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A pharmacodynamic explanation for the rapid onset/offset of rapacuronium bromide
1Department of Anesthesia, University of Newcastle-upon-Tyne, United Kingdom.
Anesthesiology
|January 23, 1999
Summary
Rapacuronium exhibits rapid muscle relaxation due to fast equilibration between plasma and effect sites. Unlike other relaxants, laryngeal muscles are not resistant to rapacuronium, showing similar pharmacodynamics to the adductor pollicis.
Area of Science:
- Anesthesiology
- Pharmacology
- Muscle Physiology
Background:
- Nondepolarizing muscle relaxants display varied effects on laryngeal and peripheral muscles.
- Differences arise from equilibration delays, muscle sensitivity, and concentration-effect relationships.
Purpose of the Study:
- To investigate the pharmacodynamic characteristics of rapacuronium.
- To determine if rapacuronium exhibits differential effects on laryngeal adductors and adductor pollicis.
Main Methods:
- 10 volunteers received anesthesia with propofol.
- Twitch tensions of adductor pollicis and laryngeal adductors were measured.
- A pharmacodynamic model analyzed rapacuronium plasma concentrations and muscle responses.
Main Results:
- Equilibration between plasma rapacuronium concentration and effect sites was rapid for both muscles.
- Equilibration was faster at the laryngeal adductors compared to the adductor pollicis.
- Steady-state concentrations and Hill factors were similar for both muscle groups.
Conclusions:
- Rapacuronium's rapid onset and offset are attributed to fast plasma-to-effect site equilibration.
- Laryngeal muscles do not show resistance to rapacuronium, differing from other nondepolarizing agents.