Autonomic Drugs in Respiratory Disease — MCQs
Aminophylline inhibits which of the following enzymes?
A 60-year-old with COPD develops tremor after a medication. Which medication is most likely responsible?
The activation of muscarinic receptors in bronchiolar smooth muscle is associated with:
A 3-year-old is diagnosed with severe acute asthma exacerbation. Which medication is given first?
Which of the following drugs is commonly used as a rescue medication for acute asthma attacks?
Which agent stimulates both beta-1 and beta-2 receptors?
The following drug antagonizes the visceral side effects of neostigmine used for reversal of vecuronium blockade:
In comparison to inhaled adrenergic agonists, the inhaled anticholinergics:
Ocular effects that include mydriasis are characteristic of which of the following drugs?
Hippus occurs in which poisoning?
Autonomic Drugs in Respiratory Disease Indian Medical PG Practice Questions and MCQs
Question 1: Aminophylline inhibits which of the following enzymes?
- A. MAO
- B. Alcohol dehydrogenase
- C. Cytochrome P450
- D. Phosphodiesterase (Correct Answer)
Explanation: ***Phosphodiesterase*** - **Aminophylline** is a methylxanthine derivative that primarily acts as a **phosphodiesterase (PDE) inhibitor** [1], [2]. - By inhibiting PDE, aminophylline increases intracellular levels of **cAMP** and **cGMP**, leading to **bronchodilation** and other effects [2], [3]. *MAO* - **MAO (monoamine oxidase)** inhibitors are antidepressants that prevent the breakdown of neurotransmitters like serotonin, norepinephrine, and dopamine. - Aminophylline does not significantly inhibit MAO. *Alcohol dehydrogenase* - **Alcohol dehydrogenase** is an enzyme responsible for metabolizing alcohol (ethanol) in the liver. - Aminophylline has no direct inhibitory effect on alcohol dehydrogenase. *Cytochrome P450* - **Cytochrome P450 (CYP450)** enzymes are a group of enzymes primarily involved in the metabolism of drugs and other xenobiotics in the liver [4]. - While aminophylline (and its active metabolite theophylline) can be metabolized by and *affect* certain **CYP450** isoenzymes (e.g., CYP1A2), it does not act as a general inhibitor of the entire CYP450 system; its primary therapeutic action is not through CYP450 inhibition.
Question 2: A 60-year-old with COPD develops tremor after a medication. Which medication is most likely responsible?
- A. Montelukast
- B. Ipratropium
- C. Fluticasone
- D. Salmeterol (Correct Answer)
Explanation: ***Salmeterol*** - Salmeterol is a **long-acting beta-2 agonist (LABA)** commonly used in COPD [1]. Beta-2 agonists can cause **tremor** due to stimulation of skeletal muscle beta-2 receptors [2]. - This side effect is dose-dependent and more common with higher doses or in sensitive individuals. *Montelukast* - Montelukast is a **leukotriene receptor antagonist** used in asthma and allergic rhinitis, not typically a primary agent for COPD, and does not commonly cause tremor. - Its mechanism of action involves blocking leukotriene D4 receptors, which are not directly linked to muscle tremor. *Ipratropium* - Ipratropium is a **short-acting muscarinic antagonist (SAMA)** used in COPD. Its primary side effects are typically anticholinergic, such as dry mouth or blurred vision [3]. - Tremor is not a common or expected side effect of ipratropium as it does not act on beta-adrenergic receptors. *Fluticasone* - Fluticasone is an **inhaled corticosteroid (ICS)** used in COPD, often in combination with LABAs [1]. While systemic corticosteroids can cause tremor, the inhaled form has minimal systemic absorption. - **Inhaled corticosteroids** are primarily associated with local side effects like oral candidiasis or dysphonia.
Question 3: The activation of muscarinic receptors in bronchiolar smooth muscle is associated with:
- A. Increase in IP3 and DAG (Correct Answer)
- B. Inhibition of protein kinase C
- C. Activation of adenylyl cyclase
- D. Opening of Na+/K+ cation channels
Explanation: ***Increase in IP3 and DAG*** - **Muscarinic receptors** on bronchial smooth muscle (M3 receptors) are **Gq protein-coupled receptors** [1]. - Activation of **Gq proteins** leads to the activation of **phospholipase C**, which hydrolyzes **PIP2** into **IP3** and **DAG** [1, 3]. *Inhibition of protein kinase C* - **DAG** (diacylglycerol), produced from the breakdown of PIP2, **activates protein kinase C (PKC)**, rather than inhibiting it [2]. - This activation of PKC contributes to downstream cellular responses, including smooth muscle contraction [1]. *Activation of adenylyl cyclase* - **Adenylyl cyclase** is typically activated by **Gs protein-coupled receptors**, leading to an increase in **cAMP**. - **Muscarinic (M3) receptors** are **Gq-coupled**, so they do not activate adenylyl cyclase; instead, they operate through the phospholipase C pathway [1, 3]. *Opening of Na+/K+ cation channels* - While some neurotransmitter receptors are **ligand-gated ion channels** (e.g., nicotinic receptors), muscarinic receptors are **G protein-coupled receptors** [1]. - Their activation does not directly lead to the opening of **Na+/K+ cation channels**; rather, they initiate intracellular signaling cascades.
Question 4: A 3-year-old is diagnosed with severe acute asthma exacerbation. Which medication is given first?
- A. Inhaled ipratropium
- B. IV corticosteroids
- C. Nebulized salbutamol (Correct Answer)
- D. IV magnesium sulfate
Explanation: ***Nebulized salbutamol*** - **Salbutamol** (albuterol) is a **short-acting beta-2 agonist (SABA)** which provides rapid bronchodilation by relaxing smooth muscles in the airways. - It is the **first-line treatment** for acute asthma exacerbations due to its quick onset of action and effectiveness in relieving bronchospasm. *Inhaled ipratropium* - **Ipratropium**, an anticholinergic, is often added to bronchodilators like salbutamol in **severe exacerbations** but is not the primary initial bronchodilator. - It works by blocking muscarinic receptors, causing **bronchodilation**, but its onset of action is slower than salbutamol. *IV corticosteroids* - **Corticosteroids** reduce airway inflammation and are crucial for preventing relapse and shortening recovery in severe asthma, but their **onset of action is delayed** (several hours). - They are typically administered after initial bronchodilation with SABAs and are not the first medication given for immediate symptom relief. *IV magnesium sulfate* - **Magnesium sulfate** is a smooth muscle relaxant that can be used in **severe, life-threatening asthma exacerbations** that are refractory to standard therapy. - It is considered a **second or third-line treatment** rather than an initial intervention for immediate bronchodilation.
Question 5: Which of the following drugs is commonly used as a rescue medication for acute asthma attacks?
- A. Salbutamol (Correct Answer)
- B. Theophylline
- C. Terbutaline
- D. Budesonide
Explanation: ***Salbutamol*** - **Salbutamol** (albuterol) is a **short-acting beta-2 agonist (SABA)** that rapidly relaxes bronchial smooth muscle. - Its quick onset of action makes it ideal for immediate relief of **bronchoconstriction** during an acute asthma attack. - It is the **most commonly used** and **first-line rescue medication** for acute asthma worldwide. *Terbutaline* - **Terbutaline** is also a **short-acting beta-2 agonist (SABA)** similar to salbutamol and can be used as a rescue medication. - While it has comparable bronchodilator effects, **salbutamol is more commonly used** as the preferred rescue inhaler in clinical practice. - Both are SABAs, but salbutamol has become the standard first-choice rescue medication globally. *Theophylline* - **Theophylline** is a **methylxanthine** that acts as a bronchodilator but has a **narrow therapeutic index** and slower onset of action. - It is used as a **maintenance therapy** for chronic asthma and not as a rescue drug for acute exacerbations. *Budesonide* - **Budesonide** is an **inhaled corticosteroid (ICS)** used as a **long-term controller medication** to reduce airway inflammation. - It has a slow onset of action and is *not* effective for immediate relief during an acute asthma attack.
Question 6: Which agent stimulates both beta-1 and beta-2 receptors?
- A. Dopamine
- B. Dobutamine
- C. Albuterol
- D. Epinephrine (Correct Answer)
Explanation: ***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.
Question 7: The following drug antagonizes the visceral side effects of neostigmine used for reversal of vecuronium blockade:
- A. Atropine (Correct Answer)
- B. Pilocarpine
- C. Pyridostigmine
- D. Nicotine
Explanation: ***Atropine*** - **Atropine** is an **anticholinergic drug** that blocks muscarinic receptors, effectively counteracting the **parasympathomimetic side effects** of neostigmine. - When neostigmine is used to reverse neuromuscular blockade, it inhibits **acetylcholinesterase**, increasing acetylcholine levels. This increased acetylcholine stimulates both nicotinic receptors (for muscle contraction) and muscarinic receptors (causing side effects like **bradycardia**, **salivation**, **bronchospasm**, and **gastrointestinal hypermotility**). Atropine selectively blocks these unwanted muscarinic effects. *Pilocarpine* - **Pilocarpine** is a **direct muscarinic agonist**, meaning it would exacerbate, rather than antagonize, the visceral side effects of neostigmine. - It is primarily used to treat **xerostomia** and **glaucoma** by increasing acetylcholine's effects on muscarinic receptors. *Pyridostigmine* - **Pyridostigmine** is another **cholinesterase inhibitor**, similar to neostigmine, and also used for reversal of neuromuscular blockade or in treating **myasthenia gravis**. - It would increase acetylcholine levels and thus enhance, not antagonize, the muscarinic side effects if used with neostigmine in this context. *Nicotine* - **Nicotine** is an agonist primarily acting on **nicotinic acetylcholine receptors**. - While neostigmine increases acetylcholine at nicotinic receptors to reverse muscle blockade, nicotine's primary action is not on muscarinic receptors to counteract the visceral side effects.
Question 8: In comparison to inhaled adrenergic agonists, the inhaled anticholinergics:
- A. Are more effective in bronchial asthma
- B. Produce a slower response in bronchial asthma (Correct Answer)
- C. Produce little benefit in chronic obstructive lung disease
- D. Are better suited for control of an acute attack of asthma.
Explanation: ***Produce a slower response in bronchial asthma*** - **Inhaled anticholinergics** (e.g., ipratropium, tiotropium) block **muscarinic receptors**, leading to bronchodilation, but their onset of action is generally **slower** (15-30 minutes) compared to the rapid action of **beta-2 adrenergic agonists** (5 minutes). - This slower response makes them less ideal for **acute asthma attacks** where immediate bronchodilation is critical. - Anticholinergics are used as **add-on therapy** in asthma management. *Are more effective in bronchial asthma* - **Inhaled beta-2 adrenergic agonists** (e.g., salbutamol, albuterol) are typically **more effective** and are the **first-line treatment** for acute bronchodilation in asthma due to their rapid onset and potent effect. - **Anticholinergics** are often considered **add-on therapy** for asthma, particularly for patients who have an inadequate response to beta-agonists. *Produce little benefit in chronic obstructive lung disease* - **Inhaled anticholinergics** (e.g., tiotropium, ipratropium) are considered **first-line agents** and provide **significant benefit** in improving lung function and reducing exacerbations in **chronic obstructive pulmonary disease (COPD)**. - Their efficacy in COPD is often **superior** to beta-agonists for long-term maintenance therapy due to the prominent role of cholinergic tone in COPD bronchoconstriction. *Are better suited for control of an acute attack of asthma* - **Short-acting inhaled beta-2 adrenergic agonists** are the **drug of choice** for the rapid relief of acute asthma symptoms due to their quick onset of action. - **Inhaled anticholinergics** like **ipratropium** have a slower onset and are generally used as **adjunctive therapy** or for patients unable to tolerate beta-agonists during acute exacerbations.
Question 9: Ocular effects that include mydriasis are characteristic of which of the following drugs?
- A. phenylephrine (alpha agonist) (Correct Answer)
- B. neostigmine (cholinesterase inhibitor)
- C. phentolamine (alpha blocker)
- D. mecamylamine (ganglionic blocker)
Explanation: ***phenylephrine (alpha agonist)*** - **Phenylephrine** is a direct-acting **alpha-1 adrenergic agonist** that causes contraction of the **pupillary dilator muscle**, leading to **mydriasis** (pupil dilation). [1] - It is frequently used clinically to dilate pupils for **ophthalmologic examinations** due to its selective action on alpha-1 receptors in the eye. [2] *neostigmine (cholinesterase inhibitor)* - **Neostigmine** inhibits acetylcholinesterase, increasing acetylcholine at the neuromuscular junction and muscarinic receptors. This leads to **miosis** (pupil constriction), not mydriasis. - Its ophthalmic use is primarily for treating **glaucoma** by improving aqueous humor outflow through cholinergic effects on the ciliary muscle. *phentolamine (alpha blocker)* - **Phentolamine** is a **non-selective alpha-adrenergic antagonist** that blocks both alpha-1 and alpha-2 receptors. - Alpha-1 receptor blockade in the eye would relax the pupillary dilator muscle, leading to **miosis** or prevention of mydriasis, not its induction. *mecamylamine (ganglionic blocker)* - **Mecamylamine** is a **ganglionic blocker** that antagonizes nicotinic receptors in both sympathetic and parasympathetic ganglia. - Blocking parasympathetic ganglia can cause some mydriasis, but ganglionic blockers have widespread, non-selective autonomic effects and are not primarily used for isolated mydriasis.
Question 10: Hippus occurs in which poisoning?
- A. Aconite poisoning (Correct Answer)
- B. Opioid poisoning
- C. Neuromuscular blocking agent poisoning
- D. Belladonna poisoning
Explanation: ***Aconite poisoning*** - **Hippus**, characterized by alternating **pupillary constriction and dilation**, is a hallmark of aconite poisoning. - This unusual pupil activity results from the **neurotoxic effects** of aconite on the autonomic nervous system. *Opioid poisoning* - Opioid poisoning typically causes characteristic **pinpoint pupils (miosis)** due to parasympathetic overstimulation. - Hippus is not a feature of opioid toxicity. *Neuromuscular blocking agent poisoning* - Neuromuscular blocking agents primarily affect the **skeletal muscles**, leading to **paralysis** but generally do not directly impact pupil size or reactivity. - Pupils usually remain **mid-dilated and fixed** in severe paralysis, but not hippus. *Belladonna poisoning* - Belladonna (atropine) poisoning causes **mydriasis (dilated pupils)** due to its anticholinergic effect, blocking parasympathetic activity. - The pupils are typically fixed and dilated, not exhibiting hippus.
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