Pharm 101: Pancuronium

Class

Paralytic agent


Pharmacodynamics
  • Non-depolarising steroid neuromuscular blocking agent
  • At low doses, acts predominately as a competitive inhibitor of Acetylcholine (ACH) at nicotinic receptors
  • At higher doses, enters pore of ion channel causing more intense neuromuscular blockade
  • Also blocks pre-junctional Na channels which interferes with ACH mobilisation at nerve endings

Pharmacokinetics
  • IV use
  • Undergoes rapid initial distribution phase followed by slower elimination phase
  • Highly ionised therefore small volume of distribution 0.1L/kg
  • Long-acting: duration of action > 35 minutes
  • Metabolism: hepatic
  • Elimination: renal (80%)

Clinical uses of neuromuscular blocking drugs
  • Rapid Sequence Induction (RSI) to facilitate relaxation of pharyngeal and laryngeal muscles for intubation
  • Clinical effects:
    • Initially motor weakness followed by skeletal muscles becoming flaccid and unexcitable to electrical stimulation
    • Larger muscles (e.g. abdominal, trunk, diaphragm) are more resistant to neuromuscular blockade and recover more rapidly than smaller muscles (e.g. facial, foot, hand)
    • Diaphragm is the last muscle to be paralysed
  • Surgical relaxation (especially for intra-abdominal and intra-thoracic procedures)
  • Control of ventilation in ventilatory failure due to pneumonia, COPD etc.
    • Reduce chest wall resistance i.e. improve thoracic compliance, decrease oxygen utilisation, and improve ventilator synchrony

Adverse effects
  • Moderate tachycardia and small increase in CO due to vagolytic action on cardiac muscarinic receptors

Precautions/contraindications
  • Enhanced neuromuscular blockade:
    • Myasthenia gravis
    • Aminoglycosides
  • Reduced neuromuscular blockade:
    • Corticosteroids
    • Phenytoin
  • Reduced clearance:
    • Renal failure
    • Advancing age

Further reading

References
  • Katzung BG. Basic & Clinical Pharmacology. 14e. 2018: 476-484

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MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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