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FNP > Prinicples of pharmacology > Flashcards

Prinicples of pharmacology Flashcards

1
Q

What is a response?

A

A function of the number of occupied receptors.

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2
Q

What are the ways of regulating cell function?

A

Altering membrane potential
Altering enzyme activity
Altering gene expression

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3
Q

How do cells regulate cell function?

A

Some drugs affect function directly - e.g. tetrodotoxin, aspirin, acridine dyes.
Most drugs affect cell functions via physiological receptors.

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4
Q

What are the natures of drug receptors?

A

Enzymes e.g. cyclooxygenase - aspirin receptor
Ion channels e.g. Ca2+ channels blocked by nifedipine, causes relaxation of blood vessels
Transporters e.g. noradrenaline transporter blocked by cocaine
Physiological receptors - for hormones, neurotransmitters, e.g. acetylcholine, histamine, insulin.

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5
Q

How are receptors classified?

A

Named according to the transmitter or hormone with which they interact
Most transmitters or hormones interact with more than one type of receptor, protein structure underlies differences between subtypes.

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6
Q

How can transmitters act at more than one receptor?

A

ACh causes a drop in blood pressure
Atropine blocks the effect of ACh.
Increased dose of ACh causes increase in blood pressure.
Muscarine mimics ACh decrease in blood pressure and is blocked by atropine.
Nicotine mimics ACh increase in blood pressure and is not blocked by Atropine.

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7
Q

What are the receptor superfamilies?

A

Integral (ligand-gated) ion channels e.g. nicotinic receptor
G protein coupled receptors e.g. muscarinic receptor
Integral tyrosine kinases e.g. insulin receptor
Steroid receptors e.g. oestrogen receptor
Cytokine receptor e.g. prolactin receptor

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8
Q

What is the drug receptor equilibrium?

A

A + R <—> AR <—> AR* —> Effect
A = drug: agonist, antagonist
R = receptor
Affinity governs binding
AR = Drug/receptor complex
<–> = Binding and dissociation
* switches drug on, efficacy governs activation

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9
Q

What is the law of mass action?

A

Predicts the rate of a chemical reaction throuh the mass or amount of reactants and product.

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10
Q

What is the law of mass action equation?

A

A+R <—> AR
At equilibrium: rate of binding and dissociation are equal - Kd.
Kd is dissociation constant, measured in amount - mol per litre

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11
Q

What is the Kd equation?

A

Kd = [A][R] / [AR]

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12
Q

What is the equation of receptors?

A

For a fixed number of receptors:
[RT] = [R] + [AR]
R total
R = concentration of unbound receptor
AR = concentration of drug bound receptor.
Fraction of receptors occupied by agonist is defined by occupancy (p)

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13
Q

What is occupancy?

A

p = [AR]/[RT]

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14
Q

What is the Langmuir isotherm equation?

A

p = [A] / Kd + [A]

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15
Q

What is the graph for Langmuir isotherm?

A

occupancy y axis, up to 1
[agonist] x axis
hyperbola
see image

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16
Q

What is the theoretical log graph for Langmuir isotherm?

A

Occupancy y axis
log [agonist] x axis
sigmoidal curve - increased concentration increases occupancy until a maximum point

17
Q

What is the experimental graph for log Langmuir isotherm?

A

Effect on y axis
log [agonist] x axis
same sigmoidal curve, indicates drug is producing effect by occupancy.

18
Q

What is affinity?

A

Affinity of a drug for its receptor is a measure of how well it binds to the receptor.
Measured using Kd - drug dissociation constant from receptor.

19
Q

What is Kd?

A

Kd is equal to the concentration at which at equilibrium, half the receptor population will be bound with the drug.

20
Q

What is EC50?

A

Effective concentration to produce 50% of the maximum response.
Allows measure of potency.

21
Q

What is potency?

A

The amount of drug required to produce a particular level of effect.

22
Q

What does the graph look like for EC50?

A

effect on y axis
log [agonist] on x axis
EC50 is half of the effect
Emax is the maximum effect
see image

23
Q

What is the relationship between drug concentration and effect?

A

There is a threshold needed to be reached to cause an effect.
It reaches a maximum so is saturated.
It is graded - increasing the concentration produces a sigmoidal curve.

24
Q

What is the relationship between drugs A and B and effect?

A

A higher concentration of B is needed to produce an effect.
EC50 values allow comparison of relative potency - drug B is less potent than A.
see graph

25
Q

What are agonists?

A

Agonists bind to a receptor or target and produce a response.

26
Q

What is the relationship between response and occupancy?

A

Response is not always proportional to occupancy - efficacy is important.

27
Q

How does drug efficacy affect the curve?

A

Drug A has higher efficacy than drug C - A is a full agonist as it has maximum response.
Drug C is a partial agonist.
see graph

28
Q

What is efficacy?

A

A measure of the degree to which an agonist produces a response when binding a given proportion of receptors.

29
Q

What is the efficacy of a full agonist?

A

The efficacy is 1.
Some highly efficacious agonists can produce a maximal response without binding to all available receptors.
this is evidence of spare receptors.

30
Q

What is the efficacy of partial agonists?

A

A partial agonist has efficacy of less than 1 but more than 0.
Partial agonists cannot produce the cell’s maximal response at low efficacy, even when bound to all available receptors.

31
Q

What is the relationship between efficacy and potency?

A

See graph
Drug B produces a larger response, EC50 is higher, so A is more potent, and the difference between EC50s is the potency difference.
The efficacy difference is between the maximal effects.

32
Q

What is an inverse agonist?

A

A drug with negative efficacy - less than 0.
These drugs inhibit and intrinsic receptor activity that might exist in the absence of a ligand.

33
Q

What is the equation for inverse agonists?

A

A + R
R <—> R*
* R changes shape by itself to become active and open.
An inverse agonist binds to the receptor and causes it to go back to the inactivated state.
Governs de-activation.

34
Q

What is the patch clamp technique?

A

A method for looking at responses generated by individual receptors.
Suction electrode - a glass barrel, applies negative pressure to cell membrane and electrically seals cell onto the end of the electrode.
Record the current and plot on dose response curve.

35
Q

What does the log dose response curve look like for the patch clamp technique?

A

Full, high efficacy agonist - opens ions channels at a range of doses, sigmoidal curve.
Partial, low efficacy agonist - opens channels, less efficacy.
No agonist - channel opens by itself - intrinsic spontaneous activity.
Inverse agonist - decreased activity, prevents intrinsic spontaneous activity.
see graph.

36
Q

What are antagonists?

A

Zero efficacy.
Block or reduce the response to an agonist
Can be competitive, irreversible, or other types.

FNP (12 decks)

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