Skeletal Muscle Relaxants Overview

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Questions and Answers

What is the primary role of neuromuscular blockers in surgical procedures?

To ensure adequate muscle relaxation (correct)

To facilitate assisted ventilation

To manage cardiac arrhythmias

To induce general anaesthesia

Which neuromuscular blocker is commonly selected for assisted ventilation in critically ill patients?

Vecuronium (correct)

Mivacurium

Atracurium

Suxamethonium

What complication can be caused by neuromuscular blockers related to the respiratory system?

Hypertension

Prolonged apnoea (correct)

Cardiac arrest

Asthma precipitation

Which condition may be managed with repeated doses of a neuromuscular blocker?

Severe tetanus Signup and view all the answers

What significant risk is associated with the use of Suxamethonium?

Postoperative muscle soreness Signup and view all the answers

What is the primary action of skeletal muscle relaxants?

Reduce muscle tone and/or cause paralysis Signup and view all the answers

Which of the following is classified as a depolarizing neuromuscular blocking agent?

Succinyl choline Signup and view all the answers

What is the mechanism of action for centrally acting muscle relaxants?

They decrease skeletal muscle tone via the cerebrospinal axis Signup and view all the answers

What effect do centrally acting muscle relaxants have on voluntary movements?

They decrease muscle tone without reducing voluntary power. Signup and view all the answers

How do competitive (nondepolarizing) blockers function at the neuromuscular junction?

They block nicotinic cholinergic receptors without intrinsic activity Signup and view all the answers

Which of the following best describes the main action of peripherally acting muscle relaxants?

They cause muscle paralysis and result in the loss of voluntary movement. Signup and view all the answers

What role do sodium channels play in the action of depolarizing blockers?

They open and depolarize muscle endplates Signup and view all the answers

Which of the following is a centrally acting skeletal muscle relaxant?

Dantrolene sodium Signup and view all the answers

Which medication is described as a GABA mimetic and glycinergic muscle relaxant?

Thiocolchicoside Signup and view all the answers

What common side effect is associated with Tizanidine?

Dry mouth Signup and view all the answers

What is one of the key differences between nondepolarizing and depolarizing neuromuscular blockers?

Depolarizing blockers cause twitching initially Signup and view all the answers

For which type of conditions are centrally acting muscle relaxants predominantly used?

Chronic spastic conditions and acute muscle spasms Signup and view all the answers

How are peripherally acting muscle relaxants typically administered?

Practically always given intravenously. Signup and view all the answers

What is a common cause of acute muscle spasms?

Overstretching of a muscle Signup and view all the answers

Which combination of medications is often used to help relieve trismus after dental procedures?

Mephenesin and analgesics Signup and view all the answers

Which centrally acting muscle relaxants can benefit spastic neurological diseases?

Baclofen, diazepam, tizanidine, and dantrolene Signup and view all the answers

Which medication is most commonly infused intravenously to treat tetanus?

Diazepam Signup and view all the answers

What is a notable side effect commonly associated with anxiety and tension related to muscle tone?

Bruxism Signup and view all the answers

What is the role of diazepam during electroconvulsive therapy?

To suppress convulsions Signup and view all the answers

Study Notes

Introduction to Skeletal Muscle Relaxants

Skeletal muscle relaxants reduce muscle tone or cause paralysis.
They can act peripherally at neuromuscular junctions or centrally in the cerebrospinal axis.

Classification of Skeletal Muscle Relaxants

Peripherally Acting:
- Neuromuscular Blocking Agents:
  - Nondepolarizing Blockers:
    - Long-acting: D-Tubocurarine
    - Intermediate-acting: Vecuronium, Atracurium
    - Short-acting: Mivacurium
  - Depolarizing Blockers:
    - Succinyl choline
Centrally Acting:
- Directly Acting Agents:
  - Mephenesin congeners, Dantrolene sodium, Chlorzoxazone
- GABA Mimetic:
  - Baclofen, Thiocolchicoside
- Benzodiazepines:
  - Diazepam
- Central α2 Agonist:
  - Tizanidine

Mechanism of Action

Competitive Block (Nondepolarizing):
- Curare and related drugs block nicotinic cholinergic receptors without intrinsic activity.
Depolarizing Block:
- Decamethonium and Succinyl choline activate NM cholinoceptors, causing initial twitching and fasciculations.

Uses of Neuromuscular Blocking Agents

Important in general anesthesia for adequate muscle relaxation, particularly in abdominal and thoracic surgeries.
Assist with ventilation in critically ill patients; vecuronium is preferred.
Prevent convulsions and trauma during electroconvulsive therapy.
Manage severe tetanus and status epilepticus with competitive blockers.

Toxicity of Neuromuscular Blocking Agents

Respiratory paralysis and prolonged apnea are the primary concerns.
Flushing may occur with atracurium and mivacurium.
Possible drop in blood pressure and cardiovascular collapse in hypovolemic patients.
Cardiac arrhythmias, especially with succinyl choline.
Potential asthma exacerbation with histamine-releasing blockers.
Postoperative muscle soreness may follow succinyl choline administration.

Centrally Acting Muscle Relaxants

Reduce skeletal muscle tone without affecting consciousness.
Primarily act on polysynaptic reflexes in the CNS.

Comparative Features

Centrally acting agents decrease muscle tone without loss of voluntary power; peripherally acting agents cause paralysis.
Centrally acting relaxants inhibit CNS reflexes, while peripherally acting block neuromuscular transmission.
Centrally acting agents have some CNS depression effects; peripherally acting do not.
Centrally acting can be given orally or parenterally; peripherally are generally administered intravenously.
Centrally acting are used for chronic conditions; peripherally are used for short-term surgical needs.

Thiocolchicoside

GABA mimetic and glycinergic muscle relaxant used for painful muscle spasms, sprains, and backaches.

Tizanidine

A central α2 adrenergic agonist that inhibits the release of excitatory amino acids.
Reduces muscle tone and spasms without diminishing muscle strength.
Indicated for spasticity due to neurological disorders and spinal-origin painful muscle spasms.
Side effects include dry mouth, drowsiness, insomnia, hallucinations, and liver enzyme elevation.

Uses of Centrally Acting Muscle Relaxants

Manage acute muscle spasms from injuries or overstretching.
Treat torticollis, lumbago, and neuralgias similarly to acute muscle spasms.
Diazepam and similar drugs reduce anxiety related muscle tone and bruxism.
Provide some benefit for spastic neurological conditions like multiple sclerosis and cerebral palsy.
Diazepam is used intravenously for managing tetanus, while methocarbamol serves as an alternative.
Diazepam can suppress convulsions during electroconvulsive therapy.
Facilitates orthopaedic manipulations under its influence.

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Description

This quiz covers the introduction and classification of skeletal muscle relaxants, focusing on their mechanisms of action and different types. It provides insights into both peripheral and central acting agents, discussing neuromuscular blocking agents and their classifications. Test your knowledge on skeletal muscle relaxants and enhance your understanding of their applications in oral surgery.