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Pharmacology > muscle relaxants > Flashcards

muscle relaxants Flashcards

1
Q

what are central muscle relaxants

A

they cause decreased motor activity or paralysis of voluntary muscles without loss of consciousness

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2
Q

medical uses of central muscle relaxants

A
  • central myorelaxants can potentiate the effect of anaesthetic drugs and combos
  • they are also used to control certain spasmodic and painful disorders of skeletal muscles
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3
Q

guaiphenesin effect

A
  • a spinal interneuronal blocking agent, blocks polysynaptic but not monosynaptic relfexes
  • effective against convulsion
  • paralyses limb muscles, whilst resp muscles unaffected
  • consciousness retained
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4
Q

guaiphenesin is effective against convulsion caused by which agents

A

strychnine and tetanus but not picrotoxin and leptazol

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5
Q

guaiphenesin secondary effect

A

expectorant

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6
Q

guaiphenesin indications

A
  • horse, cattle, sheep - to adjunct anaesthesia

- dogs - strychnine poisoning

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7
Q

guaiphenesin onset and elimination

A

fats, 2-4 and 60-80min

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8
Q

guaiphenesin distribution

A

large distribution, crosses the placenta barrier

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9
Q

guaiphenesin metabolism

A

conjugation with glucoronide -> excretion with urine

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10
Q

guaiphenesin side effects

A
  • mild at therapeutic dose slight decrease of blood pressure
  • only large doses cause resp depression
  • haemolysis
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11
Q

guaiphenesin dosing

A

due to low potency and conc large volume required

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12
Q

baclophen action

A
  • GABAb receptors agonist in the brain and spinal cord
  • hyperpolarisation of neurons due to incr K+ ion conductance
  • inhibits neural funct presynaptically, by reducing Ca ion influx-> reduced release of excitatory NTs in brain and spinal cord
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13
Q

baclophen analgesic activity

A

may reduce pain by inhibiting the release of SP in the spinal cord

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14
Q

baclophen therapeutic index

A

large

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15
Q

baclophen clinical signs of toxicosis

A
  • vomiting
  • ataxia
  • vocalisation
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16
Q

baclophen indications

A
  • spasm of skeletal muscles or rigidity
  • spinal cord injury and pain caused by injuries
  • extralabel use in dogs to treat urinary retention by reducing urethral resistance
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17
Q

baclophen dose

A

1-2mg/kg orally TID

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18
Q

carisoprodol analgesic abilites

A

especially useful against various types of pain because of its analgesic-sparing effect on opioid analgesics

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19
Q

carisoprodol effect on convulsions

A

inactive in convulsions caused by strychnine

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20
Q

carisoprodol avaliability

A

by itself or mixed with aspirin and in one preparation along with codeine and caffeine as well

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21
Q

methocarbamol features

A
  • acts on internunical neurons of the spinal cord

- reduces skeletal muscle hyperactivity without alteration in muscle tone

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22
Q

classes of neuromuscular blocking agents

A
  • depolarising neuromuscular blocking agents

- competitive neuromuscular blocking agents, prototype curare

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23
Q

whats a nicotinic receptor

A

a transmembrane ion channel receptor, a pentameric asymmetric molecule

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24
Q

where are the ligand occupation sites on nicotinic receptors

A

alpha units

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25
Q

do depolarising agents or non depolarising agents act similiarly to Ach

A

depolarising

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26
Q

uses of neuromuscular blocking agents by IV or systemic administration

A
  • adjuvant in surgical anaesthesia to obtain relaxation of skeletal muscle
  • balanced anaesthesia, TIVA
  • to assist in intubation -esp succinylcholine
  • corneal or retinal surgeries to obtain relaxation of extraocular muscles
  • therapy of spastic disorders
27
Q

uses of neuromuscular blocking agents by topical administration

A

mydriasis in birds and reptiles - only non depolarising

28
Q

succinylcholine mechanism

A
  • stimulate opening of nicotinic receptors and produce depolarisation of cell membranes
  • persists at neuroeffector junction and activates the nicotinic receptor channels cont. - inactivation of voltag egated sodium channels so they cannot reopen to support other action potentials
29
Q

succinylcholine uses

A
  • IV rapid and short lasting block -Phase 1 block
  • used to facilitate intubation
  • used illegally in blow hunting or euthansia
  • in an emergency can be given IM, but slower and less predictable action
30
Q

succinyl choline side effects

A
  • bradycardia
  • hyperkalaemia
  • incr intra-ocular and intragastric pressure
  • anaphylaxis
  • malignant hyperthermia
31
Q

succinylcholine sensitive species

A

dogs, cattle and sheep are sensitive, horse and pigs less so

32
Q

depolarising blocking agents phases

A
  • I

- II

33
Q

phase I block

A

depolarising block of motor end plate

-block is augmented, not reversed by cholinesterase inhibitors

34
Q

phase II block

A

after repolarisation the membrane cannot easily be depolarised again

35
Q

depolarising agents onset

A

rapid, 1min

36
Q

depolarising agents duration

A

short, however may revert to phase II block

37
Q

depolarising agents termination of action

A

metabolised by the plasma, pseudocholinesterase and liver

38
Q

depolarising agents initial metabolite

A

succinylmonocholine, weaker, predominantly competitive blocking action

39
Q

depolarising agents effect on muscle

A
  • fasculation
  • weakness
  • paralysis
40
Q

depolarising agents effect on cardiovascular system

A
  • incr blood pressure

- incr/decr heart rate - stim of parasympathetic and or sympathethic ganglia

41
Q

depolarising agents can be enhanced or potentiated by which

A

neostigmine, organophosphates and isoflurane

42
Q

depolarising agents undesirable side effects

A
  • muscle fasciculation, hyperkalamia
  • phase II block
  • malignant hyperthermia in genetically susceptible animals
  • muscarinic actions at high doses
43
Q

depolarising agents advantages

A

short duration of action, little histamine release

44
Q

competitive non depolarising neuromuscular blocking agents mechanism of action

A

selectively antagonise nicotinic receptors, thus preventing endogenous Ach binding and subsequent muscle cell depolarisation

45
Q

competitive neuromuscular blocking agents groups

A
  • benzylisoquinoline
  • aminosteroid
  • gallamine
46
Q

benzylisoquinoline group examples

A
  • d tubocurarine
  • atracurium
  • cisatracurium
  • mivacurium
47
Q

aminosteroid group examples

A
  • pancuronium
  • vecuronium
  • rocuronium
48
Q

benzylisoquinoline group metabolism

A

metabolism in blood plasma, histamine release

49
Q

aminosteroid group metbaolism

A

metabolism in liver, no histamine release

50
Q

classifications of agents based on their duration of action

A
  • ultra short
  • short
  • intermediate
  • long duration
51
Q

intermediate agents examples

A
  • atracurium
  • cisatracurium
  • rocuronium
  • vecuronium
52
Q

long duration agents examples

A
  • d tubocurare
  • dimethyltubocurarine
  • pancuronium
  • gallamine
53
Q

effects of competitive blockers on cardiovascular system

A
  • decr blood pressure -due to histamine release
  • incr heart rate - baroreceptor reflex
  • coagulobility of blood decr - due to release of heparin from mast cells
54
Q

d tubocurare features

A
  • long acting
  • slow onset of action
  • slight hypotension and tachycardia
  • histamine release
  • excretion via urine
  • limited use
55
Q

mivacurium features

A
  • short acting
  • succinycholine alternative developed for human use
  • HA release, hypotension can occur
  • metabolism in plasma
56
Q

atracurium features

A
  • intermediate acting
  • safe in liver and kidney disease
  • bradycardia may occur during surgical manipulations
  • precipitates in alkaline pH
  • can cause HA release at higher doses
  • probably most used in veterinary medicine
57
Q

cisatracurium features

A
  • immediate acting
  • R-cis isomer of atracurium
  • 3-4x potency
  • immediate onset
  • metabolism in plasma
  • frequently used in opthmologic surgeries
58
Q

rocuronium

A
  • intermediate acting
  • rapid onset of action
  • metabolism in liver, excretion with bile
  • lack of CV or HA-releasing effects
  • quite frequently may cause anaphylactic reaction
59
Q

vecuronium features

A
  • intermediate acting
  • lack of CV or HA releasing effects
  • drug of choice when CV stability needed
  • metabolism in liver
  • excretion with bile and urine
  • mydraitic use in birds and reptiles
60
Q

pancurium features

A
  • slight tachycardia and hypertension
  • metabolism in liver, elimination via urine
  • liver and kidney disease prolongs its effect
61
Q

gallamine features

A
  • frequently used in human surgery
  • tachycardia and hypertension
  • no HA release
  • crosses placental barrier
62
Q

antagonists of competitive blockers

A

cholinesterase inhibitors or tetanic stimulation

63
Q

whats used to control the muscarinic side effect of neostigmine

A

atropine

Pharmacology (23 decks)

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