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z Biopharm > Pharmacodynamics - part 1 > Flashcards

Pharmacodynamics - part 1 Flashcards

1
Q

Pharamcokinetics includes:

A

Absorption
Distribution
Metabolism
Excretion

These factors take a dose of drug and determine the drug concentration in target organ over time.

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2
Q

Pharmacodynamics includes:

A

Receptor binding
Signal transduction
Physiological effect

These factors use the drug concentration in target over time to determine the mechanism + magnitude of drug effect.

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3
Q

What is the therapeutic window?

A

The drug concentration above lack of effect (therapeutic failure) and below side effects (drug excess).

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4
Q

While over the counter drugs have a _________ therapeutic window, prescription drugs have a ________ therapeutic window.

A

Larger; narrow

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5
Q

The side effects/toxicity a drug can exert and pass the therapeutic window may be due to:

A

1) Same mechanism/action as the therapeutic effect but HIGHER INTENSITY

2) Same mechanism/action but NON-TARGET TISSUE

3) Different mechanism than the therapeutic effect

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6
Q

In simpler terms, PD is how the ________ affects the _________, while Pk is how the __________ affects the ________.

A

substance; organism

organism; substance

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7
Q

What are three methods a xenobiotic can make use of to induce changes in the organism?

A

1) Xenobiotic-receptor interactions (agonism, antagonism, inhibition, etc)

2) Physical actions (osmotic activity, effects of membrane)

3) Chemical actions (antacids, chelating agents, pro/antioxidants)

2/3 not as specific like 1.

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8
Q

As a mechanism of action, a drug typically exerts effects on the molecular level, which induces cellular changes, leading to tissue/organ changes that affect the whole organism (systemic).

Briefly use these terms to describe the effects of Nifedipine, Verapamil, Diltiazem (Ca2+ ion blockers).

A

Usually calcium ions go and bind to calmodulin which causes contraction in tissues/organs, leading to an increased blood pressure.

This xenobiotic:
Molecular: blocks calcium ion channels

Cellular: calcium can no longer bind to calmodulin

Tissue/organ: contraction is inhibited

Systemic: blood pressure decreases

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9
Q

What is a dose-response relationship?

A

The relationship between the concentration of a xenobiotic at the receptor site (in vitro) or in the dose/blood (clinic) and the magnitude of response.

Concentration is in reference to bioavailability (in blood or SOA).

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10
Q

What are the two types of dose response relationships?

A

1) Graded (continuous; describe the effect of various doses of a drug on an individual)

2) Quantal (all-or-none; respond or not - show the effect of various doses of a drug on a population of individuals)

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11
Q

A graded dose response is the relationship among dose/concentration, target/receptor “activation”, and the ____________ of the response.

The response elicited with each dose is plotted against the _____ dose/concentration and can be described as ______ _______________.

A

Magnitude

Log; % of Maximal Response

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12
Q

A quantal dose response is the relationship among dose/concentration and the ________ of the response.

The response elicited with each is plotted against the _____ dose and can be described as _________________.

A

Frequency

log; % of population

Responses generated with increasing dose of a drug/toxin described as the cumulative % of subjects exhibiting a defined all-or-none effect.

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13
Q

Match the following terms to their definition:

1) Emax
2) ED50
3) Tmax
4) TD50
5) LD50

A) MEDIAN EFFECTIVE DOSE the dose that produces 50% of the Emax

B) MEDIAN TOXIC DOSE - the dose that produces 50% of the Tmax

C) MEDIAN LETHAL DOSE - if the effect is death, ED50 is referred to as LD50.

D) the maximal response produced when the targeted interaction is saturated (all receptors occupied)

E) the maximum toxic response

A

Emax: the maximal response produced when the targeted interaction is saturated (all receptors occupied)

ED50: MEDIAN EFFECTIVE DOSE - the dose that produces 50% of the Emax

Tmax: the maximum toxic response

TD50: MEDIAN TOXIC DOSE - the dose that produces 50% of the Tmax

LD50: MEDIAN LETHAL DOSE - if the effect is death, ED50 is referred to as LD50.

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14
Q

(T/F) LD50s are calculated and expressed relative to a population; Quantal relationship (yes/no).

A

True!

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15
Q

What is NOEL? What is NOAEL?

A

NOEL: no observed effect level

NOAEL: no observed adverse effect level

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16
Q

In a graded dose response, first there is _______ and then a _________ and then the _______ effect.

Where is NOAEL?

A

NOEL; threshold, maximal

NOAEL is between the threshold and the maximum effect where ED50 is.

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17
Q

Some drugs can have a threshold and some do not. What is the difference between the two?

A

Having a threshold means that the patient can tolerate the drug for a little without a response. It is after crossing that threshold where the effects start showing.

Without a threshold, the patient is not able to tolerate without a response. The response is present right away.

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18
Q

Describe potency: how it is expressed, how it is determined, what it is related to, etc.

A

Potency is generally expressed as EC50 (dose that produces 50% of the maximal effect).

It is determined by the affinity of the xenobiotic for its target. A drug with high affinity requires lower dose to occupy more receptors.

Potency is inversely related to ED50; a drug with ED50 of 5 mg is 10x more potent than a drug with ED50 of 50mg.

19
Q

Efficacy is the _________ response produced by a drug.

A full agonist has a ________ efficacy.
An antagonist has a ________ efficacy.

A

Maximal

Maximal; partial agonists have below 100-50%.

No

20
Q

Drugs can have the ______ efficacy but a _______ potency or vice versa.

A

same; different

more potent drug; less dose needed to reach 50% of the max efficacy

less potent drug: more dose needed to reach 50% of the same max efficacy

21
Q

What is IC50?

A

The concentration of an inhibitor where the response is reduced by half.

The smaller the IC50 (less drug to inhibit more), the greater the potency of the drug.

22
Q

What is the slope in graded dose response curves?

High slope means ________ concentration sensitive; a ________ therapeutic window.

Low slope means _______ concentration sensitive; a _________ therapeutic window.

A

The change in response per unit dose/plasma concentration.

HIGHLY: narrow (small changes = big differences)

MIDLY; broader (OTC drugs)

23
Q

(T/F) In the slopes of graded dose response curves, a high slope drug means individual variation is less important, while a low slope drug means individual variation more import.

A

False!

High slope: individual variation important; need for personalized dose titration

Low slope: individual variation less import; common dosing schedules

24
Q

Suppose drug A has a slope of 1.0, drug B has a slope of 1.5, and drug C has a slope of 0.5 in a graded dose-response curve.

Which drug is most likely to be an OTC drug?

Which drug is least likely to be an OCT drug?

A

Drug C (lowest slope) most likely to be an OTC drug.

Drug B (highest slope) least likely to be an OTC drug.

The higher the slope, the higher the sensitive to dose. Less drug = more changes. Therapeutic window narrow.

25
Q

What is the therapeutic index (TI)?

How is TI measured?

A

TI is the mathematical measure between the toxicity and therapeutic effect.

TI = TD50/ED50

26
Q

The TI (therapeutic index) of a drug has to be _________ than 1 to be useable.

The larger the TI, the ________ the therapeutic window.

A

Greater (TI of 1 or lower = poison)

Larger

27
Q

(T/F) Therapeutic index, therapeutic window and standard safety margin all mean the same thing.

A

False!

Therapeutic window: the range of blood level wherein the drug is producing the desired effect without the feared toxicity.

Therapeutic index: the ratio of the dose that produces the desired therapeutic effect to the dose that produces a toxic effect.

Standard Safety margin: the concentration of the drug that leads to 1% of the population dying relative to treating (LD1-ED99/ED99)

28
Q

Therapeutic index (TI) and standard safety margins are based on ________ dose-response relationships.

A

Quantal

TI can be defined using a graded dose relationship curves but standard safety margin can only be quantal.

29
Q

What are the effects of competitive antagonist and competitive agonist in graded dose-response curves?

A

Competitive antagonist:
- binds REVERSIBLY to receptor at an orthosteric site
- effects can be overcome with increasing doses of the agonist
- SHIFTS the agonist’s dose-response curve to the RIGHT
- does NOT REDUCE the MAXIMAL response

Competitive agonist:
- SHIFTS the agonist’s dose-response curve to the LEFT
- does NOT REDUCE the MAXIMAL response

*parallel shift

30
Q

What are the effects of non-competitive antagonist in graded dose-response curves?

A

Non-competitive antagonist:
- binds to the receptor (reversible/irreversible) in a way that reduces the ability of the agonist to elicit a response at an ALLOSTERIC SITE

  • CANNOT be OVERCOME with greater doses of an agonist
  • REDUCES the agonist’s MAXIMAL response
  • No change in EC50 (potency)
31
Q

(T/F) Many bioactive xenobiotics exert multiple effects.

A

True!

32
Q

What is the difference between frequency distribution and cumulative frequency distribution of a quantal dose response relationships?

A

Frequency tells you how often something happened; it is a non-cumulative response.

The cumulative frequency is calculated by adding each frequency from a frequency distribution table to the sum of its predecessors. The last value will always be equal to the total for all observation.

33
Q

(T/F) A graded response can be represented/transformed to a quantal response by setting a specific endpoint along the graded response. Similarly, a quantal can become graded.

A

FALSE!

Graded can be quantal by setting a specific endpoint along the graded response but a QUANTAL CAN NOT BE GRADED.

34
Q

What does a negative 17% standard safety margin value mean?

A

(LD1-ED99)/ED99 = -17%

If you continue with the treatment for the 99% of the population, 17 people will have died.

Dose predicted to induce therapeutic effect in 99% of individuals must be DECREASED by 17% to avoid the xenobiotic being lethal to 1% of the population.

35
Q

If a drug has a ________ safety margin, they are often initiated at low dose and increased gradually. Alternative treatments are considered if the dose increases beyond _____.

A

Negative

EC50 (the concentration of a drug that is necessary to cause half of the maximum possible effect).

36
Q

(T/F) While the therapeutic index and standard safety margin are ratios, therapeutic window is a range of numbers.

A

True!

37
Q

For time/dose-response relationships,

Pharmacokinetics has _________ on the y-axis, _______ on the x-axis.

Pharmacodynamics has _________ on the y-axis, ______ on the x-axis.

PK/PD has __________ on the y-axis, __________ on the x-axis.

A

concentration; time

effect; concentration

effect; time

(dose response has concentration/dose on the x-axis)

38
Q

(T/F) We can tell a lot about time in dose-response relationship models.

A

False! Dose-response relationship models do not tell us anything about time.

39
Q

(T/F) Time response relationships and dose response relationships are both monotonic.

A

False, dose response curve is monotonic, while time response curve is non-monotonic.

40
Q

In time-response relationships:

Bigger dose, _______ onset, _______ duration

Does the Tmax remain the same if you change doses in time-response relationships?

A

earlier; longer

Yes, Tmax remains the same (if absorption and elimination processes are unsaturated)

41
Q

Out of the three routes of administration, which one would have the fastest Tmax + highest Cmax in the plasma? Which one would have the slowest Tmax + lowest Cmax?

1) Inhalation
2) Oral
3) Topical

A

Inhalation would have the fastest Tmax (time to reach Cmax) and the highest Cmax (maximum drug concentration). Strong response, early onset + long duration.

Topical would have the slowest Tmax and the lowest Cmax. Less intense effect, longer onset + short duration.

42
Q

The higher the volume of distribution, the more time for ___________.

A

Elimination

43
Q

When the rate of elimination is smaller than the rate of absorption, ______________ occurs.

A

Bioaccumulation

z Biopharm (9 decks)

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