Pharmacokinetic and pharmacodynamic modelling with pancuronium

Area of Science:

• Pharmacology
• Anesthesiology
• Clinical Pharmacokinetics

Background:

• Pancuronium is a neuromuscular blocking agent used in surgical anesthesia.
• Understanding its pharmacokinetics and pharmacodynamics is crucial for safe and effective use.
• Previous studies have established baseline parameters for pancuronium.

Purpose of the Study:

• To simultaneously model the pharmacokinetics (plasma concentrations) and pharmacodynamics (neuromuscular blockade intensity) of pancuronium.
• To investigate the relationship between pancuronium plasma concentration and the degree of neuromuscular paralysis.
• To compare different methods of assessing neuromuscular function (mechanical vs. EMG).

Main Methods:

• Intravenous infusion of pancuronium in eleven surgical patients.
• Measurement of plasma concentrations (Cp) of pancuronium.
• Simultaneous modeling of Cp and neuromuscular blockade intensity using an integrated effect model and Hill equation analysis.

Main Results:

• Reduced systemic plasma clearance (0.79 +/- 0.28 ml/min/kg) and a longer terminal half-life (169 min) were observed compared to previous reports.
• The pharmacodynamic model successfully fitted the plasma concentration and paralysis data.
• Effective plasma concentrations for 50% paralysis (ECp50) were determined, with no significant differences between mechanical and EMG assessments.

Conclusions:

• The study successfully modeled pancuronium's PK/PD relationship in surgical patients.
• Observed PK parameter changes (reduced clearance, prolonged half-life) may be specific to the studied patient population.
• Both mechanical and EMG methods provide comparable pharmacodynamic assessments of pancuronium's neuromuscular blockade.