crosses the y-axis at that number (ex: 50)
  • Draw line down to x-axis, and this is your EC50 (ex: 5)
32
Q

Will EC50 and Kd always be the same?

A

They may be identical, but need not be

33
Q

Refers to the concentration required to produce 50% of that drug’s maximal response (EC50)

A

Potency

34
Q

Reflects the upper limit of the dose-response relation on the response axis (max effect = Emax)

A

Efficacy

35
Q

On a response curve, how can you tell if a drug is more potent than another drug?

A

The further to the left it is, the more potent it is

36
Q

On a response curve, how can you tell the efficacy of a drug compared to another drug on the same chart?

A

Look at the height that it goes up to. The higher it goes, the greater the efficacy of the drug

37
Q

Do we care more about efficacy of a drug or the potency of a drug?

A

Efficacy b/c we want it to fix the issue, not worrying about the dosage of it if it works

38
Q

You have a chart that has some drugs with 100% efficacy and some with 50% efficacy. If you want the response to be in the lower part of the chart, which drugs will you pick to achieve this goal?

A

You can choose any of them because all drugs can achieve this; most likely, you’ll choose based on price

39
Q

For therapeutic purposes, how should potency of a drug be stated?

A

In dosage units and in terms of a therapeutic endpoint (ex: 50mg for mild sedation; 1mg/kg/min for an increase in HR of 25 beats/min)

40
Q

In the in-class case, raloxifene took the place of estrogen, not hindering it’s effects in the process. What type of drug is raloxifene?

A

Partial agonist

41
Q

If TD50 (same as LD50) 130, and ED50 is 4, what is the toxicity of the drug?

A

130/4 = 32.5

This means that you have to take 32.5 pills to get to toxicity when the recommended dose is 1 pill

42
Q

When is the graph relatively safe for a drug when discussing toxicity?

A

If ED50 and TD50 (or LD50) are relatively far apart

43
Q

How many drugs and receptors are involved with pharmacological antagonism?

A

2 drugs, 1 receptor

44
Q

How many drugs and receptors are involved with physiologic antagonism?

A

2 drugs, 2 receptors

45
Q

How many drugs and receptors are involved with chemical antagonism?

A

2 drugs, no receptors

46
Q

Type of antagonism where drugs may bind to and antagonize action of drug (ex: dimercaprol binds to and chelates lead and other toxic metals)

A

Chemical antagonism

47
Q

Type of antagonism where the antagonist produces a physiological action that is opposite of agonist and by a separate mechanism (ex: glucocorticoid hormone can increase blood sugar; insulin would oppose this action; these agents act on distinct receptor-effector systems) (like ANS: parasympathetic vs sympathetic)

A

Physiologic antagonism

Pharmacology (8 decks)

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