USMLE-like pharmacology quiz. Part 4: pharmacodynamics

The following are multiple choice questions in a style similar to those included in the USMLE step 1. The main topic here is: pharmacodynamics. This quiz has been uploaded to Scribd by medical student James Lamberg. The correct answers can be found in link at the end of this post.

Note: the words underlined don’t mean right answer but link to another page.

9 – Pharmacodynamics: Receptor Theory and Dose Response
1.1) Which of the following occurs on the extracellular domain of the lipid bilayer and
not the cytoplasmic domain, with regard to drug action?
a) Ligand binding
b) Coupling with membrane associated molecules
c) Trafficking
d) Signaling

1.2) Which of the following drug targets involves inhibitors, false substrates, and a pro-
drug type?
a) Receptors
b) Ion channels
c) Enzymes
d) Carriers
1.3) What is the correct order of bond strength, from strongest to weakest?
a) Van der Waals > Hydrogen > Ionic > Covalent
b) Ionic > Covalent > Hydrogen > Van der Waals
c) Covalent > Hydrogen > Ionic > Van der Waals
d) Covalent > Ionic > Hydrogen > Van der Waals
e) Van der Waals > Hydrogen > Covalent > Ionic
2) On a graded dose-response curve (or drug-receptor curve in a laboratory), at what
point does response increase the most rapidly?
a) Initially

b) At EC50

c) At LD50
d) At 90% maximal response efficacy (Emax)
e) At steady-state
3.1) Which of the following is the equilibrium dissociation constant, where the
concentration of free drug is at half-maximal binding?
a) EC50
b) Emax
c) Kd
d) Bmax
e) LD50
3.2) What kind of graph scaling is often used to compare EC50 to Kd?
a) Linear
b) Exponential
c) Semilog
d) Inverse
e) Proportional
3.3) Clinical effectiveness of a drug depends on its potency.
a) True
b) False

3.6) Intrinsic activity is a drug’s ability to elicit:
a) Strong receptor binding
b) Weak receptor binding
c) Response
d) Excretion
e) Distribution
4.4) A competitive antagonist affects the agonist ____ and a non-competitive antagonist
affect the agonist ____.
a) Potency; Efficacy
b) Efficacy; Potency
c) Duration; Speed
d) Speed; Duration
4.5) In which of the following cases could a dose-response curve be constructed?
a) Prevention of convulsions
b) Prevention of arrhythmias
c) Reduction of death
d) Reduction of fever
e) Relief of headache
5.1) For most drugs, a frequency distribution of the response plotted against the log of the
dose (quantal) produces what kind of curve?
a) Linear
b) Exponential
c) Logarithmic
d) Gaussian (normal) distribution
e) Poisson distribution
5.2) Generally, which of the following is the correct order as dosage is increased?
a) ED50 < LD50 < TD50
b) ED50 < TD50 < LD50
c) LD50 < TD50 < ED50
d) LD50 < ED50 < TD50
e) TD50 < LD50 < ED50
5.3) Which of the following is the median effective dose, or the dose at which 50% of the
individuals exhibit the specified quantal response?
a) LD50
b) ED50
c) EC50
d) TD50
e) T.I.
6.1) Which of the following is considered the therapeutic index (or ratio)?
a) T.I. = TD50 / ED50

b) T.I. = LD50 / ED50
c) T.I. = ED50 / TD50
d) T.I. = ED50 / LD50
e) A & B
6.2) Which of the following can be used as a relative indicator of the margin of safety of
a drug?
a) LD50
b) ED50
c) EC50
d) TD50
e) T.I.
6.3) Which of the following is the most relevant use of therapeutic index?
a) Guide for toxicity in therapeutic the setting
b) Multiple measures of effectiveness are possible (e.g. aspirin)
c) Measure of impunity with which an overdose may be tolerated
d) Toxicities may be idiosyncratic (e.g. propranolol in asthmatics)
7.1) Which of the following refers to an increased intensity of response to a drug?
a) Idiosyncratic
b) Hyporeactive
c) Hyperreactive
d) Hypersensitive
e) Tolerance
7.2) Tachyphylaxis refers to which of the following?
a) Responsiveness increased rapidly after administration of a drug
b) Responsiveness decreased rapidly after administration of a drug
c) Responsiveness increased rapidly after maintenance of a drug (hypersensitive)
d) Responsiveness decreased rapidly after maintenance of a drug (desensitized)

10 – Receptor-Effector Coupling
1) Which of the following would occur with an antagonist binding to a receptor and not
an agonist?
a) Ion channel closed
b) Enzyme inhibited
c) Endogenous mediator blocked
d) Ion channel modulated
e) DNA transcription
2.1) Nicotinic ACh receptors (ligand-gated) involve the movement of what ion across the
membrane?
a) K+
b) Ca++
c) Cl-
d) Na+
e) Mg++
2.2) The nicotinic receptor requires one molecule of ACh to bind to each of the two ____
receptors in order to activate the receptor and open the channel.
a) α (alpha)

b) β (beta)
c) γ (gamma)
d) δ (delta)
2.3) GABA A receptors (ligand-gated) involve the movement of what ion across the
membrane?
a) K+
b) Ca++
c) Cl-
d) Na+
e) Mg++
2.4) Which of the following is increased in intracellular concentration due to second
messengers such as IP3?
a) K+
b) Ca++
c) Cl-
d) Na+
e) Mg++
Match the G protein with the action it causes:
2.5) Activates phospholipase C (PLC) a) Gs
2.6) Activates K+ channels b) Gi
2.7) Inhibits Ca++ channels c) Go
2.8) Activates Ca++ channels d) Gq
2.9) Which of the following signaling mechanisms involves phosphorylation of substrate
proteins and has receptors that are polypeptides with cytoplasmic enzyme domains
(tyrosine kinase, serine kinase, guanylyl cyclase)?
a) Intracellular receptors for lipid soluble ligands
b) Transmembrane receptors
c) G-protein coupled receptors
d) Ligand-gated ion channels
2.10) Regulated by cytokines and growth factors, the Janus-Kinase JAK-STAT pathway
results in which of the following?
a) Ion channel closing
b) Enzyme inhibition
c) Endogenous mediator blocking
d) Ion channel modulation
e) Gene transcription
2.11) Which of the following describes the pathway of nitric oxide (NO)?
a) Stimulates guanylyl cyclase, increase cGMP concentration, vasodilation
b) Stimulates guanylyl cyclase, decreases cGMP concentration, vasodilation
c) Stimulates guanylyl cyclase, increase cGMP concentration, vasoconstriction
d) Inhibits guanylyl cyclase, increase cGMP concentration, vasodilation
e) Inhibits guanylyl cyclase, decreases cGMP concentration, vasoconstriction
2.12) Which of the following signaling mechanisms can involve heat-shock protein
(hsp90)?
a) Intracellular receptors for lipid soluble ligands

b) Transmembrane receptors

c) G-protein coupled receptors
d) Ligand-gated ion channels
3.1) All of the following interact with ligand-gated ion channels EXCEPT:
a) Benzodiazepines
b) Insulin
c) Glutamate
d) Aspartate
e) Glycine
3.2) Which of the following is NOT a second messenger associated with G proteins?
a) DAG
b) GDP
c) IP3
d) cAMP
e) cGMP
3.3) Muscarinic ACh receptors and adrenergic receptors are associated with which of the
following?
a) Intracellular receptors for lipid soluble ligands
b) Transmembrane receptors with enzymatic cytosolic domains
c) G-protein coupled receptors
d) Ligand-gated ion channels
3.4) In smooth muscle and glandular tissue, ACh binds to what muscarinic receptor,
leading to the DAG cascade?
a) M1
b) M2
c) M3
d) M4
e) M5
3.5) In the heart and intestines, what muscarinic receptor inhibits adenylyl cyclase
activity?
a) M1
b) M2
c) M3
d) M4
e) M5
3.6) Adrenergic α2 receptors ____ adenylyl cyclase and β receptors ____ adenylyl
cyclase.
a) Stimulate; Stimulate
b) Stimulate; Inhibit
c) Inhibit; Inhibit
d) Inhibit; Stimulate
3.7) Which of the following is NOT a ligand-regulated transmembrane enzyme (agent)?
a) Insulin
b) EGP
c) PDFG
d) ANP
e) NO

3.8) Which of the following cytokine receptors (transmembrane enzyme) is antagonized
by anakinra (Kineret), for treatment of rheumatoid arthritis?
a) Growth hormone
b) Erythropoietin
c) Interferons
d) Interleukin-1
3.9) Which of the following is NOT an intracellular receptor for lipid-soluble agent,
which stimulates gene transcription in the nucleus by binding to DNA sequences?
a) Steroids
b) Vitamin A
c) Vitamin D
d) Thyroid hormone
e) Nitric oxide
Match the receptors with their time scale:
4.1) Insulin receptor a) Miliseconds
4.2) Muscarinic ACh receptor b) Seconds
4.3) c) Minutes
4.4) Nicotinic ACh receptor d) Hours

Complete PDF file with answers