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 Flashcard 1 of 5

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 5

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 5

Question: aspirin

Answer:

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

Autonomic/CV Drugs Flashcard 4 of 5

Question: ouabain

Answer:

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

Autonomic/CV Drugs Flashcard 5 of 5

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

Answer: Increased ERP

Extra Information:  First Aid Pharmacology: Cardiovascular (Antiarrhythmics)  Watch Class I A C [https://dashboard.sketchy.com/study/medical/courses/medical-pharmacology/units/medical-pharmacology-cardiovascular-renal/videos/medical-pharmacology-cardiovascular-and-renal-antiarrhythmics-class-i-a-c?utm_source=anki&utm_medium=partnership&utm_campaign=february_update&utm_content=medical]Watch associated Bootcamp video [https://app.bootcamp.com/med-school/cardiology/videos/Antiarrhythmics?index=3] https://onlinemeded.org/spa/cardiac/arrhythmias/acquire?ref=anki