Pharmacodynamics

Question 1

Concentration of the drug at the site of action depends on

Answer 1

1. rate of absorption

2. blood flow to the site

Question 2

How long the drug remains at the site in effective concentrations depends on

Answer 2

1. biotransformation (metabolism)

2. excretion

Question 3

Whats responsible for selectivity of drug action?

How so?

Answer 3

Receptors!

They determine which properties are need to bind to and modify receptors in a certain way - size, shape, and electrical charge

Question 4

EC50

Answer 4

concentration of drug that gives you 1/2 maximal response

this gives you a way to compare drug potency

Question 5

Law of mass action (in words)

Answer 5

The effect of a drug is directly proportional to the amount of drug-receptor complex formed

Question 6

What important constant do we get from the law of mass action?

Answer 6

Kd - the concentration at which you occupy half the receptors

The LOWER the Kd the HIGHER the affinity

Question 7

Calculation for occupied receptors (receptor B)

Answer 7

Occupied receptor B

= (c * Bmax) / (c + Kd)

Question 8

What assumptions are made with the law of mass action?

Answer 8

1. binding is total reversible
2. D and R only exist as free and bound
3. All receptor sites are considered to have equivalent affinity for D and to be independent

Question 9

Potency

Answer 9

Dose of a drug required to produce a particular effect of given intensity

It is a comparison b/t doses that produce the SAME effect

X axis variable

Question 10

Affinity

Answer 10

Ability of the drug to interact with the receptor

Affinity is one of the determinants of potency

Question 11

Efficacy

Answer 11

Biological response resulting form the drug-receptor interaction is termed efficacy

Maximal efficacy is limited by toxicity

This is a more important property than potency

Y axis variable

Question 12

Partial agonist

Answer 12

Produces a reduced response event at full receptor occupancy

May inhibit competitively the response to a full agonist

Question 13

Competitive antagonism

Answer 13

Antagonist combines with the same site on the receptor as the agonist

Can be reversed by increasing the dose of the agonist

Will reduce the apparent EC50

Question 14

Spare receptors

Answer 14

When the maximal response can be elicited by an agonist at a concentration that does not result in 100% occupancy of available receptors

Question 15

Noncompetitive antagonist

Answer 15

Antagonist that produces its effect at a site of the receptor other than the site used by the agonist

Cannot be completely reversed by increasing concentration of agonist

Increasing antagonist concentration increase Kd and decrease Emax

Question 16

Functional (physiological) antagonism

Answer 16

Two drugs influence a physiological system but in opposite directions

Each drug is unhindered in the ability to elicit its own characteristic response

Question 17

Chemical antagonism

Answer 17

A chemical reaction occurs between an agonist and an antagonist to form an inactive product

Agonist is inactivated in direct proportion to the extent of the chemical reaction with the antagonist

Question 18

Therapeutic significance of drugs that stimulate intracellular receptors that regular gene expression

Answer 18

1. Lag period

2. Effect persist after concentration is reduce to zero (due to slow turn over of enzymes or high affinity)

Question 19

Definition of a kinase

Answer 19

Enzyme which adds a phosphate groups to a substrate

Question 20

How many times does a protein tyrosine kinase span the membrane?

Answer 20

one

Question 21

Time between binding and response with ligand-gated channels?

Answer 21

Milliseconds

Question 22

How do G protein ligands act?

Answer 22

Act by increasing intracellular concentrations of second messengers

Question 23

Threshold WRT quantal log dose-response curve

Answer 23

the minimum effective dose of the drug which evokes an all-or-none pharmacological response

Question 24

Therapeutic Index or Ratio

Answer 24

Expresses the relative safety of a drug

LD50/ED50 or TD50/ED50

The larger the ratio, the greater the relative safety (presumably)

Question 25

Tolerance

Answer 25

Condition of decreased responsiveness to a drug; acquired after prior or repeated exposure to a given drug or a closely related one

Tolerance is reversible

Question 26

Two ways in which tolerance can be developed?

Answer 26

1. Decrease in effective concentration of the agonist at the site of action due to an induction of metabolic enzymes; end result is decreased effect of drug
2. Decrease in the normal reactivity of the receptor - down reg in receptor; change in receptor affinity

Question 27

Cross tolerance

Answer 27

Tolerance develops to one drug that is also seen with drugs belonging to the same class

Question 28

Tachyphylaxis

Answer 28

ACUTE development of tolerance following rapid, repeated administration of a drug

CANNOT OVERCOME with increasing dose

Question 29

Idiosyncratic reaction

Answer 29

A genetically-determined abnormal reactivity to a drug