Neuromuscular blocking drugs

Question 1

what are motor nerves?

Answer 1

cholinergic

Question 2

How is acetylcholine synthesized?

Answer 2

acetyl CoA and choline by choline acetyltransferase

Question 3

How is acetyl choline release from the presynaptic terminal?

Answer 3

• an action potential depolarises the membrane
• opens voltage sensitive calcium channels
• calcium influx leads to vesicle exocytosis

Question 4

What are the targets for acetylcholine at neuromuscular junctions?

Answer 4

-nicotinic acetylcholine receptors on the end plate

Question 5

What is depolarisation of the membrane called?

Answer 5

end plate potential

Question 6

What is a graded potential?

Answer 6

-depends on how much acetylcholine is release and how many receptors are stimulated

Question 7

What breaks down acetylcholine and where is it found?

Answer 7

• acetylcholinesterase

- attached to the basement membrane in the synaptic cleft

Question 8

WHat are the 3 main neuromuscular blockers?

Answer 8

• tubocurarine
• atracurium
• suxamethonium

Question 9

what are the 2 subtypes of nicotinic receptors?

Answer 9

• ganglionic

- muscle

Question 10

What is the structure of nicotinic acetylcholine receptors?

Answer 10

• 5 subunits
• 2 alpha, each must bind to an acetylcholine molecule to be activated
• 2 molecules of acetylcholine for the receptor to be activated

Question 11

Where is diazepam used and during which process?

Answer 11

• spasmolytic, facilitates GABA transmission

- at the central process, where an action potential is generated in the spinal cord

Question 12

What is baclofen?

Answer 12

a GABA receptor agonist

Question 13

When are diazepam and baclofen useful?

Answer 13

• some forms of cerebral palsy

- following a stroke

Question 14

Where is local anaesthetic applied?

Answer 14

-conduction of action potentials down a motor neurone , block voltage sensitive Na+ channels

Question 15

Which drugs interfere with acetylcholine release?

Answer 15

• neurotoxins
• hemicholinium
• Ca2+ entry blockers

Question 16

What drugs act at the depolarisation of the motor end plate?

Answer 16

• suxamthonium (deplolarising)

- tubocurarine (non-depolarising)

Question 17

Which drug works in the muscle fibres themselves?

Answer 17

-dantrolene (spasmolytic)

Question 18

What 2 drugs are non -depolarising competitive nicotinic receptor antagonists?

Answer 18

• tubocurarine

- atracurium

Question 19

Which drug is a depolarising nicotinic receptor agonist?

Answer 19

-suxamethonium

Question 20

What do you ALWAYS do when giving these drugs?

Answer 20

assist respiration because of its effects on resp muscles

Question 21

What is the structure of non-depolarising drugs?

Answer 21

• big and bulky

- restricted movement around the bonds

Question 22

What is the structure of suxamethonium?

Answer 22

• 2 acetylcholine molecules

- flexible and allows rotation

Question 23

What is the mechanism of action of suxamethonium?

Answer 23

• causes extended end plate depolarisation
• leads to a depolarisation block of the NMJ
• this is called phase 1 block

-it causes fasciculations, which leads to flaccid paralysis

Question 24

How is suxamethonium administered?

Answer 24

• intravenous
• duration of paralysis 5 minutes
• metabolised by pseudocholinesterase in the liver and plasma

Question 25

Use of suxamethonium?

Answer 25

• endotracheal intubation
• relaxes the skeletal muscle of the airways
• muscle relaxant for electroconvulsive therapy

Question 26

What are the unwanted effects of suxamethonium?

Answer 26

• post-operative muscle pains
• bradycardia
• hyperkalaemia
• raised intraocular pressure

Question 27

What is the mechanism of action for tubocurarine?

Answer 27

• competitive nicotinic acetylcholine receptor antagonist

- need 70-80% block to achieve full relaxation of the muscles

Question 28

What are the effects of tubocurarine?

Answer 28

• causes an extended end plate depolarisation and phase 1 block
• flaccid paralysis

Question 29

What order do skeletal muscles relax in?

Answer 29

• extrinsic eye muscles
• small muscles of the face, limbs and pharynx
• respiratory muscles

Question 30

What are the uses of tubocurarine?

Answer 30

• relaxation of skeletal muscles during surgical operations

- permits artificial ventilation

Question 31

how is tubocurarine administered?

Answer 31

• IV
• does not cross BBB or placenta
• 40-60 min duration

Question 32

How is tubocurarine removed?

Answer 32

70% urine

30% bile

Question 33

what drug would you use id there is hepatic or renal impairment?

Answer 33

-atracurium

Question 34

What are the unwanted effects of tubocurarine

Answer 34

• histamine release from mast cells
• hypotension’=
• tachycardia
• bronchospasm
• excessive secretions
• apnoea