Skeletal Muscle Relaxants

Question 1

Normal neuromuscular function

Answer 1

Ach released from pre-synaptic nerve terminal, which activates NMJ receptors and opens mum channel.

Question 2

Neuromuscular blocking drugs (depolarizing and non depolarizing)

• Do they enter CNS?
• Administration?

Answer 2

Similar in structure to Ach
POORLY lipid soluble–> limits entry to CNS.
Highly polar and inactive oral. GIVE IV!!!

Question 3

Succinylcholine
MOA
Duration of action

Answer 3

Agonist at nicotinic receptor. is not metabolized at the synapse. Causes flaccid paralysis as phase 1 block. Made worse with cholinesterase inhibitors.

Phase 2 block- cannot be easily depolarized again after first exposure. May be reversed!

Question 4

Non depolarizing drugs
MOA
can you reverse?

Answer 4

Ach nicotinic antagonist.

Difficult to reverse with acetylcholinesterase inhibitors (neostigmine) so it is important to get dose right.

Question 5

Side effects of non depolarizing drugs

Answer 5

Cisatracurium- less toxic. May cause hypotension and ganglionic blockade.

Vecuronium and Rocuronium- Intermediate acting. Dependent on liver metabolism

Question 6

Succinylcholine side effects

Answer 6

May cause arrhythmia, increased IOP.

Question 7

General side effects of neuromuscular blocking drugs

Answer 7

Cardiovascular
Cisatrocurium- hypotension, succinylcholine- Arrhythmia
Hyperkalemia
Increased IOP with succinylcholine.
Muscle pain
Interactions with other anesthetics, antibiotics and neuromuscular blocking drugs.
(Ex succinylcholine can be antagonized by the non depolarizing drugs)

Question 8

Clinical uses for neuromuscular blocking drugs

Answer 8

Surgical relaxation of the abdomen and thorax
Intubatoin
Control ventilation
Tx confusions

Question 9

Spasmolytic drugs are used to treat

Answer 9

Spasticity- increased basal tone. Due to MS, spinal cord injury, TBI.

Spasms and muscle pain- Tension HA, lower back or neck pain.

Question 10

MOA of centrally acting spasmolytics

Answer 10

Unknown MOA. ALL ARE CNS DEPRESSANTS at different receptors.
They interrupt neuronal communication and cause sedation/alteration of pain perception.

Question 11

Gabapentin side effects

Answer 11

Fatigue, dizzy, ataxia. Nausea. Less common is nystagmus and diplopia!!!!

Can enhance the effects of opioids so do not give together !!!

Question 12

Dantrolene MOA

Answer 12

Prevents release of calcium in sarcoplasmic reticulum. Does not effect cardiac or smooth muscle.

Often first used since it works directly on the muscle and not the CNS. fewer side effects