A 65-year-old woman comes to the physician because of a 3-month history of progressive shortness of breath and a dry cough. She has also noticed gradual development of facial discoloration. She has coronary artery disease, hypertension, and atrial fibrillation. She does not remember which medications she takes. Her temperature is 37°C (98.6°F), pulse is 90/min, respirations are 18/min, and blood pressure is 150/85 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 95%. Examination shows blue-gray discoloration of the face and both hands. Diffuse inspiratory crackles are heard. An x-ray of the chest shows reticular opacities around the lung periphery and particularly around the lung bases. The most likely cause of this patient's findings is an adverse effect to which of the following medications?
Q552
A 2-year-old boy is brought to the emergency department with an enlarged left knee. The patient’s parents state that his knee began to swell up a few hours ago while the family was indoors, watching TV. This has never happened before. The boy says his knee hurts when he puts weight on it. Past medical history is unremarkable. He was born at 39 weeks gestation via spontaneous vaginal delivery. He is up to date on all vaccines and is meeting all developmental milestones. Today, his vitals are normal for his age group with a blood pressure of 104/60 mm Hg, heart rate 90/min, respiratory rate 25/min, and temperature 37.1°C (98.8°F). On physical exam the child's left knee is indurated, erythematous, and painful to palpation. An ultrasound of the knee is consistent with hemarthrosis. A hematology workup is completed and the appropriate treatment was administered. Which of the following was the most likely treatment administered to this patient?
Q553
A 31-year-old woman is brought to the emergency department for a severe throbbing headache, nausea, and photophobia for 3 hours. She has severe occipital pain and chest tightness. Prior to onset of symptoms, she had attended a networking event where she had red wine and, shortly after, a snack consisting of salami and some dried fruits. The patient has recurrent migraine headaches and depression, for which she takes medication daily. She is mildly distressed, diaphoretic, and her face is flushed. Her temperature is 37.0°C (98.6 F), pulse is 90/min, respirations are 20/min, and blood pressure is 195/130 mmHg. She is alert and oriented. Deep-tendon reflexes are 2+ bilaterally. This patient's symptoms are most likely caused by a side effect of which of the following medications?
Q554
A 39-year-old female presents to the clinic with the complaints of dry skin for a few months. She adds that she also has constipation for which she started eating vegetables and fruits but with no improvement. She lives with her husband and children who often complain when she turns the air conditioning to high as she cannot tolerate low temperatures. She has gained 5 kgs (11.2 lb) since her last visit 2 months back although her diet has not changed much. Her past medical history is relevant for cardiac arrhythmias and diabetes. She is on several medications currently. Her temperature is 98.6° F (37° C), respirations are 15/min, pulse is 57/min and blood pressure is 132/98 mm Hg. A physical examination is within normal limits. Thyroid function test results are given below:
Serum
TSH: 13.0 μU/mL
Thyroxine (T4): 3.0 μg/dL
Triiodothyronine (T3): 100 ng/dL
Which of the following medications is most likely to be responsible for her symptoms?
Q555
Three hours after undergoing a total right hip replacement, a 71-year-old woman has tingling around the lips and numbness in her fingertips. Her surgery was complicated by unintentional laceration of the right femoral artery that resulted in profuse bleeding. She appears uncomfortable. Examination shows an adducted thumb, extended fingers, and flexed metacarpophalangeal joints and wrists. Tapping on the cheeks leads to contraction of the facial muscles. Which of the following is the most likely cause of this patient's symptoms?
Q556
A 16-year-old boy is brought to the emergency department following a car accident in which he suffered multiple injuries. He is accompanied by his mother. She reports that his medical history is notable only for recurrent sinusitis and otitis as a child. He lost a significant amount of blood from the accident, and he is transfused two units of O-negative blood on arrival at the emergency department. Shortly thereafter, he complains of itching and increasing shortness of breath. He develops stridor. Which of the following could have prevented this reaction?
Q557
A 47-year-old woman presents to her physician for a routine checkup. She is in good health and has no complaints. Past medical history is significant for type 2 diabetes mellitus and obesity. She recently started metformin and is tolerating the mild side effects, but her fasting blood glucose levels range from 160–190 mg/dL. Today, her blood pressure is 125/82 mm Hg, the heart rate is 90/min, the respiratory rate is 17/min, and the temperature is 37.0°C (98.6°F). On physical exam, she appears well developed and obese. Her heart has a regular rate and rhythm and her lungs are clear to auscultation bilaterally. Her fasting glucose level is 175 mg/dL and her A1c is 7.1%. Her physician decides to add canagliflozin to her current treatment regimen. Which of the following should be evaluated before starting this medication?
Q558
A 75-year-old male is diagnosed with advanced metastatic prostate cancer. After further evaluation and staging, the patient is started on flutamide therapy. Addition of which of the following medications to this patient’s medication regimen would be of greatest benefit in the treatment of this patient’s condition?
Q559
A 27-year-old man is brought to the emergency department because of weakness, headache, and vomiting for 40 minutes. He is an amateur chef and his symptoms started 10 minutes after he ingested pufferfish that he had prepared. On arrival, he is lethargic. His temperature is 37°C (98.6°F), pulse is 120/min, respirations are 8/min, and blood pressure is 92/64 mm Hg. He is intubated and mechanical ventilation is begun. Intravenous fluid resuscitation is started. The cause of this patient's condition exerts its effect by which of the following mechanisms of action?
Q560
A 63-year-old woman comes to the physician for a follow-up examination. She has had numbness and burning sensation in her feet for 4 months. The pain is worse at rest and while sleeping. She has hypercholesterolemia and type 2 diabetes mellitus. Current medications include insulin, metformin, and atorvastatin. She has smoked one pack of cigarettes daily for 33 years. Her temperature is 37°C (98.6°F), pulse is 88/min, and blood pressure is 124/88 mm Hg. Examination shows full muscle strength and normal muscle tone in all extremities. Sensation to pinprick, light touch, and vibration is decreased over the soles of both feet. Ankle jerk is 1+ bilaterally. Biceps and triceps reflexes are 2+ bilaterally. Babinski sign is negative bilaterally. Laboratory studies show:
Hemoglobin 11.2 g/dL
Mean corpuscular volume 93 μm3
Hemoglobin A1C 8.2 %
Serum
Glucose 188 mg/dL
Which of the following is the most appropriate next step in management?
Autonomic/CV Drugs US Medical PG Practice Questions and MCQs
Question 551: A 65-year-old woman comes to the physician because of a 3-month history of progressive shortness of breath and a dry cough. She has also noticed gradual development of facial discoloration. She has coronary artery disease, hypertension, and atrial fibrillation. She does not remember which medications she takes. Her temperature is 37°C (98.6°F), pulse is 90/min, respirations are 18/min, and blood pressure is 150/85 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 95%. Examination shows blue-gray discoloration of the face and both hands. Diffuse inspiratory crackles are heard. An x-ray of the chest shows reticular opacities around the lung periphery and particularly around the lung bases. The most likely cause of this patient's findings is an adverse effect to which of the following medications?
A. Warfarin
B. Metoprolol
C. Procainamide
D. Amiodarone (Correct Answer)
E. Lisinopril
Explanation: ***Amiodarone***
- The patient's **progressive shortness of breath**, **dry cough**, and **diffuse inspiratory crackles**, along with **reticular opacities** on chest X-ray, are classic signs of **amiodarone-induced pulmonary fibrosis**.
- The distinctive **blue-gray facial and hand discoloration** is also a well-known side effect of chronic amiodarone use, due to **iodine accumulation in the skin** (amiodarone contains high iodine content).
*Warfarin*
- Warfarin is an anticoagulant used for conditions like atrial fibrillation, but its primary adverse effects include **bleeding** and **skin necrosis**, not pulmonary symptoms or blue-gray discoloration.
- It does not cause interstitial lung disease or changes in skin pigmentation.
*Metoprolol*
- Metoprolol is a beta-blocker used for hypertension and coronary artery disease; common side effects include **bradycardia**, **fatigue**, and **bronchospasm** in susceptible individuals (asthmatics).
- It does not typically cause pulmonary fibrosis or skin discoloration.
*Procainamide*
- Procainamide is an antiarrhythmic, but it is typically used for acute arrhythmias and not long-term management like amiodarone. Its major side effect is a **lupus-like syndrome** and **agranulocytosis**.
- It is not associated with pulmonary fibrosis or skin discoloration as described.
*Lisinopril*
- Lisinopril is an ACE inhibitor used for hypertension and coronary artery disease; common side effects include a **dry cough** (due to bradykinin accumulation) and **angioedema**.
- However, it does not cause pulmonary fibrosis (reticular opacities) or blue-gray skin discoloration.
Question 552: A 2-year-old boy is brought to the emergency department with an enlarged left knee. The patient’s parents state that his knee began to swell up a few hours ago while the family was indoors, watching TV. This has never happened before. The boy says his knee hurts when he puts weight on it. Past medical history is unremarkable. He was born at 39 weeks gestation via spontaneous vaginal delivery. He is up to date on all vaccines and is meeting all developmental milestones. Today, his vitals are normal for his age group with a blood pressure of 104/60 mm Hg, heart rate 90/min, respiratory rate 25/min, and temperature 37.1°C (98.8°F). On physical exam the child's left knee is indurated, erythematous, and painful to palpation. An ultrasound of the knee is consistent with hemarthrosis. A hematology workup is completed and the appropriate treatment was administered. Which of the following was the most likely treatment administered to this patient?
A. Factor IX replacement injections
B. vWF product
C. Fresh frozen plasma (FFP)
D. Desmopressin (Correct Answer)
E. Cryoprecipitate
Explanation: ***Desmopressin***
- The sudden onset of **hemarthrosis** in a 2-year-old with an otherwise unremarkable history suggests a coagulation disorder, possibly **mild hemophilia A** or **von Willebrand disease (vWD)** due to the spontaneous nature of the bleeding and lack of trauma.
- **Desmopressin (DDAVP)** is a synthetic analog of **vasopressin** that stimulates the release of **factor VIII** and **von Willebrand factor (vWF)** from endothelial cells, making it an effective treatment for mild hemophilia A and many types of vWD.
*Factor IX replacement injections*
- **Factor IX replacement** is the primary treatment for **hemophilia B**, which involves a deficiency in factor IX.
- While hemarthrosis can occur in hemophilia B, the immediate and spontaneous nature described is more suggestive of hemophilia A or vWD, for which factor VIII or vWF-related treatments are more appropriate.
*vWF product*
- A **vWF product** is used for treating more severe forms of **von Willebrand disease** where desmopressin is insufficient or contraindicated.
- While vWD is a possibility, desmopressin is often the first-line treatment for milder forms, fitting the current clinical picture.
*Fresh frozen plasma (FFP)*
- **FFP** contains all coagulation factors and is used in cases of **multiple factor deficiencies** or when specific factor concentrates are unavailable.
- Given the focused nature of a potential hemophilia or vWD diagnosis suggested by hemarthrosis, administering specific factor concentrates or desmopressin is generally preferred over FFP, which carries risks of fluid overload and allergic reactions.
*Cryoprecipitate*
- **Cryoprecipitate** is rich in **fibrinogen, factor VIII, vWF, and factor XIII**. It is used primarily for **fibrinogen deficiency** or severe vWD when specific concentrates are not available or indicated.
- While it contains vWF and factor VIII, more targeted therapies like desmopressin or specific factor concentrates are usually preferred if the patient's condition responds to them.
Question 553: A 31-year-old woman is brought to the emergency department for a severe throbbing headache, nausea, and photophobia for 3 hours. She has severe occipital pain and chest tightness. Prior to onset of symptoms, she had attended a networking event where she had red wine and, shortly after, a snack consisting of salami and some dried fruits. The patient has recurrent migraine headaches and depression, for which she takes medication daily. She is mildly distressed, diaphoretic, and her face is flushed. Her temperature is 37.0°C (98.6 F), pulse is 90/min, respirations are 20/min, and blood pressure is 195/130 mmHg. She is alert and oriented. Deep-tendon reflexes are 2+ bilaterally. This patient's symptoms are most likely caused by a side effect of which of the following medications?
A. Phenelzine (Correct Answer)
B. Topiramate
C. Ibuprofen
D. Valproic acid
E. Verapamil
Explanation: ***Phenelzine***
- This patient is experiencing a **hypertensive crisis**, characterized by a severe headache, nausea, chest tightness, diaphoresis, and significantly elevated blood pressure (195/130 mmHg). This is a classic presentation of a **tyramine-induced hypertensive crisis**, which can occur in patients taking **monoamine oxidase inhibitors (MAOIs)** like phenelzine.
- Phenelzine inhibits monoamine oxidase, which normally metabolizes **tyramine**. Ingestion of tyramine-rich foods (red wine, salami, dried fruits) leads to a buildup of tyramine, causing a massive release of **norepinephrine** and severe hypertension.
*Topiramate*
- Topiramate is an **anticonvulsant** commonly used for migraine prophylaxis.
- Its side effects typically include **paresthesias**, cognitive slowing, and weight loss, not acute hypertensive crisis from dietary interactions.
*Ibuprofen*
- Ibuprofen is a **non-steroidal anti-inflammatory drug (NSAID)** used for pain relief.
- While prolonged use can sometimes cause a mild increase in blood pressure or fluid retention, it does not typically lead to an acute, severe **hypertensive crisis** in response to specific food ingestion.
*Valproic acid*
- Valproic acid is an **anticonvulsant** and mood stabilizer, also used for migraine prophylaxis.
- Common side effects include **gastrointestinal upset**, tremor, and hepatotoxicity; it is not associated with dietary-induced hypertensive crises.
*Verapamil*
- Verapamil is a **calcium channel blocker** often used for hypertension, angina, and migraine prophylaxis.
- Its mechanism of action usually leads to a **decrease** in blood pressure, and it is not known to cause acute hypertensive reactions with specific food interactions.
Question 554: A 39-year-old female presents to the clinic with the complaints of dry skin for a few months. She adds that she also has constipation for which she started eating vegetables and fruits but with no improvement. She lives with her husband and children who often complain when she turns the air conditioning to high as she cannot tolerate low temperatures. She has gained 5 kgs (11.2 lb) since her last visit 2 months back although her diet has not changed much. Her past medical history is relevant for cardiac arrhythmias and diabetes. She is on several medications currently. Her temperature is 98.6° F (37° C), respirations are 15/min, pulse is 57/min and blood pressure is 132/98 mm Hg. A physical examination is within normal limits. Thyroid function test results are given below:
Serum
TSH: 13.0 μU/mL
Thyroxine (T4): 3.0 μg/dL
Triiodothyronine (T3): 100 ng/dL
Which of the following medications is most likely to be responsible for her symptoms?
A. Amiodarone (Correct Answer)
B. Digoxin
C. Metformin
D. Theophylline
E. Warfarin
Explanation: ***Amiodarone***
- Amiodarone is a known cause of both **hypothyroidism** and **hyperthyroidism** due to its iodine content and direct toxic effects on the thyroid gland. The patient's symptoms (dry skin, constipation, **cold intolerance**, **weight gain**, bradycardia) and thyroid function tests (high TSH, low T4, low T3) are highly consistent with drug-induced hypothyroidism.
- The patient's history of **cardiac arrhythmias** makes amiodarone a plausible medication she would be taking, as it is a common antiarrhythmic drug.
*Digoxin*
- Digoxin is primarily used to treat **heart failure** and certain arrhythmias, but it does not typically cause thyroid dysfunction.
- Its common side effects include gastrointestinal upset, visual disturbances, and various arrhythmias, which do not align with the patient's predominant symptoms of hypothyroidism.
*Metformin*
- Metformin is an oral hypoglycemic agent used to treat **Type 2 diabetes**, a condition the patient also has.
- It does not have substantial effects on thyroid hormone synthesis or metabolism and is not associated with hypothyroidism or hyperthyroidism.
*Theophylline*
- Theophylline is a bronchodilator used in the treatment of **asthma** and **COPD**.
- It is not known to cause thyroid dysfunction, and its side effects mainly involve the central nervous system, gastrointestinal tract, and cardiovascular system.
*Warfarin*
- Warfarin is an **anticoagulant** prescribed to prevent blood clots.
- It has no direct known interaction with thyroid hormone synthesis or metabolism and is not associated with thyroid dysfunction.
Question 555: Three hours after undergoing a total right hip replacement, a 71-year-old woman has tingling around the lips and numbness in her fingertips. Her surgery was complicated by unintentional laceration of the right femoral artery that resulted in profuse bleeding. She appears uncomfortable. Examination shows an adducted thumb, extended fingers, and flexed metacarpophalangeal joints and wrists. Tapping on the cheeks leads to contraction of the facial muscles. Which of the following is the most likely cause of this patient's symptoms?
A. Acute kidney injury
B. Parathyroid ischemia
C. Intravascular hemolysis
D. Calcium chelation (Correct Answer)
E. Metabolic acidosis
Explanation: ***Calcium chelation***
- The patient exhibits symptoms of **hypocalcemia**, including perioral tingling, fingertip numbness, **Trousseau sign** (adducted thumb, extended fingers, flexed metacarpophalangeal joints and wrists), and **Chvostek's sign** (facial muscle contraction upon tapping the cheek).
- Her significant blood loss and subsequent transfusion likely involved large volumes of **citrated blood products** (e.g., packed red blood cells), where citrate acts as an **anticoagulant** by chelating calcium, leading to transient hypocalcemia.
*Acute kidney injury*
- While acute kidney injury can cause electrolyte imbalances, it typically leads to **hyperphosphatemia**, not necessarily acute symptomatic hypocalcemia presenting within hours of surgery in this manner.
- The patient's immediate post-operative presentation points away from kidney injury being the primary cause of these acute neurological symptoms.
*Parathyroid ischemia*
- **Parathyroid ischemia** could cause hypocalcemia due to reduced parathyroid hormone production, but it is typically associated with **neck surgeries** (e.g., thyroidectomy) and not directly with hip replacement or arterial laceration.
- The onset of symptoms within hours of surgery is too rapid for parathyroid ischemia to fully manifest, as the half-life of PTH is short, but the subsequent drop in calcium would take longer to become clinically significant.
*Intravascular hemolysis*
- **Intravascular hemolysis** can occur due to transfusion reactions or other causes, leading to symptoms like fever, chills, and hemoglobinuria.
- It does not directly cause the specific neurological signs of hypocalcemia described (Trousseau's and Chvostek's signs).
*Metabolic acidosis*
- **Metabolic acidosis** can alter calcium binding to albumin, leading to an **increase in ionized calcium** (the physiologically active form), rather than a decrease.
- While acidosis can occur after massive blood loss and shock, it would not explain the classic signs of hypocalcemia.
Question 556: A 16-year-old boy is brought to the emergency department following a car accident in which he suffered multiple injuries. He is accompanied by his mother. She reports that his medical history is notable only for recurrent sinusitis and otitis as a child. He lost a significant amount of blood from the accident, and he is transfused two units of O-negative blood on arrival at the emergency department. Shortly thereafter, he complains of itching and increasing shortness of breath. He develops stridor. Which of the following could have prevented this reaction?
A. Administering IVIG with transfusion
B. Pre-transfusion diphenhydramine
C. Administering washed blood products (Correct Answer)
D. Pre-transfusion acetaminophen
E. Administering type-specific blood
Explanation: ***Administering washed blood products***
- The patient's history of recurrent sinusitis and otitis suggests **IgA deficiency**, making him susceptible to anaphylactic reactions from IgA in transfused blood.
- **Washed blood products** remove plasma proteins, including IgA, preventing such reactions in IgA-deficient individuals.
*Administering IVIG with transfusion*
- **IVIG** contains IgA and could potentially worsen an IgA-mediated anaphylactic reaction in an IgA-deficient patient.
- It is used to supplement antibodies in immunodeficiency, but not to prevent allergic reactions to blood products in this context.
*Pre-transfusion diphenhydramine*
- **Diphenhydramine**, an antihistamine, can alleviate mild allergic reactions but is insufficient to prevent or treat life-threatening anaphylaxis.
- It does not remove the offending allergen (IgA) from the blood product.
*Pre-transfusion acetaminophen*
- **Acetaminophen** is an antipyretic and analgesic, used to manage fever or pain.
- It has no role in preventing allergic or anaphylactic transfusion reactions mediated by IgA.
*Administering type-specific blood*
- While essential for preventing **hemolytic transfusion reactions** due to ABO incompatibility, type-specific blood does not address reactions to plasma proteins like IgA.
- The patient's reaction is an **anaphylactic response**, not a hemolytic one.
Question 557: A 47-year-old woman presents to her physician for a routine checkup. She is in good health and has no complaints. Past medical history is significant for type 2 diabetes mellitus and obesity. She recently started metformin and is tolerating the mild side effects, but her fasting blood glucose levels range from 160–190 mg/dL. Today, her blood pressure is 125/82 mm Hg, the heart rate is 90/min, the respiratory rate is 17/min, and the temperature is 37.0°C (98.6°F). On physical exam, she appears well developed and obese. Her heart has a regular rate and rhythm and her lungs are clear to auscultation bilaterally. Her fasting glucose level is 175 mg/dL and her A1c is 7.1%. Her physician decides to add canagliflozin to her current treatment regimen. Which of the following should be evaluated before starting this medication?
A. Atrial natriuretic peptide
B. Alanine aminotransferase
C. Serum creatinine (Correct Answer)
D. β-hCG levels
E. γ-glutamyltransferase
Explanation: ***Serum creatinine***
- Canagliflozin is an **SGLT2 inhibitor**, which acts by blocking glucose reabsorption in the **renal tubules**, leading to glucose excretion in the urine.
- Due to its renal mechanism of action, it is crucial to assess **kidney function** via serum creatinine (and thus eGFR) before starting canagliflozin to ensure it can be safely and effectively used.
- SGLT2 inhibitors are **less effective** when eGFR is reduced and carry increased risk of adverse effects including volume depletion and acute kidney injury.
*Atrial natriuretic peptide*
- This is a hormone primarily released from the atria in response to stretch, indicating **volume overload** or **heart failure**.
- While heart failure can be a comorbidity in diabetes, ANP levels are **not a prerequisite screening test** for initiating SGLT2 inhibitors.
*Alanine aminotransferase*
- **ALT is a liver enzyme** used to assess liver function and detect liver injury.
- While liver function is important for overall health, it is **not a primary consideration** for initiating SGLT2 inhibitors, as these drugs are primarily renally cleared and do not typically cause hepatotoxicity.
*β-hCG levels*
- **β-human chorionic gonadotropin** is a hormone measured to detect **pregnancy**.
- While SGLT2 inhibitors should be avoided in pregnancy and β-hCG testing may be appropriate for women of childbearing age, it is **not the standard required pre-treatment test** for canagliflozin.
- The **primary mandatory assessment** before initiating this drug class is **renal function**, not pregnancy testing.
*γ-glutamyltransferase*
- **GGT is an enzyme** found in the liver, bile ducts, and kidneys, often used as a marker for **cholestasis** or alcohol abuse.
- It is **not a standard or necessary test** to evaluate before starting an SGLT2 inhibitor like canagliflozin.
Question 558: A 75-year-old male is diagnosed with advanced metastatic prostate cancer. After further evaluation and staging, the patient is started on flutamide therapy. Addition of which of the following medications to this patient’s medication regimen would be of greatest benefit in the treatment of this patient’s condition?
A. Leuprolide (Correct Answer)
B. Anastrozole
C. Tamoxifen
D. Clomiphene
E. Cyproterone
Explanation: ***Leuprolide***
- **Leuprolide** is a **GnRH agonist** that initially stimulates but then downregulates GnRH receptors, leading to decreased LH and FSH secretion and thus reduced **testosterone production** by the testes.
- Combining leuprolide with flutamide (an **androgen receptor blocker**) provides **maximal androgen blockade (MAB)**, which is the most effective initial hormonal therapy for advanced prostate cancer by blocking both testicular and adrenal androgen effects.
*Anastrozole*
- **Anastrozole** is an **aromatase inhibitor** used primarily in **postmenopausal women with estrogen-receptor-positive breast cancer** by blocking estrogen synthesis.
- It is not indicated for prostate cancer, which is driven by androgens, not estrogens.
*Tamoxifen*
- **Tamoxifen** is a **selective estrogen receptor modulator (SERM)** used primarily in the treatment and prevention of **estrogen-receptor-positive breast cancer**.
- It works by blocking estrogen's effects on breast tissue and has no direct role in the treatment of androgen-dependent prostate cancer.
*Clomiphene*
- **Clomiphene** is a **SERM** used to induce ovulation in women with **anovulatory infertility** by blocking estrogen receptors in the hypothalamus, leading to increased GnRH, FSH, and LH release.
- It would actually increase testosterone levels in men by stimulating LH release, which is counterproductive in prostate cancer treatment.
*Cyproterone*
- **Cyproterone** is an **androgen receptor antagonist** and a progestin, which can reduce androgen production and block androgen receptors.
- While it's an antiandrogen and could theoretically be used, flutamide is already an androgen receptor blocker, and the question asks for the "greatest benefit" addition, which points to **GnRH agonism** for maximal androgen blockade.
Question 559: A 27-year-old man is brought to the emergency department because of weakness, headache, and vomiting for 40 minutes. He is an amateur chef and his symptoms started 10 minutes after he ingested pufferfish that he had prepared. On arrival, he is lethargic. His temperature is 37°C (98.6°F), pulse is 120/min, respirations are 8/min, and blood pressure is 92/64 mm Hg. He is intubated and mechanical ventilation is begun. Intravenous fluid resuscitation is started. The cause of this patient's condition exerts its effect by which of the following mechanisms of action?
A. Increase in cell membrane permeability to chloride ions
B. Decrease in cell membrane permeability to potassium ions
C. Increase in cell membrane permeability to calcium ions
D. Decrease in cell membrane permeability to sodium ions (Correct Answer)
E. Decrease in cell membrane permeability to calcium ions
Explanation: **Decrease in cell membrane permeability to sodium ions**
- **Tetrodotoxin (TTX)**, found in pufferfish, is a potent neurotoxin that specifically blocks **voltage-gated sodium channels**, preventing sodium influx and inhibiting nerve impulse transmission.
- This blockage leads to **paralysis of respiratory muscles**, hypotension, and loss of reflexes, explaining the patient's respiratory depression, weakness, and hypotension.
*Increase in cell membrane permeability to chloride ions*
- This mechanism is characteristic of neurotransmitters like **gamma-aminobutyric acid (GABA)**, which cause hyperpolarization and inhibition through chloride influx.
- It does not explain the widespread neurological and muscular paralysis seen in tetrodotoxin poisoning.
*Decrease in cell membrane permeability to potassium ions*
- This effect would primarily lead to **prolonged repolarization** and increased excitability of nerve and muscle cells, which is not consistent with the symptoms of weakness and paralysis.
- Toxins affecting potassium channels typically cause different clinical presentations, such as certain forms of cardiac arrhythmias or neurological hyperexcitability.
*Increase in cell membrane permeability to calcium ions*
- An increase in calcium permeability is usually associated with **muscle contraction** or **neurotransmitter release**, not the flaccid paralysis and respiratory depression observed.
- Certain venom neurotoxins might target calcium channels, but their effects are distinct from those of tetrodotoxin.
*Decrease in cell membrane permeability to calcium ions*
- While some toxins can block calcium channels (e.g., conotoxins), a decrease in calcium permeability would generally lead to reduced neurotransmitter release and weakened muscle contraction.
- However, the primary and most rapid mechanism explaining the acute, severe neurotoxicity of pufferfish poisoning is the blockage of sodium channels, leading to widespread nerve conduction failure.
Question 560: A 63-year-old woman comes to the physician for a follow-up examination. She has had numbness and burning sensation in her feet for 4 months. The pain is worse at rest and while sleeping. She has hypercholesterolemia and type 2 diabetes mellitus. Current medications include insulin, metformin, and atorvastatin. She has smoked one pack of cigarettes daily for 33 years. Her temperature is 37°C (98.6°F), pulse is 88/min, and blood pressure is 124/88 mm Hg. Examination shows full muscle strength and normal muscle tone in all extremities. Sensation to pinprick, light touch, and vibration is decreased over the soles of both feet. Ankle jerk is 1+ bilaterally. Biceps and triceps reflexes are 2+ bilaterally. Babinski sign is negative bilaterally. Laboratory studies show:
Hemoglobin 11.2 g/dL
Mean corpuscular volume 93 μm3
Hemoglobin A1C 8.2 %
Serum
Glucose 188 mg/dL
Which of the following is the most appropriate next step in management?
A. Vitamin B12 therapy
B. Venlafaxine therapy
C. Ankle-brachial index
D. MRI with contrast of the spine
E. Nerve conduction studies (Correct Answer)
Explanation: **Nerve conduction studies**
- Given the patient's **numbness** and **burning sensation** in her feet, decreased sensation, and the chronicity of symptoms, **nerve conduction studies** are the most appropriate next step to assess for **peripheral neuropathy** and determine its type and severity.
- This diagnostic test directly evaluates the function of peripheral nerves, helping to confirm the diagnosis of neuropathy and differentiate it from other conditions.
*Vitamin B12 therapy*
- While **vitamin B12 deficiency** can cause neuropathy and her hemoglobin is low, her **mean corpuscular volume (MCV)** is normal, making **macrocytic anemia** (typical for B12 deficiency) less likely.
- Although B12 levels could be checked, starting therapy empirically without direct evidence is not the most appropriate immediate next step given the clear neuropathy symptoms.
*Venlafaxine therapy*
- **Venlafaxine** is an antidepressant that can be used to treat **neuropathic pain**; however, it is a treatment modality, not a diagnostic step.
- An accurate diagnosis of the underlying cause and type of neuropathy should ideally precede the initiation of specific symptomatic treatment.
*Ankle-brachial index*
- An **ankle-brachial index** (ABI) is used to assess for **peripheral artery disease (PAD)**, which can also cause lower extremity symptoms.
- While PAD is common in patients with diabetes and smoking history, the patient's primary symptoms of **numbness** and **burning sensation**, along with decreased sensation, are more indicative of neuropathy than ischemia.
*MRI with contrast of the spine*
- An **MRI of the spine** would be indicated if there were focal neurological deficits, signs of **radiculopathy**, or suspicion of a **spinal cord lesion** (e.g., myelopathy).
- The patient's symptoms are distributed bilaterally in the feet, suggesting a diffuse peripheral process rather than a compressive spinal lesion.