Graded dose and quantal dose response

Question 1

as the dose increases, more drug molecules are delivered into

Answer 1

receptor sites

Question 2

Factors which affect the amount of drug that finally gets to the receptor
sites

Answer 2

1. Physicochemical properties of drug
2. Blood flow through the site of absorption

Question 3

If the entire administered drug dose is absorbed, there is still no assurance to
obtain a maximal response because of the following factors;

Answer 3

1. non specific binding of the drug with tissue and plasma proteins
2. biotransformation or metabolism of drug in tissues (liver, kidney) and
   plasma
3. excretion of drug before it reaches the biophase
4. initial drug effect on the effector system
5. local and systematic contra – regulation of the response

Question 4

intensity or drug
effect can increases as the drug dose is increased

Answer 4

graded dose-response

Question 5

responsible for induction of drug effect

Answer 5

drug molecules in the biophase

Question 6

individual unit of a biological system responds to a drug dose either maximally or not at all

Answer 6

all-or-none response, also termed quantal response

Question 7

smallest dose at
which death occurs

Answer 7

threshold dose or minimal lethal effective dose

Question 8

differences in the susceptibility to chemicals among
individuals

Answer 8

biologic variation

Question 9

can be constructed for responses that are measured on a continuous scale, eg, heart rate

Answer 9

graded dose-response curve

Question 10

ratio of rate constants for the reverse (k2) and forward (k1) reaction
between the drug and receptor and the drug-receptor complex

Answer 10

KD

Question 11

dissociate rapidly from receptors

Answer 11

high KD (low affinity)

Question 12

dissociate slowly from receptors

Answer 12

low KD (high affinity)

Question 13

β2-adrenoceptor agonist

Answer 13

salbutamol

Question 14

a-alergic blocking agent

Answer 14

phenoxybenzamine

Question 15

ration of the dose that results in an
undesired effect to that which results in a desired effect

Answer 15

therapeutic index of a drug

Question 16

usually defined as the ratio of LD50 to ED50, which indicates how
selective the drug is in resulting in its desired effect

Answer 16

therapeutic index

Question 17

describe how avidly the drug binds to the receptor (ie, the KD)

Answer 17

affinity

Question 18

refers to the concentration (EC50) or dose (ED50) of a drug required to
produce 50% of the drug’s maximal effect

Answer 18

potency

Question 19

ability of the drug
to elicit a response when it binds to the receptor

Answer 19

efficacy

Question 20

concentration of an
antagonist that reduces a specified response to 50% of the maximal possible
effect

Answer 20

median inhibitory concentration or IC50

Question 21

refers to a drug’s ability to preferentially produce a particular effect and is related to the structural specificity of drug binding to receptors

Answer 21

selectivity

Question 22

primary determinants of a drug’s clinical
effectiveness

Answer 22

1. drug concentration at the receptor
2. efficacy of the drug-receptor complex

Question 23

derived from a quantitive dose-response relationship for a single animal and varies among individuals

Answer 23

Emax (maximum effect)

Question 24

used to determine the dose that should be administered

Answer 24

drug’s potency

Question 25

required before a drug can produce an
observable effect

Answer 25

threshold dose

Question 26

drug concentration at which receptor occupancy is half of maximum

Answer 26

KD

Question 27

causes blockade of D2-dopamine receptors, a-adrenergic receptors, and
muscarinic receptors

Answer 27

phenothiazine

Question 28

When quantal effects are being considered information concerning
pharmacologic potency, selectivity of drug action, the margin of safety, and the
potential variability of responsiveness among individuals is obtained from

Answer 28

quantal dose-response curves

Question 29

demonstrates a clockwise hysteresis loop in the concentration-effect relationship

Answer 29

tachyphylaxis