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Introduction
Illustrated mechanism of action
Examples of Medication Brand Names (with Images)
indications
Side Effects
Precautions & Contraindications
Monographs
Reference
INTRODUCTION
INTRODUCTION
Neuromuscular Blocking Agents (NMBAs) are potent muscle relaxants used primarily during surgery to prevent muscle movement. They work by blocking transmission at the neuromuscular junction, causing paralysis of skeletal muscles. NMBAs are categorized into two types:
Depolarizing Agents: The most common is succinylcholine, which acts as an agonist at nicotinic receptors, causing initial muscle contraction followed by relaxation.
Non-Depolarizing Agents: These are competitive antagonists of acetylcholine, preventing muscle contraction. Examples include rocuronium, vecuronium, and cis-atracurium
mechanism of action
mechanism of action
Neuromuscular blockers (NMBs) disrupt signal transmission at the neuromuscular junction
(NMJ), preventing muscle contraction. They
are classified into depolarizing and non-
depolarizing agents based on their
interaction with nicotinic acetylcholine receptors.
Depolarizing Agent: Example: Succinylcholine
* Mechanism: Bind to and activate nAChRs.
causing prolonged depolarization of the motor endplate Initially, this triggers
muscle fasciculations (phase I block), but persistent depolarization renders the
muscle fiber refractory to further stimulation. Resistance: Succinylcholine resists breakdown by acetylcholinesterase(AChE), prolonging its effect.
Non-Depolarizing Agents: Examples: Rocuronium, Vecuronium ,Atracurium
Mechanism: Competitively inhibit ACh
binding to nAChRs by occupying one or
both a-subunits, preventing ion channel opening and depolarization
Reversal of Blockade: Cholinesterase Inhibitors (e.g.,
Neostigmine): Increase synaptic ACh
levels by inhibiting AChE, outcompeting non-depolarizing agents for receptor binding
Phase Il Block: After prolonged succinylcholine use, the NMJ may transition to a non-depolarizing-like state, where cholinesterase inhibitors can partially reverse paralysis .
Examples of Medication Brand Names
Examples of Medication Brand Names
Depolarizing Agents:Succinylcholine : Rapid-acting agent causing initial muscle fasciculations followed by paralysis, often used for short procedures like intubation.
Non-Depolarizing Agents:Atracurium: Benzylisoquinolinium agent with intermediate duration, metabolized independently of organ function.
Pancuronium : Long-acting steroidal agent, rarely used due to slower onset.
Cisatracurium: Atracurium isomer with fewer side effects like histamine release.
Atracurium
Pancuronium
Succinylcholine
Cisatracurium
indications
indications
Neuromuscular blocking agents (NMBAs) are used for several key indications:
Endotracheal Intubation: To facilitate intubation by relaxing vocal cords and reducing the risk of airway injury.
Surgical Procedures: To improve surgical conditions by reducing muscle tone and movement, especially in laparoscopic and thoracic surgeries.
Mechanical Ventilation: To synchronize patient breathing with ventilators, reducing asynchrony and improving oxygenation.
Critical Care: In intensive care units for patients with acute respiratory distress syndrome or those requiring therapeutic hypothermia
Side Effects
Side Effects
Prolonged paralysis:Especially with long-acting agents or in patients with hepatic/renal impairment.
Hypotension:Caused by histamine release (e.g., with tubocurarine
Tachycardia or bradycardia:Due to vagolytic or vagotonic effects (e.g., pancuronium causes tachycardia).
Malignant hyperthermia:Rare, life-threatening reaction, especially with succinylcholine.
Hyperkalemia:Especially with succinylcholine in patients with burns, trauma, or neuromuscular diseases.
Anaphylaxis:Can occur with any NMBA, more common with rocuronium
Residual neuromuscular blockade (postoperative weakness)
Precautions & Contraindications
Precautions & Contraindications
Contraindications: Patients with susceptibility to malignant hyperthermia: Succinylcholine, a depolarizing NMBA, is contraindicated in patients with a personal or family history of malignant hyperthermia, a rare but life-threatening hypermetabolic reaction triggered by certain anesthetics and succinylcholine.
precautions: precautions to take when using neuromuscular blocking agents (NMBAs):
Airway & Ventilation Preparedness: Ensure mechanical ventilation is available — NMBAs cause paralysis, including respiratory muscles. Intubation equipment must be ready before administration.
Proper Monitoring: Use a peripheral nerve stimulator (like train-of-four) to monitor neuromuscular function and avoid overdose .Monitor vital signs continuously: BP, HR, SpO2, ETCO2.
Dosage Adjustment :Adjust in renal/hepatic impairment, as some agents (e.g., pancuronium, vecuronium) are excreted by kidneys or metabolized in the liver .Be careful in elderly or debilitated patients — may need lower doses.
Drug Interactions: Potentiation with: aminoglycosides, magnesium, lithium, certain anesthetics (like halothane).Resistance possible with chronic use of anticonvulsants or burn injuries.
Reversal Readiness :Have reversal agents (e.g., neostigmine, sugammadex for rocuronium/vecuronium) on hand .Wait for spontaneous recovery signs before administering reversal agents.
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WARNING:
WARNING:
Respiratory paralysis and need for ventilation: All NMBAs cause paralysis of respiratory muscles, leading to apnea. They must be administered only by experienced personnel with immediate availability of airway management, oxygen, and ventilatory support
Cardiovascular effects: Some NMBAs can cause cardiac effects such as tachycardia or bradycardia. For example, pancuronium can cause tachycardia due to vagolytic effects, while succinylcholine can cause bradycardia by stimulating muscarinic receptors. Histamine release by agents like atracurium and succinylcholine can cause hypotension and tachycardia
NMBAs are high-risk medications requiring careful administration and monitoring, especially since they can paralyze respiratory muscles, necessitating mechanical ventilation.
Monographs
Monographs
Drug monograph.docx_20250323_221216_٠٠٠٠.pdfDrug monograph.docx_20250322_004131_0000.pdfDOC-20250322-WA0085..pdfDrug monograph.docx_20250422_222252_0000.pdfDrug Monograph1.pdfEman Hatem mono graph.pdf Reference
Reference
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