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Pharm II exam 2 > Skeletal Muscle Relaxants > Flashcards

Skeletal Muscle Relaxants Flashcards

1
Q

2 groups of drugs that effect skeletal muscle function

A

1) neuromuscular blockers (surgery and ICU for muscle paralysis)
2) drugs to reduce spasticity (spasmolytics)

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2
Q

What is the drug of choice for muscle relaxation prior to intubation, reduction in dislocation fractures?

A

Succinylcholine - very rapid onset of action

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3
Q

what causes increased expression of Ash receptors?

A

Hemiparesis, paralysis, burns and neurological injuries – for these people Succinylcholine is contraindicated because it can cause hyperkalemia

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4
Q

Possible Sites of Action for Muscle Relaxation / Paralysis

A

1) In the CNS- stop signal from brain
(2) Myelinated somatic neurons
(3) Unmyelinated motor neuron terminals
(4) Nicotinic receptors
(5) blocking Ach receptor in Motor end plate
(6) Muscle contractile apparatus itself.

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5
Q

Neuromuscular Blockers - a group of drugs that affect skeletal muscle function

A

used in surgery and ICU to induce muscle paralysis. Drugs have no CNS effects but block NT at the motor end plate (transmission).

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6
Q

spasmolytics - a group of drugs that affect skeletal muscle function

A

drugs used to reduce spasticity such as found in chronic back pain, painful fibromyalgic conditions. Act at the level (mostly) of the CNS.

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7
Q

Two main types of Blockade exam q

Antagonist

Agonist

A

antagonist: drug blocks nicotinic receptor and
blocks Ach from binding (tubocurarine).
Depolarization is blocked
(NONDEPOLARIZING DRUGS)

agonist: drug or Ach itself in excess causes
excess Depolarization and muscle paralysis
(succinylcholine) (DEPOLARIZING DRUGS)

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8
Q

How do farmers and gardeners kill garden pests?

A

Acytlcholestrase inhibitors - same nerve agents used in warfare

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9
Q

Nondepolarizing Relaxant Drugs

mostly cleared by the liver or kidney

A

(1) isoquinolines
(a) d-tubocurarine
(b) atracurium
(c) doxacurium
(d) cisatracurium
(e) mivacurium
(2) steroids
(a) pancuronium
(b) vecuronium
(c) pipecuronium
(d) rocuronium

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10
Q

Depolarizing drug (the only one)

A

succinylcholine - 2 molecules of Ach hooked together
- works by paralyzing the pt for the time necessary for performing a minor procedure or intervention - AchE takes longer to break it down

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11
Q

how do Non-depolarizing drugs work?

A

Drugs blocks neuromuscular nicotinic motor end plate receptors resulting in paralysis.

  • competes with Ach at nicotinic receptor at the neuromuscular end plate
  • AchE inhibitors (neostigmine, edrophonium, pyridostigmine) increase Ach levels which compete off the blocker drug and recovery follows [AchE inhibition]
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12
Q

The mechanism for depolarizing drugs - Phase I

REMEMBER that Succinylcholine is the only drug in this class

A

Phase I Blocking: Drug binds to a receptor
and keeps receptor open, flaccid paralysis
results.

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13
Q

Depolarizing Relaxant Drugs - what should you be careful of?

A

molecular variant results in longer patient recovery time, prolonged apnea

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14
Q

The mechanism for depolarizing drugs - Phase II

A

• Phase II Blocking: Continued drug binding to receptor leads to desensitization and
further paralysis due to NT unresponsiveness.

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15
Q

What are spasmolytic agents often associated with?

A

spinal injury, cerebral palsy, multiple sclerosis, and stroke
-the mechanism involves stretch reflex arc and/or higher centers in the CNS

  • Can stop the signal in the brain OR act at the level of the stretch reflex arch
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16
Q

What does Diazepam (Valium®) treat?

A

It helps with CNS action

17
Q

How does Diazepam (Valium®) work?

Central spinal cord and local actions

A

increases GABA activity but induces sedation at 60 mg/d doses required for muscle relaxation - can be a major sedative

(doses for anxiety <5mg/day) - DOSE Is influential

18
Q

Where is Baclofen (Lioresal®) used/helps treat?

A

It helps with CNS action

19
Q

How does Baclofen (Lioresal®) work? (MOA)

Remember GABA B= Baclofen

A

(a) baclofen (p-chlorophenyl-GABA)
(b) drug is agonist at GABAb receptors which are K conductance receptors, K outward flow blocks neuron firing
(c) causes less sedation compared to diazepam
(d) drug delivery through a catheter in the subarachnoid space also used
(e) normal dosing is po

20
Q

Where is Tizanidine (Zanaflex®) used/ helps treat?

A

also in the CNS

21
Q

How does Tizanidine (Zanaflex®) work?

A

(a) congener of clonidine an alpha 2 agonist
(b) alpha 2 agonist inhibits the release of NE
(c) reduces spasticity with fewer cardiovascular effects compared to clonidine

22
Q

How are Gabapentin (Neurontin®) and Pregabalin(Lyrica®) also effective?

A

They may be used to also treat muscle spasm - relaxants

  • extremely widely used
23
Q

Where is Dantrolene (Dantrium®) used?

A

used for muscle action

24
Q

How does Dantrolene (Dantrium®) work?

DEFINITELY EXAM Q - also covered in other lecture

A

(a) derivative of phenytoin

(b) dantrolene blocks the release of Ca from the SR stores in skeletal muscle and inhibits muscle contraction

25
Q

What is Dantrolene (Dantrium®) used for specifically? _ EXAM Q

A

MALIGNANT HYPERTHERMIA - works by Block release of Ca++ and actin-myosin
will not activate and muscle will not fire.

  • rare autosomal disorder in the muscle cells
26
Q

How does the Botulinum toxin work?

A
  • binds to Ach synaptic vesicles in neuron terminal, block release Ach into the synaptic cleft
  • spasm reducing, glutamate receptors
27
Q

What is a lethal dose of botulinum toxin?

A

1ng - leads to 35-65% fatality

28
Q

What does Botulinum toxin (Botox®) cause?

A

Produces flaccid paralysis of skeletal muscles. Inhibition lasts 3-4 months

  • blocks the muscles from firing
  • inject subcutaneously - keeps from systemic injection (would otherwise be lethal)
29
Q

What is (Botox®) approved for?

A
  • blepharospasms (people who have uncontrolled blinking
  • strabismus (lazy eye)
  • block excess sweat glands
  • cervical dystonia (neck)
  • frown lines, crows feet
  • required q 6 mo
30
Q

MISC centrally acting drugs that are not really effective but still on the market

(not sure if will be test or not)

A 
carisoprodol
chlorzoxazone
cyclobenzaprine
metaxalone
methocarbamol
orphenadrine
31
Q

What drugs is a GABAa agonist?

A

Diazepam

32
Q

what drug is an alpha2 agonist in spinal cord?

A

Tizanidine

33
Q

What is an example of a direct muscle relaxant and used for malignant hyperthermia?

A

Dantrolene (Dantrium®)

Pharm II exam 2 (3 decks)

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