A 19-year-old woman comes to the physician because of a delayed menstrual period. She has had regular menses since menarche at age 11. Her last menstrual period was 7 weeks ago. She is sexually active with two male partners. A urine pregnancy test is positive. An ultrasound of the pelvis shows a viable intrauterine pregnancy with an estimated gestational age of 6 weeks and 5 days. She does not wish to continue with the pregnancy. After carefully weighing the options with her physician, she is prescribed two medications, one of which is mifepristone. Which of the following is this drug's primary mechanism of action?
Q842
A 28-year-old woman visits the clinic expressing a desire to become pregnant. She was seen for depressed mood and disinterest in her usual leisure activities a few months ago. She also had decreased sleep and appetite and was not able to concentrate at work. She was started on fluoxetine and has been compliant for the last 6 months despite experiencing some of the side effects. She now feels significantly better and would like to stop the medication because she plans to become pregnant and thinks it is unnecessary now. Which of the following is the most appropriate counseling regarding her antidepressant therapy?
Q843
A 52-year-old woman makes a follow-up appointment with her primary care physician for evaluation of her diabetes medications. Specifically, she complains that she has been experiencing flushing, nausea, and palpitations after drinking a glass of wine with dinner after she started the latest regimen for her diabetes. She was warned that this was a side-effect of one of her medications but she did not understand the severity of the reaction. Given this experience, she asks to be placed on an alternative regimen that does not involve the medication that caused this reaction. Her physician therefore replaces the medication with another one that interacts with the same target though at a different binding site. Which of the following is a side-effect of the new medication?
Q844
Eight days after sigmoid resection for acute diverticulitis, a 61-year-old man has left-sided flank pain. He has been on bowel rest since admission. Other than multiple admissions for alcohol withdrawal, he has no history of serious illness. Current medications include intravenous cefepime and morphine. His temperature is 36.9°C (98.4°F), pulse is 89/min, and blood pressure is 118/75 mm Hg. Abdominal exam shows a well-healing incision with minimal serous drainage. Examination of the skin shows scattered spider angiomas, a large hematoma on the left flank, and numerous bruises over the abdomen and extremities. He complains of pain when his left hip is extended. Laboratory studies show:
Hemoglobin 8.4 g/dL
Mean corpuscular volume 102 μm3
Leukocyte count 8,200/mm3
Platelet count 170,000/mm3
Serum
Bleeding time 4 minutes
Prothrombin time 26 seconds
Partial thromboplastin time (activated) 39 seconds
Which of the following is the most likely underlying cause of this patient's current symptoms?
Q845
A 72-year-old patient is referred to an ophthalmologist because he has noticed some mild discomfort in his eyes though his vision remains unchanged. He cannot recall when this feeling started. His past medical history is significant for diabetes mellitus and two myocardial infarctions that have led to significant cardiac dysfunction. Specifically, he has dyspnea and peripheral edema and occasionally decompensates into more severe pulmonary edema requiring hospitalization. Testing reveals increased intra-ocular pressure so the ophthalmologist prescribes several medications. The medication for this disorder that is most likely to be contraindicated in this patient has which of the following characteristics?
Q846
A 25-year-old Caucasian female presents with symptoms of Graves' disease. Her doctor prescribes medications and sends the patient home. After two months of therapy, the patient returns upset that her exophthalmos has not gone away. Which of the following drugs should the physician have prescribed to treat the exophthalmos?
Q847
A 23-year-old college student presents with his parents for a follow-up appointment. He was recently diagnosed with schizophrenia and was started on risperidone approx. 2 months ago. He reports a significant improvement since the start of treatment. His parents report that their son’s symptoms of delusions, hallucinations, and paranoid behavior have been ameliorated. On physical examination, the patient seems uncomfortable. He frequently fidgets and repeatedly crosses and uncrosses his legs. When asked if something is troubling him, he gets up and starts pacing. He says, “It’s always like this. I cannot sit still. It is frustrating.” What is the most likely diagnosis?
Q848
Scientists are developing a new non-steroidal anti-inflammatory drug for osteoarthritis. Their hope is that the new drug will have a higher potency but the same efficacy as ibuprofen in the hope of minimizing gastrointestinal side effects. If ibuprofen is curve C in the figure provided, which of the following would be the curve for the new drug based on the scientists’ specifications? The desired therapeutic effect in patients is represented by the dashed line Y.
Q849
A 46-year-old female is brought to the emergency department by her husband 1 hour after the onset of chest palpitations. Her symptoms began suddenly while she was drinking coffee and have persisted since then. She has not had shortness of breath, chest pain, dizziness, or loss of consciousness. She has experienced these palpitations before, but they typically resolve spontaneously within a few minutes. She has no history of serious illness and takes no medications. Her temperature is 36.8°C (98.2°F), pulse is 155/min, respirations are 18/min, and blood pressure is 130/82 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 97%. Physical examination shows no abnormalities other than tachycardia. An ECG is shown. Repeated, forceful exhalation against a closed glottis while supine fails to relieve her symptoms. Which of the following is the most appropriate next step in management?
Q850
A 5-year-old boy is brought to the emergency department by his parents with complaints of severe muscle cramping and abdominal pain. They live in Virginia. The parents state that about 2 hours before, the child was playing in their outdoor shed when he suddenly ran inside crying, saying he was bitten by a bug. One hour following the bite, the child developed the symptoms of cramping and pain. He has no known medical history and takes no medications. His blood pressure is 132/86 mm Hg, the heart rate is 116/min, and the respiratory rate is 20/min. Vital signs reveal tachycardia and hypertension. On exam, there is a 1 cm area of erythema to the dorsum of his right hand without any further dermatologic findings. Palpation of his abdomen reveals firm rigidity but no discernable rebound tenderness. What arthropod is most likely responsible for his symptoms?
Autonomic/CV Drugs US Medical PG Practice Questions and MCQs
Question 841: A 19-year-old woman comes to the physician because of a delayed menstrual period. She has had regular menses since menarche at age 11. Her last menstrual period was 7 weeks ago. She is sexually active with two male partners. A urine pregnancy test is positive. An ultrasound of the pelvis shows a viable intrauterine pregnancy with an estimated gestational age of 6 weeks and 5 days. She does not wish to continue with the pregnancy. After carefully weighing the options with her physician, she is prescribed two medications, one of which is mifepristone. Which of the following is this drug's primary mechanism of action?
A. Activation of prostaglandin E1 receptors
B. Inhibition of dihydrofolate reductase
C. Blockage of progesterone receptor (Correct Answer)
D. Agonist at oxytocin receptors
E. Antagonist at gonadotropin-releasing hormone receptors
Explanation: ***Blockage of progesterone receptor***
- **Mifepristone** is a **progesterone receptor antagonist**, meaning it blocks the action of progesterone.
- Progesterone is essential for maintaining early pregnancy by supporting the **endometrium** and preventing uterine contractions.
*Activation of prostaglandin E1 receptors*
- This is the primary mechanism of action for **misoprostol**, the second medication often used in medical abortion protocols.
- **Misoprostol** causes **uterine contractions** and cervical ripening, which expels the uterine contents after mifepristone has prepared the uterus.
*Inhibition of dihydrofolate reductase*
- This is the mechanism of action for **methotrexate**, an antifolate drug that can also be used for medical abortion.
- **Methotrexate** inhibits DNA synthesis in rapidly dividing cells, leading to the termination of the pregnancy.
*Agonist at oxytocin receptors*
- **Oxytocin agonists** (like oxytocin itself) are typically used for labor induction or to control postpartum hemorrhage, not for early medical abortion.
- They cause strong uterine contractions but are usually administered later in pregnancy or postpartum.
*Antagonist at gonadotropin-releasing hormone receptors*
- **GnRH antagonists** (e.g., cetrorelix, ganirelix) are used in assisted reproductive technologies to prevent premature ovulation.
- They do not directly cause medical abortion by blocking progesterone's action or directly inducing uterine contractions.
Question 842: A 28-year-old woman visits the clinic expressing a desire to become pregnant. She was seen for depressed mood and disinterest in her usual leisure activities a few months ago. She also had decreased sleep and appetite and was not able to concentrate at work. She was started on fluoxetine and has been compliant for the last 6 months despite experiencing some of the side effects. She now feels significantly better and would like to stop the medication because she plans to become pregnant and thinks it is unnecessary now. Which of the following is the most appropriate counseling regarding her antidepressant therapy?
A. It requires careful risk-benefit analysis during pregnancy. (Correct Answer)
B. Most side effects persist throughout therapy.
C. It has the longest half-life of any drugs in the same class.
D. It can cause anorgasmia.
E. It can increase levels of concurrent medications metabolized by CYP2D6.
Explanation: ***It requires careful risk-benefit analysis during pregnancy.***
- This is the **most appropriate counseling** for this patient who wants to discontinue fluoxetine due to pregnancy planning.
- The decision to continue or discontinue **fluoxetine** during pregnancy involves weighing the risks of medication exposure to the fetus against the risks of **untreated maternal depression**, such as preterm birth, low birth weight, poor prenatal care, and postpartum depression.
- **Abrupt discontinuation** in a patient who has responded well increases the risk of depression relapse, which can be harmful during pregnancy.
- While fluoxetine is **FDA Pregnancy Category C**, it is generally considered one of the safer SSRIs for use in pregnancy when clinically indicated, with an individualized **risk-benefit discussion** being crucial.
*Most side effects persist throughout therapy.*
- Many common **side effects** of fluoxetine, such as nausea, insomnia, and anxiety, are often **transient** and tend to diminish within the first few weeks of therapy as the body adjusts.
- While some side effects, such as sexual dysfunction, may persist, most side effects do not endure throughout the entire course of treatment.
- This statement is **not the most relevant** counseling for a patient planning pregnancy.
*It has the longest half-life of any drugs in the same class.*
- **Fluoxetine** does have the longest half-life among SSRIs: approximately **2-4 days** for the parent compound and **7-15 days** for its active metabolite, **norfluoxetine**.
- While this is a **true statement** and has clinical implications (reduced withdrawal symptoms, less need for tapering), it is **not the most appropriate counseling** for this patient's specific concern about pregnancy planning.
*It can cause anorgasmia.*
- **Sexual dysfunction**, including **decreased libido**, **delayed orgasm**, and **anorgasmia**, is a common side effect of SSRIs like fluoxetine, occurring in 30-60% of patients.
- While this is a **true statement** about fluoxetine, it does not address the patient's primary concern about pregnancy planning and is therefore **not the most appropriate counseling** in this context.
*It can increase levels of concurrent medications metabolized by CYP2D6.*
- **Fluoxetine** is a **potent inhibitor** of the **CYP2D6 enzyme**, which can increase plasma levels of other drugs metabolized by this pathway (e.g., tricyclic antidepressants, beta-blockers, antiarrhythmics, antipsychotics).
- While this is a **true and clinically important statement**, it is **not the most relevant counseling** for this patient who is planning pregnancy and considering discontinuation.
Question 843: A 52-year-old woman makes a follow-up appointment with her primary care physician for evaluation of her diabetes medications. Specifically, she complains that she has been experiencing flushing, nausea, and palpitations after drinking a glass of wine with dinner after she started the latest regimen for her diabetes. She was warned that this was a side-effect of one of her medications but she did not understand the severity of the reaction. Given this experience, she asks to be placed on an alternative regimen that does not involve the medication that caused this reaction. Her physician therefore replaces the medication with another one that interacts with the same target though at a different binding site. Which of the following is a side-effect of the new medication?
A. Hepatotoxicity
B. Pancreatitis
C. Weight gain (Correct Answer)
D. Lactic acidosis
E. Urinary tract infection
Explanation: ***Weight gain***
- The patient experienced a **disulfiram-like reaction** with alcohol, indicative of a **sulfonylurea** medication like glipizide or glyburide. The physician replaces it with another medication that interacts with the same target (sulfonylurea receptor on pancreatic beta cells) but at a different binding site, which describes a **meglitinide (e.g., repaglinide)**.
- **Weight gain** is a common side effect of meglitinides, similar to sulfonylureas, due to increased insulin secretion.
*Hepatotoxicity*
- While some diabetes medications can affect the liver, **hepatotoxicity** is not a primary or common side effect associated with meglitinides.
- Pioglitazone, for instance, has a black box warning for liver failure, but is not the drug class described.
*Pancreatitis*
- **Pancreatitis** is not a characteristic side effect of meglitinides.
- This adverse effect is more commonly associated with GLP-1 receptor agonists (e.g., exenatide, liraglutide) and DPP-4 inhibitors (e.g., sitagliptin).
*Lactic acidosis*
- **Lactic acidosis** is a rare but serious side effect specifically associated with **metformin**, especially in patients with renal impairment or conditions causing tissue hypoxia.
- This side effect is not seen with meglitinides.
*Urinary tract infection*
- **Urinary tract infections (UTIs)** are a common side effect of **SGLT2 inhibitors** (e.g., canagliflozin, empagliflozin) due to increased glucose excretion in the urine which promotes bacterial growth.
- This is not a typical side effect of meglitinides.
Question 844: Eight days after sigmoid resection for acute diverticulitis, a 61-year-old man has left-sided flank pain. He has been on bowel rest since admission. Other than multiple admissions for alcohol withdrawal, he has no history of serious illness. Current medications include intravenous cefepime and morphine. His temperature is 36.9°C (98.4°F), pulse is 89/min, and blood pressure is 118/75 mm Hg. Abdominal exam shows a well-healing incision with minimal serous drainage. Examination of the skin shows scattered spider angiomas, a large hematoma on the left flank, and numerous bruises over the abdomen and extremities. He complains of pain when his left hip is extended. Laboratory studies show:
Hemoglobin 8.4 g/dL
Mean corpuscular volume 102 μm3
Leukocyte count 8,200/mm3
Platelet count 170,000/mm3
Serum
Bleeding time 4 minutes
Prothrombin time 26 seconds
Partial thromboplastin time (activated) 39 seconds
Which of the following is the most likely underlying cause of this patient's current symptoms?
A. Deficiency of folic acid
B. Decreased synthesis of thrombopoietin
C. Resistance of Factor V inactivation
D. Vitamin K deficiency (Correct Answer)
E. Administration of heparin
Explanation: ***Vitamin K deficiency***
- The patient's several signs of **coagulopathy** (large hematoma, numerous bruises, prolonged PT, slightly prolonged aPTT) following a surgery and bowel rest, coupled with a history of **alcohol abuse** and current antibiotic use (cefepime), strongly suggest vitamin K deficiency. Alcoholism causes **malnutrition** and impaired hepatic storage of vitamin K, while antibiotics like cefepime can reduce gut flora responsible for vitamin K synthesis.
- **Vitamin K** is essential for the synthesis of coagulation factors II, VII, IX, and X, as well as proteins C and S. Deficiency leads to impaired clotting and an increased **PT** (due to factor VII's short half-life and dependence on extrinsic pathway), and later a prolonged **aPTT**. The left-sided flank pain exacerbated by hip extension suggests a **retroperitoneal hematoma**, possibly involving the psoas muscle, a common complication of bleeding disorders.
*Deficiency of folic acid*
- **Folic acid deficiency** primarily causes **macrocytic anemia** (elevated MCV), which is present here. However, it does not directly explain the coagulation abnormalities such as prolonged PT and easy bruising.
- While folic acid deficiency can coexist with vitamin K deficiency in malnutrition, it is not the direct cause of the **bleeding diathesis**.
*Decreased synthesis of thrombopoietin*
- **Thrombopoietin** regulates platelet production. Decreased synthesis would lead to **thrombocytopenia** (low platelet count).
- This patient's platelet count of 170,000/mm³ is within the normal range, indicating that thrombopoietin synthesis is likely adequate and not the cause of his symptoms.
*Resistance of Factor V inactivation*
- **Resistance to activated protein C (Factor V Leiden mutation)** is a common cause of **thrombophilia** (increased clotting risk), not a bleeding disorder.
- This condition would lead to a tendency for **thrombosis**, rather than the hematoma and bruising seen in this patient.
*Administration of heparin*
- **Heparin** prolongs the **aPTT** significantly more than the PT, which is inconsistent with the patient's lab values where PT is markedly prolonged.
- While heparin can cause bleeding complications, the pattern of **coagulation derangement** and the strong predisposing factors for vitamin K deficiency make it a less likely primary diagnosis.
Question 845: A 72-year-old patient is referred to an ophthalmologist because he has noticed some mild discomfort in his eyes though his vision remains unchanged. He cannot recall when this feeling started. His past medical history is significant for diabetes mellitus and two myocardial infarctions that have led to significant cardiac dysfunction. Specifically, he has dyspnea and peripheral edema and occasionally decompensates into more severe pulmonary edema requiring hospitalization. Testing reveals increased intra-ocular pressure so the ophthalmologist prescribes several medications. The medication for this disorder that is most likely to be contraindicated in this patient has which of the following characteristics?
A. It increases adenylyl cyclase activity
B. It alters bicarbonate metabolism
C. It decreases intracellular cyclic AMP levels (Correct Answer)
D. It increases intracellular calcium levels
E. It is produced by cyclooxygenase
Explanation: ***It decreases intracellular cyclic AMP levels***
- This describes **beta-blockers** (e.g., timolol, betaxolol), which decrease intraocular pressure by reducing aqueous humor production through beta-adrenergic receptor blockade.
- Beta-blockers are **contraindicated in patients with cardiac dysfunction** and heart failure due to their negative inotropic and chronotropic effects, which can exacerbate the patient's existing heart condition and precipitate acute decompensation.
*It increases adenylyl cyclase activity*
- This mechanism does not accurately describe any major class of glaucoma medications.
- **Alpha-2 adrenergic agonists** (e.g., brimonidine) actually *decrease* adenylyl cyclase activity (Gi-coupled) and reduce aqueous humor production.
- **Prostaglandin analogs** (e.g., latanoprost) work through FP receptors to increase uveoscleral outflow, not through adenylyl cyclase.
- Both drug classes are generally safe in patients with cardiac dysfunction.
*It alters bicarbonate metabolism*
- This describes **carbonic anhydrase inhibitors** (e.g., acetazolamide, dorzolamide), which reduce aqueous humor production by inhibiting bicarbonate formation in the ciliary body.
- While they can cause systemic electrolyte imbalances and are contraindicated in patients with sulfa allergy or severe renal dysfunction, they are generally not contraindicated in cardiac dysfunction.
*It increases intracellular calcium levels*
- This mechanism is not associated with any class of glaucoma medications.
- Medications that increase intracellular calcium would theoretically worsen cardiac contractility issues, but such agents are not used for glaucoma treatment.
*It is produced by cyclooxygenase*
- **Prostaglandin analogs** (e.g., latanoprost, bimatoprost) are used for glaucoma, but the therapeutic agents are *synthetic analogs*, not naturally produced by cyclooxygenase.
- These medications increase uveoscleral outflow and are first-line treatments for glaucoma with minimal systemic cardiovascular effects, making them safe in cardiac patients.
Question 846: A 25-year-old Caucasian female presents with symptoms of Graves' disease. Her doctor prescribes medications and sends the patient home. After two months of therapy, the patient returns upset that her exophthalmos has not gone away. Which of the following drugs should the physician have prescribed to treat the exophthalmos?
A. Corticosteroids (Correct Answer)
B. PTU
C. No treatment as this will resolve naturally
D. Propranolol
E. Metoprolol
Explanation: ***Corticosteroids***
- **Corticosteroids** are the first-line medical treatment for **Graves' ophthalmopathy** (exophthalmos), as they reduce the inflammation and swelling behind the eyes.
- They work by suppressing the immune response that targets the **orbital fibroblasts and muscles**, leading to orbital tissue expansion.
*PTU*
- **Propylthiouracil (PTU)** is an **antithyroid drug** used to treat hyperthyroidism by inhibiting thyroid hormone synthesis.
- While it addresses the systemic symptoms of Graves' disease, it does **not directly treat the exophthalmos**, which is an immune-mediated orbital disease.
*No treatment as this will resolve naturally*
- **Graves' ophthalmopathy** can progress and cause significant vision impairment if left untreated, and it often does not resolve naturally.
- Early intervention, especially with inflammation-reducing agents, is crucial to prevent irreversible changes and protect ocular health.
*Propranolol*
- **Propranolol** is a **beta-blocker** used to manage the adrenergic symptoms of hyperthyroidism, such as palpitations, tremor, and anxiety.
- It does not address the underlying autoimmune inflammation responsible for exophthalmos.
*Metoprolol*
- **Metoprolol** is another **beta-blocker** primarily used for cardiovascular conditions and to control hyperthyroid symptoms like **tachycardia**.
- Similar to other beta-blockers, it has no therapeutic effect on the inflammation or progression of Graves' ophthalmopathy.
Question 847: A 23-year-old college student presents with his parents for a follow-up appointment. He was recently diagnosed with schizophrenia and was started on risperidone approx. 2 months ago. He reports a significant improvement since the start of treatment. His parents report that their son’s symptoms of delusions, hallucinations, and paranoid behavior have been ameliorated. On physical examination, the patient seems uncomfortable. He frequently fidgets and repeatedly crosses and uncrosses his legs. When asked if something is troubling him, he gets up and starts pacing. He says, “It’s always like this. I cannot sit still. It is frustrating.” What is the most likely diagnosis?
A. Generalized anxiety disorder
B. Tardive dyskinesia
C. Ataxia
D. Akathisia (Correct Answer)
E. Restless legs syndrome
Explanation: ***Akathisia***
- This patient presents with **motor restlessness** (fidgeting, pacing, inability to sit still) that emerged after starting an antipsychotic medication, risperidone. These are classic symptoms of **akathisia**, a medication side effect.
- The patient's verbalization, "I cannot sit still. It is frustrating," further supports the internal experience of restlessness characteristic of akathisia.
*Generalized anxiety disorder*
- While anxiety can cause restlessness, the specific description of physical agitation and the strong temporal relationship with starting a new antipsychotic make **akathisia** a more likely diagnosis.
- Generalized anxiety disorder typically involves chronic, excessive worry and is not primarily characterized by an irresistible urge to move.
*Tardive dyskinesia*
- Tardive dyskinesia involves **involuntary, repetitive body movements**, often in the face (e.g., grimacing, tongue protrusion) or limbs.
- It usually develops after **long-term use** of antipsychotics (months to years), whereas akathisia can occur shortly after initiation or dose changes.
*Ataxia*
- Ataxia refers to a lack of **voluntary coordination** of muscle movements, leading to an unsteady gait or impaired balance.
- The patient's symptoms are of restlessness and an uncontrollable urge to move, not a lack of coordination.
*Restless legs syndrome*
- Restless legs syndrome is characterized by an **uncomfortable sensation in the legs** with an urge to move them, typically worse at rest and relieved by movement.
- This patient's restlessness is more pervasive, involving whole-body agitation and an inability to simply sit still, not just an uncomfortable sensation primarily in the legs.
Question 848: Scientists are developing a new non-steroidal anti-inflammatory drug for osteoarthritis. Their hope is that the new drug will have a higher potency but the same efficacy as ibuprofen in the hope of minimizing gastrointestinal side effects. If ibuprofen is curve C in the figure provided, which of the following would be the curve for the new drug based on the scientists’ specifications? The desired therapeutic effect in patients is represented by the dashed line Y.
A. Curve B
B. Curve D
C. Curve C
D. Curve E
E. Curve A (Correct Answer)
Explanation: ***Curve A***
- A drug with **higher potency** will achieve its maximal effect at a lower concentration, shifting the curve to the **left** (from C to A).
- **Same efficacy** means the drug reaches the **same maximal effect** (height on the y-axis) as ibuprofen (curve C), which curve A does.
*Curve B*
- This curve represents a drug with **lower potency** than ibuprofen, as it requires a higher concentration to achieve its maximal effect, shifting the curve to the right.
- While it has the same efficacy, it does not meet the requirement of higher potency.
*Curve D*
- Curve D shows a drug with **higher potency** (shifted left) but **lower efficacy** (lower maximal effect) compared to ibuprofen.
- The scientists are looking for the same efficacy, not lower efficacy.
*Curve E*
- Curve E represents a drug with **lower efficacy** (lower maximal effect) than ibuprofen.
- It also appears to have lower potency as the curve is shifted to the right, failing both criteria.
*Curve C*
- This curve is ibuprofen itself, meaning there is no change in potency or efficacy.
- The new drug needs to have higher potency while maintaining the same efficacy as ibuprofen.
Question 849: A 46-year-old female is brought to the emergency department by her husband 1 hour after the onset of chest palpitations. Her symptoms began suddenly while she was drinking coffee and have persisted since then. She has not had shortness of breath, chest pain, dizziness, or loss of consciousness. She has experienced these palpitations before, but they typically resolve spontaneously within a few minutes. She has no history of serious illness and takes no medications. Her temperature is 36.8°C (98.2°F), pulse is 155/min, respirations are 18/min, and blood pressure is 130/82 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 97%. Physical examination shows no abnormalities other than tachycardia. An ECG is shown. Repeated, forceful exhalation against a closed glottis while supine fails to relieve her symptoms. Which of the following is the most appropriate next step in management?
A. Administer verapamil intravenously
B. Administer adenosine intravenously (Correct Answer)
C. Administer diltiazem intravenously
D. Electrical cardioversion
E. Administer digoxin intravenously
Explanation: **Administer adenosine intravenously**
- The patient has **supraventricular tachycardia (SVT)**, evidenced by sudden onset palpitations and a regular, fast heart rate (155/min) without other symptoms of hemodynamic instability. **Adenosine** is the first-line pharmacologic agent for stable SVT as it transiently blocks the AV node, allowing for termination of re-entrant pathways.
- Given that vagal maneuvers (forceful exhalation against a closed glottis) have failed and the patient is hemodynamically stable, intravenous **adenosine** is the next appropriate step to attempt rhythm conversion.
*Administer verapamil intravenously*
- **Verapamil** is a non-dihydropyridine calcium channel blocker that can slow AV nodal conduction and terminate SVT, but it is generally considered a second-line agent after adenosine, especially in patients with normal LV function.
- Its use can be associated with hypotension, and in this stable patient, **adenosine** is preferred due to its rapid onset and short half-life, allowing for easy titration and fewer sustained side effects.
*Administer diltiazem intravenously*
- **Diltiazem** is another non-dihydropyridine calcium channel blocker similar to verapamil, also used to slow AV nodal conduction and manage SVT.
- Like verapamil, it is typically used if **adenosine** is ineffective or contraindicated, or in a controlled setting for rate control rather than acute termination in stable SVT, making adenosine a more immediate and appropriate choice here.
*Electrical cardioversion*
- **Electrical cardioversion** is indicated for SVT when the patient is **hemodynamically unstable** (e.g., hypotension, altered mental status, signs of shock, acute heart failure, ischemic chest pain).
- This patient is **hemodynamically stable**, with a blood pressure of 130/82 mm Hg and no acute symptoms of instability, making pharmacologic interventions the initial preferred approach over electrical cardioversion.
*Administer digoxin intravenously*
- **Digoxin** is primarily used for **rate control in chronic atrial fibrillation** or **heart failure with reduced ejection fraction**, not for the acute termination of SVT.
- Its onset of action is slow, making it unsuitable for immediate termination of an acute episode of SVT, especially when rapid-acting agents like **adenosine** are available and indicated.
Question 850: A 5-year-old boy is brought to the emergency department by his parents with complaints of severe muscle cramping and abdominal pain. They live in Virginia. The parents state that about 2 hours before, the child was playing in their outdoor shed when he suddenly ran inside crying, saying he was bitten by a bug. One hour following the bite, the child developed the symptoms of cramping and pain. He has no known medical history and takes no medications. His blood pressure is 132/86 mm Hg, the heart rate is 116/min, and the respiratory rate is 20/min. Vital signs reveal tachycardia and hypertension. On exam, there is a 1 cm area of erythema to the dorsum of his right hand without any further dermatologic findings. Palpation of his abdomen reveals firm rigidity but no discernable rebound tenderness. What arthropod is most likely responsible for his symptoms?
A. Cryptopid centipede
B. Bark scorpion
C. Black widow (Correct Answer)
D. Brown recluse
E. Tick
Explanation: ***Black widow***
- The patient's symptoms, including **severe muscle cramping**, **abdominal pain**, **hypertension**, and **tachycardia**, are classic signs of **latrodectism** caused by a black widow spider bite.
- The location (shed in Virginia), rapid onset of symptoms (within 1-2 hours), and general systemic effects are highly consistent with this diagnosis.
*Cryptopid centipede*
- Bites from cryptopid centipedes typically cause **localized pain**, swelling, and erythema, but generally do not lead to the severe systemic symptoms of muscle cramping, abdominal rigidity, and autonomic instability described.
- While generally painful, their venom is not known to produce the neurotoxic effects seen with black widow spider envenomation.
*Bark scorpion*
- Bark scorpion stings (**Centruroides sculpturatus**) are primarily found in the **southwestern United States** (e.g., Arizona, New Mexico), making them unlikely in Virginia.
- While scorpions can cause severe pain and neurological symptoms, the geographical location and specific constellation of symptoms (especially significant muscle cramping and rigidity) point away from a bark scorpion sting.
*Brown recluse*
- Bites from a brown recluse spider (**Loxosceles reclusa**) are characterized by a **necrotic lesion** that develops over several days or weeks, often an **"_eschar_,"** which is not observed in this patient.
- Systemic symptoms are rare with brown recluse bites and typically only include fever, chills, and malaise, not the acute neurotoxic symptoms seen here.
*Tick*
- Tick bites are typically **painless** and can transmit various diseases, but they do not cause acute, severe muscle cramping and abdominal pain within hours of the bite.
- Some ticks can cause **tick paralysis**, which involves progressive *flaccid paralysis* rather than muscle rigidity and cramping, and usually takes days to develop after prolonged tick attachment.
