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33 Cards in this Set
- Front
- Back
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Modes of action |
Act peripherally as NM blockers Act centrally in the cerebrospinal axis or on the contractile mechanism |
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Classes |
Drugs acting peripherally at the NMJ - Competitive blockers - Depolarising blockers - Others Drugs acting centrally Drugs acting directly on the muscle |
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Competitive blockers |
d-Tubocurarine Pancuronium Alcuronium Atracurium Mivacurium Doxacurium Pipecuronium Vecuronium Rapacuronium Gallamine |
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Depolarising blockers |
Succinylcholine Decamethonium |
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Other drugs |
Botulinum toxin |
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Drugs acting centrally |
Benzodiazepines Baclofen Tizanidine Mephenesin and it's congeners |
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Drugs acting directly on the muscle |
Dantrolene |
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Effects of tubocurarine on skeletal muscles |
muscular weakness -> flaccid paralysis. small muscles of eyes and fingers -> limbs -> neck > trunk > intercostal muscles -> diaphragm -> respiration stops. consciousness is not affected. effects last for 30 to 60 mins. |
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Effects of tubocurarine on atonomic ganglia |
High doses tubocurarine can block autonomic ganglia and adrenal medulla resulting in hypotension |
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Effects of tubocurarine by histamine release |
Bronchospasm, tracheobronchial and gastric secretions increased, results in hypotension |
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Adverse reactions of tubocurarine |
Respiratory paralysis and prolonged apnea hypotension flushing and bronchospasm |
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Treatment of toxicity of tubocurarine |
Neostigmine and edrophonium - reverse skeletal muscle paralysis and antidotes for curare poisoning. Antihistamines |
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Sugammadex |
Used for overdosage of rocuronium and vecuronium - chelates and excreted in urine. |
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Synthetic competitive blockers |
Pancuronium Atracurium Vecuronium Gallamine Rapacuronium Rocuronium |
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Advantages of synthetic competitive blockers |
Less histamine release do not block autonomic ganglia spontaneous recovery potent than tubocurarine |
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Rocuronium |
Do not cause hypotension tachycardia and is fast acting |
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Atracurium |
safely used in patients with renal impairment because it is degraded by plasma esterases by hofmann elimination and partly metabolized in the liver |
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Effects of succinylcholine on skeletal muscle |
Initial transient muscular fasciculation and twitching in chest and abdominal region -> skeletal muscle paralysis. it is due to the stimulation of muscle fibres by the discharge of action potentials in them |
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Effects on CVS |
Hypotension and bradycardia due to stimulation of vagal ganglia. Hypertension and tachycardia due to stimulation of sympathetic ganglia. Higher doses causes cardiac arrhythmias. if injected rapidly it can cause histamine release. |
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Pharmacokinetics |
Rapidly hydrolysed by pseudo cholinesterase It is short acting - 5 minutes Abnormal pseudocholinesterase enzyme |
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Adverse reactions |
postoperative muscle pain hyperkalemia cardiac arrhythmias malignant hyperthermia increased intraocular and intragastric pressure |
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Post operative muscle pain |
Due to damage to the muscle fibres that occurred during initial fasciculations |
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Hyperkalemia |
Due to sudden release of potassium from intracellular sites due to fasciculations dangerous in patients with congestive cardiac failure results in cardiac arrest in patient with burns nerve injuries and neuromuscular disease |
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Cardiac arrhythmias |
Stimulates nicotinic receptors in the ganglia and cardiac muscarinic receptors |
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Increased intragastric pressure |
due to fasciculations and leads to regurgitation which results in aspiration of gastric contents especially in muscular patients |
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Drug interactions with skeletal muscle relaxants |
General anesthetics, aminoglycosides and calcium channel blockers agument the action of smooth muscle relaxants. Succinylcholine and halothane together increase the risk of malignant hyperthermia Anticholinesterases reverse reaction of competitive blockers. |
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Uses of peripherally acting skeletal muscle relaxants |
adjuvents to anaesthesia in minor procedures in electroconvulsive therapy in spastic disorders in status epilepticus in patient on ventilator |
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In minor procedures |
in laryngoscopy, Bronchoscopy, esophageoscopy, tracheal intubation and in orthopaedic procedures like reduction of fractures and dislocations |
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Electroconvulsive therapy |
Protect the patient from convulsions and traum |
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In spastic disorders |
Overcome this puzzle of tetanus and athetosis |
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In status epilepticus |
If convergence cannot be controlled by anticonvulsants alone or neuromuscular junction blocker is used to control the muscular component of convulsions. they do not cross the blood brain barrier and have no Central effects |
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In patient on ventilator |
To reduce the resistance of the chest wall and enhance thoracic compliance and to facilitate artificial ventilation |
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Botulinum toxin |
Produced by anaerobic bacteria clostridium botulinum. it inhibits the release of acetylcholine at cholinergic synapses resulting in flaccid paralysis of skeletal muscle Used in dystonia, sports or writer's cramps, muscle spasms, tremors, cerebral palsy and rigidity seen in extra pyramidal disorders. Botox and relieve blepharospasm. |
