Exam I: Pharmacodynamics Flashcards Preview

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Flashcards in Exam I: Pharmacodynamics Deck (24):
1

What are the most common mechanisms for drug interactions?

Synergism (potentiation)

Antagonism

Altered cellular transport

Effects on receptor sites

2

Why is understanding pharmacodynamics important?

- Provide basis for rational therapeutic use of a drug

- Design of new and superior therapeutic agents

3

The four most important parameters governing drug disposition are:

1. Bioavailability
2. Volume of Distribution
3. Clearance
4. Elimination

4

How many half-lives does it take to get to steady state? (exam purpose number)

5

5

Define steady state

rate in = rate out

The amount of drug administered in a given period is equal to the amount eliminated in that same period

6

How does a drug's clearance and elimination half-life have an effect on a dosing regimen?

Drugs w/ a faster elimination rate have a decreased half life.

Decreased (or smaller) half-lives need more frequent doses

In short:
DEC. clearance and half life = INC. frequency of doses

7

1st Order Elimination: what shape is the graph?

Linear

8

1st Order Elimination: Are drug elimination pathways typically easily or not easily saturated (maximized)?

NOT easily saturated (NOT easily maximized)

Elimination rate increases in DIRECT PROPORTION to serum drug concentration

9

Is half-life independent or dependent of drug concentrations in 1st order elimination

Independent

10

Does 1st order elimination hold true for IV administration?

Yes

11

Does 1st order elimination hold true for oral drug administration?

No.

% absorption may decline with higher doses...it may have maximized the absorption process

12

Zero-order elimination: Are drug elimination pathways easily or not easily saturated (maximized)?

Easily saturated (maximized)

13

Zero-order elimination: Relationship between dose administered and serum drug concentration

Elimination rate is CONSTANT so...

Serum drug concentration is DISPROPORTIANT to the dose administered.

Small increases produce large increases in serum concentration

14

Is half-life independent or dependent of drug concentrations in zero-order elimination?

Dependent

15

Which is more dangerous?

1st Order or Zero order elimination?

Zero Order elimination

--> A small increase in dose can have a huge increase in serum concentration and potentially reach toxic levels

16

What is the primary determinant of how long it will take for a drug regimen to reach steady-state?

A drug's half life

--> The shorter the half-life, the shorter it takes to reach steady-state

17

What are some factors that cause a drug-regimen to be "knocked out" of steady-state?

1. Frequency of dose

2. Method of administratio

3. Anything that changes absorption

4. Taking another drug

5. Liver function

**Anything that changes input or output

18

What happens to drug concentration once steady-state is reached?

Drug concentration reaches an equilibrium

19

Three types of receptor-effector systems:

1. Enzyme in intracellular space

2. Neurotransmitter reuptake transporters

3. Voltage-activated ion channels

20

5 types of transmembrane-signaling mechanisms:

1. Drug diffuses into cell membrane and then to intracellular receptor

2. Drug binds to transmembrane receptor that has an outer receptor domain and an inner effector mechanism domain converting A --> B

3. Drug binds to transmembrane receptor that activates JAKs inside which phosphorylate STAT. STAT regulates transcription

4. Drug binds to transmembrane channel that is gated open or closed

5. Drug binds to transmembrane receptor (G protein-coupled receptor) that activates a separate effector molecule

21

Tachyphylaxis

A sudden decrease in response to a drug that occurs usually from frequent or continuous exposure to agonists resulting in short-term reduction of receptor response

22

Example of drug that can cause tachyphylaxis

Albuterol for treatment of asthma

23

Down Regulation

Long-term reductions in receptor number which occur in response to continuous exposure to agonists

24

Up Regulation

Increases in receptor number which occur when receptor activation is blocked for prolonged periods by pharmacologic antagonists or by denervation