Pharm Skel Muscle Relaxants Part 1

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Pharm Skel Muscle Relaxants Part 1 - Quiz

Welcome to another instalment of our long list of pharmacology quizzes, everybody! In today’s game, we’ll be tackling the pharmaceuticals used to relax the muscles and reduce tension in them; skeletal muscle relaxants. What do you know about how these drugs work? Let’s find out together!


Questions and Answers
  • 1. 

    Directions 1- 4 (handouts) For each numbered item select the one lettered option which is most closely associated with it (each lettered option can be selected once, more than once, or not at all). This drug can block Nn receptors in the autonomic ganglia

    • A.

      Tubocurarine

    • B.

      Baclofen

    • C.

      Cisatracurium

    • D.

      Dantrolene

    • E.

      Diazepam

    • F.

      Mivacurium

    • G.

      Succinylcholine

    • H.

      Tizanidine

    Correct Answer
    A. Tubocurarine
    Explanation
    Tubocurarine is the correct answer because it is a drug that can block Nn receptors in the autonomic ganglia.

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  • 2. 

    Directions 1- 4 (handouts) For each numbered item select the one lettered option which is most closely associated with it (each lettered option can be selected once, more than once, or not at all). This drug acts as an agonist at Nm receptors.

    • A.

      Tubocurarine

    • B.

      Baclofen

    • C.

      Cisatracurium

    • D.

      Dantrolene

    • E.

      Diazepam

    • F.

      Mivacurium

    • G.

      Succinylcholine

    • H.

      Tizanidine

    Correct Answer
    G. Succinylcholine
    Explanation
    Succinylcholine is the correct answer because it is a drug that acts as an agonist at Nm receptors.

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  • 3. 

    Directions 1- 4 (handouts) For each numbered item select the one lettered option which is most closely associated with it (each lettered option can be selected once, more than once, or not at all). This drug acts as an agonist mainly at alpha-2 receptors located In the spinal cord

    • A.

      Tubocurarine

    • B.

      Baclofen

    • C.

      Cisatracurium

    • D.

      Dantrolene

    • E.

      Diazepam

    • F.

      Mivacurium

    • G.

      Succinylcholine

    • H.

      Tizanidine

    Correct Answer
    H. Tizanidine
    Explanation
    Tizanidine is the correct answer because it acts as an agonist mainly at alpha-2 receptors located in the spinal cord. This means that it activates these receptors, leading to a decrease in muscle tone and a reduction in muscle spasms. Tubocurarine, Baclofen, Cisatracurium, Dantrolene, Diazepam, Mivacurium, and Succinylcholine do not primarily act on alpha-2 receptors in the spinal cord.

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  • 4. 

    Directions 1- 4 (handouts) For each numbered item select the one lettered option which is most closely associated with it (each lettered option can be selected once, more than once, or not at all). This drug can activate M2 receptors in the heart.

    • A.

      Tubocurarine

    • B.

      Baclofen

    • C.

      Cisatracurium

    • D.

      Dantrolene

    • E.

      Diazepam

    • F.

      Mivacurium

    • G.

      Succinylcholine

    • H.

      Tizanidine

    Correct Answer
    G. Succinylcholine
    Explanation
    Succinylcholine is the correct answer because it is a drug that can activate M2 receptors in the heart. The other options listed are not known for their effects on M2 receptors in the heart.

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  • 5. 

    A 61-year-old woman underwent surgery to remove an ovarian cancer. Anesthesia was induced by thiopental and maintained by sevoflurane and tubocurarine. After surgery the anesthesiologist administered a drug to overcome the residual muscle relaxant effect fo tubocurarine. Which of the following drugs was most likely given?

    • A.

      Neostigmine

    • B.

      Succinylcholine

    • C.

      Cisatracurium

    • D.

      Tizanidine

    • E.

      Dantrolene

    • F.

      Baclofen

    Correct Answer
    A. Neostigmine
    Explanation
    Learning objective: explain the interaction between tubocurarine and neostigmine.
    Answer: A
    All nondepolarizing neuromuscular blockers (tubocurarine, cisatracurium, etc.) Cause a
    competitive blockade of Nm receptors. Their action is antagonized by acetylcholine as well as
    by drugs that increase the availability of acetylcholine at the motor end plate (cholinesterase
    inhibitors like neostigmine). This antagonism is exploited clinically and neostigmine is often
    used to speed up the recovery from the neuromuscular blockade remaining after completion of
    surgery.
    B, C, D, E, F) (see explanation above)

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  • 6. 

    A 67-year-old woman required intubation and mechanical ventilation for management of respiratory failure. Tubocurarine was given IV to reduce chest wall resistance and ineffective spontaneous ventilation. Which of the following membrane potentials was most likely blocked by tubocurarine in this patient?

    • A.

      Action potential of motor nerve

    • B.

      Miniature end plate potential

    • C.

      Resting potential of smooth muscle

    • D.

      Action potential of cardiac muscle

    • E.

      Action potential of corticospinal tract

    Correct Answer
    B. Miniature end plate potential
    Explanation
    Learning objective: describe the action of tubocurarine on miniature membrane potential.
    Answer: B
    The formation of miniature end plate potential is caused by the release of small quanta of
    acetylcholine that activate Nm receptors at the motor end plate. By blocking these receptors
    tubocurarine block the formation of this potential.
    A, D, E) Neuromuscular blocking drugs have negligible effects on the formation of action
    potentials in the motor neuron, cardiac muscle or corticospinal tract.
    C) Smooth muscle membrane has no Nm receptors. Therefore neuromuscular blocking drugs
    have no direct effects on smooth muscle.

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  • 7. 

    A 65-year-old woman underwent hysterectomy to remove a uterine carcinoma. The anesthesiologist chose thiopental sodium for induction and isoflurane and tubocurarine for maintenance of general anesthesia. The anesthesiologist also administered another drug in order to counteract tubocurarine induced hypotension. A drug belonging to which of the following classes was most likely given?

    • A.

      Beta-1 agonist

    • B.

      D1 antagonist

    • C.

      Muscarinic agonist

    • D.

      Cholinesterase inhibitor

    • E.

      H1 antagonist

    Correct Answer
    E. H1 antagonist
    Explanation
    Learning objective: describe the interaction between tubocurarine and H1 antagonists.
    Answer: E
    Tubocurarine induced hypotension is mainly due to histamine release and premedication with
    an antihistamine drug is often used in order to attenuate this adverse effect.
    A, B, C, D) Drugs from these classes would increase, not decrease, tubocurarine-induced
    hypotension.

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  • 8. 

    A 66-year-old woman was brought to the Emergency Room following a car accident. A surgical operation was needed to repair a badly damaged leg. The woman was currently receiving gentamicin and tolterodine for an urinary tract infection, timolol and latanoprost for glaucoma, and lovastatin for hypercholesterolemia. The anesthesiologist chose thiopental sodium for induction and isoflurane plus tubocurarine for maintenance of general anesthesia. Which of the following patient’s medications most likely enhanced the action of tubocurarine?

    • A.

      Gentamicin

    • B.

      Tolterodine

    • C.

      Timolol

    • D.

      Latanoprost

    • E.

      Lovastatin

    Correct Answer
    A. Gentamicin
    Explanation
    Learning objective: describe the interaction between aminoglycoside antibiotics and
    nondepolarizing neuromuscular blockers.
    Answer: A
    Aminoglycoside antibiotics inhibit acetylcholine release from cholinergic nerves by blocking a
    specific type of Ca++ channels. Therefore they enhance the blockade induced by
    nondepolarizing neuromuscular blockers.
    B, C, D, E) (see explanation above)

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  • 9. 

    A 73-year-old man underwent thoracic surgery to remove a lung cancer. General anesthesia was supplemented with tubocurarine. Which of the following molecular actions most likely mediated the muscle relaxant effect of this drug?

    • A.

      Stimulation of plasma cholinesterase

    • B.

      Long lasting activation of postsynaptic Nm receptors

    • C.

      Competitive blockade of postsynaptic Nm receptors

    • D.

      Blockade of action potential of the motor nerves

    • E.

      Blockade of Ca++ release from sarcoplasmic reticulum

    • F.

      Competitive blockade of Nn receptors in brain

    Correct Answer
    C. Competitive blockade of postsynaptic Nm receptors
    Explanation
    Learning objective: explain the mechanism of action of tubocurarine.
    Answer: C
    Tubocurarine is the prototype of nondepolarizing neuromuscular blockers. These drugs act as
    competitive antagonist at Nm receptors so preventing the activation of these receptors by
    acetylcholine. In this way they prevent depolarization of skeletal muscle cell membrane and
    inhibit muscular contraction. Their action can be overcome by increasing the concentration of
    acetylcholine in the synaptic cleft.
    A, B, D, E ,F) Nondepolarizing neuromuscular blockers are devoid of these effects.

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  • 10. 

    A 38-year-old patient was admitted to the emergency room with extensive soft-tissue burns. He was semiconscious and was artificially ventilated. His uncoordinated respiratory movements were interfering with the mechanical ventilation. Which of the following drugs was most likely administered to decrease the patient’s spontaneous breathing?

    • A.

      Atropine

    • B.

      Vecuronium

    • C.

      Botulinum toxin

    • D.

      Dantrolene

    • E.

      Neostigmine

    • F.

      Fluoxetine

    Correct Answer
    B. Vecuronium
    Explanation
    Learning objective: describe the therapeutic uses of nondepolarizing neuromuscular
    blockers
    Answer: B
    Neuromuscular blockers are often used in patient who need mechanical ventilation. They can
    facilitate intubation and can block voluntary movements that could interfere with mechanical
    ventilation. Neuromuscular blockers with an intermediate duration of action like vecuronium
    (about 30 minutes after a standard therapeutic dose) are often preferred.
    A, C, D, E, F) (see explanation above)

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  • 11. 

    A 49-year-old woman required intubation and mechanical ventilation for management of respiratory failure resulting from severe emphysema. The patient was agitated, attempting to sit up in bed and reach for his endotracheal tube. Lorazepam was give IV for sedation and the patient got drowsy but motor restlessness was only marginally improved. A muscle relaxant was given IV. The patient relaxed as paralysis developed but 5 minutes later her heart rate was 160 bpm. Which of the following drugs most likely caused this adverse effect?

    • A.

      Botulinum toxin

    • B.

      Dantrolene

    • C.

      Succinylcholine

    • D.

      Tubocurarine

    • E.

      Cisatracurium

    Correct Answer
    D. Tubocurarine
    Explanation
    Learning objective: describe the adverse effects of tubocurarine.
    Answer: D
    Agitation is a frequent problem in patients who are intubated and artificially ventilated.
    Benzodiazepines are useful agent for controlling anxiety and agitation. They also cause
    anterograde amnesia (a quite useful property in this setting) but have no analgesic properties.
    When sedating drugs are not fully effective, a muscle relaxant is added. Tubocurarine is a
    neuromuscular blocking drug whose action last more than 30 minutes. It is used because of
    effectiveness and low cost. The tachycardia that can appear after the administration of
    tubocurarine can be due either to histamine release or to blockade of nicotinic receptors of
    autonomic ganglia or, most likely, to both.
    A) Botulinum toxin is not used to limit movements in an intubated patient. It action would last for
    months.
    B) Dantrolene is a spasmolytic drug. It can reduce spasticity but is unable to cause
    neuromuscular paralysis when given at therapeutic doses. Therefore it is not used to limit
    movements in an intubated patient.
    C) Succinylcholine can cause stimulation of both nicotinic receptors of autonomic ganglia and
    cardiac muscarinic receptors. Therefore it would tend to cause bradycardia which is only
    partially counteracted by its slight tendency to cause histamine release.
    E) Cisatracurium has no effect on nicotinic receptors of autonomic ganglia and has negligible
    histamine releasing properties.

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  • 12. 

    A 57-year-old woman was admitted semiconscious to the emergency room after a car accident. Artificial ventilation was need and a drug was given to facilitate intubation. The administered drug has the lowest duration of action among the skeletal muscle relaxant. Which of the following drugs was most likely given?

    • A.

      Succinylcholine

    • B.

      Cisatracurium

    • C.

      Dantrolene

    • D.

      Vecuronium

    • E.

      Tubocurarine

    • F.

      Tizanidine

    Correct Answer
    A. Succinylcholine
    Explanation
    Answer: describe the pharmacokinetics of succinylcholine.
    Answer: A
    The duration of action of succinylcholine is about 8 minutes after a standard therapeutic dose.
    The reason is that the drug is rapidly hydrolyzed by pseudocholinesterase in plasma and liver.
    This duration of action is enough to facilitate intubation. When a longer duration of is needed
    the drug is given by IV infusion.
    B, C, D, E, F) (see explanation above)

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  • 13. 

    A 33-year-old woman was hospitalized with the diagnosis of schizophrenia and was started on a high dose of haloperidol. After 2 days of therapy she became rigid, appeared confused at times and had a fever of 104° F. The physical examination revealed tachycardia, labile blood pressure, profuse diaphoresis, sialorrhea, dyspnea and urinary incontinence. Which of the following drugs was most likely given immediately to the patient?

    • A.

      Atropine

    • B.

      Succinylcholine

    • C.

      Dantrolene

    • D.

      Dopamine

    • E.

      Prazosin

    • F.

      Baclofen

    Correct Answer
    C. Dantrolene
    Explanation
    Learning objective: describe the therapeutic uses of dantrolene.
    Answer: C
    The clinical picture of the patient suggest the diagnosis of neuroleptic malignant syndrome, a
    rare disorder very similar to the malignant hyperthermia induced by some neuromuscular
    blocking agents (mainly succinylcholine) and inhalational anesthetics. In malignant
    hyperthermia the uncontrolled release of CA++ from the sarcoplasmic reticulum of skeletal
    muscle is the initiating event. Dantrolene, a drug that blocks the release of calcium from
    sarcoplasmic reticulum is the drug of choice in malignant hyperthermia. The drug is also
    currently given in case of neuroleptic malignant syndrome, even if the association of the
    syndrome with a defect of Ca++ metabolism in skeletal muscle is less clear.
    A , D, E) These drugs are dangerous in this patient since they would worsen the tachycardia.
    B) Succinylcholine administration would be completely irrational since the drug can cause
    malignant hyperthermia.

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  • 14. 

    A 55-year-old woman was undergoing major surgery to remove a breast carcinoma. The woman, who was an heavy smoker, had been suffering from chronic obstructive pulmonary disease for 15 years. A drug was administered preoperatively and the anesthesia was supplemented with a skeletal muscle relaxant. Which of the following drugs would be contraindicated for this patient?

    • A.

      Tubocurarine

    • B.

      Glycopyrrolate

    • C.

      Clonidine

    • D.

      Vecuronium

    • E.

      Cisatracurium

    Correct Answer
    A. Tubocurarine
    Explanation
    Learning objective: describe the main contraindication of tubocurarine.
    Answer: A
    Tubocurarine can cause histamine release from mast cells. A prominent effect of histamine is
    bronchoconstriction and therefore tubocurarine should not be used in a patient with asthma or
    COPD.
    B) Glycopyrrolate is often given as a preoperative medication in order to prevent effects related
    to vagal activation (sialorrhea and bradycardia)
    C) Clonidine is sometimes given as a preoperative medication because it has sedative
    properties and potentiates the action of anesthetic agents.
    D, E) Each of these two nondepolarizing neuromuscular blocking drugs could be used since
    these agents do not release histamine

    Rate this question:

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    Quiz Edited by
    ProProfs Editorial Team
  • Jun 24, 2012
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