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PHAR > PHAR1 - Pharmacodynamics > Flashcards

PHAR1 - Pharmacodynamics Flashcards

1
Q

Define pharmacology.

A

The study of how drugs can influence the function of living systems.

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2
Q

What are the two major principles within pharmacology?

A

Pharmacodynamics and pharmacokinetics.

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3
Q

Define pharmacodynamics.

A

Study of what the drug does to the body.

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4
Q

Define pharmacokinetics.

A

Study of what the body does to the drug.

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5
Q

Where specifically does cocaine have its therapeutic effect?

A

The dopaminergic neurons in the nucleus acumens of the brain.

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6
Q

Define the drug target.

A

The site at which the drug binds to.

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7
Q

What are the four classes of drug target?

A

Receptors, protein carriers, enzymes and ion channels.

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8
Q

Which drug target does aspirin bind to? What is its effect?

A

Aspirin binds to the enzyme cyclooxygenase. Results in blocking of the production of prostaglandins. Prostaglandins control inflammation and send pain signals to the brain. Blocking this reduces symptoms of headaches.

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9
Q

What drug target do local anaesthetics bind to? What is the effect?

A

Local anaesthetics bind to sodium ion channels. This prevents nerve conduction due to presentation of the formation of action potentials.

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10
Q

What drug target does Prozac bind to? What is the effect?

A

Prozac binds to the serotonin carrier proteins. This prevents serotonin from being removed from the synapse. Serotonin is the ‘happy’ chemical therefore Prozac results in a longer state of ‘happiness’, allowing it to behave as an anti-depressant.

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11
Q

What drug target does nicotine bind to? What is the effect?

A

Binds to the nicotinic acetylcholine receptor and activates it. This means that signal transmission occurs at a faster rate, therefore acting as a stimulant.

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12
Q

What types of effects do drugs have on the body?

A

Drugs can act as both stimulants and inhibitors of specific processes in the body.

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13
Q

Discuss the idea of specificity.

A

Relates to how the drug and drug target fit together. Drugs will have high specificity for their drug target.

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14
Q

Define another word for specificity.

A

Selectivity.

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15
Q

Name three endogenous chemicals with similar chemical structures.

A

Dopamine, serotonin, noradrenaline.

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16
Q

What is an endogenous chemical?

A

Chemicals produced naturally and internally of the body.

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17
Q

What are the receptors for the following endogenous chemicals:
Dopamine
Serotonin
Noradrenaline

A

Dopamine receptors - dopamine.
Serotonin receptors - serotonin.
Adrenergeic receptors - noradrenaline.

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18
Q

Are drugs specific to one drug target only? If yes/no, give example.

A

Drugs have specificity for a variety of drug targets if they have similar chemical structures. E.g dopamine has the highest specificity for dopamine receptors however shows some specificity for adrenergic and serotonin receptors.

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19
Q

How are side effects of drugs generally produced?

A

Drugs interact with their non specific drug target which leads to unwanted side effects.

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20
Q

Discuss the link between drug dosage and specificity of drug effect.

A

A lower drug dosage results in more specific effects as drugs are more likely to interact with the specific drug target only. As the drug dosage is increased, drugs can interact with more drug targets, leading to more unwanted effects, resulting in overall less specific drug effects.

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21
Q

Can you accurately predict the amount of drug arriving at a specific drug target? If yes/no, why?

A

No as drugs can interact with many different targets if some level of specificity is present. As a result, it is difficult to accurately say how much drug is where.

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22
Q

Discuss the use and desired role of Pergolide.

A

Drug used in the treatment of Parkinson’s disease. Pergolide is a dopamine-receptor agonist so binds to dopamine receptors.

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23
Q

Give examples of side effects of pergolide and how they arise.

A

Increasing dosage to approx 8-10nM leads to hallucinations as pergolide interacts with serotonin receptors.
Increasing dosage to approx 60-100nM leads to hypotension as pergolide interacts with adrenergic receptors.

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24
Q

How is the therapeutic window quantified?

A

Therapeutic index.

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25
Q

What does therapeutic window/index give an indication of and how?

A

Indication of the safety of the drug. The higher the value for therapeutic index, the larger the therapeutic window therefore the safer the drug.

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26
Q

How is the therapeutic effect measured for therapeutic index?

A

Measured by ED50 - the effective dosage of drug required to produce a specific therapeutic effect in 50% of the population.

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27
Q

How is the toxic effect measured for the therapeutic index?

A

Measured by TD50 - the drug dosage required to produce a specific toxic effect in 50% of the population.

28
Q

What units for used for TD50 and ED50?

A

Mg/kg

29
Q

What axes are present on log dose response curves?

A

Log dose - x axis.

Response (%) - y axis.

30
Q

How can a log dose response curve to used to visualise the therapeutic window?

A

Drawing a sigmoid curve for both the therapeutic effects at various drug doses from 0-100% and the toxic effects from 0-100%. The lower the overlap between the two curves, leads to a larger therapeutic window therefore a safer drug.

31
Q

Discuss the equilibrium that exists between drugs and receptors (drug targets).

A

Drugs bind to receptors transiently, forming drug-receptor complexes.

32
Q

What happens to the equilibrium between a drug and a receptor, if the concentration of the drug is increased?

A

Increasing the [drug] causes equilibrium to shift to the right. More drug is available to bind to the free receptors resulting in more drug-receptor complexes being formed.

33
Q

What happens to the equilibrium between a drug and a receptor, if the concentration of the drug is decreased?

A

Decreasing the concentration of drug causes the equilibrium to shift to the left. Less drug is available therefore less binds to the free receptors. This results in fewer drug-receptor complexes being formed.

34
Q

Define affinity.

A

Drug affinity relates to the strength at which the drug is able to bind to the receptor/drug target.

35
Q

Discuss receptor occupancy and its link to affinity.

A

Receptor occupancy defines what proportion of receptors are bound towards a drug molecule at that point in time. The higher the affinity, the more likely it is that receptor occupancy is high.

36
Q

Discuss the interactions between drugs and receptor.

A

Drugs and receptor form transient interactions to form drug-receptor complexes.

37
Q

Discuss efficacy and it’s link to affinity.

A

Efficacy is the ability of an individual drug molecule to produce an effect when bound to the drug receptor. Closely linked to affinity however are two separate pharmacological factors.

38
Q

What is the Emax?

A

The maximum response that can be achieved from a specific drug dosage.

39
Q

Discuss the equilibrium that exists between agonists/antagonists and the receptor.

A

Agonist OR antagonist + receptor -> agonist/antagonist-receptor complex

40
Q

Discuss the role of noradrenaline in the body.

A

Noradrenaline binds to adrenergic receptors, acting as the endogenous agonist for it. Involved in the control of heart rate.

41
Q

Discuss the effect of an added exogenous agonist on the role of noradrenaline.

A

Exogenous agonist would mimic the effect of noradrenaline and result in an increase in heart rate as its therapeutic effect.

42
Q

Discuss the effect of an antagonist on the role of noradrenaline in the body.

A

Antagonist prevents noradrenaline from binding to the adrenergic receptors, inhibiting its effects. A decrease in heart rate would be observed.

43
Q

How does an agonist behave?

A

Binds to the receptor, leading to a therapeutic effect.

44
Q

How does an antagonist behave?

A

Binds to the receptor, preventing therapeutic effect. Types include competitive and irreversible antagonists.

45
Q

What endogenous chemicals are present for each receptor in the body?

A

Endogenous receptor agonists are present in the body for each receptor.

46
Q

Give one advantage and disadvantage of exogenous agonists, compared to endogenous agonist.

A

Adv - can produce a greater response with a high dose as more drug is avAilable to bind to the receptors.
Disadv- difficult to design the drug in a way that it is accurately delivered to the site of action.

47
Q

Discuss the affinity and efficacy of agonists.

A

Agonists have high affinity for the receptor and high efficacy resulting in an effect when bound to the receptor.

48
Q

Discuss the affinity and efficacy of antagonists.

A

Antagonists have affinity for the receptors however zero efficacy, as they do not cause an effect.

49
Q

What are the two types of agonists and how are they differentiated?

A

Full agonist - increase of drug dosage results in the maximal response of drug effect. Full efficacy.
Partial agonist - continued increase of drug dosage does not reach 100% response as it is capped. Partial efficacy.

50
Q

What are the two types of antagonists and how are they different?

A

Competitive antagonist - binds reversible to the receptor, temporarily blocking it. The agonist will compete for the receptor with the competitive antagonist.
Irreversible antagonist - binds permanently to the receptor, blocking it long term or permanently. The antagonist is unable to bind to the receptor.

51
Q

Discuss the link between potency and dosage.

A

A drug with a higher potency requires a lower dosage to produce a particular effect.

52
Q

Drug A and Drug B have equal efficacy. Drug A has higher potency than Drug B. Which one should be used?

A

Either is able to produce the maximal response although drug B would require higher dosage.

53
Q

What value is used to compare potency?

A

ED50

54
Q

Discuss the reciprocity of specificity.

A

Drugs should be specific to a drug target. Drug targets should be specific to the drug also.

55
Q

Discuss the two types of side effects and what they are.

A

On-target - side effects which occur at the specific drug target.
Off-target - side effects which occur at non specific drug targets.

56
Q

What are the curves that can be dawn for in vivo and in vitro experiments?

A

In vitro - log concentration-effect curves

In vivo - log dose-effect curves

57
Q

Define receptor occupancy.

A

Determines the proportion of receptors that are transiently binding to drugs.

58
Q

Discuss the spare receptor theory.

A

If Emax can be achieved without using all of the receptors, then spare receptors are present, which is referred to as the spare receptor theory.

59
Q

Define Emax.

A

The maximal response that can be achieved from a tissue.

60
Q

What are the two types of efficacy? Define each type.

A

Intrinsic - ability of the drug to cause an effect once bound to the receptor.
Extrinsic - ability of the tissue to produce the response once it has been activated by a drug binding to it.

61
Q

Discuss the link between partial/ full agonists and receptor occupancy.

A

Drugs can appear as full agonists if the tissue has a high number of receptors. The same drug can appear as a partial agonist in a tissue with low receptors.

62
Q

Is there a link between potency and receptor occupancy?

A

Generally, drugs with a high potency also have a high affinity which would lead to a high receptor occupancy.

63
Q

What happens to the ED50 if a competitive receptor antagonist is added at the same drug dose?

A

Direct decrease.

64
Q

If two drugs are able to induce a 100% response, one at a lower drug dosage and the other at a higher drug dosage, which is considered more potent?

A

The lower drug dosage drug is considered more potent.

65
Q

Can potency be determined by the response evoked by different drugs at different dosages? If yes/no, how?

A

No - would require response at one specific dosage across all drugs.

66
Q

If drug binds to specific target and the production of an endogenous compound is increased, what is the drug target likely to be?

A

Enzyme. Involved in production of many chemical species.

67
Q

If a drug binds to a target and the response is an influx of ions, what is the drug target likely to be?

A

Ion channel. Aids the rapid movement of ions into or out of a cell.

PHAR (9 decks)

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