Block 9 Rx Antimuscarinic MCQ's

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Block 9 Rx Antimuscarinic MCQ

Questions and Answers
  • 1. 

    A 25-year-old healthy female volunteer was given injection norepinephrine that caused a drop in heart rate by 20 beats per minute (bpm). After 2 days she was given an oral Nn blocking antimuscarinic drug before injection norepinephrine. This led to an increase in heart rate by 50 bpm. Which of the following anti-muscarinic drugs was she most likely given?

    • A.

      Atropine

    • B.

      Ipratropium

    • C.

      Glycopyrrolate

    • D.

      Darifenacin

    • E.

      Scopolamine

    Correct Answer
    C. Glycopyrrolate
    Explanation
    The most likely anti-muscarinic drug that the female volunteer was given is glycopyrrolate. This is because glycopyrrolate is known to block the effects of acetylcholine on the heart, leading to an increase in heart rate. In this case, the oral administration of glycopyrrolate before the injection of norepinephrine caused a significant increase in heart rate, suggesting that glycopyrrolate was able to counteract the bradycardic effects of norepinephrine. Atropine is also an anti-muscarinic drug, but it is not the most likely answer in this case as glycopyrrolate is more commonly used for this purpose.

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  • 2. 

    Which of the following molecular actions can result from the blockade of M3 receptors by antimuscarinic drugs in non-vascular smooth muscle?

    • A.

      Less negative resting membrane potential

    • B.

      Binding of Ca++ to troponin C

    • C.

      Increased concentration of cytosolic calcium

    • D.

      Decreased synthesis of intracellular IP3

    • E.

      Direct opening of K+ channels

    Correct Answer
    D. Decreased synthesis of intracellular IP3
    Explanation
    Antimuscarinic drugs block M3 receptors, which are involved in the synthesis of intracellular IP3. Therefore, the blockade of M3 receptors by these drugs would result in a decreased synthesis of intracellular IP3.

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  • 3. 

    Which of the following is an effect of atropine upon the respiratory system?

    • A.

      Increased contraction of airway smooth muscle

    • B.

      Decreased pulmonary vital capacity

    • C.

      Increased secretion of bronchial glands

    • D.

      Decreased diaphragmatic performance

    • E.

      Decreased mucociliary clearance

    Correct Answer
    E. Decreased mucociliary clearance
    Explanation
    Atropine is a medication that blocks the action of acetylcholine, a neurotransmitter that stimulates the contraction of smooth muscles. The mucociliary clearance refers to the movement of mucus and foreign particles out of the respiratory tract by the coordinated action of cilia. Atropine inhibits the activity of cilia, leading to a decrease in mucociliary clearance. Therefore, the correct answer is "Decreased mucociliary clearance."

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  • 4. 

    Which of the following is a common side effect of quaternary ammonium antimuscarinic drugs?

    • A.

      Urge incontinence

    • B.

      Drowsiness

    • C.

      Constipation

    • D.

      AV block

    • E.

      Difficulty in near vision

    • F.

      Hallucinations

    Correct Answer
    E. Difficulty in near vision
    Explanation
    Difficulty in near vision is a common side effect of quaternary ammonium antimuscarinic drugs. These drugs work by blocking the action of acetylcholine, a neurotransmitter that is involved in various bodily functions. By blocking the muscarinic receptors, these drugs can affect the muscles of the eyes, leading to difficulty in near vision. This side effect is often temporary and reversible once the drug is discontinued.

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  • 5. 

    Antimuscarinic drugs usually increase the heart rate because they can counteract which of the following acetylcholine-induced actions?

    • A.

      Release of nitric oxide

    • B.

      Opening of K+ channels in SA node

    • C.

      Decrease in cardiac contractility

    • D.

      Opening of Na-1- channels in ganglionic neurons

    • E.

      Activation of cardiac presynaptic autoreceptors

    Correct Answer
    B. Opening of K+ channels in SA node
    Explanation
    Antimuscarinic drugs usually increase the heart rate because they can counteract the opening of K+ channels in the SA node. The SA node is responsible for initiating the electrical impulses that regulate the heart rate. Opening of K+ channels in the SA node leads to hyperpolarization, which slows down the heart rate. Antimuscarinic drugs block the effects of acetylcholine on the SA node, preventing the opening of K+ channels and allowing the heart rate to increase.

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  • 6. 

    Which of the following statements correctly pairs the antimuscarinic drug with one of its common adverse effects?

    • A.

      Atropine - cough

    • B.

      Darifenacin - constipation

    • C.

      Glycopyrrolate -insomnia

    • D.

      Ipratropium -restlessness

    • E.

      Scopolamine - impairment of far vision

    Correct Answer
    B. Darifenacin - constipation
    Explanation
    Darifenacin is an antimuscarinic drug used to treat overactive bladder. One of the common adverse effects of antimuscarinic drugs is constipation. Therefore, the statement "Darifenacin - constipation" correctly pairs the drug with its common adverse effect.

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  • 7. 

    Antimuscarinic drugs are contraindicated, or should be used with caution, in which of the following disease states?

    • A.

      Irritable bowel syndrome

    • B.

      Urinary urge incontinence

    • C.

      Sialorrhea

    • D.

      Sinus bradyeardia

    • E.

      Travelers' diarrhea

    • F.

      Ulcerative colitis

    Correct Answer
    F. Ulcerative colitis
    Explanation
    Antimuscarinic drugs are contraindicated in ulcerative colitis because they can worsen the symptoms of this inflammatory bowel disease. These drugs work by blocking the action of acetylcholine, a neurotransmitter that plays a role in gastrointestinal motility and secretions. In ulcerative colitis, there is already inflammation and damage to the lining of the colon, so blocking acetylcholine can further disrupt normal bowel function and exacerbate symptoms. Therefore, caution should be exercised when considering the use of antimuscarinic drugs in patients with ulcerative colitis.

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  • 8. 

    Atropine can most effectively counteract which of the following drug-induced effects?

    • A.

      Physostigmine-induced sweating

    • B.

      Epinephrine-induced increased in blood pressure

    • C.

      Nicotine-induced increase in peripheral vascular resistance

    • D.

      Prazosin-induced reflex tachycardia

    • E.

      Scopolamine-induced sleepiness

    Correct Answer
    A. Physostigmine-induced sweating
    Explanation
    Atropine can most effectively counteract physostigmine-induced sweating. Atropine is an anticholinergic drug that blocks the effects of acetylcholine, the neurotransmitter responsible for stimulating sweat glands. Physostigmine, on the other hand, is a cholinesterase inhibitor that increases the levels of acetylcholine in the body, leading to excessive sweating. By blocking the effects of acetylcholine, atropine can effectively reduce or eliminate the sweating caused by physostigmine.

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  • 9. 

    A 32-year-old woman suffering from irritable bowel syndrome was prescribed glycopyrrolate. The blockade of which of the following pairs of receptors best explains the mechanism of the therapeutic effect of  the drug in this patient?

    • A.

      Beta-2 and Nm

    • B.

      M2 and Nn

    • C.

      M3 Nn

    • D.

      Alpha-1 and M2

    • E.

      M1 & M3

    Correct Answer
    C. M3 Nn
    Explanation
    Glycopyrrolate is a medication commonly used to treat irritable bowel syndrome. The therapeutic effect of the drug in this patient can be explained by the blockade of M3 and Nn receptors. M3 receptors are found in the smooth muscles of the gastrointestinal tract, and blocking these receptors can help reduce the symptoms of irritable bowel syndrome such as abdominal pain and cramping. Nn receptors are nicotinic receptors found in the enteric nervous system, and blocking these receptors can also help alleviate symptoms by reducing the excessive activity in the gut. Therefore, the blockade of M3 and Nn receptors best explains the mechanism of action of glycopyrrolate in this patient.

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  • 10. 

    A 56-year-old male with chronic obstructive pulmonary disease started a therapy with ipratropium bromide through a metered dose inhaler. Which of the following statements best explains why ipratropium is the only antirnuscarinic drug used to treat bronchospastic disorders?

    • A.

      It is more potent than other antimuscarinic drugs

    • B.

      Its oral bioavailabdity is higher than that of other antimuscarinic drugs

    • C.

      It has an excellent absorption, when given by inhaiatory route

    • D.

      It does not decrease bronchial secretions and mucociliary clearance

    • E.

      Central effects are negligible since it does not cross the blood brain barrier

    Correct Answer
    D. It does not decrease bronchial secretions and mucociliary clearance
    Explanation
    Ipratropium bromide is the only antimuscarinic drug used to treat bronchospastic disorders because it does not decrease bronchial secretions and mucociliary clearance. This is important because bronchospastic disorders, such as chronic obstructive pulmonary disease, involve excessive narrowing of the airways, leading to difficulty in breathing. By not decreasing bronchial secretions and mucociliary clearance, ipratropium allows for better clearance of mucus and maintains normal function of the cilia in the airways, helping to alleviate symptoms and improve airflow.

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  • 11. 

    Which of the following is the most likely central effect of a moderate dose of nicotine?

    • A.

      Depression of the reticular formation

    • B.

      Stimulation of respiratory center

    • C.

      Depression of vomiting center

    • D.

      Inhibition of ADH secretion

    • E.

      Depression of vasomotor centers

    Correct Answer
    B. Stimulation of respiratory center
    Explanation
    A moderate dose of nicotine is most likely to stimulate the respiratory center. Nicotine is a stimulant drug that affects the central nervous system. It can increase heart rate, blood pressure, and respiration. Stimulation of the respiratory center would result in an increase in breathing rate and depth.

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  • 12. 

    Which of the following statement best explains the nicotine-induced ganglionic blockade that usually occurs after an initial stimulating action?

    • A.

      Long-lasting activation of nicotinic receptors

    • B.

      Long lasting blockade of M2 receptors

    • C.

      Long lasting blockade of M1 receptors

    • D.

      Prevention of acetylcholine release from presynaptic terminals

    • E.

      Prevention of catecholamine release from small intensely fluorescent cells

    Correct Answer
    A. Long-lasting activation of nicotinic receptors
    Explanation
    Nicotine is a stimulant that initially activates nicotinic receptors, leading to increased release of neurotransmitters like acetylcholine and catecholamines. However, with prolonged exposure to nicotine, desensitization of these receptors occurs, resulting in a long-lasting activation of the receptors. This leads to a ganglionic blockade, where the transmission of signals between neurons in the autonomic ganglia is inhibited. Therefore, the best explanation for the nicotine-induced ganglionic blockade is the long-lasting activation of nicotinic receptors.

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  • 13. 

    Pretreatment with a ganglionic blocker will most effectively prevent which of the following drug-induced effects?

    • A.

      Neostigmine-induced increase in intestinal peristalsis

    • B.

      Epinephrine-induced tachycardia

    • C.

      Mcotine-inclucecl contraction of skeletal muscle

    • D.

      Norepinephrine-induced bradycardia

    • E.

      Propranolol-induced hypotension

    Correct Answer
    D. Norepinephrine-induced bradycardia
    Explanation
    Pretreatment with a ganglionic blocker will most effectively prevent norepinephrine-induced bradycardia. Ganglionic blockers block the transmission of signals between the pre- and post-ganglionic neurons in the autonomic nervous system. Norepinephrine acts on post-ganglionic sympathetic neurons to cause bradycardia. By blocking the ganglionic transmission, the effect of norepinephrine on the post-ganglionic neurons is prevented, resulting in the prevention of bradycardia.

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  • 14. 

    1. A new synthetic drug X was studied for its cardiovascular effects. The drug was given IV to four laboratory animals while the heart rate was recorded. The animals had received either no pretreatment or an effective dose of the drugs indicated below, The NET CHANGES (+ or -) induced by drug X (not by the pretreatment) are shown in the following table:
    In the animal receiving: Heart rate after X was : No pretreatment -25 Mecamylamine +20 Atropine +20 Prazocin +20 Which of the following drugs did the new agent most resemble?

    • A.

      Propranolol

    • B.

      Acetylcholine

    • C.

      Albuterol

    • D.

      Norepinephrine

    • E.

      Isoproterenol

    Correct Answer
    D. Norepinephrine
    Explanation
    The new synthetic drug X most closely resembles norepinephrine based on the changes in heart rate observed in the laboratory animals. Norepinephrine is a neurotransmitter and hormone that increases heart rate. Similarly, drug X also caused an increase in heart rate when administered to the animals. This suggests that drug X may have similar effects on the cardiovascular system as norepinephrine.

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  • Current Version
  • Mar 21, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • May 18, 2012
    Quiz Created by
    Chachelly
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