Which of the following illnesses is an example of a type III hypersensitivity reaction?
A
Explanation:
A type III hypersensitivity reaction is mediated by immune complex deposition. In lupus, auto-
antibodies are formed and these complexes are deposited in other tissues, especially in the kidneys,
skin, and joints. Graves disease and myasthenia gravis are examples of type II but in some
classification systems they are called type V reactions. The auto-antibodies created in Graves attack
TSH receptors in the thyroid, whereas in
Myasthenia the target is the acetylcholine receptor. Hashimoto’s thyroiditis is usually considered an
example of a combination of type II and IV reactions, as T cells are directed at thyroid antigens and
antibodies are also produced. Allergic rhinitis is a classic example of a type I, IgE mediated reaction.
Which of the following is a side effect of valproic acid?
B
Explanation:
Pancreatitis is one of the most serious adverse effects that can be caused by valproic acid. Gingival
hyperplasia is a side effect of Phenytoin. Kidney stones and weight loss can be a side effect of
zonisamide or topiramate.
A 55-year-old female is receiving chemotherapy for metastatic carcinom
a. She threatens to stop her treatment because of severe nausea and vomiting. The oncologist plans
to use prochlorperazine to reduce the nausea and vomiting associated with chemotherapeutic
agents. What is the mechanism of action of prochlorperazine?
B
Explanation:
B: A variety of drugs have been found to be of some value in the prevention and treatment of
vomiting, especially cancer chemotherapy-induced vomiting. With the exception of thioridazine,
most of the neuroleptic drugs have antiemetic effects that are mediated by blocking D2
dopaminergic receptors of the chemoreceptor trigger zone of the medulla. Phenothiazines, such as
prochlorperazine, were the first drugs shown to be effective antiemetic agents and act by blocking
dopamine receptors. They are effective against low to moderately emetogenic chemotherapeutic
agents (for example, fluorouracil and doxorubicin). Although increasing the dose improves
antiemetic activity, side effects, including hypotension and restlessness, are dose limiting. Other
adverse reactions include extrapyramidal symptom and sedation. A: Serotonin 5-HT3 antagonist is
incorrect. The specific antagonists of the 5-HT3 receptor, ondansetron and granisetron, selectively
block 5-HT3 receptors in the periphery and in the brain (chemoreceptor trigger zone). C:
Cannabinoids related is incorrect. Cannabinoids are marijuana derivatives including dronabinol and
nabilone and are effective against moderately emetogenic chemotherapy. However, they are seldom
first-line antiemetics because of serious side effects. D: Blockage of prostaglandins is incorrect.
Dexamethasone and methylprednisolone used alone are effective against mildly to moderately
emetogenic chemotherapy. Their antiemetic mechanism is not known, but it may involve blockade of
prostaglandins. E: H2 receptor antagonist is incorrect. Antagonists of histamine H2 receptor block the
action of histamine at all H2 receptors; their chief clinical use is as inhibitors of gastric acid secretion.
A 27-year-old female with ovarian cancer is undergoing chemotherapy. She develops subsequent
renal failure.
Which of the following drugs is most likely responsible for this?
C
Explanation:
Cisplatin. All chemotherapeutics have similar generalized side effects related to their effects on
rapidly growing cells. These include hair loss, nausea, and fatigue. However, many
chemotherapeutics have unique toxicities as well which are often tested. Cisplatin (C) is notable for
its nephrotoxicity and ototoxicity. Cyclophosphamide
(A) is known to cause hemorrhagic cystitis. This is a distinct process from nephrotoxicity. The most
noteworthy side effect of bleomycin (B) is pulmonary toxicity that can lead to pulmonary fibrosis.
Vinblastine (D) is known for bone marrow suppression. Vincristine (E) causes neuropathy.
Your patient is a 43-year-old male who is experiencing post-operative voiding difficulty after an
elective inguinal hernia repair. His post void residual volume was 280 cc.
Which of the following medications is the most appropriate choice of therapy for this patient?
A
Explanation:
The patient is experiencing a common complication of low abdominal surgery. Post-operative urinary
retention occurs in almost 25% of patients after low abdominal surgical procedures. A normal post-
void residual volume is less than 50 cc or urine. The effects of anesthesia and analgesia both
contribute to bladder distension, decreased micturition reflex, reduction of contractility of the
detrusor muscle of the bladder, and incomplete voiding. The detrusor muscle of the bladder is
stimulated to contract by muscarinic cholinergic agonists. Bethanechol is a muscarinic agonist and is
frequently used in this setting to improve bladder emptying. Finasteride is a drug that is a 5 alpha
reductase inhibitor indicated for use in patients with bladder outlet obstruction as a result of
prostatic hypertrophy. The inhibition of 5 alpha reductase decreases local conversion of testosterone
to dihydrotestosterone in the prostate gland, which results in gradual shrinkage over a period of six
to twelve months. Phenylephrine is an alpha-adrenergic agonist that is selective for alpha-1
receptors. Activation of the alpha 1 receptors in the bladder results in contraction of the trigone
muscle and sphincter.
This promotes urinary retention. Oxybutynin is an antimuscarinic agent that is useful for treatment
of urge incontinence, and would have a detrimental effect on this patient’s bladder disorder.
Imipramine is a medication with anticholinergic properties that would also cause worsening of the
patient’s condition. Take home message: Post-operative urinary retention with concomitant
incomplete voiding is a complication that results from a decreased micturition reflex, increased
vesical sphincter tone, or decreased contractility of the detrusor muscle of the bladder. It can be
successfully treated with a muscarinic agonist, such as bethanechol, or with an alpha-1 adrenergic
antagonist.
Which of the following statements is true regarding Drug-receptor bonds?
E
Explanation:
Drugs mainly interact with the receptors by means of chemical forces or bonds. There are three
major types of drug receptor bonds: - Covalent - Electrostatic - Hydrophobic Covalent bonds are very
strong bonds and in most of the cases they are irreversible under biologic conditions. For example,
the covalent bond between the acetyl group of aspirin and cyclo-oxygenase enzyme (target enzyme
present on the platelets) does not breaks easily. The platelet aggregation effect of aspirin lasts long
after free acetyl-salicylic acid has disappeared from the blood (about 15 minutes) and it is reversed
only by the synthesis of new cyclo-oxygenase enzyme in new platelets which takes a long time.
Hence the effect of aspirin is seen after the drug is stopped. Among the drug receptor interactions,
electrostatic bond is much more commonly found than covalent bond. The electrostatic bonds vary
from relatively strong linkages between permanently charged ionic molecules to weaker hydrogen
bonds and very weak induced dipole interactions such as van der Waals force. The electrostatic
bonds are weaker than covalent bonds. Hydrophobic bonds are usually very weak bonds and
probably important in the interactions of highly lipid soluble drugs with the lipids of cell membranes
and perhaps in the interactions of the drugs with the internal walls of receptor “pockets”.
Which of the following NSAIDs is an Enolic acid derivative?
B
Explanation:
The following NSAIDs belong to the propionic acid derivatives group - Ibuprofen - Ketoprofen -
Naproxen - Fenoprofen - Flurbiprofen - Oxaprozin whereas piroxicam belongs to the class of Enolic
acid derivative which also includes other agents like meloxicam and Nabumetone. They are non-
selective COX inhibitors and act by preventing the production of certain prostaglandins.
A 67-year-old female presents to your clinic complaining of fatigue, diarrhea, headaches and a loss of
appetite. Upon examination you find that she is having some cognitive difficulty. Laboratory results
reveal: MCV: 109fL; Hgb: 9g/dL; MMA and homocystine are both elevated. Shilling test is positive.
What is the next best step in the management of this patient?
B
Explanation:
Lifelong Vitamin B12 supplementation. Vitamin B12 (cyanocobalamin) deficiency generally presents
in patients as fatigue, diarrhea and headaches but can also be the cause of cognitive changes
(difficulty concentrating, even mild dementia). Pernicious anemia is a macrocytic anemia, therefore
laboratory findings indicate an increased mean corpuscular volume (MCV), with a decreased
hemoglobin. A positive Schilling test indicates that the B12 deficiency is due to a lack of intrinsic
factor. Lifelong cyanocobalamin supplementation (either orally or via injections) is needed to treat
pernicious anemia. A is incorrect. Folic acid deficiency anemia is another common type of macrocytic
anemia. However, cognitive deficits are not typically seen with folic acid deficiency. Furthermore, a
schilling test would be negative and the methylmalonic acid (MMA) would be normal, rather than
elevated. C is incorrect. Iron deficiency anemia causes a microcytic anemia, characterized by a
decreased MCV. D is incorrect. A Coomb’s test is used to detect autoimmune hemolysis that may be
suspected in patients with normocytic anemia (anemia with an MCV in the normal range). E is
incorrect. Corticosteroids and iron supplementation are indicated as treatment in hemolytic anemia.
Your patient, a 25-year-old G1P0 female at 26 weeks gestation presents due to an abnormal glucose
tolerance test. One week prior, she was given 50 g of oral glucose and demonstrate a venous plasma
glucose level of 156 mg/dL one hour later.
Which of the following is the most appropriate next step of management?
B
Explanation:
Gestational diabetes is typically asymptomatic but identified via a 1-hour 50g oral glucose challenge
administered at 24–28 weeks of gestation. A venous plasma glucose blood level of > 140 mg/dL is
suggestive, and must be confirmed with a 3-hour 100g oral glucose tolerance test. After
administration of the 100g glucose challenge, at least two of the following are required for diagnosis:
(1) fasting glucose > 95 mg/dL, (2) one-hour glucose >180 mg/dL, (3) two hour glucose >155 mg/dL,
and (4) three hour glucose > 140 mg/dL. Choice A –
To diagnose gestational diabetes, a positive 1-hour 50g oral glucose challenge must be followed up
by a three-hour 100g oral glucose challenge. The diagnosis is only confirmed after both challenges
are completed and the thresholds are met. Choice C – Following the diagnosis of gestational
diabetes, the first step is strict glycemic control (fasting glucose).
A 23-year-old female presents to your clinic complaining of intermittent throbbing headaches that
usually last for several hours and are made worse by the presence of light. She endorses occasional
nausea without vomiting during the most severe episodes. Physical examination is unrevealing, and
she has no significant past medical history.
Which of the following treatments is considered an abortive therapy for this patient’s underlying
condition?
A
Explanation:
Correct: A. Migraine headaches typically affect females more often than males, and patients most
frequently present in their early 20s. Classic symptoms of migraine include throbbing headaches
lasting between 2–24 hours in duration, with triggers such as red wine, fasting, stress, and menses.
Primary prevention is aimed at the identification and avoidance of triggers. Over the counter NSAIDS
can be used if symptoms persist. Failing this, PRN abortive therapy is indicated, including the triptans
(e.g. – sumatriptan) and metoclopramide. Choice B – Gabapentin is an anticonvulsant that is
considered to be a second-line, prophylactic treatment for recurrent migraine headaches. Its utility is
limited by its lengthy side effect profile. Choice C – Amitriptyline, a tricyclic antidepressant, can also
be utilized for migraine prophylaxis. However, it will not abort a migraine currently in progress, and
extensive side effects limit its use. Choices D + E – Propranolol and diltiazam are beta-blockers and
calcium channel blockers, respectively. As with the anticonvulsants and tricyclic antidepressants,
these
are considered migraine prophylaxis and will not interrupt a migraine once it has begun.