2 Pharm: Neuromuscular Blockers

Front 1

guaifenesin (glycerol guaicolate)

Back 1

guaifenesin (glycerol guaicolate):
- centrally acting muscle relaxant
- mimics glycine
- blocks or disrupts connecting (intranuncial) neurons in spine, brainstem, and reticular formation
- flaccid paralysis, little or no effect on respiration
- use in prego: up to 30% passes placenta in mare
- decogestant, antitussive
- met by liver
- mimic glycine action

Front 2

guaifenesin conc

Back 2

guaifenesin conc:
- in soln: 5% dextrose, 5% guaifenesin
- 10%: causes hemolysis, precipitation in cold weather
- reversal: not neostigmine, cal dextrose

Front 3

mephenesin

Back 3

mephenesin :
similar to guaifenesin

Front 4

methocarbamol (robaxin)

Back 4

methocarbamol (robaxin):
- CNS level muscle relaxant, no direct effect on motor endplate
- reduces muscular spasm in skeletal muscle trauma
- used with other anti-inflammatories for pain relief

Front 5

diazepam

Back 5

diazepam:
- muscle relaxant

Front 6

dantrolene

Back 6

dantrolene:
- prevention of malignant hyperthermia before set in
- dec Ca release from sarcoplasmic reticulum by allowing Ca uptake by sarcoplasmic reticulum

Front 7

acetylcholinesterase inhibitors

Back 7

actylcholinesterase inhibitors:
1. neostigmine
2. edrophonium
3. pyridostigmine
4. physostigmine
5. organophosphates

Front 8

physostigmine

Back 8

physostigmine:
- acetylcholinesterase inhibitors
- not commonly used a neuromuscular blocker reversal as centrally mediated
- use in atropine overdose, toxicity

Front 9

clinical uses

Back 9

clinical uses:
- generally reduce amount of gen anesthesia required in sx due to
1. muscle relaxation
2. intubation: prevent laryngospasm
3. control of artifical respiration: paralyzing resp mm

Front 10

neuromuscular blockers gen

Back 10

neuromuscular blockers gen:
- highly polar, IV, not easy PO abs
- don't cross B-B barrier: no CNS side effects, animals fully conscious although paralyzed
- wildlife immobilization: IM
- few alter ganglionic transmission (Nr), not clinically significant

Front 11

types

Back 11

types:
1. depolarizing
2. non-depolarizing
3. acting on spinal cord and CNS
4. otherd

Front 12

depolarizing agents

Back 12

depolarizing agents:
1. ACh
2. pentamethonium
3. hexamethonium
4. suxamthonium (succinylcholine)
5. decamethonium

Front 13

methonium compounds

Back 13

methonium compounds:
- depolarizing
- bis-quarternary ammonium comp'ds
- N attached to terminal C of polmethylene chains of different lengths
- potency inc w/ chain length

Front 14

penta, hexa, suxa and decamethonium

Back 14

- depolarizing:
1. pentamethonium: 5C
2. hexamethonium: 6C, ganglionic blocker
3. suxamethonium/ succinylcholine
4. decamethonium

Front 15

depolarizing phase 1 block

Back 15

depolarizing phase 1 block:
- like ACh as action short, rapid depolarization and firing
- hydrolysis of succinylcholine slower, resulting in sustained depol
- accompanied by skeletal mm fasiculation: gen depol

Front 16

phase 2 depolarizing block

Back 16

phase 2 depolarizing block:
- muscle end plate recovers
- mem repol but desensitized
- characterized as non-depolarizing: possible to reverse by AChE inhibitors such as neostigmine

Front 17

depolarizing adverse side effects

Back 17

depolarizing adverse side effects:
1. cardiac dysrhythmias
2. hyperkalemia
3. myalgia (muscle ache): cause by m fasiculation
4. myoglobinurea
5. inc intragastic P
6. inc intracranial P
7. sustained skeletal mm contraction
8. histamine rel

Front 18

depolarizing met and duration

Back 18

depolarizing:
1. met: succinylcholine hydrolyzed by plasma cholinesterase (pseudocholinesterase) into succinic acid and choline wi 3-5 min
2. duration: short, IV drips eg for open thoracic sx

Front 19

non-depolarizing gen

Back 19

non-depolarizing gen:
- competitive with ACh:
1. combine with alpha subunit of postjunctional Nr
2. don't cause confirmational change of Nr= don't activate
3. not as important: act at chan and prejunctional

Front 20

non-depolarizing agents

Back 20

non-depolarizing agents:
- can be reversed by neostigmine
1. d-turbocurarine
2. metocurine
3. gallamine
4. pancuronium
5. atracurium
6. vecuronium
7. alcuronium
8. pipercuronium, doxacurium, mivacurium, rocuronium

Front 21

d- tubocurarine

Back 21

d-tubocurarine:
- non-depolarizing
- highly ionized, quarternary ammonium
- limited lipid sol: cannot cross B-B barrier, renal tubular epi, GI epi, placenta (can give to pregos)
- no effective PO
- 40-60% excreted in urine
- poss histamine release, vagal block (drops BP)--> not used often

Front 22

metocurine

Back 22

metocurine:
- non-depolarizing
- iodine of dimethyl-tubocurarine
- 2-3x more potent that dTc

Front 23

gallamine

Back 23

gallamine:
- non-depolarizing
- similar to dTc but no histamine
- poss vagal block, tachycardia
- 100% urine excretion, doesn't go through liver

Front 24

pancuronium

Back 24

pancuronium:
- non-depolarizing
- quartenary ammonium/ amino steroid
- more rapid than dTc
- lacks histamine rel
- met by liver
- 50-60% excr by kidney: not recc for renal problem, may prolong duration of action
- commonly used

Front 25

atracurium

Back 25

atracurium:
- non-depolarizing
- amino steroid, bisquarternary isoquinolone
- met by Hoffman elim: longer acting, smaller dose in met acidosis
- also met by pseudocholinesterase
- use in liver and kidney problems

Front 26

vecuronium

Back 26

vecuronium:
- similar to pancuronium
- no histamine rel
- met by liver, excr in bile (60% unchanged): do not use in liver dz
- use in renal dz

Front 27

factors that interfere with antagonism

Back 27

factors that interfere with antagonism:
1. large dose after inhibition of AChE: may block themselves
2. low K: enhance effects of non-depolarizing drugs
3. aminoglycosides and other antibiotics: may act as nm blockers, enhancing their effects

Front 28

Hoffman rxn

Back 28

Hoffman rxn:
- drug disintegrates into non-active
- eg atracurium
- may be longer acting, req smaller dose in met acidosis