Autonomic Nervous System Drugs Practice Questions

Q: Cisatracurium is better than atracurium because:-

Less histamine release. ***Less histamine release*** - **Cisatracurium** causes significantly less **histamine release** compared to atracurium, reducing the risk of **hypotension** and **bronchospasm**. [1] - This makes cisatracurium a safer choice for patients with **cardiovascular instability** or **asthma**. *No active metabolites* - While cisatracurium produces **laudanosine** as a metabolite, this is also true for **atracurium**. - The difference lies in the **concentration** of laudanosine and its potential for central nervous system toxicity, which is generally lower with cisatracurium. *Shorter half-life* - **Cisatracurium** generally has a **slightly longer half-life** than atracurium, but both are characterized by a relatively rapid onset and offset of action. - Their elimination primarily occurs via **Hoffman elimination** and **ester hydrolysis**, independent of renal or hepatic function. *Better neuromuscular blockade* - Both **cisatracurium** and **atracurium** are effective **neuromuscular blockers** when administered at appropriate doses. - The "better" aspect for cisatracurium relates more to its **improved safety profile** (less histamine release) rather than a significantly superior blockade efficacy. [1]

Q: Agent used for eliciting diagnostic differentiation of Myasthenia Gravis from Cholinergic crisis is:-

Edrophonium. ***Edrophonium*** - **Edrophonium** is a **short-acting acetylcholinesterase inhibitor** (duration 5-10 minutes) used in the **Tensilon test** to differentiate myasthenic crisis from cholinergic crisis - In **myasthenic crisis**, edrophonium temporarily improves muscle strength due to increased acetylcholine at the neuromuscular junction - In **cholinergic crisis**, it worsens weakness or shows no improvement - The rapid onset and short duration allow clear observation of transient response, making it ideal for diagnostic differentiation *Neostigmine* - **Neostigmine** is a longer-acting acetylcholinesterase inhibitor (duration 2-4 hours) used for chronic management of myasthenia gravis - Its prolonged effect makes it unsuitable for rapid diagnostic differentiation in acute crisis situations - The extended duration would make it difficult to observe transient changes and could worsen a cholinergic crisis for a prolonged period *Ecothiophate* - **Ecothiophate** is an irreversible acetylcholinesterase inhibitor used primarily in ophthalmology for glaucoma - Its irreversible action and prolonged effect (days to weeks) make it completely inappropriate for crisis differentiation - Would severely exacerbate cholinergic symptoms with sustained effect that cannot be reversed *Ambenonium* - **Ambenonium** is another long-acting acetylcholinesterase inhibitor (duration 3-8 hours) used for chronic treatment of myasthenia gravis - Similar to neostigmine, its extended duration makes it unsuitable for acute diagnostic challenge - The rapid onset and offset required for the Tensilon test cannot be achieved with this agent

Q: Which of the following is a uterine relaxant?

Ritodrine. ***Ritodrine*** **Ritodrine** is a **beta-2 adrenergic agonist** primarily used as a **tocolytic agent** to relax the uterus and prevent premature labor. It works by stimulating beta-2 receptors in the myometrium, leading to a decrease in intracellular calcium and subsequent **uterine smooth muscle relaxation** [1]. *Salmeterol* **Salmeterol** is a **long-acting beta-2 adrenergic agonist (LABA)** primarily used in the management of **asthma and COPD** to relax bronchial smooth muscle, not uterine muscle [2]. While it also stimulates beta-2 receptors, its primary clinical application is in the **airways**, not the uterus [2]. *Tiotropium* **Tiotropium** is a **long-acting anticholinergic (LAMA)** bronchodilator used for the maintenance treatment of **COPD and asthma** [2]. It functions by blocking muscarinic receptors in the bronchial smooth muscle, leading to **bronchodilation**, and has no significant effect on uterine muscle [2]. *Tolterodine* **Tolterodine** is an **antimuscarinic agent** used to treat **overactive bladder (OAB)** symptoms like urinary urgency, frequency, and urge incontinence. It works by blocking muscarinic receptors in the bladder smooth muscle, leading to **bladder relaxation**, but does not affect the uterus.

Q: Which agent stimulates both beta-1 and beta-2 receptors?

Epinephrine. ***Epinephrine*** - **Epinephrine** is a potent agonist at both **beta-1 (β1)** and **beta-2 (β2)** adrenergic receptors, leading to widespread sympathetic nervous system effects. - Its β1 stimulation increases **heart rate** and **contractility**, while β2 stimulation causes **bronchodilation** and vasodilation in certain vascular beds. *Dopamine* - **Dopamine** acts on different receptors depending on the dose: at low doses, it primarily activates **D1 receptors** (renal vasodilation), at intermediate doses, it activates **β1 receptors** (cardiac stimulation), and at high doses, it activates **α1 receptors** (vasoconstriction). - It does not significantly stimulate **beta-2 receptors** at therapeutic concentrations, distinguishing it from epinephrine. *Dobutamine* - **Dobutamine** is a synthetic catecholamine that acts primarily as a **β1-selective agonist**, significantly increasing **myocardial contractility** and heart rate. - While it has some weak β2 agonist activity, its predominant effect is on **β1 receptors**, making it less effective for widespread β2 stimulation compared to epinephrine. *Albuterol* - **Albuterol** is a **short-acting β2-adrenergic agonist** primarily used in the treatment of **asthma** to induce **bronchodilation**. - It has a high selectivity for **β2 receptors** in the lungs and has minimal effects on **β1 receptors** at therapeutic doses.

Q: How does botulinum toxin affect synaptic transmission?

Prevents ACh release. ***Prevents ACh release*** - Botulinum toxin acts by **cleaving SNARE proteins** (SNAP-25, synaptobrevin, syntaxin) which are essential for the fusion of acetylcholine (ACh) vesicles with the presynaptic membrane [2]. - By preventing vesicle fusion, it effectively **blocks the release of ACh** into the synaptic cleft, leading to muscle paralysis [1, 2]. *Inhibits Ca2+ release* - While **calcium influx** is crucial for neurotransmitter release, botulinum toxin's primary mechanism is not direct inhibition of calcium release from the sarcoplasmic reticulum or entry into the presynaptic terminal. - Its action is further downstream, targeting the machinery involved in **vesicle fusion** rather than the initial calcium signal. *Increases K+ influx* - An increase in **potassium (K+) influx** would typically cause hyperpolarization or counteract depolarization, which is not the direct action of botulinum toxin. - Botulinum toxin specifically targets the **release mechanism of neurotransmitters**, not the ion channels responsible for maintaining resting membrane potential or repolarization. *Blocks Na+ channels* - Blocking **sodium (Na+) channels** would prevent depolarization and action potential generation, similar to the mechanism of local anesthetics. - Botulinum toxin does not directly interfere with sodium channel function; its effect is focused on the **vesicular release process of acetylcholine**.

Q: Which drug is commonly used for pupil dilation during an eye exam?

Tropicamide. ***Tropicamide*** - **Tropicamide** is an **anticholinergic** agent that blocks **muscarinic receptors** in the iris **sphincter muscle**, causing **mydriasis** (pupil dilation) and also **cycloplegia** (paralysis of the ciliary muscle). - It has a rapid onset and relatively short duration of action, making it ideal for routine eye examinations. *Latanoprost* - **Latanoprost** is a **prostaglandin analog** primarily used to reduce intraocular pressure in **glaucoma**. - It increases **uveoscleral outflow** of aqueous humor and does not cause pupil dilation. *Timolol* - **Timolol** is a **beta-blocker** used to lower intraocular pressure in **glaucoma** by decreasing the production of aqueous humor. - It does not cause pupil dilation and is often used as a first-line treatment for open-angle glaucoma. *Prednisolone* - **Prednisolone** is a **corticosteroid** used to treat ocular inflammation. - It does not cause pupil dilation and, if used long-term, can actually lead to side effects such as increased intraocular pressure and cataract formation.

Q: A 65-year-old male with benign prostatic hyperplasia (BPH) is prescribed a drug that relaxes smooth muscle in the bladder neck and prostate. Which alpha-1 blocker is most likely to be prescribed?

Tamsulosin. ***Tamsulosin*** - **Tamsulosin** is a **selective alpha-1A blocker** that specifically targets alpha-1A receptors in the prostate and bladder neck, leading to smooth muscle relaxation and improved urine flow. - Its **uroSelectivity** minimizes cardiovascular side effects (orthostatic hypotension, dizziness), making it the **most commonly prescribed** alpha-1 blocker for **BPH**. - Preferred for patients who need symptomatic relief without significant blood pressure lowering effects. *Alfuzosin* - **Alfuzosin** is a **non-selective alpha-1 blocker** that acts on alpha-1A, 1B, and 1D receptors. - While effective for **BPH**, it has more cardiovascular effects than tamsulosin, including potential for orthostatic hypotension. - Often requires dose titration and may not be suitable for all patients. *Terazosin* - **Terazosin** is a **non-selective alpha-1 blocker** used for both **BPH** and hypertension. - Has significant blood pressure-lowering effects and is associated with **first-dose hypotension**. - Requires gradual dose titration starting from low doses, making it less convenient than tamsulosin. *Doxazosin* - **Doxazosin** is a **non-selective alpha-1 blocker** that relaxes smooth muscle in the prostate and also significantly affects systemic blood pressure. - While effective for **BPH**, its non-selectivity leads to orthostatic hypotension and dizziness, especially with the first dose (**first-dose phenomenon**). - Less preferred when BP control is not needed.

Q: A patient is diagnosed with benign prostatic hyperplasia (BPH) and is prescribed a selective alpha-1 receptor blocker. Which drug fits this description?

Tamsulosin. ***Tamsulosin*** - **Tamsulosin** is a **selective alpha-1a receptor blocker** specifically approved for the treatment of **benign prostatic hyperplasia (BPH)** [1]. - It works by **relaxing the smooth muscle** in the prostate and bladder neck, improving urine flow without significantly affecting blood pressure [1], [2]. *Propranolol* - **Propranolol** is a **non-selective beta-blocker** used primarily for conditions like **hypertension**, angina, and arrhythmias. - It has no significant alpha-1 blocking activity and is not used in the treatment of BPH. *Labetalol* - **Labetalol** is an **alpha and beta-blocker**, used primarily for **hypertension**. - While it has some alpha-1 blocking effects, it is not selective for the alpha-1a receptors in the prostate and its beta-blocking effects make it inappropriate for BPH [2]. *Clonidine* - **Clonidine** is an **alpha-2 adrenergic agonist** that acts centrally to reduce sympathetic outflow. - It is used for **hypertension** and **ADHD**, and does not act as an alpha-1 blocker to relieve BPH symptoms.

Q: A patient is prescribed a topical prostaglandin analog for glaucoma. Which drug increases the outflow of aqueous humor and may cause iris pigmentation as a side effect?

Latanoprost. ***Latanoprost*** - **Latanoprost** is a **prostaglandin F2α analog** that increases the outflow of aqueous humor through the **uveoscleral pathway**. - A common and unique side effect associated with latanoprost and other prostaglandin analogs is **increased iris pigmentation** (darkening of the iris) and eyelid skin, as well as increased eyelash growth. *Timolol* - **Timolol** is a **non-selective beta-blocker** that reduces aqueous humor production, thereby lowering intraocular pressure. - It does not significantly affect aqueous humor outflow and is not associated with iris pigmentation changes. *Brimonidine* - **Brimonidine** is an **alpha-2 adrenergic agonist** that reduces aqueous humor production and also slightly increases uveoscleral outflow. - While effective in lowering intraocular pressure, it is not primarily associated with iris pigmentation changes. *Acetazolamide* - **Acetazolamide** is a **carbonic anhydrase inhibitor** that decreases the production of aqueous humor. - It is often used systemically or topically (dorzolamide, brinzolamide) but does not impact aqueous humor outflow or cause iris pigmentation.

Question 1

Cisatracurium is better than atracurium because:-

Accepted Answer

Less histamine release

Answer

No active metabolites

Answer

Shorter half-life

Answer

Better neuromuscular blockade

Question 2

Agent used for eliciting diagnostic differentiation of Myasthenia Gravis from Cholinergic crisis is:-

Accepted Answer

Edrophonium

Answer

Neostigmine

Answer

Ecothiophate

Answer

Ambenonium

Question 3

Mechanism of action of d-tubocurarine is:

Accepted Answer

Competitive, nondepolarizing block at the Nm cholinergic receptor

Answer

Noncompetitive, depolarizing block at the Nm cholinergic receptor

Answer

Non-competitive, nondepolarizing block at the Nm cholinergic receptor

Answer

Competitive, depolarizing block at the Nm cholinergic receptor

Question 4

Which of the following is a uterine relaxant?

Accepted Answer

Ritodrine

Answer

Salmeterol

Answer

Tiotropium

Answer

Tolterodine

Question 5

Which agent stimulates both beta-1 and beta-2 receptors?

Accepted Answer

Epinephrine

Answer

Dopamine

Answer

Dobutamine

Answer

Albuterol

Question 6

How does botulinum toxin affect synaptic transmission?

Accepted Answer

Prevents ACh release

Answer

Inhibits Ca2+ release

Answer

Increases K+ influx

Answer

Blocks Na+ channels

Question 7

Which drug is commonly used for pupil dilation during an eye exam?

Accepted Answer

Tropicamide

Answer

Latanoprost

Answer

Timolol

Answer

Prednisolone

Question 8

A 65-year-old male with benign prostatic hyperplasia (BPH) is prescribed a drug that relaxes smooth muscle in the bladder neck and prostate. Which alpha-1 blocker is most likely to be prescribed?

Accepted Answer

Tamsulosin

Answer

Alfuzosin

Answer

Terazosin

Answer

Doxazosin

Question 9

A patient is diagnosed with benign prostatic hyperplasia (BPH) and is prescribed a selective alpha-1 receptor blocker. Which drug fits this description?

Accepted Answer

Tamsulosin

Answer

Propranolol

Answer

Labetalol

Answer

Clonidine

Question 10

A patient is prescribed a topical prostaglandin analog for glaucoma. Which drug increases the outflow of aqueous humor and may cause iris pigmentation as a side effect?

Accepted Answer

Latanoprost

Answer

Timolol

Answer

Brimonidine

Answer

Acetazolamide

Autonomic Nervous System Drugs — MCQs

Autonomic Nervous System Drugs — MCQs

On this page

Practice by Chapter

Want unlimited practice?