Download USMLE I

USMLE I
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1. At the end of a balanced anaesthetic technique
with a muscle relaxant, a patient recovered
spontaneously from the effects of relaxant without
any reversal. Which is the most probable relaxant
the patient received?
A. Pancuronium
B. Gallamine
C. Atracurium
D. Vencuronium
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C. Atracurium needs no Neostigmine to
reverse its effects. This is because it
undergoes self degradation.
2. A cardiovascular pharmacologist is researching the
effects of new compounds on arteriolar resistance. Drug
X maximally increases vascular resistance by 50% at a
dose of 20 mg/mL. Drug Y maximally increases vascular
resistance by 75% at a dose of 40 mg/mL. Which of the
following conclusions can the researcher draw from this
experiment?
A. Drug X has a smaller volume of distribution than Drug
Y
B. Drug X has a shorter half-life than Drug Y
C. Drug X is less efficacious than Drug Y
D. Drug X is less potent than Drug Y
E. Drug X has a lower LD50 than Drug Y
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The correct answer is C. The only conclusion that can
be drawn from this data is that Drug X is less
efficacious than Drug Y. Efficacy is defined as the
maximum effect that can be produced by a drug,
regardless of dose. Drug X can only produce a 50%
change in resistance, whereas Drug Y can produce a
75% change in resistance. Therefore, Drug X is less
efficacious than Drug Y.
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3. A 24-year-old woman on her honeymoon
presents to the cruise ship physician with a
dilated right pupil and complains that she
could not read the lunch menu with the same
eye. Which of the following drugs is most likely
responsible for her symptoms?
A. Phenylephrine
B. Physostigmine
C. Pilocarpine
D. Scopolamine
E. Timolol
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The question is asking for a drug that dilates the
pupil (mydriasis) and prevents accommodation by
paralyzing the ciliary muscle (cycloplegia).
Scopolamine would produce both of these actions
by blocking muscarinic acetylcholine receptors on
the pupillary constrictor muscle (leading to
mydriasis) and on the ciliary muscle (producing
cycloplegia). An additional hint to arrive at this
answer is the fact that she is on a cruise ship.
Scopolamine patches are used to prevent motion
sickness. The woman most likely applied the patch
and subsequently rubbed her eye.
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4.The pharmacokinetic properties of a new drug
are being studied under phase 1 clinical trials. The
vol of distribution and clearance of the drug is 80
l and 3 l /hr. The half life of the drug is
A. 0.03
B. 14 hrs
C. 18 hrs
D. 139 hrs
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B. 0.693
vd (80)
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Cl (3)
18
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5. A new antifungal medication is being tested in
Phase I clinical trials. Examination of the
pharmacokinetic properties of the drug reveals that
the half-life of the drug is 3 hours. If a continuous
intravenous infusion of this drug were started on a
research subject, how long would it take to reach
75% of steady state?
A. 3 hours
B. 6 hours
C. 9 hours
D. 12 hours
E. 18 hours
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The correct answer is B. The rule of thumb
is that the plasma concentration will reach
50% in one half-life, 75% in two half-lives,
87.5% in three half-lives, etc., so that the
difference between the current drug level
and 100% halves with each half-life. In this
instance, it takes two half-lives to reach
75%. The half-live of this drug is 3 hours,
so two half-lives is 6 hours.
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6. A 15-year-old boy presents to the emergency
room with agitation, mydriasis, and hot, dry
skin. Physical examination reveals decreased
bowel sounds and tachycardia. Assuming that
he is suffering from a drug overdose, which
class of drugs is most likely responsible for his
symptoms?
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A. Anticholinergic
B. Cholinomimetic
C. Opioid
D. Salicylate
E. Sedative-hypnotic
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7. A 24 year old woman is under going surgery
and is anesthetised with an inhalant anesthetic.
She is also given an iv dose of succinyl choline.
within minutes she develops a heart rate of 124
and increasing core body temperature. what is the
mechanism of action of the drug of choice for this
condition?
a. interferes with release of calcium
b. competitive antagonist of acth
c. gaba receptor agonist
d. uncouples oxidative phosphorylation
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A. Dantrolene. Condition – malignant
hyperthermia. Interferes with release of
calcium.
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8. A 29-year-old male uses secobarbital to satisfy his
addiction to barbi- turates. During the past week, he is
imprisoned and is not able to obtain the drug. He is
brought to the prison medical ward because of the onset of
severe anxiety, increased sensitivity to light, dizziness, and
generalized tremors. On physical examination, he is
hyperreflexic. Which of the fol- lowing agents should he
be given to diminish his withdrawal symptoms?
 a. Buspirone
 b. Chloral hydrate
 c. Chlorpromazine
 d. Diazepam
 e. Trazodone
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The answer is d. A long-acting
benzodiazepine, such as diazepam, is
effective in blocking the secobarbital
withdrawal symptoms. The anxiolytic
effects of buspirone take several days to
develop, obviating its use for acute severe
anxiety.
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9. A 24-year-old farm worker is rushed to a
nearby emergency room after an accidental
exposure to parathion. He is in respiratory distress
and is bradycardic. Which of the following drugs
can be given to increase the activity of his
acetylcholinesterase?
A. Atropine
B. Deferoxamine
C. Dimercaprol
D. N-acetylcysteine
E. Physostigmine
F. Pralidoxime
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Pralidoxime (2-PAM) 2-pyridine aldoxime methiodide is
an acetylcholinesterase (AChE) reactivating agent. It is
only useful for counteracting AChE inhibitors which act
by
 phosphorylating the enzyme (organophosphates).
Pralidoxime can remove the phosphate group from AChE,
thus regenerating the enzyme.
 This must be done in a timely fashion because normally
after the phosphate group is bound to the enzyme, it
undergoes a chemical reaction known as "aging." Once
this bond ages, pralidoxime will no longer be effective.
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10. A 25 year old patient comes to the ENT opd
with a stuffy, runny nose. Which of the following
is most likely to be presribed?
a. Oxymetazoline
b. Albuterol
c. Clonidine
d. Terbutaline
e. Metoprolol
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a. Oxymetazoline is an α-adrenergic
agonist. It causes vasoconstriction of the
nasal mucosa. Because of its long duration
of action, it is useful in decreasing nasal
congestion, especially due to upper
respiratory infections. Pseudoephedrine and
phenylephrine are other α-adrenergic
agonists used for similar purposes