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Pharmacology Midterm (edit) > Lecture 1 Part 2 > Flashcards

Lecture 1 Part 2 Flashcards

1
Q

how do drugs interact with their receptors

A

by chemical forces or bonds

3 types:
-covalent (strongest)
-electrostatic
-hydrophobic (weakest)

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2
Q

true or false

covalent bonds are very strong and in most cases are NOT REVERSIBLE under biologic conditions

A

true

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3
Q

give 2 examples of drugs that use covalent bonding in their mechanism

A

phenoxybenzamine forms a covalent bond to the alpha receptor for norepinephrine which blocks the receptor.

DNA alkylating agents used in cancer chemotherapy

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4
Q

explain the mechanism of phenoxybenzamine

A

when there is a tumor on the adrenal gland, too much epinephrine is secreted.

phenoxybenzamine is administered which covalently binds to the alpha receptor for norepinephrine which BLOCKS the receptor.

this bond is not readily broken and the blocking effect lasts LONG AFTER THE FREE DRUG HAS DISSAPPEARED FROM THE BLOODSTREAM

only reversed by the synthesis of new alpha receptors (takes ~48 hours)

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5
Q

how do DNA alkylating agents work?

A

they disrupt cell division in neoplastic (cancerous) tissue

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6
Q

when there is a tumor on the adrenal gland, what happens

A

too much epinephrine is secreted which causes vasoconstriction and HBP.
phenoxybenzamine can help to lower BP by blocking the alpha receptor for norepinephrine

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7
Q

which is more common in drug-receptor interactions:
covalent bonding or electrostatic bonding

A

electrostatic bonding

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8
Q

electrostatic bonds can be what 2 things

A

-relatively strong linkages between permanently charged ionic molecules to weaker H bonds

-weak H bonds to very weak dipole-induced interactions such as van der waals forces

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9
Q

true or false

electrostatic bonds are stronger than covalent bonds

A

false - weaker

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10
Q

what are van der waals forces

A

the relatively weak attractive forces that act on neutral atoms and molecules. arises bc of electric polarization in each of the particles

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11
Q

true or false

hydrophobic bonds are usually quite weak

A

true

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12
Q

hydrophobic bonds are probably important in what kind of interactions

A

interactions of highly lipid soluble drugs with the lipids of cell membranes

and perhaps in interaction of drugs with the internal walls of receptor “pockets”

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13
Q

drugs which bind through weak bonds to their receptors are generally more or less selective than drugs that bind to their receptor with strong bonds?

A

weak is generally MORE SELECTIVE

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14
Q

WHY are weak drug-receptor interactions more selective than strong ones?

A

bc a weak bond requires a very precise fit of the drug to its receptor for an interaction to occur.
only a few receptor types are likely to provide such a precise fit for a particular drug structure

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15
Q

what is the requirement for the shape of a drug molecule

A

must be able to permit binding to its receptor under optimal conditions.
shape should be complementary to the receptor site like a LOCK AND KEY model

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16
Q

the phenomenon of chirality (stereoisomerism) is common in ____

A

biology

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17
Q

how many useful drugs are chiral molecules that exist as enantiomeric pairs?

A

more than half of all useful drugs

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18
Q

drugs with 2 asymmetric centers have how many diastereomers?
give a specific example of a drug with these properties

A

4 diastereomers

labetolol (an alpha beta receptor blocking drug)

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19
Q

chiral refers to what kind of molecule?

A

with a center of 3D asymmetry

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20
Q

define stereoisomers

A

compounds that have the same molecular formula but different arrangement of the atoms in space

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21
Q

mirror images

A

enantiomers

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22
Q

4 different groups attached

A

chiral

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23
Q

true or false

enantiomers are associated with CHEMICAL IDENTITY

A

true

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24
Q

Define diastereomers

A

not mirror images and not super imposable

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25
Q

if a molecule has 1 asymmetric center - is it an enantiomer or diastereomer? what about 2 asymmetric centers

A

1 = enantiomer
2 = diasteromer

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26
Q

R,R
R,S

A

diasteromers

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27
Q

R,R
S,S

A

enantiomers

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28
Q

R,R
S,R

A

diasteromers

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29
Q

R,S
S,S

A

diasteromers

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30
Q

R,S
S,R

A

enantiomers

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31
Q

S,R
R,S

A

enantiomers

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32
Q

S,R
S,S

A

diasteromers

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33
Q

____ are usually stereospecific

A

enzymes

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34
Q

enzymes are usually stereospecific

therefore…

A

1 drug enantiomer is often more susceptible than the other to drug-metabolizing enzymes

THEREFORE, the duration of action of 1 enantiomer may be quite different from the other

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35
Q

most studies of clinical efficacy and drug elimination in humans has been carried out with what?
what does this mean?

A

racemic mixture

therefore, many patients are receiving drug doses of which 50% or more is either inactive or actively toxic

36
Q

rational design of a drug implies the ability to predict what?

A

the appropriate molecular structure of a drug on the basis of information about its RECEPTOR

37
Q

rational drug design implies the ability to predict the needed molecular structure of a drug on the basis of information about its biologic receptor.

until recently, no receptor was known in enough detail to permit such drug design,
what was used instead?

A

most drugs were developed through random screening of chemicals or modification of drugs that were already known to have some effect

however, during the last 3 decades many receptors have been isolated and characterized

38
Q

Gleevec/STI571/Imatinib is used for what

A

a specific therapy used for CML
(chronic myelogenous leukemia)

39
Q

how was Gleevec developed?

A

through a molecular design based on knowledge of the 3D structure of the receptor site

40
Q

for the last several years, ________________ are new anticancer agents

A

EGFR-TK inhibitors

41
Q

who discovered Gleevec/STI571/Imatinib mesylate? what is it?

A

Novartis

a small molecule compound approved by the FDA to treat CML (chronic myelogenous leukemia) and GIST (gastrointestinal stromal tumor) in 2001

42
Q

efforts at establishing a clear naming system of receptors has been made by whom?

A

international union of pharmacology committee on receptor nomenclature and drug classification

43
Q

the interactions between a drug and the body are conveniently divided into how many classes?

A

2 -
pharmacodynamic processes and pharmacokinetic processes

44
Q

pharmacodynamic processes are the actions of the drug on the body.

these properties determine what about the drug?

A

-the group the drug is classified
-plays a major role in deciding whether that group is the appropriate therapy for a system or disease

45
Q

pharmacokinetic processes are the actions of the body on the drug.

these properties determine what

A

the ADME of drugs

great importance in the choice and administration of a particular drug for a PARTICULAR PATIENT (ie: pt with impaired renal function)

46
Q

when treating a patient with impaired organ function, which parameters would be most helpful - pharmacodynamics or pharmacokinetics

A

pharmacokinetics

47
Q

explain agonists

do they have affinity, efficacy, or both?

A

agonists bind to and activate the receptor in some fashion which DIRECTLY or INDIRECTLY produces the effect

an agonist has both affinity and efficacy

48
Q

explain how it is possible for an agonist to produce the effect of the receptor either directly or indirectly

A

direct – some receptors have effector machinery within their same molecule. therefore, when the drug binds the effect occurs.

indirect – some receptors are linked through 1 or more intervening coupling molecules to a separate effector molecule

49
Q

give 2 examples of how an agonist brings about a DIRECT EFFECT

A

-opening of an ion channel
-activation of enzyme activity

50
Q

explain antagonist drugs

A

bind to a receptor and PREVENT (BLOCK) binding by other molecules

51
Q

do antagonists have affinity, efficacy, or both?

A

affinity but no efficacy

52
Q

give an example and explain an antagonist

A

acetylcholine receptor blockers (ATROPINE)

prevent the access of acetylcholine (and similar agonist drugs) to the acetylcholine receptor.

thus, reduces the effects of acetylcholine and similar drugs in the body

53
Q

drug —> ____ —>_____

A

drug –> receptor –> effects

54
Q

the concept of an agonist, competitive inhibitor, allosteric activator, and alloseteric inhibitor are ________ principles

A

pharmacodynamic

55
Q

define a competitive inhibitor

A

competes with the agonist for the same receptor site.
therefore this decreases the action of the agonist and a larger dose of agonist is needed to produce the desired effect

56
Q

true or false

an allosteric activator could be another drug

A

true

57
Q

what is the most/least efficacious?
which is the most/least potent?

-agonist
-agonist + allosteric activator
-agonist + competitive inhibitor
-agonist + allosteric inhibotir

A

most efficacious = allosteric activator + agonist

least efficacious = allosteric inhibitor + agonist

least potent = agonist + competitive inhibitor

most potent = allosteric activator + agonist (agonist is also pretty potent – very close)

58
Q

which have the SAME EFFICACY, but different potency:

-agonist
-agonist + allosteric activator
-agonist + competitive inhibitor
-agonist + allosteric inhibitor

A

same efficacy but different potency= agonist & agonist + competitive inhibitor

agonist by itself is much more potent.

in the presence of competitive inhibitor, just needs a very high concentration to get the same effect

59
Q

true or false

agonist + allosteric activator has a higher efficacy than the agonist by itself

A

true

60
Q

true or false

agonist + agonist and competitive inhibitor have decreased efficacy

A

false

potency is decreased but efficacy remains the same

61
Q

define a partial agonist

A

a drug that binds to and activates a receptor, but at PARTIAL EFFICACY (relative to a full agonist)

62
Q

how can some drugs mimic agonist drugs?

A

by inhibiting the molecules responsible for terminating the action of the endogenous agonist

63
Q

give an example of how some drugs mimic agonist drugs

A

acetylcholine esterase inhibitors

-they slow down the destruction of acetylcholine by inhibiting acetylcholine esterase

this causes cholinomimetic effects even though these ACHE inhibitors are not actually acting as true agonists and binding to the cholinoceptors

64
Q

explain how some drugs bind to receptors and activate them but do NOT evoke as great of a response as a full agonist

A

pindolol - a “partial agonist”
can act as agonist or antagonist to the Beta-adrenoceptor.

if no full agonist is present, it will act as an agonist

HOWEVER, if there is an agonist present (like isoproterenol) it will act as an antagonist

65
Q

name a true beta-adrenoceptor full agonist

A

isoproterenol

if in the presence of pindolol, pindolol will act as an antagonist

66
Q

“even at maximal capacity, does not produce the full effects of an agonist”

A

partial agonist

67
Q

true or false

if enough of partial agonist binds to the receptors, it can eventually act as a full agonist

A

FALSE

a partial agonist, even at MAXIMAL receptor occupancy, will never produce as great of a response as the full agonist

68
Q

name 3 processes in which drug activity can be terminated at the receptor level

A

-drug effect only lasts as long as the drug occupies the receptor. once the drug dissociates = termination of effects

-the action of the drug may persist after the drug has dissociated

-if drugs COVALENTLY bind to the receptor, the effect may persist until the drug-receptor complex is destroyed and new receptors are synthesized

69
Q

in many cases, the action of the drug may still persist even after the drug has dissociated from its receptor.

give an example of this

A

some coupling molecules may still be in their active form and signaling, even though the drug is no longer bound

70
Q

give an example of a drug that covalently binds to its receptor and thus the effect does not stop until the receptor-drug complex is destroyed and new receptors are made

A

phenoxxybenzamine

71
Q

explain what desensitization mechanisms are

A

they prevent excessive activation in a case of when the drug molecules continue to be present there for very long periods of time

this is responsible for drug addiction
-more drug is taken before all the receptors have been recycled and are ready to bind. thus, more and more dose keeps being taken because the person wants to achieve the effect, but there are not as many receptors available

don’t discontinue immediately - will lead to withdrawals

72
Q

to function as a receptor, an endogenous molecule must FIRST do what

A

be SELECTIVE in choosing ligands (drugs) to bind

73
Q

why is it that an endogenous molecule must have selective binding to be a receptor

A

to prevent the promiscuous binding of many different ligands

74
Q

to function as a receptor, an endogenous molecule must 1st be selective.

what next

A

it must change its function when binding such that the function of the biological system is altered (required to produce a pharmacological effect)

75
Q

true or false

the body contains MANY molecules that are capable of binding drugs, but not all of these molecules are “regulatory molecules”
(receptors)

A

TRUE

ie: plasma protein albumin is a nonregulatory molecule

76
Q

what happens when a drug binds to a nonregulatory molecule such as plasma albumin?

thus, what can albumin be called?

A

there will be no detectable change in function of the biologic system

can be called an inert binding site

77
Q

albumin is considered an inert binding site and therefore has no significance.

true or false

A

FALSE

has significance.

binding affects the distribution of the drug in the body. thus, this binding will determine the amount of free drug in circulation

78
Q

true or false

only free drug can get metabolized

A

true

79
Q

in practical therapeutics, a drug should be able to do what?
is this a pharmacokinetic or pharmacodynamic principle?

A

to reach its intended site of action after administration by some convenient route

pharmacokinetic principle

80
Q

is it ever possible to directly apply a drug to its target tissue?

A

yes - in a few situations

topical application of an anti-inflammatory agent to inflamed skin/mucus membrane

IV and circulate in the blood directly to the target blood vessels or other parts of the body

81
Q

which is more common - a drug being directly administered to its tissue target or the requirement for a drug being able to reach its intended site of action

A

more common for a drug to have to move from one compartment to another

ie: drug is given into the gut (oral) and it must move to its site of action in another compartment (brain)

82
Q

usually, a drug is given into 1 body compartment and must move to its site of action in another compartment.

what does this require?

A

the drug must be absorbed into the blood from its site of administration and DISTRIBUTED to its site of action.

after effect, drug should be eliminated by metabolic inactivation, excretion, or combo of the 2

83
Q

a basic drug will be excreted in what kind of urine?
(acidic or basic)

A

acidic
it will be ionized and thus easily leave the body

84
Q

a drug is given orally to produce an effect in the CNS.

name some barriers this drug will face

A

-the tissues of the intestinal walls

-the walls of the capillaries that perfuse the gut

-BBB

-the walls of the capillaries that perfuse the brain

85
Q
A

Pharmacology Midterm (edit) (12 decks)

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