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Questions and Answers
What is the mechanism of action of succinylcholine?
Which of the following is a characteristic of non-depolarizing NMBDs?
What is a common adverse effect of NMBDs?
How do NMBDs work?
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What is a pharmacokinetic characteristic of NMBDs?
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Which of the following is NOT a characteristic of depolarizing NMBDs?
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What is the primary use of NMBDs in anesthesia?
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Which of the following is a factor that can affect the dose-response curve of NMBDs?
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What is a potential adverse effect of non-depolarizing NMBDs?
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What determines the duration of action of NMBDs?
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Study Notes
Mechanism of Action
- Neuromuscular blocking drugs (NMBDs) work by blocking the action of acetylcholine (ACh) at the neuromuscular junction
- They compete with ACh for binding sites on the nicotinic receptor, preventing muscle contraction
- Can be classified as depolarizing or non-depolarizing blockers
Depolarizing NMBDs
- Examples: Succinylcholine (SCh)
- Mechanism: Causes persistent depolarization of the muscle membrane, leading to muscle paralysis
- Characteristics:
- Fast onset and short duration of action
- Can cause muscle fasciculations, hyperkalemia, and cardiac arrhythmias
- Not reversed by anticholinesterases
Non-Depolarizing NMBDs
- Examples: Atracurium, Vecuronium, Rocuronium, Cisatracurium
- Mechanism: Competitive inhibition of ACh at the nicotinic receptor
- Characteristics:
- Slower onset and longer duration of action compared to depolarizing blockers
- Can be reversed by anticholinesterases (e.g., neostigmine)
- May cause histamine release, leading to hypotension and bronchospasm
Pharmacokinetics and Pharmacodynamics
- NMBDs are highly protein-bound and have a large volume of distribution
- Elimination half-lives vary among agents, ranging from minutes (SCh) to hours (Atracurium)
- Dose-response curves are steep, with significant interindividual variability
- NMBDs can be affected by factors such as age, renal and hepatic function, and underlying medical conditions
Clinical Uses and Adverse Effects
- Used in anesthesia to facilitate tracheal intubation and provide muscle relaxation during surgery
- Adverse effects:
- Respiratory: respiratory depression, bronchospasm
- Cardiovascular: hypotension, tachycardia
- Neuromuscular: postoperative residual curarization, muscle weakness
- Other: anaphylaxis, malignant hyperthermia
Mechanism of Action
- Neuromuscular blocking drugs (NMBDs) block the action of acetylcholine (ACh) at the neuromuscular junction by competing for binding sites on the nicotinic receptor.
- This competition prevents muscle contraction, leading to muscle paralysis.
Depolarizing NMBDs
- Succinylcholine (SCh) is an example of a depolarizing NMBD.
- Depolarizing NMBDs cause persistent depolarization of the muscle membrane, leading to muscle paralysis.
- Characteristics of depolarizing NMBDs:
- Fast onset and short duration of action
- Can cause muscle fasciculations, hyperkalemia, and cardiac arrhythmias
- Not reversed by anticholinesterases
Non-Depolarizing NMBDs
- Examples of non-depolarizing NMBDs: Atracurium, Vecuronium, Rocuronium, Cisatracurium
- Non-depolarizing NMBDs work through competitive inhibition of ACh at the nicotinic receptor.
- Characteristics of non-depolarizing NMBDs:
- Slower onset and longer duration of action compared to depolarizing blockers
- Can be reversed by anticholinesterases (e.g., neostigmine)
- May cause histamine release, leading to hypotension and bronchospasm
Pharmacokinetics and Pharmacodynamics
- NMBDs are highly protein-bound and have a large volume of distribution.
- Elimination half-lives of NMBDs vary among agents, ranging from minutes (SCh) to hours (Atracurium).
- Dose-response curves are steep, with significant interindividual variability.
- Factors affecting NMBDs: age, renal and hepatic function, and underlying medical conditions.
Clinical Uses and Adverse Effects
- Clinical uses of NMBDs: facilitating tracheal intubation and providing muscle relaxation during surgery.
- Adverse effects of NMBDs:
- Respiratory: respiratory depression, bronchospasm
- Cardiovascular: hypotension, tachycardia
- Neuromuscular: postoperative residual curarization, muscle weakness
- Other: anaphylaxis, malignant hyperthermia
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Description
Learn about the mechanism of action of neuromuscular blocking drugs, including how they work and their classification into depolarizing and non-depolarizing blockers.
