Neuromuscular blockers

1. NEUROMUSCULAR BLOCKERS
DR. FOUZIA

3. NEUROMUSCULAR BLOCKING DRUGS
They prevent interaction between Ach and Nicotinic receptors in the skeletal
muscles.
It results in muscle relaxation.
Drugs are classified according to their mechanism of action
1- Depolarizing agents- Non competitive, agonist
2- Non depolarizing, Competitive, antagonist.

4. CLASSIFICATION OF NEUROMUSCULAR BLOCKERS
1- Depolarizing agents- Non competitive, agonist
Succinylcholine
2- Non depolarizing, Competitive, antagonist
d-Tubocurarine
Metocurine
Atracurium
Mivacurium
Cisatracurium

5. DEPOLARIZING AGENTS- NON COMPETITIVE AGONIST
Succinylcholine (Suxamethonium) :
Mechanism of action:
It attaches to the nicotinic receptor and acts like Ach to depolarize the junction.
Phase I:
Depolarization of the receptor, transient fasciculation or muscle twitching
Phase II:
Continuous depolarization Gradual repolarization, and flaccid paralysis

7. DEPOLARIZING AGENTS- NON COMPETITIVE, AGONIST
Therapeutic Indications of succinylcholine:
1- Endotracheal intubation for induction of anaesthesia
2- During electroconvulsive shock treatment.
Adverse effects of succinylcholine:
Apnea
Hyperkalemia
Muscle pains ( myalgia)

8. DEPOLARIZING AGENTS- NON COMPETITIVE, AGONIST
Malignant hyperthermia
Persistent release of Ca from sarcoplasmic reticulum
1-Rigidity
2- Heat production
3- Metabolic acidosis
4- Tachycardia
Treatment:
Dentrolene- it blocks the Ca release from sarcoplasmic reticulum
Temperature control with cooling blankets.

9. NON DEPOLARIZING, COMPETITIVE, ANTAGONIST.
Tubocurarine
Mechanism of action:
Competitively block Ach at the nicotinic receptors
Prevent depolarization and inhibit muscular contraction.
Their competitive action can be overcome by administration of cholinesterase
inhibitors, such as
Neostigmine
Edrophonium

10. NON DEPOLARIZING, COMPETITIVE, ANTAGONIST.
Therapeutic uses of Tubocurarine:
1-Maintenance of anesthesia.
2-For intubation where succinylcholine is contraindicated
3-Muscle relaxation during surgery
4-Facilitation of mechanical ventilation
Adverse effects of Tubocurarine:
Respiratory arrest
Tachycardia, Hypotension
Bronchospasm
Skin wheals

11. NON DEPOLARIZING, COMPETITIVE, ANTAGONIST.
Atracurium:
It is an intermediate-acting muscle relaxant..
It is inactivation in plasma by spontaneous non enzymatic degradation
Its metabolite -Laudanosine-crosses BBB-may cause seizure
Causes mild histamine release
Duration of action : 25 -35min
Stereoisomers of Atracurium
Cisatracurium
Gantacurium