Autonomic/CV Drugs

Autonomic/CV Drugs US Medical PG Question 1: Which antithyroid drug is safer during the first trimester of pregnancy?

• A. Radioactive iodine
• B. Carbimazole
• C. Propylthiouracil (Correct Answer)
• D. Methimazole
• E. Propranolol

Autonomic/CV Drugs Explanation: ***Propylthiouracil*** - **Propylthiouracil (PTU)** is the preferred drug for treating hyperthyroidism in the **first trimester of pregnancy** due to a lower risk of teratogenic effects compared to methimazole or carbimazole. - While PTU carries a risk of hepatic toxicity, it is generally favored during early pregnancy to avoid the established teratogenic risks of other thionamides. *Radioactive iodine* - **Radioactive iodine (RAI)** is absolutely contraindicated in pregnancy as it crosses the placenta and can cause permanent **fetal hypothyroidism** or **agenesis of the fetal thyroid gland**. - Its use can lead to the destruction of the fetal thyroid, which is unacceptable given the availability of safer alternatives. *Carbimazole* - **Carbimazole** is converted to methimazole in the body and is associated with a higher risk of **fetal embryopathy** during the first trimester, including aplasia cutis, choanal atresia, and esophageal atresia. - It should generally be avoided in the first trimester if possible, switching to PTU instead. *Methimazole* - **Methimazole** is structurally similar to carbimazole and also carries a significant risk of **teratogenic effects** such as **aplasia cutis**, omphalocele, and choanal atresia when used in the first trimester. - It is often reserved for the second and third trimesters if a thionamide is required, or for patients who cannot tolerate PTU, but ideally avoided in early pregnancy. *Propranolol* - **Propranolol** is a beta-blocker used for symptomatic management of hyperthyroidism (controlling tachycardia, tremor, anxiety) but is not an antithyroid drug and does not treat the underlying hyperthyroidism. - While generally safe in pregnancy, it only provides adjunctive therapy and cannot replace definitive antithyroid treatment.

Autonomic/CV Drugs US Medical PG Question 2: A patient on SSRI sertraline was also prescribed amitriptyline and subsequently developed serotonin toxicity. What is the likely treatment for serotonin toxicity?

• A. Flumazenil
• B. Cyproheptadine (Correct Answer)
• C. L-Carnitine
• D. Leucovorin
• E. Naloxone

Autonomic/CV Drugs Explanation: ***Cyproheptadine*** - **Cyproheptadine** is a serotonin antagonist that can help reverse the effects of excessive serotonin in the central nervous system. - It works by blocking **serotonin 5-HT2A receptors**, which are implicated in the pathophysiology of serotonin toxicity. *Flumazenil* - **Flumazenil** is a benzodiazepine receptor antagonist used to reverse the effects of benzodiazepine overdose. - It has no role in the treatment of **serotonin toxicity**, as it does not affect serotonin pathways. *L-Carnitine* - **L-Carnitine** is a mitochondrial co-factor used in fatty acid metabolism, sometimes supplemented for certain metabolic disorders or muscle pain. - It does not have any direct action on **serotonin receptors** or the serotonin system, making it ineffective for serotonin toxicity. *Leucovorin* - **Leucovorin** (folinic acid) is used to counteract the effects of methotrexate toxicity or to enhance the effects of fluorouracil in chemotherapy. - It is not involved in modulating **neurotransmitter levels** or reversing the symptoms of serotonin toxicity. *Naloxone* - **Naloxone** is an opioid receptor antagonist used to reverse opioid overdose. - It has no effect on **serotonin receptors** or serotonergic pathways, making it ineffective for treating serotonin toxicity.

Autonomic/CV Drugs US Medical PG Question 3: Which of the following drugs is used in opioid maintenance therapy?

• A. Naltrexone
• B. Clonidine
• C. Buprenorphine (Correct Answer)
• D. Disulfiram
• E. Naloxone

Autonomic/CV Drugs Explanation: ***Buprenorphine*** - **Buprenorphine** is a **partial opioid agonist** used in opioid maintenance therapy to reduce cravings and withdrawal symptoms without producing the full euphoric effects of other opioids. - It is often combined with **naloxone** (as Suboxone) to prevent misuse by injection, as naloxone is only active if injected. - Buprenorphine has a **ceiling effect** for respiratory depression, making it safer than full agonists like methadone. *Naltrexone* - **Naltrexone** is an **opioid antagonist** that blocks opioid receptors, preventing the euphoric effects of opioids and reducing cravings. - While used in opioid use disorder treatment, it is primarily for relapse prevention and not typically for the active maintenance phase where agonist effects are desired. *Clonidine* - **Clonidine** is an **alpha-2 adrenergic agonist** primarily used to manage the **autonomic symptoms of opioid withdrawal**, such as anxiety, sweating, and rapid heart rate. - It does not directly act on opioid receptors and is not a primary agent for long-term opioid maintenance therapy. *Disulfiram* - **Disulfiram** is a drug used in the treatment of **alcohol use disorder**, not opioid use disorder. - It works by inhibiting acetaldehyde dehydrogenase, leading to an unpleasant reaction when alcohol is consumed. *Naloxone* - **Naloxone** is an **opioid antagonist** used for **emergency reversal of opioid overdose**, not for maintenance therapy. - It rapidly displaces opioids from receptors and reverses respiratory depression. - While combined with buprenorphine in Suboxone to prevent misuse, naloxone itself is not used for maintenance therapy.

Autonomic/CV Drugs US Medical PG Question 4: Which of the following growth hormone analogues is not used for the treatment of GH deficiency but is used in the treatment of HIV associated lipodystrophy?

• A. Tesamorelin (Correct Answer)
• B. Sermorelin
• C. Somatropin
• D. Pegvisomant
• E. Mecasermin

Autonomic/CV Drugs Explanation: ***Tesamorelin*** - **Tesamorelin** is a **growth hormone-releasing hormone (GHRH) analogue** approved specifically for the treatment of **HIV-associated lipodystrophy**. - It works by stimulating the natural production and release of endogenous growth hormone, which helps reduce **visceral adipose tissue** observed in this condition. - **Key distinction:** NOT used for GH deficiency, but specifically for lipodystrophy. *Sermorelin* - **Sermorelin** is also a **GHRH analogue**, but it is primarily used to diagnose and treat **growth hormone deficiency** in children. - It is not approved for lipodystrophy and works by stimulating the pituitary to secrete growth hormone. *Somatropin* - **Somatropin** is the recombinant form of **human growth hormone (GH)** itself, used to treat **growth hormone deficiency** in both children and adults. - While it can affect body composition, its primary indication is not HIV-associated lipodystrophy. *Mecasermin* - **Mecasermin** is recombinant **insulin-like growth factor-1 (IGF-1)** used to treat severe primary IGF-1 deficiency. - It is used for growth failure in children with GH gene deletion or GH receptor defects, not for HIV-associated lipodystrophy. *Pegvisomant* - **Pegvisomant** is a **growth hormone receptor antagonist** used to treat **acromegaly**, a condition caused by excessive growth hormone. - It works by blocking the action of growth hormone at its receptor, directly opposing the therapeutic goal for lipodystrophy.

Autonomic/CV Drugs US Medical PG Question 5: Caffeine is a widely used stimulant that promotes wakefulness. Which of the following mechanisms is responsible for this effect?

• A. Adenosine antagonism (Correct Answer)
• B. Increased discharge of norepinephrine from the locus ceruleus
• C. Release of histamine
• D. Inhibition of phosphodiesterase
• E. Dopamine reuptake inhibition

Autonomic/CV Drugs Explanation: ***Adenosine antagonism*** - Caffeine acts as a **competitive antagonist** at **adenosine receptors** (primarily A1 and A2A) in the brain. - **Adenosine** is an inhibitory neurotransmitter that promotes drowsiness and reduces neuronal activity; by blocking its receptors, caffeine prevents this sedation and promotes wakefulness. - This is the **primary mechanism** responsible for caffeine's stimulant effects at typical dietary doses. *Increased discharge of norepinephrine from the locus ceruleus* - While increased **norepinephrine** can promote wakefulness, it is not the primary direct mechanism by which caffeine exerts its stimulant effects. - Caffeine may indirectly affect norepinephrine release as a downstream consequence of adenosine receptor blockade, but this is a secondary effect. *Release of histamine* - **Histamine** is indeed a neurotransmitter involved in wakefulness and arousal, but caffeine does not primarily promote wakefulness by directly causing histamine release. - Some antihistamines cause drowsiness by blocking central histamine receptors, but caffeine's mechanism is distinct from the histaminergic system. *Inhibition of phosphodiesterase* - Caffeine does inhibit **phosphodiesterase (PDE)** enzymes, leading to increased intracellular **cAMP** levels. - However, PDE inhibition occurs at significantly **higher concentrations** than those required for adenosine receptor antagonism, making it a less important mechanism for caffeine's typical stimulant effects at common dietary doses (1-3 cups of coffee). *Dopamine reuptake inhibition* - While some CNS stimulants (e.g., **methylphenidate**, **cocaine**) work primarily through dopamine reuptake inhibition, this is **not** caffeine's primary mechanism. - Caffeine may have minor indirect effects on dopamine neurotransmission through its adenosine receptor antagonism, but direct dopamine reuptake inhibition is not a significant mechanism of action.

Autonomic/CV Drugs US Medical PG Question 6: Which of the following is commonly used for maintenance therapy in opioid abuse?

• A. Clonidine
• B. Buprenorphine (Correct Answer)
• C. Butorphanol
• D. Naloxone
• E. Methadone

Autonomic/CV Drugs Explanation: ***Buprenorphine*** - **Buprenorphine** is a **partial opioid agonist** commonly used for the maintenance treatment of **opioid use disorder** due to its ability to reduce cravings and prevent withdrawal symptoms. - It has a "ceiling effect," meaning that its opioid effects level off at higher doses, which contributes to its **safety profile** and lower risk of overdose compared to full agonists. - Preferred over methadone in many settings due to its **superior safety profile**, lower abuse potential, and ability to be prescribed in office-based settings. *Clonidine* - **Clonidine** is an **alpha-2 adrenergic agonist** primarily used to manage **autonomic symptoms** of opioid withdrawal (e.g., sweating, hypertension), but it does not address cravings or provide opioid effects. - It is not considered a primary maintenance therapy for opioid use disorder. *Butorphanol* - **Butorphanol** is a **mixed opioid agonist-antagonist** often used for pain relief, but its partial agonist activity and potential for withdrawal in opioid-dependent individuals make it unsuitable for maintenance therapy in opioid abuse. - It can precipitate **opioid withdrawal** in patients who are opioid-dependent. *Naloxone* - **Naloxone** is an **opioid antagonist** used to rapidly reverse the effects of opioid overdose by blocking opioid receptors. - While critical in overdose situations, it is not used for maintenance therapy as it would induce immediate and severe opioid withdrawal symptoms. *Methadone* - **Methadone** is a **full opioid agonist** that is also used for maintenance therapy in opioid use disorder, particularly in specialized opioid treatment programs. - However, it requires **daily supervised dosing** in most jurisdictions, has a higher risk of overdose, respiratory depression, and QT prolongation, making buprenorphine often the **preferred first-line agent** for maintenance therapy.

Autonomic/CV Drugs US Medical PG Question 7: A patient presents with symptoms of tachycardia, tachypnea, hypertension, and hypocalcemia after consuming an unknown substance. The patient also has high anion gap metabolic acidosis. Which of the following substances was most likely consumed?

• A. Iron
• B. Methanol
• C. Ethylene glycol (Correct Answer)
• D. Digoxin
• E. Isopropanol

Autonomic/CV Drugs Explanation: ***Ethylene glycol*** - Ethylene glycol poisoning is characterized by **tachycardia**, **tachypnea**, **hypertension**, **hypocalcemia**, and a **high anion gap metabolic acidosis** due to the accumulation of toxic metabolites like oxalic and glycolic acids. - The formation of **calcium oxalate crystals** in the kidneys contributes to hypocalcemia and acute kidney injury, a hallmark of severe ethylene glycol toxicity. *Iron* - Iron overdose typically presents with **gastrointestinal symptoms** (vomiting, diarrhea, abdominal pain), shock, and metabolic acidosis, but not specifically with hypocalcemia or the characteristic crystal formation seen with ethylene glycol. - While it can cause metabolic acidosis, the absence of **hypocalcemia** and specific renal effects pointing to oxalate crystals differentiates it from ethylene glycol. *Methanol* - Methanol poisoning causes a **high anion gap metabolic acidosis**, visual disturbances (e.g., "snowstorm" vision), and central nervous system depression. - It does not typically lead to **hypocalcemia** or the kidney damage associated with calcium oxalate crystal formation. *Isopropanol* - Isopropanol (rubbing alcohol) poisoning causes **CNS depression**, **hypotension**, and an **osmolar gap** without significant anion gap metabolic acidosis. - It does not cause **hypocalcemia** or the high anion gap metabolic acidosis characteristic of ethylene glycol toxicity. *Digoxin* - Digoxin toxicity primarily affects the **cardiac system**, causing bradycardia, arrhythmias (e.g., ventricular fibrillation, heart block), and **gastrointestinal symptoms**. - It does not cause a high anion gap metabolic acidosis, hypocalcemia, or the other systemic sympathetic effects described in the scenario.

Autonomic/CV Drugs US Medical PG Question 8: A 45-year-old male with a history of chronic alcohol use is admitted to the hospital. He presents with anxiety, tremors, and agitation after his last drink 24 hours ago. Which of the following medications is most appropriate for controlling alcohol withdrawal symptoms?

• A. Lorazepam (Correct Answer)
• B. Fomepizole
• C. Disulfiram
• D. Buspirone
• E. Naltrexone

Autonomic/CV Drugs Explanation: ***Lorazepam*** - **Lorazepam**, a **benzodiazepine**, is the first-line treatment for alcohol withdrawal symptoms due to its ability to enhance **GABAergic activity**, which is deficient during withdrawal. - Its **intermediate half-life** and **lack of active metabolites** make it suitable for patients with liver impairment, common in chronic alcohol users. *Fomepizole* - **Fomepizole** is an antidote used to treat poisoning from **methanol** or **ethylene glycol**, not alcohol withdrawal. - It works by inhibiting **alcohol dehydrogenase**, an enzyme involved in the metabolism of these toxic alcohols. *Disulfiram* - **Disulfiram** is an **aldehyde dehydrogenase inhibitor** used to deter alcohol consumption in recovering alcoholics by causing unpleasant reactions if alcohol is consumed. - It is **not used to treat acute alcohol withdrawal symptoms** and can be dangerous if given during withdrawal due to potential interactions. *Buspirone* - **Buspirone** is an **anxiolytic** that acts as a **serotonin receptor agonist** and is used for generalized anxiety disorder. - It is **ineffective for acute alcohol withdrawal** due to its slow onset of action and lack of anticonvulsant properties. *Naltrexone* - **Naltrexone** is an **opioid receptor antagonist** used for relapse prevention and reducing alcohol craving in patients with alcohol use disorder. - It is **not effective for acute alcohol withdrawal symptoms** and does not prevent seizures or delirium tremens, which are life-threatening complications of withdrawal.

Autonomic/CV Drugs US Medical PG Question 9: A patient being treated for hypertriglyceridemia developed flushing, gout, hyperglycemia, and raised liver enzymes. Which drug is the most likely cause?

• A. Atorvastatin
• B. Fenofibrate
• C. Nicotinic acid (Correct Answer)
• D. Ezetimibe
• E. Gemfibrozil

Autonomic/CV Drugs Explanation: ***Nicotinic acid*** - **Nicotinic acid (Niacin)** is known to cause **flushing** due to prostaglandin release. - It also commonly leads to **hyperglycemia**, **hyperuricemia** (which can precipitate gout), and **elevated liver enzymes** as side effects. *Atorvastatin* - While atorvastatin can cause **elevated liver enzymes** and, less commonly, **myopathy**, it does not typically cause flushing, gout, or hyperglycemia. - Its primary role is to lower **LDL cholesterol**, with a lesser effect on triglycerides. *Fenofibrate* - **Fenofibrate** is used to treat hypertriglyceridemia and can rarely cause **elevated liver enzymes** and **gallstones**. - It is not associated with significant flushing, hyperglycemia, or gout. *Gemfibrozil* - **Gemfibrozil** is another fibrate used for hypertriglyceridemia treatment. - While it can cause **elevated liver enzymes** and **myopathy** (especially when combined with statins), it does not cause the characteristic flushing or hyperglycemia seen with nicotinic acid. *Ezetimibe* - **Ezetimibe** primarily inhibits cholesterol absorption and is generally well-tolerated. - Common side effects are mild and include abdominal pain and diarrhea, with no association to flushing, gout, or hyperglycemia.

Autonomic/CV Drugs US Medical PG Question 10: Lidocaine is used in a loading dose for the treatment of arrhythmias. The loading dose of this drug depends upon which of the following factors?

• A. Clearance
• B. Volume of distribution (Correct Answer)
• C. Half-life
• D. Bioavailability
• E. Elimination rate constant

Autonomic/CV Drugs Explanation: ***Volume of distribution*** - The **loading dose** of a drug is primarily determined by its **volume of distribution (Vd)** and the **target plasma concentration**. - A larger **Vd** means the drug distributes widely into tissues, requiring a larger loading dose to achieve the desired concentration in the central compartment. *Clearance* - **Clearance** dictates the **maintenance dose** needed to sustain a steady-state concentration once the loading dose has been administered. - It reflects the rate at which the drug is eliminated from the body, not how much is initially needed to fill the distribution volume. *Half-life* - **Half-life** determines the **time required to reach steady-state** and the **dosing interval** for maintaining therapeutic concentrations. - While related to clearance and Vd, it does not directly determine the magnitude of the initial loading dose itself. *Bioavailability* - **Bioavailability** is the fraction of administered drug that reaches the systemic circulation in an unchanged form. - It influences the oral dose required to achieve a certain plasma concentration, but the concept of loading dose is typically considered for the intravenous route where bioavailability is 100%. *Elimination rate constant* - The **elimination rate constant (ke)** describes the rate of drug elimination and is related to clearance and volume of distribution (ke = Cl/Vd). - Like clearance, it determines the **maintenance dose** and dosing frequency, not the initial loading dose required to achieve therapeutic levels.

Autonomic/CV Drugs Flashcard 1 of 10

Question: vardenafil

Answer: PDE5 inhibitor

Extra Information: erectile dysfunctionpatients taking nitrates (lethal hypotension)inhbit phosphodiesterase 5, resulting in increased cGMP and smooth muscle relaxation in corpus cavernosumheadache, flushing, impaired blue-green color vision, hypotension, dyspepsia

Autonomic/CV Drugs Flashcard 2 of 10

Question: sildenafil

Answer: PDE5 inhibitor

Extra Information: erectile dysfunctionpatients taking nitrates (lethal hypotension)inhbit phosphodiesterase 5, resulting in increased cGMP and smooth muscle relaxation in corpus cavernosumheadache, flushing, impaired blue-green color vision, hypotension, dyspepsia

Autonomic/CV Drugs Flashcard 3 of 10

Question: aspirin

Answer:

Extra Information: increases permeability of the mitochondrial membrane (incomplete)inhibit oxidative phosphorylation

Autonomic/CV Drugs Flashcard 4 of 10

Question: ouabain

Answer:

Extra Information: inhibits Na+-K+ ATPase by binding to K+ site

Autonomic/CV Drugs Flashcard 5 of 10

Question: What effect do class IA antiarrhythmics have on the effective refractory period in the ventricular tissue? _____

Answer: Increased ERP

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Autonomic/CV Drugs Flashcard 6 of 10

Question: _____ patients are more sensitive to the side effects of nonbenzodiazepine hypnotics (e.g. cognitive impairment, headache, delirium)

Answer: Elderly

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Autonomic/CV Drugs Flashcard 7 of 10

Question: Ischemic priapism is treated with corporal aspiration, intracavernosal _____, or surgical decompression to prevent ischemia

Answer: phenylephrine

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Autonomic/CV Drugs Flashcard 8 of 10

Question: What effect do class IC antiarrhythmics have on the effective refractory period in the Purkinje and ventricular tissue? _____

Answer: No effect

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Autonomic/CV Drugs Flashcard 9 of 10

Question: What formula is used to calculate maintenance dose? _____

Answer:

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Autonomic/CV Drugs Flashcard 10 of 10

Question: Fibrates lead to _____ in serum LDL by reducing VLDL

Answer: mild decreases

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