Pharm Skel Muscle Relaxants Part 1
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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?
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Neostigmine
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Succinylcholine
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Cisatracurium
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Tizanidine
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Dantrolene
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Baclofen
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About This 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!
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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.
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Tubocurarine
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Baclofen
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Cisatracurium
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Dantrolene
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Diazepam
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Mivacurium
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Succinylcholine
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Tizanidine
Correct Answer
A. SuccinylcholineExplanation
Succinylcholine is the correct answer because it is a drug that acts as an agonist at Nm receptors.Rate this question:
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- 3.
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?
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Stimulation of plasma cholinesterase
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Long lasting activation of postsynaptic Nm receptors
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Competitive blockade of postsynaptic Nm receptors
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Blockade of action potential of the motor nerves
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Blockade of Ca++ release from sarcoplasmic reticulum
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Competitive blockade of Nn receptors in brain
Correct Answer
A. Competitive blockade of postsynaptic Nm receptorsExplanation
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.Rate this question:
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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 acts as an agonist mainly at alpha-2 receptors located In the spinal cord
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Tubocurarine
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Baclofen
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Cisatracurium
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Dantrolene
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Diazepam
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Mivacurium
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Succinylcholine
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Tizanidine
Correct Answer
A. TizanidineExplanation
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.Rate this question:
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- 5.
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?
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Succinylcholine
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Cisatracurium
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Dantrolene
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Vecuronium
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Tubocurarine
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Tizanidine
Correct Answer
A. SuccinylcholineExplanation
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)Rate this question:
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- 6.
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
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Tubocurarine
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Baclofen
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Cisatracurium
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Dantrolene
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Diazepam
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Mivacurium
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Succinylcholine
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Tizanidine
Correct Answer
A. TubocurarineExplanation
Tubocurarine is the correct answer because it is a drug that can block Nn receptors in the autonomic ganglia.Rate this question:
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- 7.
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?
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Tubocurarine
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Glycopyrrolate
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Clonidine
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Vecuronium
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Cisatracurium
Correct Answer
A. TubocurarineExplanation
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 histamineRate this question:
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- 8.
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?
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Atropine
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Vecuronium
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Botulinum toxin
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Dantrolene
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Neostigmine
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Fluoxetine
Correct Answer
A. VecuroniumExplanation
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)Rate this question:
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- 9.
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?
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Gentamicin
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Tolterodine
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Timolol
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Latanoprost
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Lovastatin
Correct Answer
A. GentamicinExplanation
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)Rate this question:
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- 10.
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.
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Tubocurarine
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Baclofen
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Cisatracurium
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Dantrolene
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Diazepam
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Mivacurium
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Succinylcholine
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Tizanidine
Correct Answer
A. SuccinylcholineExplanation
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.Rate this question:
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- 11.
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?
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Action potential of motor nerve
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Miniature end plate potential
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Resting potential of smooth muscle
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Action potential of cardiac muscle
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Action potential of corticospinal tract
Correct Answer
A. Miniature end plate potentialExplanation
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.Rate this question:
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- 12.
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?
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Atropine
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Succinylcholine
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Dantrolene
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Dopamine
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Prazosin
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Baclofen
Correct Answer
A. DantroleneExplanation
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.Rate this question:
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- 13.
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?
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Botulinum toxin
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Dantrolene
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Succinylcholine
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Tubocurarine
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Cisatracurium
Correct Answer
A. TubocurarineExplanation
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.Rate this question:
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- 14.
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?
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Beta-1 agonist
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D1 antagonist
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Muscarinic agonist
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Cholinesterase inhibitor
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H1 antagonist
Correct Answer
A. H1 antagonistExplanation
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.Rate this question:
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Current Version
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Aug 21, 2023Quiz Edited by
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Jun 24, 2012Quiz Created by
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