LIPPINCOTT Drug receptor interactions and PD Flashcards
2.1 Isoproterenol produces maximal contraction of cardiac
muscle in a manner similar to epinephrine. Which of the
following best describes isoproterenol?
A. Full agonist.
B. Partial agonist.
C. Competitive antagonist.
D. Irreversible antagonist.
E. Inverse agonist
Correct answer = A. A full agonist has an Emax similar to the
endogenous ligand. A partial agonist would only produce
a partial effect. An antagonist would block the effects of
an endogenous agonist. An inverse agonist would reverse
the constitutive activity of receptors and exert the opposite
pharmacological effect.
2.2 If 10 mg of naproxen produces the same analgesic
response as 100 mg of ibuprofen, which of the following
statements is correct?
A. Naproxen is more efficacious than is ibuprofen.
B. Naproxen is more potent than ibuprofen.
C. Naproxen is a full agonist, and ibuprofen is a partial
agonist.
D. Naproxen is a competitive antagonist.
E. Naproxen is a better drug to take for pain relief than
is ibuprofen.
Correct answer = B. Without information about the maximal
effect of these drugs, no conclusions can be made about
efficacy or intrinsic activity. E is false because the maximal
response obtained is often more important than the amount
of drug needed to achieve it.
2.3 If 10 mg of morphine produces a greater analgesic
response than can be achieved by ibuprofen at any dose,
which of the following statements is correct?
A. Morphine is less efficacious than is ibuprofen.
B. Morphine is less potent than is ibuprofen.
C. Morphine is a full agonist, and ibuprofen is a partial
agonist.
D. Ibuprofen is a competitive antagonist.
E. Morphine is a better drug to take for pain relief than
is ibuprofen.
Correct answer = E. Based on the information presented
here, since morphine is more efficacious than is ibuprofen,
it is going to provide more pain relief. As long as the
situation warrants the necessity of such efficacious pain
relief and without any information about differences in side
effects caused by the two drugs, morphine is the better
choice. Choice C would only be true if both drugs bound to
the same receptor population, and that is not the case. The
other choices are incorrect statements.
2.4 In the presence of naloxone, a higher concentration of
morphine is required to elicit full pain relief. Naloxone
by itself has no effect. Which of the following is correct
regarding these medications?
A. Naloxone is a competitive antagonist.
B. Morphine is a full agonist, and naloxone is a partial
agonist.
C. Morphine is less efficacious than is naloxone.
D. Morphine is less potent than is naloxone.
E. Naloxone is a noncompetitive antagonist.
Correct answer = A. Since naloxone has no effect by itself,
B and C are incorrect. Since it decreases the effect of an
agonist but this inhibition can be overcome by giving a
higher dose of morphine, naloxone must be a competitive
antagonist. No information is given about potency of either
drug.
2.5 In the presence of pentazocine, a higher concentration of
morphine is required to elicit full pain relief. Pentazocine by
itself has a smaller analgesic effect than does morphine,
even at the highest dose. Which of the following is correct
regarding these medications?
A. Pentazocine is a competitive antagonist.
B. Morphine is a full agonist, and pentazocine is a
partial agonist.
C. Morphine is less efficacious than is pentazocine.
D. Morphine is less potent than is pentazocine.
E. Pentazocine is a noncompetitive antagonist.
Correct answer = B. Pentazocine has a lower Emax value
than does morphine but still has some efficacy. Thus, pentazocine
is a partial agonist. Even though pentazocine
blocks some of the actions of morphine, since it has some
efficacy, it cannot be an antagonist. No information is given
about the potency of either drug.
2.6 In the presence of picrotoxin, diazepam is less efficacious
at causing sedation, regardless of the dose. Picrotoxin
by itself has no sedative effect even at the highest dose.
Which of the following is correct?
A. Picrotoxin is a competitive antagonist.
B. Diazepam is a full agonist, and picrotoxin is a partial
agonist.
C. Diazepam is less efficacious than is picrotoxin.
D. Diazepam is less potent than is picrotoxin.
E. Picrotoxin is a noncompetitive antagonist.
Correct answer = E. Picrotoxin has no efficacy alone, so B
and C are false. Since it decreases the maximal effect of
diazepam, it is a noncompetitive antagonist. No information
is given about potency of either drug.
2.7 Which of the following statements most accurately
describes a system having spare receptors?
A. The number of spare receptors determines the
maximum effect.
B. Spare receptors are sequestered in the cytosol.
C. A single drug–receptor interaction results in many
cellular response elements being activated.
D. Spare receptors are active even in the absence of an
agonist.
E. Agonist affinity for spare receptors is less than their
affinity for “non-spare” receptors.
Correct answer = C. One explanation for the existence of
spare receptors is that any one agonist–receptor binding
event can lead to the activation of many more cellular
response elements. Thus, only a small fraction of the total
receptors need to be bound to elicit a maximum cellular
response. The other choices do not accurately describe
spare receptor systems.
2.8 Which of the following would up-regulate postsynaptic β1
adrenergic receptors?
A. Daily use of amphetamine that causes
norepinephrine to be released.
B. A disease that causes an increase in the activity of
norepinephrine neurons.
C. Daily use of isoproterenol, a β1 receptor agonist.
D. Daily use of formoterol, a β2 receptor agonist.
E. Daily use of propranolol, a β1 receptor antagonist.
Correct answer = E. Up-regulation of receptors occurs
when receptor activation is lower than normal, such as
when the receptor is continuously exposed to an antagonist
for that receptor. Down-regulation of receptor number
occurs when receptor activation is greater than normal
because of continuous exposure to an agonist.
2.8 Which of the following would up-regulate postsynaptic β1
adrenergic receptors?
A. Daily use of amphetamine that causes
norepinephrine to be released.
B. A disease that causes an increase in the activity of
norepinephrine neurons.
C. Daily use of isoproterenol, a β1 receptor agonist.
D. Daily use of formoterol, a β2 receptor agonist.
E. Daily use of propranolol, a β1 receptor antagonist.
Correct answer = E. Up-regulation of receptors occurs
when receptor activation is lower than normal, such as
when the receptor is continuously exposed to an antagonist
for that receptor. Down-regulation of receptor number
occurs when receptor activation is greater than normal
because of continuous exposure to an agonist.
