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Pharmacology > Pharmacodynamics > Flashcards

Pharmacodynamics Flashcards

1
Q

What are the molecular targets for drug action?

A 
RITE:
Receptors
Ion Channels
Transporters
Enzymes
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2
Q

What relationship do receptors have with drugs?

A

The quantitative relationship between drug dose and pharmacological effect.

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3
Q

What is a dose-reponse curve?

A

Shows the effects of active, allosteric (active/inhibitor), and competitive inhibitor binding sites on receptors.

  • Agonist
  • Competitive Inhibitor
  • Allosteric inhibitor
  • Allosteric activator

Each of these either helps or prevents drug binding and effect.

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4
Q

What are two types of dose response relationship?

A

Graded and Quantal

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5
Q

What is a graded relationship?

A

It is the single response to an individual effect on a drug dose. Also reflects max efficacy of a drug.

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6
Q

What is a quantal relationship?

A

Looking at drug dose to the proportion of individuals displaying the desired pharmacologic response.

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7
Q

What can both curve types tell us about the drug?

A

The potency and selectivity.

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8
Q

What does a graded curve look like? Why?

A

It looks sigmoidal because as you increase the dose (X axis) the desired effect (efficacy of the drug: Y axis) will also increase in the individual.

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9
Q

What is EC50?

A

It is the drug concentration that gives 50% maximal response.

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10
Q

Explain efficacy.

A

It is the max dose and effective response.

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11
Q

What is potency?

A

Is a relative term but when looking at two drugs, whichever has the smaller ED50, is the more potent drug.
- Less drug dose for equal or better effectiveness

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12
Q

What is the quantal dose response?

A 
The frequency (Y axis) with which a given drug dose (X axis) produces an all-or-none response. (In a population of subjects)
- existing in only one of two possible states
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13
Q

What is the therapeutic index and how is it found?

A

It is the range in which a drug is stable within the body. A large TI gives more room for error. A smaller TI leaves little room for error. It is found by graphing the quantal curves for sets of individuals relating to a drug. The cumulative curve is then graphed out and ED50 is measured to LD50. This is the therapeutic zone for the drug.

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14
Q

Three graded curves are on a graph. How can you tell which is more potent?

A

The most potent drug will be to the very left. We can tell because Emax is reached with a lower dose of the drug.

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15
Q

Can two drugs have the same efficacy but different potency? What does it look like on a graph? Are their ED50’s the same?

A

Yes. Drug A can be more potent than Drug B but they can both have similar efficacies. On a graph DA would be shifted to the left and DB would still have the same Emax. ED50’s will NOT be the same.

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16
Q

How does the route of administration effect potency?

A

Drugs will be more potent when administered IV, IM etc. because they do not go through the first pass clearance through the liver.

17
Q

Explain Tachyphylaxis.

A

This is the rapid tolerance that can take effect (during surgery). This acute tolerance occurs quickly and reverses quickly. The number of receptors is not constant; in fact dynamic.

18
Q

Explain Tolerance.

A

The hyporeactivity form chronic exposure. Takes long to develop and reverses slowly. A higher dose is needed to reach the same desired effect.

19
Q

What does a graded curve look like in tolerance compared to a normal individual with the same drug?

A

The curve will be shifted to the right. The individual whom has the higher tolerance will need a higher dose to reach the same effect.

20
Q

What are full drug agonists? What type of efficacy do they produce?

A

Bind to a receptor and produce a molecular response with cellular response. Produce positive efficacy.

21
Q

What are partial drug agonists? What can they do to full agonists?

A

Bind to a receptor but even the highest drug concentration cannot produce the same effect of the full drug agonist. They can displace the effectiveness of a full agonist and antagonize it.

22
Q

What are inverse drug agonists? What type of efficacy do they produce?

A

They have a higher binding affinity for the resting state than the active site. They have a negative efficacy.

23
Q

What will a Full-Partial Agonist Dose curve look like?

A

Full agonist curve will be above the Partial agonist (despite concentration) in a quarter sphere shape.

24
Q

Will ED50 increase or decrease in the presence of a reversible competitive antagonist? What happens to Efficacy? (Emax) What are some examples?

A

ED50 will increase and shift a full agonist curve to the right (parallel shift). Emax will be unchanged.
ex) naloxone(narcan: for opioid OD), propanolol, flumazenil(valium OD)

25
Q

What effect on efficacy do irreversible competitive antagonists have? What are some examples?

A

They diminish the maximal efficacy.

ex) phenoxybenzamine (anti-hypertensive due to efficacy reducing vasoconstriction), aspirin at the platelet

26
Q

Explain Phase I

A

non-synthetic, preparatory; we are preparing the drug to do something.

27
Q

Explain Phase II

A

synthetic; we are adding something to the drug.

28
Q

What is biotransformation?

A

It is the process from administration of the drug to metabolism to elimination.

29
Q

Explain Prodrugs

A

Prodrugs improve the selectivity the desired drug has with the cell or processes that it may not be intended to target. (these are inactive until at the site of action)

30
Q

What two functions do Cytochrome P450 (Isozymes) enzymes have?

A
  • Endogenous compound
    METABOLISM
  • Exogenous compound detoxification –> Drug METABOLISM
31
Q

90% of drugs utilize which CYP Isoforms?

A

3A, 2D6, and 2C8-10

32
Q

What role do inhibitors play in isozyme function?

A

Inhibitors impede the ability of specific enzymes to metabolize the drug. This keeps drug conc higher within the blood.

33
Q

What role do inducers play in isozyme function?

A

Inducers help enzymes metabolize drugs faster.

34
Q

What is polymorphism, and how does it play into Isozyme effectiveness?

A

The genetic variability in different races. If a given isozyme is not produced for an individual they can have more dramatic effects (isozyme not there to metabolize drug out of the system).

35
Q

What % of individuals have deficiency in 2C19?

A
  • 16% Asians
  • 4-8% African Americans
  • 3-5% Caucasians
36
Q

What % of individuals have deficiency in 2D6?

A
  • 5-10% Caucasians
  • 3.8% African Americans
  • 0.9% Asians
  • 1% Arabs
37
Q

List some Important generalizations about P450 enzymes:

A
  • some substrates for P450 enzymes are inhibitors for the same enzyme
  • some inhibitors affect more than one P450 isozyme
  • some subs are metabolized by >1 isozyme
  • an inhibitor may produce inhibition of one enzyme at one dose but require a larger dose to inhibit another isozyme
  • Isomers in racemic mixtures tend to be metabolized by different P450’s

Pharmacology (9 decks)

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