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Y2 BRS Pharmacology > Principles of Pharmacology > Flashcards

Principles of Pharmacology Flashcards

1
Q

What does pharmacodynamics deals with?

A

‘what the drug does to the body’

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2
Q

What dos pharmacokinetics deal with?

A

‘what the body does to the drug’

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3
Q

If we want to consider how a drug exerts its effects on the body, what questions should you consider?

A
  1. Where is this effect produced?
  2. What is the target for the drug?
  3. What is the response that is produced after interaction with this target?
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4
Q

What are the four types of drug target proteins?

A
  1. Receptors
  2. Enzymes
  3. Ion channels
  4. Transport proteins
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5
Q

What is aspirin’s action?

A

Binds to the ‘enzyme’ cyclooxygenase and blocks the production of prostaglandins.

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6
Q

What are local anaesthetics action?

A

Block sodium ‘ion channels’ and thus prevent nerve conduction.

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7
Q

What is Prozac’s (Anti-depressant) action?

A

Block serotonin ‘carrier proteins’ and prevent serotonin being removed from the synapse.

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8
Q

What is nicotine’s action?

A

Binds to and activates the nicotinic acetylcholine ‘receptor’

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9
Q

What is the relationship between dose and effect?

A

As the dose increases, the effect becomes less specific

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10
Q

What types of chemical interactions can drugs interact with receptors?

A
  • Electrostatic interactions
  • Hydrophobic interactions
  • Covalent bonds
  • Stereospecific interactions
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11
Q

What are electrostatic interactions?

A

This is the most common mechanism and includes hydrogen bonds and Van der Waals forces

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12
Q

What are hydrophobic interactions?

A

This is important for lipid soluble drugs

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13
Q

What are covalent bonds?

A

These are the least common as the interactions tend to be irreversible

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14
Q

What are stereospecific interactions?

A

A great many drugs exist as stereoisomers and interact stereospecifically with receptors

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15
Q

What does the affinity of a drug determine?

A

Determines strength of binding of the drug to the receptor (strength of the drug-receptor complex)

As a result, affinity is strongly linked to receptor occupancy

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16
Q

What does efficacy relate to?

A

The ability of an individual drug molecule to produce an effect once bound to a receptor

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17
Q

What are 3 classes of drug interactions at the receptor based level based on efficacy?

A
  1. Antagonists
  2. Partial agonist
  3. Full agonist
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18
Q

What is a receptor antagonist?

A

Has affinity for the receptor but no efficacy.

When bound to the receptor, it is effectively ‘blocking’ that receptor and preventing an agonist from binding to the receptor and inducing activation.

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19
Q

What is a partial agonist?

A

Has affinity for the receptor and sub-maximal efficacy.

When bound to the receptor, it can produce a partial response, but cannot induce the maximal response from that receptor.

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20
Q

What is a full agonist?

A

Has affinity for the receptor and maximal efficacy.

When bound to the receptor, it can produce the maximal response expected from that receptor.

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21
Q

What is potency?

A

The concentration or dose of a drug required to produce a defined effect.

As a result, the standard measure of potency is to determine the concentration or dose of a drug required to produce a 50% tissue response.

22
Q

What is EC50?

A

Half maximal effective concentration

23
Q

What is ED50?

A

Half maximal effective dose

24
Q

What is the difference between potency and efficacy?

A

A highly potent drug produces a large response at relatively low concentrations.

A highly efficacious drug can produce a maximal response and this effect is not particularly related to drug concentration.

25
Q

What is the clinical relevance of the difference between potency and efficacy?

A

Efficacy is more important. You want to know if the drug you are giving can induce a maximal response.

The potency simply determines the dose that you will need to administer to produce a response.

If you have two drugs that have equal efficacy, then it doesn’t really matter if one is more potent than the other, since you can still produce the maximal response with the less potent drug – you just need to administer a slightly higher concentration.

26
Q

What are the major pharmacokinetic concepts?

A
  • Absorption
  • Distribution
  • Metabolism
  • Excretion
27
Q

What is absorption in relation to pharmacokinetics?

A

The passage of a drug from the site of administration into the plasma

28
Q

What is bioavailability?

A

The fraction of the initial dose that gains access to the systemic circulation

29
Q

What is the difference with absorption and bioavailability?

A

Absorption deals with the process for drug transfer into the systemic circulation

Bioavailability deals with the outcome of drug transfer into the systemic circulation (i.e. how much)

30
Q

Why is site of administration important?

A

E.g. intra-venous administration.
The process for drug passage is injecting the full dose straight into the circulation.

The outcome if the full dose is administered straight into the circulation is that the bioavailability must be 100%.

31
Q

What are examples of forms of drug admission?

A
  • Oral
  • Inhalational
  • Dermal (Percutaneous)
  • Intra-nasal
32
Q

How can drugs move around the body?

A
  1. Bulk flow transfer (i.e. in the bloodstream)

2. Diffusional transfer (i.e. molecule by molecule across short distances)

33
Q

How would drugs be moved around the body when intravenously administrated versus the other routes?

A

The drug is injected straight into the bloodstream, and therefore bulk flow transfer will then deliver the drug to its intended site of action.

With all other routes of administration, in order for the drug to reach the bloodstream it is first going to need to diffuse across at least one lipid membrane.

34
Q

How do most drugs cross the lipid membrance?

A
  1. Diffusion (lipid soluble)

2. Carrier mediated transport (transmembrane protein)

35
Q

What are methods to cross the plasma membrane rarely used by drugs?

A
  1. Pinocytosis

2. Diffusion across aqueous pores

36
Q

When is pinocytosis used by drugs to cross a plasma membrane?

A

Insulin -> brain

37
Q

What determines whether a drug will be ionised or not?

A
  1. the dissociation constant (pKa) for that drug

2. the pH in that particular part of the body.

38
Q

What is the significance of a drug being unionised?

A

Retains more lipid solubility -> more likely to diffuse across plasma membranes

39
Q

What form will a drug be in if the pKa of the drug and the pH of the tissue are equal?

A

Equally dissociated between the two forms i.e. 50% ionised and 50% unionised.

40
Q

For weak acids, what happens with pH increases?

A

Unionised form dominates

41
Q

For weak bases, what happens when pH changes?

A

As the pH decreases, the ionised form starts to dominate.

As the pH increases, the unionised form starts to dominate.

42
Q

Where will a weak acid be more unionised?

A

Areas of low pH like the stomach

43
Q

Where will a weak base be more unionised?

A

Areas of higher pH like the blood and urine

44
Q

In terms of pharmacokinetics, where are the most important carrier systems relating to drug action found?

A

1) Renal tubule
2) Biliary tract
3) Blood brain barrier
4) Gastrointestinal tract

45
Q

What carrier systems are useful in drug function?

A
  1. For drug access to the bloodstream (absorption from the gastro-intestinal tract)
  2. For drug access to certain tissues (absorption across the blood brain barrier)
    3, For excretion of drugs from the body (excretion from the kidney of the gastro-intestinal tract)
46
Q

Why are transport proteins needed for weak bases?

A

Poorly absorbed from the stomach due to the low pH leading to a high drug ionisation.

However, once the drug eventually reaches the small intestine, it will be able to access a huge number of transport proteins that will enable absorption from the gastrointestinal tract.

47
Q

Why are transport proteins needed for weak acids?

A

Potentially be absorbed from the stomach in its unionised state. However, it would then become more ionised at physiological pH and potentially become ‘trapped’ in the blood.
Once again, however, most tissues possess transport proteins that could potentially move the ionised drug from the blood into the tissue.

48
Q

What factors affect tissue distribution of drugs?

A
  • Regional blood flow
  • Plasma protein binding
  • Capillary permeability
  • Tissue localisation
49
Q

What factors affect the amount of drug that is bound?

A
  • The free drug concentration
  • The affinity for the protein binding sites
  • The plasma protein concentration
50
Q

What plasma protein is good at binding acidic drugs?

A

Albumin

51
Q

What kind of drug can diffuse out of blood access tissues?

A

Free drug

Bound to plasma proteins = cannot until dissociates from protein

Y2 BRS Pharmacology (9 decks)

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