This slide gives brief and complete description about depolarising and non depolarising skeletal muscle relaxants. The font size is also big and the number of words in each slide is also optimum so that it looks good when projected.

1. Depolarising and non
depolarising SMR
M. Aravind
MBBS II yr.

2. NEUROMUSCULAR
BLOCKERS
 DEPOLARISING BLOCKERS:
 Succinyl choline, decamethonium
 NON DEPOLARIZING BLOCKERS:
 d- Tubocurarine
 Pancuronium
 Doxacurium
 Pipercuronium
Vecuronium
Atracurium
cisatracurium
Rocuronium
Rapacuronium
Mivacurium

3. Depolarising blockers
 SUCCINYL CHOLINE /
SUXAMETHONIUM:
 Only depolarising SMR in use at present
 Resembling 2 molecules of Ach joined
together
 Stimulates Nm receptors- depolarisation of
membrane. It is responsible for initial
fasciculations (post op muscle pain or
soreness)
 Constant depolarisation makes end plate
refractory to other impulses and muscle

4.  It is a type of flaccid paralysis that
cannot be reversed with neostigmine
(phase I block)
 On prolonged use, membrane
becomes desensitized which leads to
phase II block that can be reversed
with anticholinesterases.
 It potentiates its effects

5. Pharmacological actions
 On iv administration, onset is rapid
within 1 min.
 Initial transient muscular fasciculations
and twitchings mostly in the chest and
abdominal regions are followed by
skeletal muscle paralysis
 Fasciculations are due to stimulation
of muscle fibers by the discharge of
action potential (max 2mins & subside
in 5 mins)
 SA- given continuously as an infusion
for longer effect

6. CVS
 Initially hypotension and bradycardia
due to stimulation of vagal ganglia
 Followed by hypertension &
tachycardia due to stimulation of
sympathetic ganglia
 Higher doses cause cardiac
arrythmias
 Cause histamine release if injected
rapidly
 Preferred SMR for endotracheal

7. Pharmacokinetics
 Rapidly hydrolysed by
pseudocholinesterase (about 3-8 mins)-
Shortest A & fastest acting
 Transient apnoea is usually seen at peak
of its action
 In people with liver disease or atypical
pseudo cholinesterase due to genetic
defect, metabolism of Sch becomes slow
which results in severe neuromuscular
blockade leading to respiratory paralysis

8. Adverse reactions
 Muscle pain due to initial fasciculations
 Hyperkalaemia- esp. in nerve and
muscle disorders. dangerous
particularly in CCF patients.
 Cardiac arrythmias
 Increases all pressure- IOP, intracranial
pressure, blood pressure due to
stimulation of sympathetic ganglia and
intragastric pressure responsible for
nausea & vomiting

9. Malignant hyperthermia
 Rare genetically determined condition
where there is a sudden increase in body
temperature & severe muscle spasm due
to release of intracellular Ca++ from the
sarcoplasmic reticulum
 Drugs like halothane, isoflurane,
sevoflurane, Sch can trigger the process.
Combination of these anaesthetics with
Sch is fatal.
 IV dantrolene –DOC
 Rapid cooling, inhalation of 100% oxygen
& control of acidosis

10. Contraindications
 Nerve diseases- paraplegia, hemiplegia,
Guillain barre syn
 Muscle diseases- muscular dystrophy,
myasthenia gravis, crush injury, burns,
rhabdomylosis
 Glaucoma
 Head injury

11. Non depolarising blockers
 Competetive blockers
 Competetively inhibit Nm receptors- block
actions of Ach- cause muscle relaxation
without any fasciculations
 These compounds slowly dissociate from
the receptors & transmission is gradually
restored.
 Reversed by anticholinesterases

12. d- Tubocurarine
 Curare was used by the indeginous
South Americans as arrow poison for
hunting animals because curare
paralysed animals
 Natural sources- Strychnos toxifera,
Chondrodendron tomentosum
 Active principles- tubocurarine, toxiferins
 Not absorbed orally because of too large
& highly charged to pass through lining
of digestive tract

13.  Benjamin collins- curare did not kill the
animal & recovery is complete is
respiration is maintained artificially
 Charles waterton- curarized female
donkey alive by artificial respiration by
tracheostomy
 Claude Bernard- NMJ

14. Pharmacological actions &
 Flaccid paralysis- small muscles of the
eyes and fingers are the first to be
affected, followed by those of the
limbs, neck and trunk later intercostal
muscles, and finally diaphragm.
 Recovery occurs in the reverse order.
 Consciousness and appreciation of
pain are not affected

15.  In high doses tubocurarine can block
autonomic ganglia and adrenal
medulla resulting in hypotension
 Histamine release (d-TC, mivacurium,
atracurium) hypotension,
bronchospasm, increased
tracheobronchial and gastric
secretion, hypotension
 Release HT by Direct effect on mast
cells

16.  Hypotension
 Respiratory paralysis
 Bronchospasm, flushing- not seen with
newer agents
 Aspiration of gastric contents
 Treatment of toxicity:
 Neostigmine/ pyridostigmine - antidote
 Antihistamines should be given to
counter the side effects of histamine
Adverse effects

17.  Rocuronium- fastest acting DSMR. Used
as an alternative to Sch for rapid
sequences of endotracheal intubation
 Rapacuronium- fastest acting.
Withdrawn due to reports of severe
bronchocontriction
 Vecuronium- preferred in cardiac
patients because of better cardiovascular
stability, contraindicated in hepatic
disease and biliary obstruction
 Doxacurium- most potent & longest
acting

18.  Mivacurium- shortest acting. Alt to Sch
 Atracurium & cis-atracurium – agents of
choice for patients with hepatic or renal
insufficiency. Cis-atracurium- much less
histamine release (hoffman’s
elimination)
 Gantacurium- undergoing phase III
clinical trials- fastest & shortest acting.
Alt to Sch
 Gallamine- least potent. Rarely used
because of nephrotoxic & terotogenic
potential, tachycardia

19. Drug interactions
 Antagonist: Anticholinesterases like
physostigmine, neostigmine
 Agonistic: General anaesthetics like
halothane, isoflurane
 CCBs- verapamil, diltiazem
 Antibiotics: aminoglycosides,
tetracyclines, polypeptides

20. Uses
 Adjuvant to anaesthesia: -for producing
satisfactory skeletal muscle relaxation
during surgical procedures
 In minor procedures- laryngoscopy,
bronchoscopy, tracheal intubation,
orthopaedic procedures like reduction of
fracture dislocations
 In electro convulsive therapy to prevent
trauma

21.  Spastic disorders- tetanus, athetosis
 Status epilepticus
 Ventilatory support- to reduce
resistance of the chest wall and
enhance thoracic compliance to
facilate artificial ventilation in ICUs