Muscle Relaxants

Question 1

Block neuromuscular transmission inducing skeletal muscle relaxation.
?

Answer 1

Skeletal muscle relaxants

Question 2

Classification of skeletal muscle relaxants ?

Answer 2

1. Peripherally acting (neuromuscular blockers):

A. Competitive (non-depolarizing):

• Long acting: d-tubocurarine (prototype), Pancuronium
• Intermediate acting: Vecuronium, Atracurium
• Short acting: Mivacurium

B. Depolarizing: Succinylcholine (suxamethonium)

2. Direct acting: Dantrolene
3. Centrally acting: Baclofen, Diazepam

Question 3

Neuromuscular Blockers ● Uses

?

Answer 3

● Control convulsions, so used in electroshock therapy in psychotic patient
● Relieve tetanus and epileptic convulsion
● Facilitate endoscope procedures
● As adjuvant in general anesthesia to induce muscle relaxation
● Orthopedic surgery

Question 4

Mechanism of action:
● Compete with acetyl choline at nicotinic receptors of post-junction
membrane of motor end plate.

Type of relaxant ?

Answer 4

Peripherally acting Competitive non-depolarizing neuromuscular blockers

Question 5

Long acting Competitive non-depolarizing neuromuscular blockers
Example?

Answer 5

d-tubocurarine (prototype), Pancuronium

Question 6

Competitive non-depolarizing neuromuscular blockers

Example? Intermediate acting

Answer 6

Vecuronium, Atracurium

Question 7

Competitive non-depolarizing neuromuscular blockers

Example? Short acting?

Answer 7

Mivacurium

Question 8

Competitive non-depolarizing neuromuscular blockers

Properties?

Answer 8

● Mostly quaternary compounds, thus not absorbed orally & given IV
● Do not cross blood brain barrier or placenta
● Do not cause analgesia or loss of consciousness

Question 9

How to overcome Competitive non-depolarizing neuromuscular blockers? Mechanism? Examples ?

Answer 9

Competitive: action overcome by higher acetylcholine
● Acetyl cholinestrase enzyme inhibitors increase acetyl choline:
Pyridostigmine
Physostigmine
Edrophonium
● Anesthetist use them to prevent competitive neuromuscular blocker
overdose.

Question 10

Which muscles are paralyzed first? And last?

Answer 10

Small and rapidly contracting muscles: more sensitive, paralyze first
● Respiratory muscles are last to be affected and first to recover

Question 11

d-Tubocurarine

Type? Duration? Side effects ? Contraindications?

Answer 11

• Competitive non depoliticization
• long
• Adverse effects (release histamine causing bronchospasm & hypotension)
• Kidney failure

Question 12

Type? Duration? Side effects ? Contraindications?

Pancuronium

Answer 12

• Competitive non depolarization
• long
• Side effects: Hypertension and tachycardia (due to norepinephrine release)
• coronary diseases and renal failure

Question 13

Type? Duration? Side effects ? Contraindications?

Vecuronium

Answer 13

• competitive nonpolarizing
• intermediate
• Few side effects
• liver failure ( cause it metabolized by the liver )

Question 14

Type? Duration? Side effects ? Contraindications? Used in?

Atracurium

Answer 14

• competitive non polarizing
• intermediate
• Hypotension Histamine release
• Used in liver & kidney failure
• Bronchial asthma

Question 15

Type? Duration? Side effects ? Contraindications? Used in?

Mivacurium

Answer 15

• competitive non polarizing
• short
• histamine release = hypotension
• psuedo cholinesterase deficiency

Question 16

Type? Duration? Side effects ? Contraindications? Used in?

Succinyl choline

Answer 16

• competitive depolarizing
• short
• Hyperkalemia -Arrhythmia -Increase intra- ocular pressure
• Cardiovascular diseases
  Glaucoma Liver disease

Question 17

Type? Duration? Side effects ? Contraindications? Used in?

Dantrolene

Answer 17

• Directly acting
• long
• few side effect
• Malignant hyperthermia ● Spastic states (spasmolytic effect) as spinal cord injury and cerebral palsy

Question 18

Malignant hyperthermia

● Rare inherited condition that occurs during administration of drugs as: ?

Answer 18

Depolarizing neuromuscular blockers as succinylcholine

Question 19

Malignant hyperthermia

Caused by?

Answer 19

Caused by inability to bind calcium by sarcoplasmic reticulum due to genetic defect
● This will cause increase calcium release, intense muscle spasm, and increase in body temperature (hyperthermia)

Question 20

Malignant hyperthermia

Treatment?

Answer 20

dantrolene

Question 21

Dantrolene

● Mechanism of Action: (directly acting muscle relaxant) ?

Answer 21

Interferes with release of calcium from its stores in skeletal muscles
sarcoplasmic reticulum ● Calcium is released from the sarcoplasmic reticulum via a specific calcium
channel (ryanodine channel) and dantrolene blocks these channels ● This inhibits contraction of muscles.

Question 22

Muscle relaxants are contraindicated in this disease

?

Answer 22

Myasthenia Gravis

Question 23

Myasthenia Gravis

Treatment?

Answer 23

choline esterase inhibitors as pyridostigmine may be used (side effects: weakness, abdominal colic, diarrhea)

Question 24

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Answer 24

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