Skeletal Muscle Relaxants

Question 1

What is the clinical use of blocking drugs?

Answer 1

muscle relation for surgery and for electroshock therapy

Question 2

What is the clinical use of anticholinesterases?

Answer 2

diagnosis and therapy of myasthenia gravis

Question 3

Is the whole length of the muscle DIRECTLY affected by synapse activities?

Answer 3

nooooo

Question 4

Random reminders about skeletal muscle APs

Answer 4

Ach is NT (released from vesicles), Na+ channel, all-or-none.

Question 5

What about the Ach receptors?

Answer 5

nicotinic, ligand-gated, pentameric

Question 6

How does Botox work?

Answer 6

inhibits release of Ach from vesicle

Question 7

What does Acetylcholinesterase?

Answer 7

in post-synaptic receptors, stops depolarizaion by hydrolizing Ach

Question 8

What are the 3 major conformations or states of the skeletal muscle nicotinic acetylcholine receptor?

Answer 8

resting, open, desensititized

Question 9

Which states of the Ach receptor do the nicotinic agonists stabilize?

Answer 9

the open and desensitized

Question 10

Which states of the Ach receptor do the competitive antagonists stabilize?

Answer 10

the resting state

Question 11

During the desensitized state, is the Na channel open or closed? What is the purpose of this state?

Answer 11

There is still high affinity for the agonist, but the channel is closed. Purpose is protective from overstimulation

Question 12

non-depolarizing muscle relaxants AKA…?

Answer 12

nicotinic receptor antagonists

Question 13

What is the prototype non-depolarizing drug?

Answer 13

Vecuronium

Question 14

What is an adverse effect of Vecuronium? Why?

Answer 14

hypotension. it is not selective for skeletal muscle nicotinic receptors and therefore also has affinity for autonomic nicotinic receptors.

Question 15

What is Neostigmine?

Answer 15

Anticholinesterase

Question 16

What does Neostigmine (anticholinesterase) do?

Answer 16

Reversal of Vecuronium block (there is competition between the anticholinesterase and the non-depolarizing drug)

Question 17

What causes the adverse effect of hypotension with Vecuronium?

Answer 17

basophil histamine release, blockade of autonomic neurotransmission

Question 18

How is Vecuronium eliminated?

Answer 18

largely by biliary secretion

Question 19

What is Atracurium?

Answer 19

another non-depolarizing drug thats spontaneously breaks down at physiological pH

Question 20

depolarizing muscle relaxants AKA…?

Answer 20

Nicotinic Agonists

Question 21

What is the prototype nicotinic agonist/depolarizing blocker?

Answer 21

Succinylcholine

Question 22

What is succinylcholine?

Answer 22

essentially a stable form of Ach

Question 23

What are the two stages of SuCH block?

Answer 23

depolarizing, non-depolarizing

Question 24

What do anticholinesterases do to stage 1 SuCH block?

Answer 24

they fail to reverse stage 1 block

Question 25

What are fasciculations?

Answer 25

muscle twitches with use of depolarizing drug (succinulcholine). produce post-operative soreness

Question 26

Which stages of SuCH block are important when SuCH is used for tracheal intubation?

Answer 26

Only the first, depolarizing stage. Stage 2 block is not observed because of its slow onset

Question 27

Which stage block for tracheal intubation?

Answer 27

stage 1 (depolarizing)

Question 28

Which stage block for desensitization?

Answer 28

stage 2 (non-depolarizing)

Question 29

What are the ion channel states during stage one block (depolarizing, tracheal intubation)?

Answer 29

nicotinic receptor open, sodium channel closed (refractory)

Question 30

What are the ion channel states during stage 2 block (non-depolarizing, desensitization)?

Answer 30

nicotinic receptor closed (desensitized), sodium channel read to open

Question 31

What are some disadvantages of depolarizing blockers (4)?

Answer 31

1) muscle soreness of SuCH-induced muscle relaxation 2) inability to reverse stage 1 block with anti-ChEs 3) K+ release may be life-threatening in burn patients displaying skeletal muscle denervation hypersensitivity 4) SuCH biotransformation is abnormally slow in certain people

Question 32

Which drug can be used for treatment of malignant hyperthermia and spasticity disorders?

Answer 32

Dantrolene

Question 33

How does Dantrolene work?

Answer 33

relaxes muscle in a unique way, but inhibiting Ca ion release from skeletal muscle sarcoplasmic reticulum

Question 34

What is Myasthenia Gravis?

Answer 34

autoimmune loss of muscle nicotinic ACh receptors

Question 35

Which drugs are used to treat myasthenia gravis?

Answer 35

Neostigmine and Pyridostigmine

Question 36

How are Neostigmine and Pyridostigmine administered and what are their durations of action?

Answer 36

administered orally, intermediate durations of action

Question 37

Which drug is used for diagnosis of myasthenia gravis?

Answer 37

Edrophonium

Question 38

What else is Edrophonium used for and how?

Answer 38

adjustment of antiChE dose. If Edro produces improvement in contractility, then patient is under-medicated. if worsens contractility, over-medicated.

Question 39

What happens when the patient is under-medicated with a long-duration cholinesterase inhibitor?

Answer 39

myasthenic weakness

Question 40

What happens when the patient is over-medicated?

Answer 40

cholinergic crisis