Q 1
You
are discussing anticonvulsant therapy with a group of medical students on
rounds.
The
statement you are MOST likely to include in your discussion is that:
A. azithromycin
should not be prescribed with carbamazepine
B. gabapentin
has significant drug interactions
C. lamotrigine
frequently causes a benign, self-limited rash
D. phenobarbital
has little impact on school performance
E. valproic
acid is commonly associated with behavioral changes
Answer
A
Answer
A
All antiepileptic drugs probably have some effect on behavior and school
performance, with phenobarbital causing cognitive impairment and behavioral side
effects most frequently (in up to 50% of children). Of the commonly used
anticonvulsants, valproic acid is least likely to affect behavior and cognitive
performance adversely. However, it can be associated with weight gain,
thrombocytopenia, tremor, and fulminant hepatic failure, particularly in
children younger than age 3 years who are receiving multiple antiepileptic
medications.
Carbamazepine,
one of the most commonly used anticonvulsants in childhood, rarely causes
significant leukopenia or hepatotoxicity and seldom produces hyponatremia.
Macrolides such as erythromycin and azithromycin should be used very cautiously
or, if possible, avoided in children receiving carbamazepine because these
drugs compete for hepatic metabolism, leading to increasing carbamazepine
levels and acute toxicity. Phenytoin is similar to carbamazepine in efficacy
for seizures, but it is used less commonly in children because of significant
cosmetic adverse effects, including hirsutism, gingival hyperplasia, and facial
coarsening. Phenytoin is poorly absorbed from the gastrointestinal tracts of
infants and metabolized at a variable rate in the liver.
Lamotrigine
is used in a number of refractory seizure disorders and generally is well
tolerated, with occasional drowsiness, headache, and blurred vision. However,
its use is associated with the development of maculopapular rash that may
progress to Stevens-Johnson syndrome (Figure 138A) during the early months of
use, especially when administered with valproate. The development of such a
rash should prompt immediate drug discontinuation. In an attempt to avoid these
reactions, lamotrigine is administered initially at a low dose and very
gradually increased over months, particularly if valproate also is being
administered.
Gabapentin,
a second or add-on drug for partial seizures, usually is well tolerated.
Because it is not metabolized by the liver and is excreted unchanged by the
kidneys, it has no significant drug interactions. Adverse effects include very
occasional fatigue, dizziness, headache, and weight gain.
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Q 2 :
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Q 2 :
Of
the following, the class of drugs MOST likely to cause bladder outlet
obstruction is:
A. antiarrhythmics
B. anticholinergics
C. antihistamines
D. antipyretics
E. antitussives
Answer
B
-----------------------------
Q 3 :
Answer
B
Answer
B
To
understand how anticholinergics cause bladder outlet obstruction, it is
important to review the muscular anatomy and neural innervation of the bladder.
Normal bladder function depends on the central and peripheral nervous systems
and the detrusor muscle and external sphincter of the bladder. Muscular fibers
in the bladder interdigitate around the bladder neck, resulting in the
formation of a sphincter, which controls the outflow of urine. The somatic and
autonomic nervous systems (ANS) control bladder function. The ANS involves
sympathetic (from T10 and L1) and parasympathetic (from S2 to S4) control. The
sympathetic nervous system stimulates alpha- and beta-receptor sites in the
bladder smooth muscle. The primary neurotransmitter for sympathetic control is
norepinephrine (NE). When NE interacts with alpha receptors in the bladder, the
bladder smooth muscle tone increases, allowing for stretch. Stimulation of beta
receptors in the bladder by NE results in relaxation of the detrusor muscle.
Thus, NE allows the bladder to expand, thereby accommodating the inflow of
urine from the kidneys and ureters. The primary neurotransmitter of the
parasympathetic nervous system is acetylcholine (ACH). Release of ACH from the
parasympathetic nervous system results in bladder contraction. Combined with
reduced output from the sympathetic nervous system, the bladder releases urine
into the urethra.
Because
ACH is a cholinergic substance, anticholinergic medications may counteract its
effects, including promotion of bladder emptying. For patients taking
anticholinergic medication, the bladder is under only sympathetic control, with
a net result of prolonged bladder filling and expansion. In the absence of
bladder emptying, spasms inevitably ensue. The effect is identical to that seen
in children who have spinal cord lesions at S2 to S4, in which parasympathetic
stimulation is reduced.
Treatment
for bladder spasms due to anticholinergic therapy is discontinuation of the
medication. Antiarrhythmics, antihistamines, antipyretics, and antitussives all
have significant adverse effects, but they do not include abnormalities in
neural stimulation of the urinary bladder.
-----------------------------
Q 3 :
The
parents of an adopted 3-year-old Guatemalan boy are concerned about his bowel
movements. He usually has one formed bowel movement a day. However, about once
a week, it is loose. He has had no apparent abdominal pain and no vomiting. His
height and weight are at the 30th percentile for age. Laboratory examination of
a direct fecal smear reveals eggs of Ascaris lumbricoides.
Of
the following, the BEST initial management for the boy is administration of:
A. iodoquinol
B. mebendazole
C. metronidazole
D. praziquantel
E. thiabendazole
Answer
B
Recommended
treatment regimens for children who have uncomplicated gastrointestinal
ascariasis include oral albendazole, mebendazole, or pyrantel pamoate. Cautious
use of piperazine is indicated for children who have a heavy worm load,
especially in the presence of intestinal biliary obstruction. Piperazine causes
a neuromuscular paralysis of the worm, preventing migration and promoting
excretion. Intestinal or biliary obstruction may require surgical intervention.
External massage of an obstructing intestinal worm bolus is preferred over
intestinal incision.
Iodoquinol
is the drug of choice for asymptomatic amebiasis. Metronidazole is used most
commonly for the treatment of trichomonas, giardiasis, and amebiasis.
Praziquantel is used for the treatment of schistosomiasis, cysticercosis, and
flukes. Thiabendazole has been used for the treatment of cutaneous larva
migrans and strongyloides.
---------------------------------
Q 4:
---------------------------------
Q 4:
A
term newborn is being treated with 3.5 mg/kg intravenous infusion of gentamicin
over 30 minutes for Escherichia coli sepsis. The dosing interval is every 24 hours.
A trough serum concentration 30 minutes before the fourth dose is 0.9 mg/L, and
a peak serum concentration 30 minutes after completion of infusion of the
fourth dose is 20 mg/L.
Of
the following, the MOST appropriate next step is to:
A. administer
furosemide
B. decrease
gentamicin dose
C. discontinue
gentamicin
D. increase
gentamicin dosing interval
E. replace
gentamicin with tobramycin
Answer
B
Answer
B
The
desired peak serum concentration of gentamicin is 5 to 12 mg/L, which is less
than that measured for the infant described in the vignette. The appropriate
adjustment for a peak serum concentration that is higher than the desired range
is to decrease the dose of the antibiotic.
Furosemide
has no role in the treatment of gentamicin overdosage or toxicity. In fact, the
addition of furosemide increases the potential risk of oto- and nephrotoxicity.
Discontinuing
gentamicin is likely to lead to incomplete treatment of sepsis, and it may
place the infant at risk for the complications of partially treated sepsis.
The
desired trough serum concentration of gentamicin is 0.5 to 1.0 mg/L, and the
concentration reported for the infant in the vignette is within that desired
range. Therefore, no adjustment in the dosing interval is warranted.
The
pharmacokinetics, antimicrobial profile, and adverse effects of tobramycin are
similar to those of gentamicin. Replacing one aminoglycoside with another is
unlikely to be of any benefit.
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