Pharm 101: Vecuronium

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
  • Onset of action: within 1 minute
  • Maximal effect at 3-5 minutes
  • Intermediate-acting: duration of action 20-35 minutes
  • Rapidly distributed to extracellular space
  • Metabolism: liver
  • Elimination: liver (75-90%) and kidney
Clinical uses
  • Rapid Sequence Induction (RSI)
    • Dose 0.1mg/kg
  • 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
Sugammadex
  • Sugammadex is a modified cyclodextrin antidote used for rapid reversal of rocuronium and vecuronium
  • Binds tightly to rocuronium in a 1:1 ratio, and this complex is excreted unchanged in the urine
  • This decreases free plasma concentration and establishes a concentration gradient for rocuronium to diffuse away from the neuromuscular junction back into circulation for further binding to free sugammadex
  • Dosing varies for desired reversal effects:
    • 2mg/kg: reversal of shallow neuromuscular blockade
    • 4mg/kg: reversal of deeper blockade
    • 16mg/kg: immediate reversal following administration of single dose 1.2mg/kg rocuronium
  • Adverse effects:
    • Anaphylaxis in 0.3% of patients receiving 16mg/kg dosage
    • Hypersensitivity reactions are common
    • Bradycardia (may progress rapidly to cardiac arrest)
    • Coagulopathy: 25% elevation of APTT and PT/INR values lasting up to one hour
Precautions/contraindications
  • Enhanced neuromuscular blockade:
    • Myasthenia gravis
    • Aminoglycosides
  • Reduced neuromuscular blockade:
    • Corticosteroids
    • Phenytoin
  • Reduced clearance:
    • Hepatic failure
    • Advancing age
References
  • The Royal Children’s Hospital Melbourne. Parkville, Victoria, Australia. July 2017. Medication guidelines: Vecuronium
  • Katzung BG. Basic & Clinical Pharmacology. 14th ed. United States of America: McGraw-Hill Education; 2018. 476-484 p.
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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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