Internal-Medicine

270 13: Clinical Pharmacology
30. (C) Epinephrine results in a more rapid heart
rate and more powerful systolic contraction
resulting in increased cardiac output. Norepinephrine
results in an unchanged or even
decreased cardiac output. (Brunton, pp. 244–248)
31. (C) Both epinephrine and norepinephrine
decrease renal blood flow. Epinephrine decreases
total peripheral resistance whereas norepinephrine
increases total peripheral resistance.
Both drugs decrease cutaneous blood flow and
only epinephrine increases muscle blood flow.
(Brunton, p. 244)
32. (C) The preferential effect of dobutamine on
contractility makes it useful in low cardiac
output states. Both drugs are very short-acting,
can potentiate cardiac ischemia, and affect
smooth muscle. Unlike isoproterenol, dobutamine
frequently increases blood pressure quite
significantly thus requiring dosage adjustment.
(Brunton, pp. 250–251)
33. (E) Most of the side effects from the use of betaadrenergic
agonists in asthma come from stimulation
of the beta1-receptors in the heart. Thus,
beta2-selective agonists, which act primarily in
the lung, are safer to use. Both selective and
nonselective beta-agonists will decrease airway
resistance. This is their major therapeutic effect.
The effects on mucociliary transit, mast cells,
and microvascular permeability occur with
both nonselective and selective agonists, but
the clinical importance of these effects is
unclear. (Brunton, pp. 251–253)
34. (C) It is felt that innate tolerance is a polygenic
characteristic. Frequently, variation in pharmacokinetic
variables (absorption, metabolism,
excretion), which can be inherited, are
the cause of different levels of innate tolerance.
Those who have high levels of innate tolerance
are more likely to become addicted to
alcohol. There is a higher concordance rate
for alcoholism among identical twins than
fraternal twins, but it is not 100%. (Brunton,
pp. 601–602)
35. (D) The most common cause of pharmacokinetic
tolerance is an increase in the metabolism
of the drug. Since these same enzymes can then
metabolize other drugs, this kind of tolerance
is not necessarily specific to the drug that
induced it. (Brunton, pp. 609–611)
36. (C) Learned tolerance refers to the reduction of
the effect of a drug due to compensatory mechanisms
that are learned. An example is walking
a straight line despite the motor impairment
caused by alcohol. This likely represents both
acquisition of motor skills and the learned
awareness of one’s deficit; thus the person
walks more carefully. (Brunton, p. 610)
37. (D) Sensitization is the reverse of tolerance. It
refers to an increase in effect of the drug with
repetition of the same dose. It does not occur
during an acute binge. The dose response curve
would be shifted to the left. (Brunton, p. 611)
38. (B) Cocaine and amphetamines are the drugs
most likely to cause sensitization. It is poorly
studied in humans, but it is thought that stimulant
psychosis results from sensitization after
prolonged use. (Brunton, p. 611)
39. (B) Almost one-third of people who have tried
tobacco become addicted. In comparison, about
15% become addicted to alcohol. Heroin is also
highly addictive (23% of users become addicted),
but since so few people even try heroin, the
addiction rate in society as a whole is quite low
(0.4%). (Brunton, pp. 608–609)
40. (E) Muscle cramps, anxiety, insomnia, and dizziness
are among the common side effects of withdrawal
from moderate dose usage. Withdrawal
seizures and delirium occur usually in withdrawal
from high dosage. Withdrawal should
be done gradually, often over many months.
(Brunton, pp. 614–615)
41. (D) Craving for opioids, restlessness, irritability,
and anxiety are common symptoms of
heroin withdrawal. Piloerection, pupillary
dilatation, sweating, tachycardia, and blood
pressure elevation are frequently seen signs of
heroin withdrawal. It starts within 6–12 hours
of the last dose and is quite unpleasant, but
not life-threatening. (Brunton, pp. 618–619)