A 22-year-old woman presents to the emergency department because of agitation and sweating. History shows she is currently being treated for depression with citalopram. She also takes tramadol for back pain. Her temperature is 38.6°C (101.5°F), the pulse is 108/min, the respirations are 18/min, and the blood pressure is 165/110 mm Hg. Physical examination shows hyperreflexia and mild tremors in all 4 extremities. Which of the following should be used in the next step of management for this patient?
Q372
A 44-year-old man seeks evaluation at a clinic because he is experiencing a problem with his sexual health for the past month. He says he does not get erections like he used to, despite feeling the urge. In addition to heart failure, he has angina and hypertension. His regular oral medications include amlodipine, atorvastatin, nitroglycerin, spironolactone, and losartan. After a detailed evaluation of his current medications, it is concluded that he has drug-induced erectile dysfunction. Which one of the following medications may have caused this patient's symptom?
Q373
A 28-year-old man comes to the emergency department for an injury sustained while doing construction. Physical examination shows a long, deep, irregular laceration on the lateral aspect of the left forearm with exposed fascia. Prior to surgical repair of the injury, a brachial plexus block is performed using a local anesthetic. Shortly after the nerve block is performed, he complains of dizziness and then loses consciousness. His radial pulse is faint and a continuous cardiac monitor shows a heart rate of 24/min. Which of the following is the most likely mechanism of action of the anesthetic that was administered?
Q374
A 9-year-old boy is brought to the physician by his mother to establish care after moving to a new city. He lives at home with his mother and older brother. He was having trouble in school until he was started on ethosuximide by a previous physician; he is now performing well in school. This patient is undergoing treatment for a condition that most likely presented with which of the following symptoms?
Q375
A 41-year-old woman is brought to the emergency department by ambulance because of a sudden onset severe headache. On presentation, the patient also says that she is not able to see well. Physical examination shows ptosis of the right eye with a dilated pupil that is deviated inferiorly and laterally. Based on the clinical presentation, neurosurgery is immediately consulted and the patient is taken for an early trans-sphenoidal surgical decompression. Which of the following will also most likely need to be supplemented in this patient?
Q376
A 70-year-old female with a history of congestive heart failure presents to the emergency room with dyspnea. She reports progressive difficulty breathing which began when she ran out of her furosemide and lisinopril prescriptions 1-2 weeks ago. She states the dyspnea is worse at night and when lying down. She denies any fever, cough, or GI symptoms. Her medication list reveals she is also taking digoxin. Physical exam is significant for normal vital signs, crackles at both lung bases and 2+ pitting edema of both legs. The resident orders the medical student to place the head of the patient's bed at 30 degrees. Additionally, he writes orders for the patient to be given furosemide, morphine, nitrates, and oxygen. Which of the following should be checked before starting this medication regimen?
Q377
A 41-year-old woman comes to the emergency room because she has been taking phenelzine for a few years and her doctor warned her that she should not eat aged cheese while on the medication. That night, she unknowingly ate an appetizer at a friend's party that was filled with cheese. She is concerned and wants to make sure that everything is all right. What vital sign or blood test is the most important to monitor in this patient?
Q378
A 21-year-old college student comes to the physician for intermittent palpitations. She does not have chest pain or shortness of breath. The symptoms started 2 days ago, on the night after she came back to her dormitory after a 4-hour-long bus trip from home. A day ago, she went to a party with friends. The palpitations have gotten worse since then and occur more frequently. The patient has smoked 5 cigarettes daily for the past 3 years. She drinks 4–6 alcoholic beverages with friends once or twice a week and occasionally uses marijuana. She is sexually active with her boyfriend and takes oral contraceptive pills. She does not appear distressed. Her pulse is 100/min and irregular, blood pressure is 140/85 mm Hg, and respirations are at 25/min. Physical examination shows a fine tremor in both hands, warm extremities, and swollen lower legs. The lungs are clear to auscultation. An ECG is shown below. Which of the following is the most appropriate next step in management?
Q379
A 69-year-old woman comes to the clinic for an annual well exam. She reports no significant changes to her health except for an arm fracture 3 weeks ago while she was lifting some heavy bags. Her diabetes is well controlled with metformin. She reports some vaginal dryness that she manages with adequate lubrication. She denies any weight changes, fevers, chills, palpitations, nausea/vomiting, incontinence, or bowel changes. A dual-energy X-ray absorptiometry (DEXA) scan was done and demonstrated a T-score of -2.7. She was subsequently prescribed a selective estrogen receptor modulator, in addition to vitamin and weight-bearing exercises, for the management of her symptoms. What is the mechanism of action of the prescribed medication?
Q380
A 58-year-old man with a 10-year history of type 2 diabetes mellitus and hypertension comes to the physician for a routine examination. Current medications include metformin and captopril. His pulse is 84/min and blood pressure is 120/75 mm Hg. His hemoglobin A1c concentration is 9.5%. The physician adds repaglinide to his treatment regimen. The mechanism of action of this agent is most similar to that of which of the following drugs?
Autonomic/CV Drugs US Medical PG Practice Questions and MCQs
Question 371: A 22-year-old woman presents to the emergency department because of agitation and sweating. History shows she is currently being treated for depression with citalopram. She also takes tramadol for back pain. Her temperature is 38.6°C (101.5°F), the pulse is 108/min, the respirations are 18/min, and the blood pressure is 165/110 mm Hg. Physical examination shows hyperreflexia and mild tremors in all 4 extremities. Which of the following should be used in the next step of management for this patient?
A. Diazepam
B. Chlorpromazine
C. Cyproheptadine
D. Selegiline
E. Discontinue tramadol and citalopram (Correct Answer)
Explanation: ***Discontinue tramadol and citalopram***
- This patient presents with symptoms highly suggestive of **serotonin syndrome**, characterized by **agitation, sweating, hyperthermia, tachycardia, hypertension, hyperreflexia, and tremors**, stemming from the concomitant use of **citalopram (SSRI)** and **tramadol (serotonergic properties)**.
- The immediate priority in managing serotonin syndrome is to **discontinue all serotonergic agents** definitively, as continued exposure can worsen symptoms and lead to severe complications.
*Diazepam*
- While **benzodiazepines** like diazepam are often used to manage agitation and hyperreflexia in serotonin syndrome, they are **symptomatic treatments** and do not address the underlying cause.
- Their use would be **adjunctive to discontinuing the causative agents**, not the primary next step.
*Chlorpromazine*
- **Chlorpromazine** is an antipsychotic with **dopamine-blocking effects** and anticholinergic properties; it is **not indicated** for the treatment of serotonin syndrome.
- In fact, its use could **exacerbate certain symptoms** or lead to adverse effects due to its other pharmacological actions.
*Cyproheptadine*
- **Cyproheptadine** is a **serotonin antagonist** that can be used in some cases of severe serotonin syndrome to counteract the excessive serotonin activity.
- However, the **initial and most critical step** is to discontinue the offending medications before considering pharmacologic interventions like cyproheptadine, which is typically reserved for moderate to severe cases after initial drug cessation.
*Selegiline*
- **Selegiline** is a **monoamine oxidase B (MAO-B) inhibitor** that increases dopamine levels and, at higher doses, can also inhibit MAO-A, leading to increased serotonin.
- Administering another serotonergic agent would be **contraindicated** and potentially fatal in a patient experiencing serotonin syndrome.
Question 372: A 44-year-old man seeks evaluation at a clinic because he is experiencing a problem with his sexual health for the past month. He says he does not get erections like he used to, despite feeling the urge. In addition to heart failure, he has angina and hypertension. His regular oral medications include amlodipine, atorvastatin, nitroglycerin, spironolactone, and losartan. After a detailed evaluation of his current medications, it is concluded that he has drug-induced erectile dysfunction. Which one of the following medications may have caused this patient's symptom?
A. Atorvastatin
B. Amlodipine
C. Spironolactone (Correct Answer)
D. Losartan
E. Nitroglycerin
Explanation: ***Spironolactone***
- **Spironolactone** is a **potassium-sparing diuretic with anti-androgenic effects** and can cause **gynecomastia** and **erectile dysfunction** due to competitive inhibition at androgen receptors and inhibition of testosterone biosynthesis.
- The patient's history of **heart failure, angina, and hypertension** makes him susceptible to various medications, but spironolactone specifically targets hormonal pathways involved in sexual function.
*Atorvastatin*
- **Atorvastatin**, a **statin**, can rarely cause sexual dysfunction but is generally not a primary cause of erectile dysfunction.
- Its main roles are in **cholesterol reduction** and **cardiovascular risk prevention**.
*Amlodipine*
- **Amlodipine**, a **calcium channel blocker**, manages hypertension and angina by dilating blood vessels.
- It is **less likely to cause erectile dysfunction** compared to other antihypertensives like diuretics or beta-blockers.
*Losartan*
- **Losartan**, an **angiotensin receptor blocker (ARB)**, is used for hypertension and heart failure.
- ARBs are generally well-tolerated and have a **low incidence of erectile dysfunction** compared to other antihypertensive classes.
*Nitroglycerin*
- **Nitroglycerin** is a vasodilator used for angina and has **no direct association with erectile dysfunction**.
- Medications like sildenafil (Viagra) work via similar pathways (nitric oxide) and are used to treat erectile dysfunction.
Question 373: A 28-year-old man comes to the emergency department for an injury sustained while doing construction. Physical examination shows a long, deep, irregular laceration on the lateral aspect of the left forearm with exposed fascia. Prior to surgical repair of the injury, a brachial plexus block is performed using a local anesthetic. Shortly after the nerve block is performed, he complains of dizziness and then loses consciousness. His radial pulse is faint and a continuous cardiac monitor shows a heart rate of 24/min. Which of the following is the most likely mechanism of action of the anesthetic that was administered?
A. Activation of acetylcholine receptors
B. Inactivation of ryanodine receptors
C. Inactivation of sodium channels (Correct Answer)
D. Activation of GABA receptors
E. Inactivation of potassium channels
Explanation: ***Inactivation of sodium channels***
- Local anesthetics primarily work by reversibly blocking **voltage-gated sodium channels** in nerves.
- This prevents the influx of sodium ions, inhibiting the generation and propagation of **action potentials**, thus blocking pain signals.
- The clinical presentation of dizziness, loss of consciousness, and bradycardia represents systemic toxicity from intravascular absorption of the local anesthetic.
*Activation of acetylcholine receptors*
- Activation of **nicotinic or muscarinic acetylcholine receptors** is the primary mechanism of action for neuromuscular stimulants or parasympathomimetics, not local anesthetics.
- This would typically lead to muscle contraction or increased parasympathetic activity rather than analgesia and local nerve block.
*Inactivation of ryanodine receptors*
- Inactivation of **ryanodine receptors** primarily affects calcium release from the sarcoplasmic reticulum in muscle cells, crucial for excitation-contraction coupling.
- This mechanism is associated with drugs like dantrolene used for malignant hyperthermia, not local anesthetics.
*Activation of GABA receptors*
- Activation of **GABA-A receptors** is the primary mechanism of action for benzodiazepines and barbiturates, leading to widespread CNS depression and sedation.
- While systemic absorption of local anesthetics can cause CNS effects (as seen in toxicity), their primary therapeutic mechanism for nerve block is sodium channel inactivation, not GABA receptor activation.
*Inactivation of potassium channels*
- Inactivation of **potassium channels** would typically prolong repolarization and increase neuronal excitability or cause arrhythmias, depending on the specific channel.
- This is not the mechanism of action for local anesthetics, which prevent depolarization by blocking sodium channel activation.
Question 374: A 9-year-old boy is brought to the physician by his mother to establish care after moving to a new city. He lives at home with his mother and older brother. He was having trouble in school until he was started on ethosuximide by a previous physician; he is now performing well in school. This patient is undergoing treatment for a condition that most likely presented with which of the following symptoms?
A. Recurrent motor tics and involuntary obscene speech
B. Episodic jerky movements of the arm and impaired consciousness
C. Overwhelming daytime sleepiness and hypnagogic hallucinations
D. Frequent episodes of blank staring and eye fluttering (Correct Answer)
E. Limited attention span and poor impulse control
Explanation: ***Frequent episodes of blank staring and eye fluttering***
- The patient is taking **ethosuximide**, which is a primary treatment for **absence seizures**.
- **Absence seizures** typically present as brief episodes of **blank staring**, unresponsiveness, and sometimes **eye fluttering**, often mistaken for daydreaming, which can impair school performance.
*Recurrent motor tics and involuntary obscene speech*
- This description is characteristic of **Tourette's disorder**, which involves both motor and phonic tics, and can include coprolalia (obscene speech).
- Tourette's disorder is not typically treated with ethosuximide, nor does it commonly respond to it as a monotherapy.
*Episodic jerky movements of the arm and impaired consciousness*
- This presentation suggests a type of **myoclonic seizure** or a focal seizure with secondary generalization, depending on the extent of consciousness impairment.
- While ethosuximide can sometimes be used as an adjunct, it is not the primary treatment for these types of seizures, and the classic description for absence seizures is distinct.
*Overwhelming daytime sleepiness and hypnagogic hallucinations*
- These symptoms are highly suggestive of **narcolepsy**, a chronic neurological condition characterized by overwhelming daytime sleepiness and other sleep-related phenomena.
- Narcolepsy is treated with stimulants or other agents to promote wakefulness, not ethosuximide.
*Limited attention span and poor impulse control*
- These symptoms are hallmark features of **Attention-Deficit/Hyperactivity Disorder (ADHD)**, which can also affect school performance.
- ADHD is treated with stimulants or non-stimulant medications targeting neurotransmitter systems, not ethosuximide.
Question 375: A 41-year-old woman is brought to the emergency department by ambulance because of a sudden onset severe headache. On presentation, the patient also says that she is not able to see well. Physical examination shows ptosis of the right eye with a dilated pupil that is deviated inferiorly and laterally. Based on the clinical presentation, neurosurgery is immediately consulted and the patient is taken for an early trans-sphenoidal surgical decompression. Which of the following will also most likely need to be supplemented in this patient?
A. Erythropoietin
B. Aldosterone
C. Parathyroid hormone
D. Insulin
E. Corticosteroids (Correct Answer)
Explanation: ***Corticosteroids***
- This patient's presentation of sudden onset headache, visual disturbance, **ptosis of the right eye with a dilated pupil deviated inferiorly and laterally** strongly suggests a pituitary apoplexy, a life-threatening condition caused by hemorrhage or infarction of the pituitary gland. Patients with pituitary apoplexy can develop **adrenal insufficiency** due to disruption of the hypothalamic-pituitary-adrenal axis, necessitating immediate corticosteroid supplementation.
- Neurosurgical decompression, especially **trans-sphenoidal surgery**, can further stress the adrenal axis and worsen adrenal insufficiency, making postoperative corticosteroid replacement vital to prevent **adrenal crisis**.
*Erythropoietin*
- **Erythropoietin** is a hormone involved in red blood cell production, primarily used to treat **anemia**, particularly in chronic kidney disease.
- While patients undergoing surgery might experience some blood loss, there is no direct indication from the clinical presentation or immediate post-surgical needs for erythropoietin supplementation in this acute setting.
*Aldosterone*
- **Aldosterone** is a mineralocorticoid primarily involved in regulating blood pressure through sodium and potassium balance.
- While adrenal insufficiency associated with pituitary apoplexy can lead to reduced aldosterone production, the primary life-threatening concern is **cortisol deficiency**, which is addressed by corticosteroid (glucocorticoid) supplementation. Aldosterone replacement is rarely the immediate and sole priority in acute adrenal crisis.
*Parathyroid hormone*
- **Parathyroid hormone** is crucial for **calcium and phosphorus regulation**.
- There is no clinical information or direct physiological link between pituitary apoplexy or its surgical management and an immediate need for parathyroid hormone supplementation.
*Insulin*
- **Insulin** is a hormone essential for glucose metabolism and is primarily used to treat **diabetes mellitus**.
- While pituitary dysfunction can sometimes lead to changes in glucose regulation, there is no immediate indication for insulin supplementation based on the presented symptoms of pituitary apoplexy. **Hypoglycemia** can be a concern with adrenal insufficiency if not managed with glucose and glucocorticoids, but insulin itself is not typically supplemented unless the patient has pre-existing or stress-induced hyperglycemia.
Question 376: A 70-year-old female with a history of congestive heart failure presents to the emergency room with dyspnea. She reports progressive difficulty breathing which began when she ran out of her furosemide and lisinopril prescriptions 1-2 weeks ago. She states the dyspnea is worse at night and when lying down. She denies any fever, cough, or GI symptoms. Her medication list reveals she is also taking digoxin. Physical exam is significant for normal vital signs, crackles at both lung bases and 2+ pitting edema of both legs. The resident orders the medical student to place the head of the patient's bed at 30 degrees. Additionally, he writes orders for the patient to be given furosemide, morphine, nitrates, and oxygen. Which of the following should be checked before starting this medication regimen?
A. Basic metabolic panel (Correct Answer)
B. Complete blood count
C. Brain natriuretic peptide
D. Urinalysis
E. Chest x-ray
Explanation: ***Basic metabolic panel***
- A **basic metabolic panel (BMP)** is essential before starting this regimen to assess **kidney function** (creatinine, BUN) and **electrolytes**, particularly **potassium**.
- **Critical safety consideration**: The patient is on **digoxin**, which has significantly increased toxicity when potassium is low. Furosemide (a loop diuretic) causes potassium loss, making baseline potassium assessment essential to prevent life-threatening digoxin toxicity.
- **Renal function** must be checked before administering furosemide and lisinopril, both of which are renally cleared and can worsen renal function or accumulate in renal impairment.
*Complete blood count*
- A **complete blood count (CBC)** assesses for anemia, infection, and hematologic abnormalities.
- While potentially useful, it doesn't provide the immediate biochemical information (renal function, electrolytes) needed to safely initiate the prescribed heart failure medications, especially given the digoxin interaction risk.
*Brain natriuretic peptide*
- **Brain natriuretic peptide (BNP)** is a biomarker of heart failure severity and can help differentiate cardiac from non-cardiac causes of dyspnea.
- However, this patient's clinical presentation (orthopnea, bilateral crackles, pitting edema, medication non-adherence) already strongly confirms acute decompensated heart failure, making BNP less critical than checking renal function and electrolytes before medication administration.
*Urinalysis*
- **Urinalysis** can detect urinary tract infections, proteinuria, or other renal abnormalities.
- This patient's symptoms are classic for acute decompensated heart failure due to medication non-adherence, making urinalysis less immediately relevant for managing her acute presentation and medication safety.
*Chest x-ray*
- A **chest x-ray** can confirm pulmonary edema (cardiomegaly, cephalization, Kerley B lines) and rule out other causes of dyspnea like pneumonia or pneumothorax.
- While important for confirming the diagnosis, it is not required **before** starting medications and does not provide the critical biochemical information (renal function, electrolytes) needed to safely administer diuretics and ACE inhibitors in a patient on digoxin.
Question 377: A 41-year-old woman comes to the emergency room because she has been taking phenelzine for a few years and her doctor warned her that she should not eat aged cheese while on the medication. That night, she unknowingly ate an appetizer at a friend's party that was filled with cheese. She is concerned and wants to make sure that everything is all right. What vital sign or blood test is the most important to monitor in this patient?
A. Oxygen saturation
B. Blood pressure (Correct Answer)
C. Temperature
D. Creatine phosphokinase
E. Heart rate
Explanation: ***Blood pressure***
- Phenelzine is a **monoamine oxidase inhibitor (MAOI)**, and consuming foods rich in **tyramine**, like aged cheese, can lead to a **hypertensive crisis**.
- Monitoring blood pressure is crucial to detect and manage this potentially life-threatening elevation.
*Oxygen saturation*
- While overall patient stability is important, there is no direct physiological mechanism that would cause a critical drop in oxygen saturation due to a tyramine-induced hypertensive crisis.
- This parameter would not be the primary or most important vital sign to monitor in this specific drug-food interaction.
*Temperature*
- Though fever can sometimes be a non-specific symptom in severe medical conditions, a significant change in body temperature is not a primary or direct anticipated sign of a **tyramine-induced hypertensive crisis**.
- Monitoring temperature would not directly address the most immediate and critical complication associated with MAOI and tyramine interaction.
*Creatine phosphokinase*
- **Creatine phosphokinase (CPK)** levels are elevated in conditions involving muscle damage, such as rhabdomyolysis.
- While severe complications of a hypertensive crisis could theoretically lead to organ damage, CPK is not the primary or most sensitive indicator for the initial assessment or immediate monitoring of a tyramine reaction with an MAOI.
*Heart rate*
- **Tachycardia** can occur during a hypertensive crisis; however, the primary danger is the elevation in blood pressure which can lead to stroke or myocardial infarction.
- While important to monitor, heart rate is a secondary indicator compared to the direct measure of **blood pressure** in this specific scenario.
Question 378: A 21-year-old college student comes to the physician for intermittent palpitations. She does not have chest pain or shortness of breath. The symptoms started 2 days ago, on the night after she came back to her dormitory after a 4-hour-long bus trip from home. A day ago, she went to a party with friends. The palpitations have gotten worse since then and occur more frequently. The patient has smoked 5 cigarettes daily for the past 3 years. She drinks 4–6 alcoholic beverages with friends once or twice a week and occasionally uses marijuana. She is sexually active with her boyfriend and takes oral contraceptive pills. She does not appear distressed. Her pulse is 100/min and irregular, blood pressure is 140/85 mm Hg, and respirations are at 25/min. Physical examination shows a fine tremor in both hands, warm extremities, and swollen lower legs. The lungs are clear to auscultation. An ECG is shown below. Which of the following is the most appropriate next step in management?
A. Measure D-Dimer levels
B. Measure TSH levels (Correct Answer)
C. Send urine toxicology
D. Administer intravenous adenosine
E. Observe and wait
Explanation: ***Measure TSH levels***
- The patient exhibits classic signs and symptoms of **hyperthyroidism**, including new-onset **atrial fibrillation** (irregular pulse on ECG), **tachycardia** (pulse 100/min), **warm extremities**, fine tremor, and *possibly* hypertension (140/85 mmHg).
- The recent stressors (bus trip, party, worsened palpitations) may exacerbate underlying thyroid dysfunction; measuring **TSH** is the most appropriate initial diagnostic step.
*Measure D-Dimer levels*
- While the patient has leg swelling and recent immobility (bus trip), suggesting a potential **deep vein thrombosis (DVT)** or **pulmonary embolism (PE)**, her primary symptoms revolve around palpitations and classic hyperthyroid signs.
- The ECG shows atrial fibrillation, not findings typical for acute PE, and D-dimer is a non-specific test for PE/DVT in the absence of other strong indicators.
*Send urine toxicology*
- The patient uses marijuana and smokes cigarettes, and drug use can certainly cause **palpitations** and **tachycardia**.
- However, the combination of **tremor**, **warm extremities**, and the ECG finding of new-onset atrial fibrillation points more strongly towards **hyperthyroidism** as the primary underlying cause, which can be exacerbated by stimulants.
*Administer intravenous adenosine*
- **Adenosine** is used to terminate re-entrant supraventricular tachycardias (SVT) and can help diagnose wide-complex tachycardias by temporarily blocking AV nodal conduction.
- The ECG shows **atrial fibrillation** (irregular rhythm, no distinct P waves), which is an irregular rhythm in which adenosine is not typically the first-line treatment and could be destabilizing if the patient is already tachycardic due to an underlying cause like hyperthyroidism.
*Observe and wait*
- The patient has new-onset **atrial fibrillation with rapid ventricular response** (tachycardia), along with other concerning symptoms such as **hypertension**, **tremor**, and **possible heart failure symptoms** (swollen lower legs).
- These findings necessitate prompt investigation and management rather than observation alone, especially given the potential for serious complications of untreated hyperthyroidism and atrial fibrillation.
Question 379: A 69-year-old woman comes to the clinic for an annual well exam. She reports no significant changes to her health except for an arm fracture 3 weeks ago while she was lifting some heavy bags. Her diabetes is well controlled with metformin. She reports some vaginal dryness that she manages with adequate lubrication. She denies any weight changes, fevers, chills, palpitations, nausea/vomiting, incontinence, or bowel changes. A dual-energy X-ray absorptiometry (DEXA) scan was done and demonstrated a T-score of -2.7. She was subsequently prescribed a selective estrogen receptor modulator, in addition to vitamin and weight-bearing exercises, for the management of her symptoms. What is the mechanism of action of the prescribed medication?
A. Estrogen antagonist in cervix and agonist in bone
B. Estrogen agonist in bone and breast
C. Estrogen antagonist in breast and agonist in bone (Correct Answer)
D. Partial estrogen agonist in endometrium and bone
E. Partial estrogen agonist in bone and antagonist in cervix
Explanation: ***Estrogen antagonist in breast and agonist in bone***
- Selective estrogen receptor modulators (SERMs) like **raloxifene** act as **estrogen agonists in bone**, helping to prevent osteoporosis by increasing bone mineral density.
- They also act as **estrogen antagonists in breast tissue**, which can reduce the risk of breast cancer in high-risk postmenopausal women.
- This is the mechanism of the medication prescribed for this patient's osteoporosis (T-score -2.7).
*Estrogen antagonist in cervix and agonist in bone*
- While SERMs are **agonists in bone**, they do not typically have significant antagonistic effects on the cervix, which is not a primary target for their therapeutic action or side effect profile.
- The primary antagonism is observed in breast tissue, not the cervix.
*Estrogen agonist in bone and breast*
- This describes the action of **estrogen replacement therapy (ERT)**, which increases breast cancer risk, whereas SERMs are designed to avoid this by being antagonists in breast tissue.
- The goal of SERMs is to achieve the beneficial bone effects of estrogen without the undesirable estrogenic effects on breast tissue.
*Partial estrogen agonist in endometrium and bone*
- Some SERMs, particularly **tamoxifen**, can act as a **partial estrogen agonist in the endometrium**, which can increase the risk of endometrial hyperplasia or cancer.
- However, raloxifene (a common SERM for osteoporosis) is typically **neutral or minimally agonistic** on the endometrium, and the primary description here is for its breast and bone effects.
*Partial estrogen agonist in bone and antagonist in cervix*
- SERMs are indeed **agonists in bone**, but their antagonistic action is primarily in the breast, not the cervix.
- The cervix is not a key target for either agonist or antagonist effects in the context of SERM therapeutic use for osteoporosis and breast cancer risk reduction.
Question 380: A 58-year-old man with a 10-year history of type 2 diabetes mellitus and hypertension comes to the physician for a routine examination. Current medications include metformin and captopril. His pulse is 84/min and blood pressure is 120/75 mm Hg. His hemoglobin A1c concentration is 9.5%. The physician adds repaglinide to his treatment regimen. The mechanism of action of this agent is most similar to that of which of the following drugs?
A. Linagliptin
B. Glyburide (Correct Answer)
C. Pioglitazone
D. Miglitol
E. Metformin
Explanation: ***Glyburide***
- **Repaglinide** is a meglitinide, and **glyburide** is a sulfonylurea; both classes of drugs stimulate insulin release from pancreatic **beta cells** by closing ATP-sensitive potassium channels.
- This action leads to depolarization of the beta cell membrane, opening of **voltage-gated calcium channels**, and subsequent release of insulin from storage granules.
*Linagliptin*
- **Linagliptin** is a **dipeptidyl peptidase-4 (DPP-4) inhibitor** that works by preventing the breakdown of incretins like GLP-1, thereby increasing postprandial insulin secretion and decreasing glucagon secretion.
- Its mechanism is distinct from repaglinide's direct stimulation of insulin release.
*Pioglitazone*
- **Pioglitazone** is a **thiazolidinedione** that acts by activating **peroxisome proliferator-activated receptor-gamma (PPAR-γ)** in adipose tissue, increasing insulin sensitivity in peripheral tissues.
- This mechanism centers on improving insulin utilization rather than stimulating insulin secretion.
*Miglitol*
- **Miglitol** is an **alpha-glucosidase inhibitor** that delays carbohydrate absorption in the gastrointestinal tract, leading to a flatter postprandial glucose curve.
- Its action focuses on reducing glucose absorption, which is different from directly influencing insulin secretion or sensitivity.
*Metformin*
- **Metformin** is a biguanide that primarily reduces **hepatic glucose production** and improves insulin sensitivity in peripheral tissues.
- It does not directly affect insulin secretion from the pancreas, distinguishing it from repaglinide.
