An investigator is developing a drug that results in contraction of the pupillary dilator muscle when instilled topically. The drug works by increasing neurotransmitter release from the presynaptic nerve terminal. When administered intravenously, this drug is most likely to have which of the following additional effects?
Q422
A 39-year-old man comes to the physician because of frequent urination for the past 2 months. He has been urinating 10–12 times during the day and 3–4 times during the night. He says he is drinking a lot of water to compensate for any dehydration. He has no history of serious illness and takes no medications. Vital signs are within normal limits. Physical examination shows no abnormalities. He is concerned he may have diabetes mellitus like his parents. Laboratory studies show:
Hemoglobin 14.3 g/dL
Serum
Na+ 149 mEq/L
K+ 3.9 mEq/L
Cl- 102 mEq/L
Glucose 90 mg/dL
Osmolality 306 mOsmol/kg H2O
Urine
Osmolality 210 mOsmol/kg H2O
A water deprivation test is conducted. After 2 hours of fluid restriction, his plasma osmolality is 315 mOsmol/kg H2O and his urine osmolality is 210 mOsmol/kg H2O. One hour after an ADH analog injection, his plasma osmolality is 276 mOsmol/kg H2O and his urine osmolality is 425 mOsmol/kg H2O. Which of the following is the most appropriate next step in management?
Q423
A 36-year-old female presents to her primary care provider for tremor. She reports that she has always had a mild tremor but that she has begun noticing it more since learning to paint. She feels that she has trouble dipping her paintbrush in the paint and making precise strokes on the canvas. She has taken to painting while drinking wine, as she notices that the wine seems to improve her tremor. Her temperature is 97.6°F (36.4°C), blood pressure is 105/61 mmHg, pulse is 58/min, and respirations are 12/min. On exam, she has a high frequency bilateral hand tremor elicited on finger-to-nose testing. Her neurological exam is otherwise unremarkable. The patient is started on a new medication for her symptoms. One week later, she returns with a new complaint of abdominal pain for one day. She reports that she has noticed a darkening of her urine and now has difficulty raising her arms over her head to brush her hair.
This patient was most likely treated with which of the following medications?
Q424
A 23-year-old G1P0 woman presents to the emergency department with regular and painful contractions that occur every 3 minutes. She was at home cooking dinner when she experienced a deluge of clear fluid between her legs followed by painful contractions. The patient has a past medical history of obesity. Her pregnancy was not followed by an obstetrician, but she notes that she experienced abdominal pain and headaches frequently towards the end of her pregnancy. Her temperature is 99.5°F (37.5°C), blood pressure is 187/128 mmHg, pulse is 110/min, respirations are 17/min, and oxygen saturation is 98% on room air. The patient is started on magnesium sulfate and labetalol. The patient delivers her baby vaginally 2 hours later. On the labor and delivery floor, the patient is notably somnolent. Vitals are notable for respirations of 6 per minute. Physical exam reveals a somnolent woman who is minimally responsive. Cardiopulmonary exam is notable for hypopnea. Neurological exam reveals absent deep tendon reflexes and 3/5 strength in her upper and lower extremities. Which of the following is the next best step in management?
Q425
An investigator is studying a drug that acts on the thyroid hormone pathway. Levels of serum free T3 and T4 in healthy participants are measured before and after administration of the drug. After administration, there is a decrease in the average serum free T3 level, while the average serum free T4 level is increased compared to initial serum studies. Inhibition of which of the following is the most likely mechanism of action of this drug?
Q426
A 48-year-old man comes to the emergency room for a persistent painful erection for the last 4 hours. Three weeks ago, he had a deep vein thrombosis following a 13-hour flight. He also has a history of sickle cell trait, gastroesophageal reflux disease, major depressive disorder, and hypertension. He has smoked 1 pack of cigarette daily for the past 9 years. He takes warfarin, propranolol, citalopram, trazodone, lisinopril, and omeprazole. He is alert and oriented but in acute distress. His temperature is 37°C(98.6°F), pulse is 109/min, and blood pressure is 139/88 mm Hg. Examination shows a rigid erection with no evidence of trauma, penile discharge, injection, or prosthesis. Which of the following is the most likely cause of his condition?
Q427
A 37-year-old woman, gravida 3, para 2, at 28 weeks' gestation comes to the physician for a follow-up examination. One week ago, an oral glucose tolerance screening test showed elevated serum glucose levels. She has complied with the recommended diet and lifestyle modifications. Over the past week, home blood glucose monitoring showed elevated fasting and post-prandial blood glucose levels. Which of the following describes the mechanism of action of the most appropriate pharmacotherapy for this patient?
Q428
A 33-year-old man comes into the urgent care clinic with an intensely itchy rash on the bilateral mid-lower extremities, with a fine linear demarcation approximately an inch above his socks. The rash is arranged in streaks of erythema with superimposed vesicular lesions. The patient states that he recently began hiking in the woods behind his house, but he denies any local chemical exposures to his lower extremities. His vital signs include: blood pressure of 127/76, heart rate of 82/min, and respiratory rate of 12/min. Of the following options, which is the mechanism of his reaction?
Q429
An 8-year-old boy is brought to the pediatrician by his parents due to recurrent episodes of wheezing for the last 2 years. He uses a salbutamol inhaler for relief from wheezing, but his symptoms have recently worsened. He often coughs during the night, which awakens him from sleep almost every other day. He is not able to play football because he starts coughing after 10–15 minutes of play. His current physical examination is completely normal and auscultation of his chest does not reveal any abnormal breath sounds. His peak expiratory flow rate (PEFR) is 75% of expected for his age, gender, and height. After a complete diagnostic evaluation, the pediatrician prescribes a low-dose inhaled fluticasone daily for at least 3 months. He also mentions that the boy may require continuing inhaled corticosteroid (ICS) therapy for a few years if symptoms recur after discontinuation of ICS. However, the parents are concerned about the side effects of corticosteroids. Which of the following corticosteroid-related adverse effects is most likely?
Q430
A 36 year-old woman presents to the doctor’s office for evaluation of substernal chest pain and a metallic taste in her mouth. The patient has a history of metabolic syndrome and hypothyroidism. She takes levothyroxine daily. The patient’s vital signs are currently stable. On examination, she appears to be in mild discomfort, but is alert and oriented. The abdomen is mildly tender to palpation without guarding. Which of the following is the most appropriate treatment choice based on her history and physical examination?
Autonomic/CV Drugs US Medical PG Practice Questions and MCQs
Question 421: An investigator is developing a drug that results in contraction of the pupillary dilator muscle when instilled topically. The drug works by increasing neurotransmitter release from the presynaptic nerve terminal. When administered intravenously, this drug is most likely to have which of the following additional effects?
A. Acceleration of gut peristalsis
B. Contraction of skeletal muscles
C. Release of epinephrine by the adrenal medulla
D. Relaxation of the bladder neck sphincter
E. Increase in pyloric sphincter tone (Correct Answer)
Explanation: ***Increase in pyloric sphincter tone***
- The drug causes contraction of the **pupillary dilator muscle** by increasing neurotransmitter release from presynaptic terminals, indicating it is an **indirect sympathomimetic** (e.g., amphetamine, tyramine, ephedrine)
- These drugs release **norepinephrine** from postganglionic sympathetic nerve terminals
- The **pyloric sphincter** contains **α1-adrenergic receptors**, and sympathetic stimulation via norepinephrine causes **increased tone and contraction**
- This would result in **increased pyloric sphincter tone**, consistent with generalized sympathetic activation
*Relaxation of the bladder neck sphincter*
- The **bladder neck sphincter** is under **α1-adrenergic control**
- Sympathetic stimulation via α1-receptor activation causes **contraction**, not relaxation
- An indirect sympathomimetic releasing norepinephrine would cause **contraction** of the bladder neck sphincter
- Relaxation would require α1-blockade or parasympathetic activation, not sympathetic stimulation
*Acceleration of gut peristalsis*
- **Gut peristalsis** is primarily increased by the **parasympathetic nervous system**
- The **sympathetic nervous system** generally **inhibits gut motility** through α- and β-adrenergic receptor activation
- An indirect sympathomimetic would cause **decreased peristalsis**, not acceleration
*Contraction of skeletal muscles*
- **Skeletal muscle contraction** is mediated by **acetylcholine** at the **neuromuscular junction** acting on nicotinic receptors
- Sympathetic neurotransmitters (norepinephrine/epinephrine) do not directly cause skeletal muscle contraction
- While catecholamines can enhance muscle performance metabolically, they do not trigger contraction
*Release of epinephrine by the adrenal medulla*
- The **adrenal medulla** is stimulated by **preganglionic sympathetic neurons** that release **acetylcholine** at nicotinic receptors
- Indirect sympathomimetics work at **postganglionic** nerve terminals by releasing norepinephrine
- Since the drug releases NE from postganglionic terminals (not ACh from preganglionic terminals), it would **not significantly stimulate** the adrenal medulla to release epinephrine
Question 422: A 39-year-old man comes to the physician because of frequent urination for the past 2 months. He has been urinating 10–12 times during the day and 3–4 times during the night. He says he is drinking a lot of water to compensate for any dehydration. He has no history of serious illness and takes no medications. Vital signs are within normal limits. Physical examination shows no abnormalities. He is concerned he may have diabetes mellitus like his parents. Laboratory studies show:
Hemoglobin 14.3 g/dL
Serum
Na+ 149 mEq/L
K+ 3.9 mEq/L
Cl- 102 mEq/L
Glucose 90 mg/dL
Osmolality 306 mOsmol/kg H2O
Urine
Osmolality 210 mOsmol/kg H2O
A water deprivation test is conducted. After 2 hours of fluid restriction, his plasma osmolality is 315 mOsmol/kg H2O and his urine osmolality is 210 mOsmol/kg H2O. One hour after an ADH analog injection, his plasma osmolality is 276 mOsmol/kg H2O and his urine osmolality is 425 mOsmol/kg H2O. Which of the following is the most appropriate next step in management?
A. Hydrochlorothiazide therapy
B. Fluid restriction
C. Desmopressin therapy (Correct Answer)
D. Tolvaptan therapy
E. Amiloride therapy
Explanation: ***Desmopressin therapy***
- The patient's urine osmolality significantly increased after exogenous **ADH analog (desmopressin)** administration during the water deprivation test, indicating a renal response to ADH.
- This response points to **central diabetes insipidus**, where the body does not produce enough ADH, making desmopressin (an ADH analog) the appropriate replacement therapy.
*Hydrochlorothiazide therapy*
- **Thiazide diuretics** are sometimes used in **nephrogenic diabetes insipidus** (where kidneys don't respond to ADH) to induce a mild volume depletion, increasing proximal tubule reabsorption of water, but they are not the primary treatment for central DI.
- The patient's response to exogenous ADH rules out nephrogenic DI as the primary problem.
*Fluid restriction*
- This patient is already experiencing **polyuria** and **polydipsia**, and fluid restriction would worsen his **hypernatremia** and dehydration without addressing the underlying ADH deficiency.
- Fluid restriction is part of the diagnostic **water deprivation test**, not a therapeutic management for diabetes insipidus.
*Tolvaptan therapy*
- **Tolvaptan** is an **ADH receptor antagonist** used in conditions like **hyponatremia** due to SIADH to promote water excretion, which would be counterproductive in a patient with diabetes insipidus.
- It would worsen the patient's condition by further impairing water reabsorption and increasing urine output.
*Amiloride therapy*
- **Amiloride**, a **potassium-sparing diuretic**, is primarily used for hypertension, heart failure, and to counteract potassium loss from other diuretics.
- It has no role in the direct treatment of diabetes insipidus and would not address the ADH deficiency or renal unresponsiveness to ADH.
Question 423: A 36-year-old female presents to her primary care provider for tremor. She reports that she has always had a mild tremor but that she has begun noticing it more since learning to paint. She feels that she has trouble dipping her paintbrush in the paint and making precise strokes on the canvas. She has taken to painting while drinking wine, as she notices that the wine seems to improve her tremor. Her temperature is 97.6°F (36.4°C), blood pressure is 105/61 mmHg, pulse is 58/min, and respirations are 12/min. On exam, she has a high frequency bilateral hand tremor elicited on finger-to-nose testing. Her neurological exam is otherwise unremarkable. The patient is started on a new medication for her symptoms. One week later, she returns with a new complaint of abdominal pain for one day. She reports that she has noticed a darkening of her urine and now has difficulty raising her arms over her head to brush her hair.
This patient was most likely treated with which of the following medications?
A. Clozapine
B. Propranolol
C. Alprazolam
D. Primidone (Correct Answer)
E. Topiramate
Explanation: ***Correct Option: Primidone***
- The patient's initial presentation of a **high-frequency bilateral hand tremor** that improves with **alcohol consumption** is characteristic of **essential tremor**.
- **Primidone** is a first-line treatment for essential tremor and is metabolized to **phenobarbital**, a barbiturate.
- **Barbiturates are well-known porphyrinogenic drugs** that can precipitate **acute intermittent porphyria (AIP)**.
- The new symptoms one week after starting treatment—**abdominal pain**, **dark urine** (due to porphobilinogen and porphyrins), and **proximal muscle weakness/neuropathy** (difficulty raising arms)—form the classic triad of an **acute porphyric crisis**.
- This is a recognized adverse effect of primidone therapy.
*Incorrect Option: Propranolol*
- Propranolol is a **beta-blocker** and another first-line agent for essential tremor.
- However, **propranolol is considered SAFE in porphyria** and is not a porphyrinogenic drug.
- Beta-blockers do not precipitate acute porphyric crises.
- Side effects of propranolol include bradycardia, bronchospasm, and fatigue, not the symptoms described.
*Incorrect Option: Topiramate*
- Topiramate is an **anticonvulsant** that can be used off-label for essential tremor, though it is not first-line.
- Common side effects include **cognitive impairment**, **paresthesias**, **metabolic acidosis**, and **kidney stones**.
- It does not cause acute porphyric crises with dark urine and proximal muscle weakness.
*Incorrect Option: Alprazolam*
- Alprazolam is a **benzodiazepine** used for anxiety disorders that may transiently reduce tremor due to **anxiolytic effects**.
- It is not a primary treatment for essential tremor.
- Side effects include sedation and dependence, not porphyric crises.
*Incorrect Option: Clozapine*
- Clozapine is an **atypical antipsychotic** used for **treatment-resistant schizophrenia**.
- It is not indicated for tremor treatment.
- Major side effects include **agranulocytosis**, **myocarditis**, and **seizures**, not acute porphyria.
Question 424: A 23-year-old G1P0 woman presents to the emergency department with regular and painful contractions that occur every 3 minutes. She was at home cooking dinner when she experienced a deluge of clear fluid between her legs followed by painful contractions. The patient has a past medical history of obesity. Her pregnancy was not followed by an obstetrician, but she notes that she experienced abdominal pain and headaches frequently towards the end of her pregnancy. Her temperature is 99.5°F (37.5°C), blood pressure is 187/128 mmHg, pulse is 110/min, respirations are 17/min, and oxygen saturation is 98% on room air. The patient is started on magnesium sulfate and labetalol. The patient delivers her baby vaginally 2 hours later. On the labor and delivery floor, the patient is notably somnolent. Vitals are notable for respirations of 6 per minute. Physical exam reveals a somnolent woman who is minimally responsive. Cardiopulmonary exam is notable for hypopnea. Neurological exam reveals absent deep tendon reflexes and 3/5 strength in her upper and lower extremities. Which of the following is the next best step in management?
A. Discontinue current drug infusion (Correct Answer)
B. Remove retained fetal parts
C. Ultrasound
D. CT scan of the head
E. Supportive therapy
Explanation: ***Discontinue current drug infusion***
- The patient's symptoms, including **somnolence, respiratory depression (hypopnea, 6 respirations/minute), absent deep tendon reflexes, and muscle weakness (3/5 strength)**, are highly suggestive of **magnesium toxicity**.
- Immediate discontinuation of the **magnesium sulfate infusion** is the critical first step to prevent further accumulation and worsening of toxicity.
*Remove retained fetal parts*
- This step is indicated for **postpartum hemorrhage** or infection due to retained placental fragments.
- The patient's symptoms are neurological and respiratory, not related to uterine bleeding or infection.
*Ultrasound*
- An ultrasound might be useful to assess for retained products of conception or other intra-abdominal issues if there were signs of hemorrhage or infection.
- However, the patient's primary symptoms indicate neurological and respiratory depression, which is not an indication for ultrasound.
*CT scan of the head*
- A CT scan of the head would be considered if there were concerns for **intracranial hemorrhage**, stroke, or other neurological emergencies, especially given her history of headaches and severe hypertension.
- While hypertension is present, the constellation of absent deep tendon reflexes and respiratory depression points more directly to drug toxicity than to an acute intracranial event.
*Supportive therapy*
- Supportive therapy (e.g., **calcium gluconate as antidote**, airway management, mechanical ventilation) is essential and should be provided **concurrently** with stopping the magnesium infusion.
- However, the *next best step* prioritizes **stopping the source of toxicity** first, as continued infusion would worsen the patient's condition despite supportive measures.
- Without discontinuing the magnesium sulfate, supportive therapy alone would be insufficient to reverse the ongoing toxicity.
Question 425: An investigator is studying a drug that acts on the thyroid hormone pathway. Levels of serum free T3 and T4 in healthy participants are measured before and after administration of the drug. After administration, there is a decrease in the average serum free T3 level, while the average serum free T4 level is increased compared to initial serum studies. Inhibition of which of the following is the most likely mechanism of action of this drug?
A. Thyroid-stimulating hormone
B. Follicular iodotyrosine deiodinase
C. Follicular thyroid peroxidase
D. Peripheral 5'-deiodinase (Correct Answer)
E. Follicular thyroid proteases
Explanation: ***Peripheral 5'-deiodinase***
- Inhibition of **peripheral 5'-deiodinase** would decrease the conversion of **T4 to T3** in the periphery, resulting in lower **free T3** and higher **free T4** levels.
- This enzyme is crucial for activating T4 into the more potent T3, and its blockade explains the observed changes in hormone levels.
*Thyroid-stimulating hormone*
- Inhibition of **TSH** would lead to a decrease in the production and release of both **T3 and T4** from the thyroid gland.
- This contradicts the observed increase in **free T4** levels.
*Follicular iodotyrosine deiodinase*
- This enzyme is involved in recycling iodine from **monoiodotyrosine (MIT)** and **diiodotyrosine (DIT)** within the thyroid follicular cells, which is important for efficient thyroid hormone synthesis.
- Its inhibition would primarily affect iodine availability and synthesis, not directly lead to increased T4 and decreased T3 in the periphery.
*Follicular thyroid peroxidase*
- **Thyroid peroxidase (TPO)** is critical for the **iodination of tyrosine residues** on thyroglobulin and the **coupling of MIT and DIT** to form T3 and T4.
- Inhibition of TPO would decrease the synthesis of both **T3 and T4**, contrary to the observed increase in **free T4**.
*Follicular thyroid proteases*
- **Thyroid proteases** cleave thyroglobulin to release mature **T3 and T4** into the bloodstream.
- Inhibition of these proteases would lead to a decrease in the release of both **T3 and T4**, which does not align with the observed increase in **free T4**.
Question 426: A 48-year-old man comes to the emergency room for a persistent painful erection for the last 4 hours. Three weeks ago, he had a deep vein thrombosis following a 13-hour flight. He also has a history of sickle cell trait, gastroesophageal reflux disease, major depressive disorder, and hypertension. He has smoked 1 pack of cigarette daily for the past 9 years. He takes warfarin, propranolol, citalopram, trazodone, lisinopril, and omeprazole. He is alert and oriented but in acute distress. His temperature is 37°C(98.6°F), pulse is 109/min, and blood pressure is 139/88 mm Hg. Examination shows a rigid erection with no evidence of trauma, penile discharge, injection, or prosthesis. Which of the following is the most likely cause of his condition?
A. Sickle cell trait
B. Trazodone (Correct Answer)
C. Citalopram
D. Warfarin
E. Cigarette smoking
Explanation: ***Trazodone***
- **Trazodone** is an antidepressant known to cause **priapism** as a rare but serious side effect (approximately 1 in 6,000 patients)
- Mechanism: **Alpha-1 adrenergic receptor blockade** leads to impaired venous outflow from the corpus cavernosum
- The patient's presentation of **persistent, painful erection for 4 hours** in the context of trazodone use is highly suspicious for drug-induced priapism
- This is a **medical emergency** requiring immediate intervention to prevent ischemic damage
*Sickle cell trait*
- While **sickle cell disease** is a common cause of priapism due to vaso-occlusion, **sickle cell trait** (heterozygous state) typically only causes priapism under extreme conditions (high altitude, severe dehydration, extreme exertion)
- The patient's clinical context does not suggest these extreme precipitants
- Given clear medication history with trazodone, drug-induced priapism is more likely
*Citalopram*
- **Citalopram** is an SSRI (selective serotonin reuptake inhibitor)
- SSRIs are **not associated with priapism**; they more commonly cause sexual dysfunction (decreased libido, anorgasmia)
- Priapism is not a recognized adverse effect of this drug class
*Warfarin*
- **Warfarin** is an anticoagulant that inhibits vitamin K-dependent clotting factors
- Primary adverse effects involve **bleeding complications**, not priapism
- Does not directly affect erectile mechanisms or cause prolonged erections
*Cigarette smoking*
- **Smoking** is associated with **erectile dysfunction** (ED) due to endothelial damage and reduced nitric oxide bioavailability
- Smoking causes **difficulty achieving/maintaining erections**, not persistent unwanted erections
- Not a cause of priapism
Question 427: A 37-year-old woman, gravida 3, para 2, at 28 weeks' gestation comes to the physician for a follow-up examination. One week ago, an oral glucose tolerance screening test showed elevated serum glucose levels. She has complied with the recommended diet and lifestyle modifications. Over the past week, home blood glucose monitoring showed elevated fasting and post-prandial blood glucose levels. Which of the following describes the mechanism of action of the most appropriate pharmacotherapy for this patient?
A. Inhibition of alpha-glucosidase
B. Closure of ATP-dependent K+-channels
C. Inhibition of dipeptidyl peptidase 4
D. Activation of peroxisome proliferator-activated receptor-gamma
E. Binding to receptors with tyrosine kinase activity (Correct Answer)
Explanation: ***Binding to receptors with tyrosine kinase activity***
- This mechanism describes **insulin**, which is the **first-line pharmacotherapy for gestational diabetes mellitus (GDM)** that is not controlled by diet and lifestyle modifications. Insulin binds to its receptor, activating **tyrosine kinase activity** and initiating a cascade of intracellular signaling that promotes glucose uptake and utilization.
- Given the **elevated fasting and post-prandial blood glucose levels** despite dietary changes, insulin therapy is indicated to manage GDM, which relies on this mechanism of action.
*Inhibition of alpha-glucosidase*
- **Alpha-glucosidase inhibitors** (e.g., acarbose, miglitol) delay carbohydrate absorption in the gut, primarily targeting post-prandial hyperglycemia.
- While these can be used in some forms of diabetes, they are generally **not preferred for GDM due to potential gastrointestinal side effects** and less effective control over fasting hyperglycemia compared to insulin.
*Closure of ATP-dependent K+-channels*
- Drugs like **sulfonylureas** (e.g., glyburide) act by **closing ATP-dependent K+-channels** on pancreatic beta cells, leading to depolarization and insulin release.
- **Glyburide** can be used in GDM but is a controversial choice due to its potential to **cross the placenta** and cause fetal hypoglycemia.
*Inhibition of dipeptidyl peptidase 4*
- **Dipeptidyl peptidase-4 (DPP-4) inhibitors** (e.g., sitagliptin, saxagliptin) enhance the action of incretin hormones, stimulating glucose-dependent insulin release and suppressing glucagon secretion.
- There is **limited data on the safety and efficacy of DPP-4 inhibitors in pregnancy**, and they are not typically recommended for GDM.
*Activation of peroxisome proliferator-activated receptor-gamma*
- This mechanism describes **thiazolidinediones (TZDs)**, such as pioglitazone and rosiglitazone, which improve insulin sensitivity.
- **TZDs are contraindicated in pregnancy** due to potential adverse effects on the fetus, including increased risk of cardiovascular defects and fluid retention.
Question 428: A 33-year-old man comes into the urgent care clinic with an intensely itchy rash on the bilateral mid-lower extremities, with a fine linear demarcation approximately an inch above his socks. The rash is arranged in streaks of erythema with superimposed vesicular lesions. The patient states that he recently began hiking in the woods behind his house, but he denies any local chemical exposures to his lower extremities. His vital signs include: blood pressure of 127/76, heart rate of 82/min, and respiratory rate of 12/min. Of the following options, which is the mechanism of his reaction?
A. Type III–immune complex-mediated hypersensitivity reaction
B. Type IV–cell-mediated (delayed) hypersensitivity reaction (Correct Answer)
C. Type II–cytotoxic hypersensitivity reaction
D. Type I–anaphylactic hypersensitivity reaction
E. Type III and IV–mixed immune complex and cell-mediated hypersensitivity reactions
Explanation: **Type IV–cell-mediated (delayed) hypersensitivity reaction**
- The described rash with **erythema**, **vesicular lesions**, and a **linear demarcation** after hiking is classic for **allergic contact dermatitis**, often caused by plants like poison ivy, which is a **Type IV hypersensitivity reaction**.
- This reaction is **delayed**, usually appearing 24-72 hours after exposure, and is mediated by **T lymphocytes** and **macrophages** reacting to the antigen.
*Type III–immune complex-mediated hypersensitivity reaction*
- This type of reaction involves the formation of **immune complexes** (antigen-antibody), leading to inflammation and tissue damage.
- Clinically, it often presents as **vasculitis**, **serum sickness**, or conditions like **lupus nephritis**, which do not match the localized, vesicular rash described.
*Type II–cytotoxic hypersensitivity reaction*
- This reaction involves **antibodies** (IgG or IgM) binding to antigens on cell surfaces, leading to cell destruction or dysfunction.
- Examples include **hemolytic transfusion reactions** and **autoimmune hemolytic anemia**, which are distinct from allergic contact dermatitis.
*Type I–anaphylactic hypersensitivity reaction*
- This is an **immediate hypersensitivity** reaction mediated by **IgE antibodies** binding to mast cells, leading to histamine release.
- Symptoms typically include **urticaria**, **angioedema**, **bronchospasm**, and **anaphylaxis**, occurring rapidly after exposure.
*Type III and IV–mixed immune complex and cell-mediated hypersensitivity reactions*
- While some conditions can involve features of both Type III and Type IV, the clinical picture of **allergic contact dermatitis** is predominantly a **pure Type IV (delayed cell-mediated) reaction**.
- The primary mechanism of the described rash does not involve immune complex deposition.
Question 429: An 8-year-old boy is brought to the pediatrician by his parents due to recurrent episodes of wheezing for the last 2 years. He uses a salbutamol inhaler for relief from wheezing, but his symptoms have recently worsened. He often coughs during the night, which awakens him from sleep almost every other day. He is not able to play football because he starts coughing after 10–15 minutes of play. His current physical examination is completely normal and auscultation of his chest does not reveal any abnormal breath sounds. His peak expiratory flow rate (PEFR) is 75% of expected for his age, gender, and height. After a complete diagnostic evaluation, the pediatrician prescribes a low-dose inhaled fluticasone daily for at least 3 months. He also mentions that the boy may require continuing inhaled corticosteroid (ICS) therapy for a few years if symptoms recur after discontinuation of ICS. However, the parents are concerned about the side effects of corticosteroids. Which of the following corticosteroid-related adverse effects is most likely?
A. Suppression of hypothalamus-pituitary-adrenal (HPA) axis
B. Short stature
C. Posterior subcapsular cataract
D. Steroid psychosis
E. Hoarseness of voice (Correct Answer)
Explanation: ***Hoarseness of voice***
- **Hoarseness (dysphonia)** is the **most common local side effect** of inhaled corticosteroids (ICS) due to irritation of the vocal cords or laryngeal deposition.
- Other local effects include **oral candidiasis (thrush)**, though less common in children than adults.
- These adverse effects are localized to the upper airway and are generally **mild and reversible**.
- Can be **minimized** by using a spacer device and rinsing the mouth after each use.
*Suppression of hypothalamus-pituitary-adrenal (HPA) axis*
- While systemic corticosteroids can cause HPA axis suppression, **low-dose inhaled corticosteroids** have minimal systemic absorption (typically <1% bioavailability).
- HPA suppression is unlikely unless used at **very high doses** (>800 mcg/day fluticasone equivalent) or for prolonged periods.
- The pediatrician prescribed a **low-dose ICS**, significantly reducing the risk of this systemic effect.
*Short stature*
- Some studies have shown a small, **transient reduction in growth velocity** (approximately 1 cm in the first year) during ICS therapy in children.
- This effect is typically **minor and does not significantly impact final adult height**.
- The benefits of asthma control **far outweigh** this minimal growth effect.
- Poorly controlled asthma itself can impair growth more than ICS therapy.
*Posterior subcapsular cataract*
- **Systemic corticosteroids**, particularly with prolonged use, are a known risk factor for posterior subcapsular cataracts.
- **Low-dose inhaled corticosteroids** have a **very low risk** of causing cataracts due to minimal systemic exposure.
- Risk increases only with high doses (>1000 mcg/day) used for many years.
*Steroid psychosis*
- **Steroid psychosis** is a rare but serious neuropsychiatric side effect primarily associated with **high-dose systemic corticosteroids**.
- It is **highly unlikely** to occur with **low-dose inhaled corticosteroids** due to their limited systemic bioavailability.
- This effect is not relevant to the clinical scenario presented.
Question 430: A 36 year-old woman presents to the doctor’s office for evaluation of substernal chest pain and a metallic taste in her mouth. The patient has a history of metabolic syndrome and hypothyroidism. She takes levothyroxine daily. The patient’s vital signs are currently stable. On examination, she appears to be in mild discomfort, but is alert and oriented. The abdomen is mildly tender to palpation without guarding. Which of the following is the most appropriate treatment choice based on her history and physical examination?
A. Omeprazole (Correct Answer)
B. Famotidine
C. Metoclopramide
D. Magnesium hydroxide
E. Bismuth subsalicylate
Explanation: ***Omeprazole***
- The patient's symptoms of **substernal chest pain** and **metallic taste** are highly suggestive of **gastroesophageal reflux disease (GERD)**.
- **Omeprazole** is a **proton pump inhibitor (PPI)**, which is the most effective class of medications for suppressing gastric acid production and treating GERD.
*Famotidine*
- **Famotidine** is an **H2 receptor antagonist** that reduces gastric acid production.
- While it can be used for GERD, PPIs like omeprazole are generally more effective and provide superior symptom relief and healing of erosive esophagitis.
*Metoclopramide*
- **Metoclopramide** is a **prokinetic agent** that increases gastrointestinal motility.
- It could be considered an adjunct in GERD management, especially if there's evidence of gastroparesis, but it is not a first-line treatment for typical GERD symptoms.
*Magnesium hydroxide*
- **Magnesium hydroxide** is an **antacid** that provides temporary relief by neutralizing stomach acid.
- It does not address the underlying pathology of GERD (acid reflux) and is not suitable for long-term or definitive treatment.
*Bismuth subsalicylate*
- **Bismuth subsalicylate** primarily acts as an **antidiarrheal** and has some **antimicrobial properties** (e.g., against *H. pylori*).
- It is not a primary treatment for GERD and would not effectively address substernal chest pain or a metallic taste related to acid reflux.